Expanding the clinical spectrum associated with defects in CNTNAP2 and NRXN1.

Abstract

Heterozygous copy-number and missense variants in CNTNAP2 and NRXN1 have repeatedly been associated with a wide spectrum of neuropsychiatric disorders such as developmental language and autism spectrum disorders, epilepsy and schizophrenia. Recently, homozygous or compound heterozygous defects in either gene were reported as causative for severe intellectual disability.
99 patients with severe intellectual disability and resemblance to Pitt-Hopkins syndrome and/or suspected recessive inheritance were screened for mutations in CNTNAP2 and NRXN1. Molecular karyotyping was performed in 45 patients. In 8 further patients with variable intellectual disability and heterozygous deletions in either CNTNAP2 or NRXN1, the remaining allele was sequenced.
By molecular karyotyping and mutational screening of CNTNAP2 and NRXN1 in a group of severely intellectually disabled patients we identified a heterozygous deletion in NRXN1 in one patient and heterozygous splice-site, frameshift and stop mutations in CNTNAP2 in four patients, respectively. Neither in these patients nor in eight further patients with heterozygous deletions within NRXN1 or CNTNAP2 we could identify a defect on the second allele. One deletion in NRXN1 and one deletion in CNTNAP2 occurred de novo, in another family the deletion was also identified in the mother who had learning difficulties, and in all other tested families one parent was shown to be healthy carrier of the respective deletion or mutation.
We report on patients with heterozygous defects in CNTNAP2 or NRXN1 associated with severe intellectual disability, which has only been reported for recessive defects before. These results expand the spectrum of phenotypic severity in patients with heterozygous defects in either gene. The large variability between severely affected patients and mildly affected or asymptomatic carrier parents might suggest the presence of a second hit, not necessarily located in the same gene.

Full text

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RESEARCH ARTICLE Open Access
Expanding the clinical spectrum associated with
defects in CNTNAP2 and NRXN1
Anne Gregor1, Beate Albrecht2, Ingrid Bader3, Emilia K Bijlsma4, Arif B Ekici1, Hartmut Engels5, Karl Hackmann6,
Denise Horn7, Juliane Hoyer1, Jakub Klapecki8, Jürgen Kohlhase9, Isabelle Maystadt10, Sandra Nagl11, Eva Prott2,
Sigrid Tinschert6, Reinhard Ullmann12, Eva Wohlleber5, Geoffrey Woods13, André Reis1, Anita Rauch14and
Christiane Zweier1*
Abstract
Background: Heterozygous copy-number and missense variants in CNTNAP2 and NRXN1 have repeatedly been
associated with a wide spectrum of neuropsychiatric disorders such as developmental language and autism
spectrum disorders, epilepsy and schizophrenia. Recently, homozygous or compound heterozygous defects in
either gene were reported as causative for severe intellectual disability.
Methods: 99 patients with severe intellectual disability and resemblance to Pitt-Hopkins syndrome and/or
suspected recessive inheritance were screened for mutations in CNTNAP2 and NRXN1. Molecular karyotyping was
performed in 45 patients. In 8 further patients with variable intellectual disability and heterozygous deletions in
either CNTNAP2 or NRXN1, the remaining allele was sequenced.
Results: By molecular karyotyping and mutational screening of CNTNAP2 and NRXN1 in a group of severely
intellectually disabled patients we identified a heterozygous deletion in NRXN1 in one patient and heterozygous
splice-site, frameshift and stop mutations in CNTNAP2 in four patients, respectively. Neither in these patients nor in
eight further patients with heterozygous deletions within NRXN1 or CNTNAP2 we could identify a defect on the
second allele. One deletion in NRXN1 and one deletion in CNTNAP2 occurred de novo, in another family the
deletion was also identified in the mother who had learning difficulties, and in all other tested families one parent
was shown to be healthy carrier of the respective deletion or mutation.
Conclusions: We report on patients with heterozygous defects in CNTNAP2 or NRXN1 associated with severe
intellectual disability, which has only been reported for recessive defects before. These results expand the spectrum
of phenotypic severity in patients with heterozygous defects in either gene. The large variability between severely
affected patients and mildly affected or asymptomatic carrier parents might suggest the presence of a second hit,
not necessarily located in the same gene.
Background
Recent data suggested that heterozygous variants or
defects in NRXN1(Neurexin 1) or CNTNAP2 (contactin
associated protein 2), both genes encoding neuronal cell
adhesion molecules, represent susceptibility factors for a
broad spectrum of neuropsychiatric disorders such as
epilepsy, schizophrenia or autism spectrum disorder
(ASD) with reduced penetrance and no or rather mild
intellectual impairment [1-23]. In contrast, biallelic
defects in either gene were reported to result in fully
penetrant, severe neurodevelopmental disorders. Strauss
et al. reported on a homozygous stop mutation in
CNTNAP2 in Old Order Amish children causing CDFE
(Cortical Dysplasia - Focal Epilepsy) syndrome (MIM
#610042), characterized by cortical dysplasia and early
onset, intractable focal epilepsy leading to language
regression, and behavioral and mental deterioration
[24,25]. In a former study we reported on homozygous
or compound heterozygous defects in CNTNAP2 or
NRXN1 in four patients with intellectual disability and
* Correspondence: christiane.zweier@uk-erlangen.de
1Institute of Human Genetics, Friedrich-Alexander-University Erlangen-
Nuremberg, Erlangen, Germany
Full list of author information is available at the end of the article
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© 2011 Gregor et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in
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Page 2

epilepsy [26], resembling Pitt-Hopkins syndrome (PTHS,
MIM #610954). A possible shared synaptic mechanism
that was observed in Drosophila might contribute to the
similar clinical phenotypes resulting from both heterozy-
gous and recessive defects in human CNTNAP2 or
NRXN1 [26].
To further delineate the clinical phenotype associated
with potentially recessive defects in any of the two
genes, we screened a group of patients with either
severe intellectual disability resembling Pitt-Hopkins
syndrome or the phenotypes caused by recessive
CNTNAP2 or NRXN1 defects. Additionally, we per-
formed mutational testing in patients found to harbor
heterozygous deletions in either gene.
Methods
Patients
Our total cohort of patients comprised four different sub-
sets: 1. our new Pitt-Hopkins syndrome-like (PTHSL)
screening group, 2. parts of our old PTHSL screening
group [26], 3. a group of patients with suspected reces-
sive inheritance, and 4. patients with known heterozygous
deletions in one of the two genes. 1. The new PTHSL
screening group consisted of 90 patients who were initi-
ally referred with suspected Pitt-Hopkins syndrome for
diagnostic testing of the underlying gene, TCF4, which
encodes transcription factor 4. They all had severe intel-
lectual disability and variable additional features reminis-
cent of the PTHS spectrum such as dysmorphic facial
gestalt or breathing anomalies. Mutational testing of
TCF4 revealed normal results. In all of these 90 patients
mutational screening of NRXN1 and CNTNAP2 was per-
formed in the current study. Molecular Karyotyping was
performed in 22 of them. This cohort does not overlap
with the second subset, our old PTHSL screening group,
which is a similar group of 179 patients, reported in a
former study [26]. No published information on muta-
tional screening of that group was included in the current
study, but previously unpublished information on Mole-
cular Karyotyping of 23 patients. 3. Nine patients with
severe intellectual disability were referred to us specifi-
cally for CNTNAP2/NRXN1 testing because of suspected
autosomal-recessive inheritance and/or phenotypic over-
lap with the previously published patients [26]. 4. In eight
patients copy number changes in either NRXN1 or
CNTNAP2 were identified in other genetic clinics. These
were referred to us for mutational screening of the sec-
ond allele. These patients had variable degrees of intellec-
tual disability and various other anomalies. An overview
on tested patients is given in Table 1. This study was
approved by the ethics committee of the Medical Faculty,
University of Erlangen-Nuremberg, and written consent
was obtained from parents or guardians of the patients.
Molecular Karyotyping
Molecular karyotyping was performed in 45 patients
without TCF4 mutation with an Affymetrix 6.0 SNP
Array (Affymetrix, Santa Clara, CA), in accordance with
the supplier’s instructions. Copy-number data were ana-
lyzed with the Affymetrix Genotyping Console 3.0.2
software. In patient C3 molecular karyotyping was per-
formed with an Affymetrix 500K array and data analysis
was performed using the Affymetrix Genotyping Con-
sole 3.0.2 software.
The patients with heterozygous copy number variants
(CNVs) referred for sequencing of the second allele, had
been tested on different platforms. An overview on the
array platforms, validation methods and segregation in
the families is given in Tables 2 and 3.
Mutational Screening and MLPA
DNA samples of 107 patients were derived from periph-
eral blood, and if sample material was limited, whole
genome amplification was performed using the Illustra
GenomiPhi V2 DNA Amplification Kit (GE Healthcare,
Little Chalfont, Buckinghamshire, United Kingdom)
according to the manufacturer’s instructions. All coding
exons with exon-intron boundaries of CNTNAP2
(NM_014141) and of isoforms alpha1, alpha2 and beta
of NRXN1 (NM_004801; NM_001135659; NM_138735)
were screened for mutations by unidirectional direct
sequencing (ABI BigDye Terminator Sequencing Kit v.3;
AppliedBiosystems, Foster City, CA) with the use of an
automated capillary sequencer (ABI 3730; Applied Bio-
systems). Mutations were confirmed with an indepen-
dent PCR and bidirectional sequencing from original
DNA. Primer pairs and conditions were used as pre-
viously described [26]. For splice site prediction, eight
different online tools were used as indicated in Table 4.
Multiplex Ligation Dependent Probe Amplification
(MLPA) for all coding exons of CNTNAP2 was per-
formed for patients C1-C4 as described previously [26].
Results
Molecular Testing
Mutational screening of NRXN1 in 90 TCF4 mutation
negative patients and nine families with suspected reces-
sive inheritance of severe intellectual disability did not
reveal any point mutation, while in CNTNAP2 the het-
erozygous mutation c.1083G>A in the splice donor site
of exon 7 was found in two patients (C3, C4). Eight pre-
diction programs (Table 4) showed diminished splice
site recognition for this mutation, which is therefore
predicted to result in an in-frame loss of exon 7. This
possible splice site mutation was found in one of 384
control chromosomes. Furthermore, in patient C1 the
heterozygous frameshift mutation p.D393RfsX51 in exon
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Table 1 Overview on screened patients
Patient samples used in this
study
Sequencing of NRXN1 number of
patients
Sequencing of CNTNAP2 number of
patients
Molecular karyotyping number of
patients
1. new screening sample,
n = 90
2. old screening sample[26],
n=179
3. specific testing sample*
4. NRXN1/CNTNAP2 deletion
group**
90 90, including C1-C422, including N1
published [26], results not used in
this study
9
5, N2-N6
published [26], results not used in this
study
9
3, C5-C7
23, not published before
8, (details on arrays see Table 3)
* Patients were referred to us specifically for NRXN1/CNTNAP2 testing due to suspected autosomal recessive inheritance and/or phenotypic overlap with the
previously published cases.
** Patients were referred to us because of copy number changes in either NRXN1 or CNTNAP2 for screening of the respective second allele.
Table 2 Molecular findings in NRXN1
NRXN1
Defect Array Platform
and
details of NRXN1/
CNTNAP2 deletion
Validation of
Array data
InheritanceCarrier
parent
Other non-
polymorphic
CNVs
NRXN1
sequen-
cing
CNTNAP2
sequen-
cing
N1
NRXN1 deletion of
exons 1-4
Affymetrix 6.0 SNP
Array
chr2:50.860.393-
51.208.000
348 kb (230 array
marker)
Agilent 244K
+customized array
chr2:50.270.203-
51.257.206
987 kb
Agilent 244A
chr2:51.011.745-
51.144.527
133 kb
Agilent 244A
chr2:50.800.974-
51.286.171
425 kb
MLPA as
reported
previously [26]
paternal healthy,
normal
intelligence
noneno 2nd
mutation
normal
N2
NRXN1 deletion of
exons 1-18
customized
Oligonucleotide
array
maternallearning
disabilities
and
behavioral
problems
healthy
noneno 2nd
mutation
normal
N3
NRXN1 deletion of
exons 1-2
qPCR as
reported
previously [31]
maternal 21q22.3:44.534.530-
44.820.473 pat dup
Xp22.33:0.000.001-
2.710.316 mat dup
15q26.1:88.028.337-
88.072.545 mat del
16q12.1:50.773.658-
51.135.179 mat
dup
none
no 2nd
mutation
normal
N4
NRXN1 deletion of
exons 1-4
FISH analysis
with BAC clones
RP11-67N9 and
RP11-643L22
paternalhealthy
no 2nd
mutation
normal
N5
NRXN1 deletion of
exons 3-4
Agilent 244A
chr2:50.861.527-
51.090.563,
229 kb
qPCR as
reported
previously [31]
paternal muscular
problems
& stroke;
parents
consang.
no 2nd
mutation
normal
N6
NRXN1 deletion of
exons 1-2
Agilent 244A
chr2:51.033.865-
51.496.143
462 kb
Agilent 244A of
the parents
de novo noneno 2nd
mutation
normal
published
biallelic
defect
P3, Zweier et
al. 2009
n = 1 [26]
published
heterozygous
defects ass.
with ASD
n = 18
[5,9,14,16,22]
NRXN1 deletion of
exons 1-4 + p.
S979X
Affymetrix 6.0 SNP
Array
113 kb
parents
heterozygous
carriers
healthy
15x NRXN1 deletion
[5,14,16,22], 2x
NRXN1 gain [14],
1x balanced
chromosomal
rearrangement
disrupting NRXN1
[9]
12x Agilent 244K
[5], 3x NimbleGen
custom arrays [14],
1x Affymetrix 100 K
Assay [16], 1x
Affymetrix 10 K
Assay [22],
66 kb-5 Mb
6x de novo
[5,16,22]; 5x
mat [5,14]; 4x
pat [5,9]; 3x
not available
[5,14]
1x duplication
14q24 [14]
mat, maternal; pat, paternal; dup, duplication; del, deletion; ass., associated; FISH, fluorescence in-situ hybridization; qPCR, quantitative Real-Time-PCR; non-
polymorphic CNVs: CNVs that have not been reported in the Toronto Database of Genome Variants or have not been identified in one of our molecularly
karyotyped healthy control indivuals
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Table 3 Molecular findings in CNTNAP2
Defect
CNTNAP2
Array Platform
and
details of
NRXN1/
CNTNAP2
deletion
Validation of
Array data
InheritanceCarrier
parent
Other non-
polymorphic
CNVs
NRXN1
sequencing
CNTNAP2
sequencing
C1
CNTNAP2
c.1175_1176dup; p.
D393RfsX51
Affymetrix 6.0
SNP Array,
normal results
for CNTNAP2
and NRXN1
paternalhealthy chr9:9.337.920-
10.207.671 mat
dup
chr13:19.104.340-
19.477.398 mat
dup
none
normal no 2nd
mutation;
MLPA
normal
C2
CNTNAP2
c.2153G>A, p.
W718X
Affymetrix 6.0
SNP Array,
normal results
for CNTNAP2
and NRXN1
Affymetrix 500 K
SNP Array,
normal results
for CNTNAP2
and NRXN1
Illumina 317 K
SNP Array,
normal results
for CNTNAP2
and NRXN1
not known not
known
normal no 2nd
mutation;
MLPA
normal
C3
CNTNAP2
c.1083G>A, splice
site (p.V361V)
paternal healthy none normalno 2nd
mutation;
MLPA
normal
C4
CNTNAP2
c.1083G>A, splice
site (p.V361V)
maternalhealthy
pathogenic
frameshift
mutation in
MEF2C (P7,
Zweier et al.
2010) [28]
none
normalno 2nd
mutation;
MLPA
normal
C5
CNTNAP2 deletion
of exons 2-3
Affymetrix 6.0
SNP Array
chr7:146.079.333-
146.194.785
115 kb (69 array
marker)
Illumina Human
660W-Quad
chr7:146.144.267-
146.374.539
230 kb (53 array
marker)
Agilent 2 × 400
K
chr7:147.702.165-
148.378.711
677 kb
Affymetrix 6.0
SNP Array of the
parents
maternal healthy normal, one
silent
variant
no 2nd
mutation
C6
CNTNAP2 deletion
of exons 3-4
qPCR as
reported
previously [32]
maternalhealthynone normal no 2nd
mutation
C7
CNTNAP2
deletion of exons
21-24
customized
Oligonucleotide
array
de novohealthy chr7:92.394.428-
92.530.356 del
chr7:93.464.449-
94.430.690 del,
both de novo
conventional
karyotyping: 46,
XX,der(4)t(4;10)
(q25;q24), der(7)t
(4;7)(q25;q32),
der(10)inv(10)
(p13q24)(7;10)
(q32;p13), de
novo
normalno 2nd
mutation
published
biallelic
defects
n = 13[24,25]
2x CNTNAP2
deletion of exons 2-
9, homozygous [26];
1x CNTNAP2
deletion of exons 5-
8 + IVS10-1G>T [26];
10x CNTNAP2
c.3709delG,
homozygous [24,25]
2x Affymetrix
500 K/250 K Nsp
SNP Array; 1x
Affymetrix 6.0
SNP Array [26];
10x no
parents
heterozygous
carriers
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8 and in patient C2 the heterozygous stop mutation p.
W718X in exon 14 were identified. Due to their nature
and location both truncating mutations are predicted to
result in mRNA decay and loss of the affected allele. For
patient C2 parents were not available, but all other
mutations were shown to be inherited from a healthy
parent. No defect on the second allele was identified in
any of these patients by sequencing and subsequent
MLPA-analysis of all coding exons. In 942 controls
sequenced by Bakkaloglu et al. [3], no truncating muta-
tion in CNTNAP2 was found. No CNTNAP2 deletion
was found in 667 control individuals molecularly karyo-
typed [26].
Molecular karyotyping with an Affymetrix 6.0 SNP
Array in 45 TCF4 mutation negative patients revealed a
heterozygous deletion within the NRXN1 gene in one
patient (N1). The father was shown to be healthy car-
rier, and no mutation on the second allele was found in
this patient by sequencing of all coding exons.
In three patients with CNTNAP2 deletions (C5-C7)
and in five patients with NRXN1 deletions (N2-N6) we
could not identify any pathogenic mutation on the sec-
ond allele by sequencing all coding exons. In patient N6
and in patient C7 the deletion within NRXN1 or
CNTNAP2 was shown to be de novo. In all other
families the deletion in CNTNAP2 or NRXN1 was also
identified in one of the parents.
In all patients with a heterozygous defect in
CNTNAP2 we also screened NRXN1 and vice versa,
without observing any anomalies. An overview of locali-
zation of novel and published mutations and deletions is
shown in Figure 1 and 2. Mutation and array data of
novel patients are shown in Tables 2 and 3.
Clinical Findings
Four of six patients with heterozygous CNVs in NRXN1
were severely intellectually disabled (N1-N4). Three had
epilepsy and one episodic hyperbreathing. Patients N5
and N6 were only mildly intellectually disabled and N5
additionally had various malformations like choanal atre-
sia, anal atresia, and skeletal anomalies. All patients had
absent or impaired language abilities, while motor devel-
opment was normal or only mildly delayed in four of
them. The deletion in patient N6 was shown to be de
novo, in all other families one parent was shown to be
carrier of the deletion. The mother of N2 was reported to
have had learning difficulties, all others were reported to
be healthy and of normal intelligence. However, detailed
neuropsychiatric testing was not performed. Summarized
clinical details of the patients are shown in Table 5.
Table 3 Molecular findings in CNTNAP2 (Continued)
published
heterozygous
defects
n = 12
[1,3,7,12,21,33]
2x translocation
disrupting CNTNAP2
[12,33], 1x inversion
disrupting CNTNAP2
[3], 5x CNTNAP2
deletion [1,7,21], 4x
missense variant in
CNTNAP2 [3]
3x BAC array [7],
1x NimbleGen
custom array
[21], 220 kb-11
Mb
2x not reported
[7], 4x inherited
[3], 2x paternal
[1,21], 2x de
novo [3,7] 2x
balanced in
parent
(translocation)
[12,33]
mat, maternal; pat, paternal; dup, duplication; del, deletion; ass., associated; qPCR, quantitative Real-Time-PCR; non-polymorphic CNVs: CNVs that have not been
reported in the Toronto Database of Genome Variants or have not been identified in one of our molecularly karyotyped healthy control indivuals
Table 4 Splice site prediction for splice donor variant c.1083G>A
Program wild type scoremutant score
NNSplice 0.9 [34]
HSF V2.4 [35]
MaxEntScan [36]
Maximum Entropy Model
Maximum Dependence Decomposition Model
First-order Markov Model
Weight Matrix Model
Splice Site Score Calculation [37]
Splice Site Analyzer-Tool [38]
0.99
91.56
0.6
80.98
8.37
11.88
7.5
8.9
8.1
83.27
ΔG -7.1
0.967
0.95
1.06619
3.38
9.78
3.88
5.73
5.2
71.36
ΔG -4
splice site not recognized
0.55
0.26169
Splice Predictor [39]
NetGene2 [40]
SplicePort [41]
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All seven patients with heterozygous defects in
CNTNAP2 in this study showed severe to profound intel-
lectual disability. Speech was lacking in four patients (C1,
C4-C6) and reported to be simple in C7. Patient C3 lost
her speech ability at age 2.5 years. Motor impairment
was also severe with no walking abilities in three patients
(C4-C6), patient C7 started to walk at the age of 15
months, and patients C1 and C3 lost this function at age
2.5 - 3 years. Five patients had seizures. As far as data
were available, epilepsy was of early onset and difficult to
treat. At least in two of the patients episodes of hyper-
breathing were reported. Congenital anomalies and mal-
formations such as tetralogy of Fallot, pyloric stenosis,
and variable other anomalies or septo-optical dysplasia
were reported in patients C1 and C5, respectively. In the
parents shown to be carriers, no neuropsychiatric anoma-
lies were reported. However, detailed neuropsychiatric
testing was not performed.
Summarized clinical details of the patients are shown
in Table 6.
Discussion
NRXN1. While the majority of the novel patients had
severe intellectual disability, only two of the patients, N5
and N6, with heterozygous deletions in NRXN1 had
mild intellectual disability as reported before for this
kind of defects [5,9,11,14,16]. Additionally, patient N5
had various congenital malformations and anomalies.
Interestingly, one recently published patient with a
NRXN1 defect and no significant intellectual impairment
was reported with similar malformations resembling the
VACTERL spectrum [5]. Mild skeletal anomalies were
also reported in the patient published by Zahir et al.
[16]. A larger number of patients and therefore further
delineation of the phenotype will probably clarify a pos-
sible relation of such malformations to NRXN1 defects.
Figure 1 Schematic drawing of NRXN1 with localization of novel and published mutations and deletions. Schematic drawing of genomic
structure of alpha 1 isoform of NRXN1 showing domain-coding exons and localization of mutations and deletions. Deletions found in our study
are represented by black bars. Published biallelic aberrations are shown with black dotted lines, whereas heterozygous losses and gains are
marked by grey solid and dashed lines, respectively. Abbreviations are as follows: SP, signal peptide; LamG, laminin-G domain; EGF, epidermal
growth factor like domain; TM, transmembrane region; PDZBD, PDZ-domain binding site.
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All other four patients with heterozygous NRXN1 dele-
tions were severely intellectually disabled without speci-
fic further anomalies. Their phenotype resembled the
patient reported with a compound heterozygous defect
in this gene [26]. Except for patient N4, speech impair-
ment was severe compared to a rather mild motor
delay. Because of the severe phenotype in the patients in
contrast to the normal or only mildly impaired intellec-
tual function in the respective carrier parent, a defect of
the second allele was suspected in the patients, but not
found.
CNTNAP2. Most of the clinical aspects and the sever-
ity of intellectual disability in the herewith reported
patients with heterozygous CNTNAP2 defects resembled
those observed in patients with biallelic defects in
CNTNAP2 reported before (Table 6). Two of the
patients (C1, C3) showed language and motor regression
correlating with onset of epilepsy. All others showed
lacking or severely impaired speech development. How-
ever, in contrast to the published patients with recessive
defects and normal or only mildly delayed motor devel-
opment [24,26], all but one patients in this study also
showed severe motor retardation. We could not identify
a defect on the second allele in any of the novel
patients. In most of the families the defect was inherited
from a healthy parent. Despite a significantly higher fre-
quency (p < 0.01, Fisher’s exact test) of two truncating
mutations in our cohort of 99 severely to profoundly
intellectually disabled patients compared to no truncat-
ing mutation in 942 normal controls [3] definite proof
that the respective mutation is fully responsible for the
phenotype is so far lacking. This also applies to the
other identified defects in CNTNAP2 or NRXN1.
Congenital malformations as described in patients C1
or C5 (Table 6) have not yet been reported in any other
patient with a CNTNAP2 defect. Furthermore, the fact
that the expression of the gene is restricted to the ner-
vous system [27] does not explain these anomalies.
Therefore, another genetic cause for these malforma-
tions might exist. Thus it is difficult to define if the
intellectual disability is associated with the CNTNAP2
mutation at all in these patients. Other factors like pre-
mature complicated birth in patient C6 might contribute
to impaired intellectual function. C3 and C4 carried the
Figure 2 Schematic drawing of CNTNAP2 with localization of novel and published mutations and deletions. Schematic drawing of
genomic structure of CNTNAP2 showing domain-coding exons and localization of mutations and deletions. Mutations and deletions found in
our study are represented by black arrows and bars. Published biallelic aberrations are shown with black dotted lines, whereas heterozygous
defects are shown in grey. Abbreviations are as follows: SP, signal peptide; DISC, discoidin-like domain; LamG, laminin-G domain; EGF, epidermal
growth factor like domain; FIB, fibrinogen-like domain; TM, transmembrane region; PDZBD, PDZ-domain binding site.
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Table 5 Clinical findings associated with defects in NRXN1
Sex
&
Age
NRXN1
ID Speech Age of
Walking
Seizures
age of
onset
Birth
parameters
Weight,
Heigth,
OFC
Weight
Height
OFC
Behavioral
anomalies/
Stereotypies
Facial
dysmorphisms
Other findings
N1
m,
14y
Severe at 3y: max.
10 single
words, lost
this function
14moyes 2900 g
52 cm
34 cm
P25-P50
P25-P50
P90
yes,
puts objects
in his mouth
large mouth,
widely spaced
teeth,
upslanting
palpebral
fissures,
strabism
macrocephaly
(also maternal
and paternal),
large mouth,
retrogenia
hyperbreathing
N2
m,
6y
Severe at 24mo:
single words
and two
word
combinations,
receptive
better than
expressive
no active
speech
16mo none3740 g
51 cm
38.5 cm
Normal
<P3
>P95
none
muscular
hypotonia, MRI:
wide ventricles
N3
m,
3y
4mo
f,
16y
Severe 14monone 3350 g
52 cm
35 cm
3530 g
51 cm
33 cm
3300 g
51 cm
33 cm
P50-P75
P75-P90
P50-P75
P10-P25
P25-P50
<P5
P3-P10
<P3
P50
yes nonenone
N4
Severenoneno grand
mal
4y
grand
mal,
6y (until
age 11y)
yes,
hand licking
broad nasal tip,
pointed chin
drooling, friendly
N5
m,
21y
Mild impaired not
known
nonemild facial
asymmetry,
small ears,
broad nose,
broad mouth,
bushy eye
brows, high
arched palate,
cleft lip
pectus
excavatum,
single transverse
palmar crease,
choanal atresia,
anal atresia, thick
finger joints,
ureter stenosis,
delayed bone
age,
spondyloptosis
L5/S1
muscular
hypotonia
(improved),
scapulae alatae,
mild lordosis,
tendency to
diarrhea
N6
f, 6y
3mo
Mild2 y: first
words,
speech delay
mainly
affecting
active speech
21mo none2820 g
50 cm
35 cm
P10-P25
P3
P10-P25
noneprotruding ears
published
biallelic
defect
P3, Zweier et
al. 2009
N = 1 [26]
f,
18y
Severenone 2ynone3450 g
normal
P50-P75
P50-P75
P25
yes,
hypermotoric
behavior
broad mouth,
strabism,
protruding
tongue
excessive
drooling,
developmental
regression,
abnormal sleep-
wake-cycles,
decreased deep-
tendon reflexes
upper
extremities,
hyperbreathing
1x VACTERL
association [5],
1x mild skeletal
anomalies [16],
4x hypotonia, 2x
ventricular
septum defect,
3x hemangioma
[5]
published
heterozygous
defects ass.
with ASD
N = 18
[5,9,14,16,22]
7x normal
[5], 3x
learning
problems
[5,14] 2x
dev. Delay
[5,22], 3x
mild ID
[9,14,16], 2x
moderate
ID [5]
14x language
delay
[5,14,16,22]
5x
motor
delay
[5,16]
1x yes
[5]
not
reported
not
reported
11x ASD or
Asperger
syndrome
[5,9,14,16,22]
11x mild
dysmorphic
features
[5,14,16]
TOF, tetralogy of Fallot; f, female; m, male; y, year; mo, month; ASD, autism spectrum disorder; published reports on CNTNAP2 and NRXN1: only papers
containing clinical data are cited; ass., associated; P, centile; ass., associated
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Table 6 Clinical findings associated with defects in CNTNAP2
Sex &
Age
CNTNAP2
ID SpeechAge of
Walking
Seizures
age of
onset
Birth
parameters
Weight,
Heigth,
OFC
Weight
Height
OFC
Behavioral
anomalies/
Stereotypies
Facial dysmorphismsOther findings
C1
f, 8y Severenone 2y with aid,
lost this
function
(3y)
yes, resist.
to
treatment
2430 g
45 cm
not
reported
<P3
<P3
<P3
hand
movements
synophrys, long
eyelashes, prominent
columella, short
philtrum, arched palate,
widely spaced teeth,
prominent jaw
happy, affectionate, TOF, pyloric stenosis,
vesicoureteric reflux, agenesis of labia
minora, hirsutism, tapering fingers
C2
m, 18ySevere?? complex,
early
onset
3y
??? hyperbreathing, apnoe episodes
C3
f, 11y Severe few words, lost
this function
2,5y, lost
this
function
3510 gP10
<P3
P10
yesbroad mouth,
protruding tongue
develop. regression from 15 m,
swallowing problems, nocturnal
laughing, scoliosis, spastic tetraparesis,
hyperreflexia, constipation,
hyperbreathing
exotropia, heterochromasia, high pain
threshold, cold feet, sleeping problems,
joint hyperlaxity
C4
Zweier et al.,
2010 [28]
f, 7y Profoundnone no3-6mo 3400 g P5
<P2
P50
yes broad forehead,
prominent ear lobes,
widely spaced teeth,
tented upper lip
high arched palate,
upslanting palpebral
fissures, small teeth,
prominent forehead
mild synophrys, low
set, large ears, fleshy
ear lobes, thin upper
lip, low frontal hairline
C5
f, 2y 8moProfound noneno,
no crawling
none4030 g
53 cm
38 cm
P75
P25-50
septo-optical dysplasia, MRI: agenesis of
septum pellucidum
C6
f, 8y Profoundnone noyes, resist.
to
treatment
1160 g
35 cm
28 cm
<P3
<P3
<P5
birth at 29thweek of gestation,
blindness, hydrocephalus, ductus
arteriosus, syndactyly toes 2-3,
hypotonia, spasticity of legs, obstipation,
liquid uptake by PEG tube
overfriendliness, pubertas praecox,
delayed bone age, retentive memory,
excessive empathy, autoagressive
behavior, flat feet
C7
f, 8y moderate to
severe
simple15mo none3860 g
54 cm
34 cm
P25-P50
P50
<P5
suspected in
infancy
epicanthal folds, tented
upper lip, short
columella, bulbous
nose
published
biallelic
defects
N = 13 [24,25]
2x f, 1x
m, 10x
not
reported,
1-20y
Severe2x no, 1x single
words [26], 10x
yes, but
regression
[24,25]
2x normal,
1x not
known [26],
10x 16mo-
30mo
[24,25]
13x yes,
4mo-
30mo
not
reported
<P3-
normal
not
reported
<P3-P99
8x yes [24,26],
1x tooth
grinding and
repetitive
hand
movements
[26]
2x wide mouth and
thick lips [26]
1x dry skin, 1x regression, 1x cerebellar
hypoplasia,
3x hyperbreathing [26], 10x
developmental regression with onset of
seizures, 9x decreased deep tendon
reflexes [24,25], 4x MRI: cortical dysplasia
[24], 1x MRI: leukomalacia, 1x
hepatosplenomegaly [25]
1x multiple congenital malformations
[33], 1x Gilles de la Tourette syndrome
[12], 3x Schizophrenia [7]
published
heterozygous
defects
N = 12
[1,3,7,12,21,33]
6x not reported
[1,3,21], 1x
normal [7], 2x
mild-moderate
[3,7], 3x severe
[7,12,33]
6x not reported
[1,3,21], 1x
normal [7], 3x
speech
impairment
[7,12] 2x no
[7,33]
11x not
reported
[1,3,7,12,21],
1x no [33]
5x not
reported
[1,3], 2x
no [12,33],
5x yes
[3,7,21],
0y-34y
not
reported
not
reported
8x yes [1,3,7]
not reported
TOF, tetralogy of Fallot; f, female; m, male; y, year; mo, month; ASD, autism spectrum disorder; published reports on CNTNAP2 and NRXN1: only papers containing clinical data are cited; ass., associated; P, centile;
ass., associated
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same splice site mutation and both showed a similar
phenotype with severe intellectual disability and sei-
zures, C3 also with breathing anomalies. In a parallel
research project, a mutation in the MEF2C gene was
identified in patient C4 and shown to be capable of
causing all of her symptoms [28]. Therefore, it remains
unclear if this splice mutation has a pathogenic effect at
all, or only a mild effect that is masked by the severe
consequences of the MEF2C mutation. The fact that
this variant is supposed to lead to an in-frame loss of a
single exon with a possibly milder effect than more dele-
terious defects supports the idea of no or only minor
relevance of this splice mutation. Regarding the rela-
tively high frequency of the splice site mutation in two
families and one control, a founder effect might be con-
sidered, however, common regional background in these
persons is not obvious.
Expanding the observations from previous studies we
now found that heterozygous defects in CNTNAP2 or
NRXN1 can also be seen in association with severe
intellectual disability. Possible explanations might be:
1. No pathogenic relevance of the identified defect.
This might indeed be the case for those patients with
a “mild mutation” such as the splice-site mutation in
CNTNAP2, or for patients with an atypical phenotype
or congenital malformations. In those, the true causa-
tive defect might not be detected yet. However, pub-
lished data and our data together still support a
pathogenic role for both genes in neurodevelopmental
disorders. 2. Inability to identify a defect on the second
allele in spite of extensive screening for mutations and/
or deletions. However, mutations in regulatory ele-
ments or in additional alternative isoforms cannot be
excluded in any case. 3. A larger phenotypic variability
associated with heterozygous defects in each gene. The
finding of homozygous or compound heterozygous
defects in previous patients with severe phenotypes
[24-26] indicates the existence of second hits or addi-
tional major contributors. These might not necessarily
be affecting the same gene. Only recently, a two-hit
model for severe developmental delay in patients with
a recurrent 16p12.1 microdeletion was postulated [29].
This might also be the case for microdeletions or even
point mutations within a single gene as already
reported for digenic inheritance in specific ciliopathies
like Bardet-Biedl syndrome [30]. In four of our patients
additional de novo or parentally inherited CNVs were
identified (see Tables 2 and 3), however, the signifi-
cance of these CNVs is unclear. The possible func-
tional synaptic link between CNTNAP2 and NRXN1
[24-26] prompted us to screen CNTNAP2 in patients
with NRXN1 defects and vice versa, however, without
any mutation detected.
Conclusion
We found heterozygous defects in CNTNAP2 and
NRXN1 in patients with severe intellectual disability,
therefore expanding the clinical spectrum associated
with monoallelic defects in either gene. This large varia-
bility implicates difficulties for genetic counseling in
such families. To explain the larger phenotypic variabil-
ity and severity in some patients we suggest a contribu-
tion of major additional genetic factors. To identify
these possible contributors and modifiers will be a great
challenge for the near future.
Acknowledgements
We thank the contributing clinicians, the patients and their families for
participating. We thank Christine Zeck-Papp for excellent technical assistance
and Dr. D. Müller and Dr. A. Kobelt for providing clinical details. This study
was funded by a grant from the DFG (ZW184/1-1) and by the German MR-
NET funded by the BMBF.
Author details
1Institute of Human Genetics, Friedrich-Alexander-University Erlangen-
Nuremberg, Erlangen, Germany.2Institut für Humangenetik,
Universitätsklinikum, Universität Duisburg-Essen, Essen, Germany.
3Department of Medical Genetics, Kinderzentrum Munich, Munich, Germany.
4Department of Clinical Genetics, Leiden University Medical Centre, Leiden,
The Netherlands.5Institute of Human Genetics, Rheinische Friedrich-
Wilhelms-University, Bonn, Germany.6Institut für Klinische Genetik,
Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden,
Dresden, Germany.7Institute of Medical Genetics and Human Genetics,
Charité - Universitätsmedizin Berlin, Berlin, Germany.8Department of Medical
Genetics, Institute of Mother and Child, Warsaw, Poland.9Center for Human
Genetics, Freiburg, Germany.10Centre de Genetique Humaine, Institut de
Pathologie et de Genetique, Gosselies (Charleroi), Belgium.11Synlab
Medizinisches Versorgungszentrum Humane Genetik Munich GmbH, Munich,
Germany.12Department of Human Molecular Genetics, Max Planck Institute
for Molecular Genetics, Berlin, Germany.13Cambridge Institute for Medical
Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Cambridge,
UK.14Institute of Medical Genetics, University of Zurich, Zurich-
Schwerzenbach, Switzerland.
Authors’ contributions
BA, IB, EKB, DH, JH, JKl, IM, EP, ST, EW, and GW acquired and provided
clinical data and samples of their patients. AG, ABE, HE, KH, JKo, SN, RU, ARe,
and CZ created and analysed the molecular data. ARe and ARa revised the
manuscript critically for important intellectual content. CZ designed and
supervised the project, and together with AG drafted the manuscript. All
authors read and approved the manuscript.
Competing interests
The authors declare that they have no competing interests.
Received: 17 May 2011 Accepted: 9 August 2011
Published: 9 August 2011
References
1.Alarcon M, Abrahams BS, Stone JL, Duvall JA, Perederiy JV, Bomar JM,
Sebat J, Wigler M, Martin CL, Ledbetter DH, Nelson SF, Cantor RM,
Geschwind DH: Linkage, association, and gene-expression analyses
identify CNTNAP2 as an autism-susceptibility gene. AmJHumGenet 2008,
82(1):150-159.
2.Arking DE, Cutler DJ, Brune CW, Teslovich TM, West K, Ikeda M, Rea A,
Guy M, Lin S, Cook EH, Chakravarti A: A common genetic variant in the
neurexin superfamily member CNTNAP2 increases familial risk of autism.
AmJHumGenet 2008, 82(1):160-164.
3. Bakkaloglu B, O’Roak BJ, Louvi A, Gupta AR, Abelson JF, Morgan TM,
Chawarska K, Klin A, Ercan-Sencicek AG, Stillman AA, Tanriover G,
Gregor et al. BMC Medical Genetics 2011, 12:106
http://www.biomedcentral.com/1471-2350/12/106
Page 10 of 12

Page 11

Abrahams BS, Duvall JA, Robbins EM, Geschwind DH, Biederer T, Gunel M,
Lifton RP, State MW: Molecular cytogenetic analysis and resequencing of
contactin associated protein-like 2 in autism spectrum disorders.
AmJHumGenet 2008, 82(1):165-173.
Bucan M, Abrahams BS, Wang K, Glessner JT, Herman EI, Sonnenblick LI,
varez Retuerto AI, Imielinski M, Hadley D, Bradfield JP, Kim C, Gidaya NB,
Lindquist I, Hutman T, Sigman M, Kustanovich V, Lajonchere CM,
Singleton A, Kim J, Wassink TH, McMahon WM, Owley T, Sweeney JA,
Coon H, Nurnberger JI, Li M, Cantor RM, Minshew NJ, Sutcliffe JS, Cook EH,
et al: Genome-wide analyses of exonic copy number variants in a family-
based study point to novel autism susceptibility genes. PLoSGenet 2009,
5(6):e1000536.
Ching MS, Shen Y, Tan WH, Jeste SS, Morrow EM, Chen X, Mukaddes NM,
Yoo SY, Hanson E, Hundley R, Austin C, Becker RE, Berry GT, Driscoll K,
Engle EC, Friedman S, Gusella JF, Hisama FM, Irons MB, Lafiosca T, LeClair E,
Miller DT, Neessen M, Picker JD, Rappaport L, Rooney CM, Sarco DP,
Stoler JM, Walsh CA, Wolff RR, et al: Deletions of NRXN1 (neurexin-1)
predispose to a wide spectrum of developmental disorders. Am J Med
Genet B Neuropsychiatr Genet 2010, 153B(4):937-947.
Feng J, Schroer R, Yan J, Song W, Yang C, Bockholt A, Cook EH Jr,
Skinner C, Schwartz CE, Sommer SS: High frequency of neurexin 1beta
signal peptide structural variants in patients with autism. NeurosciLett
2006, 409(1):10-13.
Friedman JI, Vrijenhoek T, Markx S, Janssen IM, van dV, Faas BH, Knoers NV,
Cahn W, Kahn RS, Edelmann L, Davis KL, Silverman JM, Brunner HG, van
Kessel AG, Wijmenga C, Ophoff RA, Veltman JA: CNTNAP2 gene dosage
variation is associated with schizophrenia and epilepsy. MolPsychiatry
2008, 13(3):261-266.
Glessner JT, Wang K, Cai G, Korvatska O, Kim CE, Wood S, Zhang H, Estes A,
Brune CW, Bradfield JP, Imielinski M, Frackelton EC, Reichert J, Crawford EL,
Munson J, Sleiman PM, Chiavacci R, Annaiah K, Thomas K, Hou C,
Glaberson W, Flory J, Otieno F, Garris M, Soorya L, Klei L, Piven J, Meyer KJ,
Anagnostou E, Sakurai T, et al: Autism genome-wide copy number
variation reveals ubiquitin and neuronal genes. Nature 2009,
459(7246):569-573.
Kim HG, Kishikawa S, Higgins AW, Seong IS, Donovan DJ, Shen Y, Lally E,
Weiss LA, Najm J, Kutsche K, Descartes M, Holt L, Braddock S, Troxell R,
Kaplan L, Volkmar F, Klin A, Tsatsanis K, Harris DJ, Noens I, Pauls DL,
Daly MJ, MacDonald ME, Morton CC, Quade BJ, Gusella JF: Disruption of
neurexin 1 associated with autism spectrum disorder. AmJHumGenet
2008, 82(1):199-207.
Marshall CR, Noor A, Vincent JB, Lionel AC, Feuk L, Skaug J, Shago M,
Moessner R, Pinto D, Ren Y, Thiruvahindrapduram B, Fiebig A, Schreiber S,
Friedman J, Ketelaars CE, Vos YJ, Ficicioglu C, Kirkpatrick S, Nicolson R,
Sloman L, Summers A, Gibbons CA, Teebi A, Chitayat D, Weksberg R,
Thompson A, Vardy C, Crosbie V, Luscombe S, Baatjes R, et al: Structural
variation of chromosomes in autism spectrum disorder. AmJHumGenet
2008, 82(2):477-488.
Rujescu D, Ingason A, Cichon S, Pietilainen OP, Barnes MR, Toulopoulou T,
Picchioni M, Vassos E, Ettinger U, Bramon E, Murray R, Ruggeri M, Tosato S,
Bonetto C, Steinberg S, Sigurdsson E, Sigmundsson T, Petursson H,
Gylfason A, Olason PI, Hardarsson G, Jonsdottir GA, Gustafsson O, Fossdal R,
Giegling I, Moller HJ, Hartmann AM, Hoffmann P, Crombie C, Fraser G, et al:
Disruption of the neurexin 1 gene is associated with schizophrenia.
HumMolGenet 2009, 18(5):988-996.
Verkerk AJ, Mathews CA, Joosse M, Eussen BH, Heutink P, Oostra BA:
CNTNAP2 is disrupted in a family with Gilles de la Tourette syndrome
and obsessive compulsive disorder. Genomics 2003, 82(1):1-9.
Vernes SC, Newbury DF, Abrahams BS, Winchester L, Nicod J, Groszer M,
Alarcon M, Oliver PL, Davies KE, Geschwind DH, Monaco AP, Fisher SE: A
functional genetic link between distinct developmental language
disorders. NEnglJMed 2008, 359(22):2337-2345.
Wisniowiecka-Kowalnik B, Nesteruk M, Peters SU, Xia Z, Cooper ML,
Savage S, Amato RS, Bader P, Browning MF, Haun CL, Duda AW,
Cheung SW, Stankiewicz P: Intragenic rearrangements in NRXN1 in three
families with autism spectrum disorder, developmental delay, and
speech delay. Am J Med Genet B Neuropsychiatr Genet 2010,
153B(5):983-993.
Yan J, Noltner K, Feng J, Li W, Schroer R, Skinner C, Zeng W, Schwartz CE,
Sommer SS: Neurexin 1alpha structural variants associated with autism.
NeurosciLett 2008, 438(3):368-370.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16. Zahir FR, Baross A, Delaney AD, Eydoux P, Fernandes ND, Pugh T,
Marra MA, Friedman JM: A patient with vertebral, cognitive and
behavioural abnormalities and a de novo deletion of NRXN1alpha.
JMedGenet 2008, 45(4):239-243.
Awadalla P, Gauthier J, Myers RA, Casals F, Hamdan FF, Griffing AR, Cote M,
Henrion E, Spiegelman D, Tarabeux J, Piton A, Yang Y, Boyko A,
Bustamante C, Xiong L, Rapoport JL, Addington AM, DeLisi JL, Krebs MO,
Joober R, Millet B, Fombonne E, Mottron L, Zilversmit M, Keebler J,
Daoud H, Marineau C, Roy-Gagnon MH, Dube MP, Eyre-Walker A, et al:
Direct measure of the de novo mutation rate in autism and
schizophrenia cohorts. Am J Hum Genet 2010, 87(3):316-324.
Bradley WE, Raelson JV, Dubois DY, Godin E, Fournier H, Prive C, Allard R,
Pinchuk V, Lapalme M, Paulussen RJ, Belouchi A: Hotspots of large rare
deletions in the human genome. PLoS One 2010, 5:(2):e9401.
Kirov G, Gumus D, Chen W, Norton N, Georgieva L, Sari M, O’Donovan MC,
Erdogan F, Owen MJ, Ropers HH, Ullmann R: Comparative genome
hybridization suggests a role for NRXN1 and APBA2 in schizophrenia.
Hum Mol Genet 2008, 17(3):458-465.
Magri C, Sacchetti E, Traversa M, Valsecchi P, Gardella R, Bonvicini C,
Minelli A, Gennarelli M, Barlati S: New copy number variations in
schizophrenia. PLoS One 2010, 5:(10):e13422.
Mefford HC, Muhle H, Ostertag P, von Spiczak S, Buysse K, Baker C,
Franke A, Malafosse A, Genton P, Thomas P, Gurnett CA, Schreiber S,
Bassuk AG, Guipponi M, Stephani U, Helbig I, Eichler EE: Genome-wide
copy number variation in epilepsy: novel susceptibility loci in idiopathic
generalized and focal epilepsies. PLoS Genet 2010, 6(5):e1000962.
Szatmari P, Paterson AD, Zwaigenbaum L, Roberts W, Brian J, Liu XQ,
Vincent JB, Skaug JL, Thompson AP, Senman L, Feuk L, Qian C, Bryson SE,
Jones MB, Marshall CR, Scherer SW, Vieland VJ, Bartlett C, Mangin LV,
Goedken R, Segre A, Pericak-Vance MA, Cuccaro ML, Gilbert JR, Wright HH,
Abramson RK, Betancur C, Bourgeron T, Gillberg C, Leboyer M, et al:
Mapping autism risk loci using genetic linkage and chromosomal
rearrangements. Nat Genet 2007, 39(3):319-328.
Vrijenhoek T, Buizer-Voskamp JE, van dSI, Strengman E, Sabatti C, Geurts
van KA, Brunner HG, Ophoff RA, Veltman JA: Recurrent CNVs disrupt three
candidate genes in schizophrenia patients. AmJHumGenet 2008,
83(4):504-510.
Strauss KA, Puffenberger EG, Huentelman MJ, Gottlieb S, Dobrin SE,
Parod JM, Stephan DA, Morton DH: Recessive symptomatic focal epilepsy
and mutant contactin-associated protein-like 2. NEnglJMed 2006,
354(13):1370-1377.
Jackman C, Horn ND, Molleston JP, Sokol DK: Gene associated with
seizures, autism, and hepatomegaly in an Amish girl. Pediatr Neurol 2009,
40(4):310-313.
Zweier C, de Jong EK, Zweier M, Orrico A, Ousager LB, Collins AL,
Bijlsma EK, Oortveld MA, Ekici AB, Reis A, Schenck A, Rauch A: CNTNAP2
and NRXN1 are mutated in autosomal-recessive Pitt-Hopkins-like mental
retardation and determine the level of a common synaptic protein in
Drosophila. Am J Hum Genet 2009, 85(5):655-666.
Poliak S, Gollan L, Martinez R, Custer A, Einheber S, Salzer JL, Trimmer JS,
Shrager P, Peles E: Caspr2, a new member of the neurexin superfamily, is
localized at the juxtaparanodes of myelinated axons and associates with
K+ channels. Neuron 1999, 24(4):1037-1047.
Zweier M, Gregor A, Zweier C, Engels H, Sticht H, Wohlleber E, Bijlsma EK,
Holder SE, Zenker M, Rossier E, Grasshoff U, Johnson DS, Robertson L,
Firth HV, Ekici AB, Reis A, Rauch A: Mutations in MEF2C from the
5q14.3q15 microdeletion syndrome region are a frequent cause of
severe mental retardation and diminish MECP2 and CDKL5 expression.
Hum Mutat 2010, 31(6):722-733.
Girirajan S, Rosenfeld JA, Cooper GM, Antonacci F, Siswara P, Itsara A,
Vives L, Walsh T, McCarthy SE, Baker C, Mefford HC, Kidd JM, Browning SR,
Browning BL, Dickel DE, Levy DL, Ballif BC, Platky K, Farber DM, Gowans GC,
Wetherbee JJ, Asamoah A, Weaver DD, Mark PR, Dickerson J, Garg BP,
Ellingwood SA, Smith R, Banks VC, Smith W, et al: A recurrent 16p12.1
microdeletion supports a two-hit model for severe developmental delay.
Nat Genet 2010, 42(3):203-209.
Katsanis N: The oligogenic properties of Bardet-Biedl syndrome. Hum Mol
Genet 2004, 13(Spec No 1):R65-71.
Borozdin W, Boehm D, Leipoldt M, Wilhelm C, Reardon W, Clayton-Smith J,
Becker K, Muhlendyck H, Winter R, Giray O, Silan F, Kohlhase J: SALL4
deletions are a common cause of Okihiro and acro-renal-ocular
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
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syndromes and confirm haploinsufficiency as the pathogenic
mechanism. J Med Genet 2004, 41:(9):e113.
Engels H, Wohlleber E, Zink A, Hoyer J, Ludwig KU, Brockschmidt FF,
Wieczorek D, Moog U, Hellmann-Mersch B, Weber RG, Willatt L, Kreiss-
Nachtsheim M, Firth HV, Rauch A: A novel microdeletion syndrome
involving 5q14.3-q15: clinical and molecular cytogenetic characterization
of three patients. Eur J Hum Genet 2009, 17(12):1592-1599.
Belloso JM, Bache I, Guitart M, Caballin MR, Halgren C, Kirchhoff M,
Ropers HH, Tommerup N, Tumer Z: Disruption of the CNTNAP2 gene in a
t(7;15) translocation family without symptoms of Gilles de la Tourette
syndrome. EurJHumGenet 2007, 15(6):711-713.
NNSplice 0.9. [http://www.fruitfly.org/seq_tools/splice.html].
HSF V2.4. [http://www.umd.be/HSF/].
MaxEntScan. [http://genes.mit.edu/burgelab/maxent/
Xmaxentscan_scoreseq.html].
Splice Site Score Calculation. [http://rulai.cshl.edu/new_alt_exon_db2/
HTML/score.html].
Splice Site Analyzer-Tool. [http://ibis.tau.ac.il/ssat/SpliceSiteFrame.htm].
Splice Predictor. [http://deepc2.psi.iastate.edu/cgi-bin/sp.cgi].
NetGene2. [http://www.cbs.dtu.dk/services/NetGene2/].
SplicePort. [http://spliceport.cs.umd.edu/].
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
Pre-publication history
The pre-publication history for this paper can be accessed here:
http://www.biomedcentral.com/1471-2350/12/106/prepub
doi:10.1186/1471-2350-12-106
Cite this article as: Gregor et al.: Expanding the clinical spectrum
associated with defects in CNTNAP2 and NRXN1. BMC Medical Genetics
2011 12:106.
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