Molecular Genetics and Metabolism 84 (2005) 112–126
1096-7192/$ - see front matter. Published by Elsevier Inc.
3?-Hydroxysterol ?7-reductase and the Smith–Lemli–Opitz syndrome
Lina S. Correa-Cerro, Forbes D. Porter¤
Unit on Molecular Dysmorphology, Heritable Disorders Branch, Department of Health and Human Services, National Institute of Child Health
and Human Development, National Institutes of Health, Bld. 10, Rm. 9S241, 10 Center Dr., Bethesda, MD 20892, USA
Received 2 July 2004; received in revised form 28 September 2004; accepted 28 September 2004
Available online 19 December 2004
In the Wnal step of cholesterol synthesis, 7-dehydrocholesterol reductase (DHCR7) reduces the double bond at C7-8 of 7-dehydro-
cholesterol to yield cholesterol. Mutations of DHCR7 cause Smith–Lemli–Opitz syndrome (SLOS). Over 100 diVerent mutations of
DHCR7 have been identiWed in SLOS patients. SLOS is a classical multiple malformation, mental retardation syndrome, and was the
Wrst human malformation syndrome shown to result from an inborn error of cholesterol synthesis. This paper reviews the biochemi-
cal, molecular, and mutational aspects of DHCR7.
Published by Elsevier Inc.
Keywords: Smith–Lemi–Opitz syndrome; 7-Dehydrocholesterol reductase; Inborn error of cholesterol synthesis
Cholesterol is an essential lipid found in all mamma-
lian cells, and is a major lipid component of the mem-
brane. In addition to cholesterol’s structural role in
cellular membranes, cholesterol is a precursor molecule
for sterol-based compounds including bile acids, oxys-
terols, neurosteroids, glucocorticoids, mineralocortic-
oids, and sex steroids such as estrogen and testosterone.
Cholesterol is synthesized from acetate in a series of
enzymatic reactions that can be separated into pre-squa-
lene synthesis of isoprenoids and the post-squalene con-
version of lanosterol to cholesterol. The rate limiting step
for both isoprenoid and cholesterol synthesis is the conver-
sion of 3-hydroxy-3-methylglutaryl-CoA to mevalonic acid
catalyzed by 3-hydroxy-3-methylglutaryl-CoA reductase
. The Wrst sterol formed in the cholesterol biosynthetic
pathway is lanosterol. Lanosterol is a 30-carbon sterol
formed by the cyclization of the squalene. Multiple enzy-
matic steps are involved in the conversion of 30-carbon
lanosterol to 27-carbon cholesterol.
The principal route of cholesterol synthesis in
humans is the Kandutsch–Russell pathway . In this
biosynthetic pathway, the immediate precursor of cho-
lesterol is 7-dehydrocholesterol (7DHC). As shown in
Fig. 1, the reduction of 7DHC to yield cholesterol is cat-
alyzed by 3?-hydroxysterol ?7-reductase (DHCR7). Tis-
sues such as brain, testes, and exocrine breast can have
signiWcant levels of desmosterol in addition to choles-
terol [3–5]. Desmosterol is a 27-carbon sterol that diVers
from cholesterol due to the presence of a C24–25 double
bond in the side chain. In the synthesis of desmosterol,
DHCR7 is required for the reduction of 7-dehydrodes-
mosterol (Fig. 1).
To date, eight inborn errors of cholesterol synthesis
have been described. Although multiple enzymatic steps
are involved in the synthesis of squalene from acetyl-
CoA, only one enzymatic defect of pre-squalene choles-
terol synthesis has been identiWed. Mevalonic aciduria
(MIM 251170) [6–8], and the Hyper-IgD with Periodic
Fever syndrome (MIM 260920) [9–13] are both caused
by mutations of the mevalonate kinase gene (MVK). The
*Corresponding author. Fax: +1 301 480 5791.
E-mail address: email@example.com (F.D. Porter).
L.S. Correa-Cerro, F.D. Porter / Molecular Genetics and Metabolism 84 (2005) 112–126
post-squalene cholesterol biosynthetic defects are associ-
ated with congenital malformation syndromes. The pro-
totypical example of this group of disorders is the
Smith–Lemli–Opitz syndrome (SLOS). Other human
malformation syndromes due to inborn errors of choles-
terol synthesis include desmosterolosis, lathosterolosis,
CHILD syndrome, autosomal dominant chondrodys-
plasia type 2, HEM dysplasia, and some cases of Antley–
Desmosterolosis (MIM 602398) and lathosterolosis
(MIM 607330) are rare autosomal recessive disorders of
cholesterol synthesis that have clinical overlap with
SLOS. To date, only two patients have been identiWed
with each of these disorders. Desmosterolosis is due to
deWciency of 3?-hydroxysterol ?24-reductase (DHCR24)
activity, and desmosterolosis patients have increased
desmosterol levels in plasma, tissues, and cultured cells
. DHCR24 reduces the unsaturated C24–25 bond in
the side chain of desmosterol to yield cholesterol, and
DHCR24 maps to chromosome 1p33–p31.1 . Muta-
tions of DHCR24 have been identiWed in patients with
desmosterolosis . Lathosterolosis patients have a
deWciency of lathosterol 5-desaturase (SC5D) activity
due to mutation of the SC5D gene [16,17]. SC5D cata-
lyzes the conversion of lathosterol to 7DHC. The SC5D
gene maps to chromosome 11q23.3 .
Autosomal dominant chondrodysplasia punctata
type 2 (CDPX2, MIM 302960) and CHILD syndrome
(MIM 308050) are two X-linked disorders of choles-
terol synthesis. CDPX2 is due to mutation of the
emopamil-binding protein gene (EBP) which encodes
3?-hydroxysterol-?8,?7-isomerase [19–21]. EBP cata-
lyzes the conversion of cholesta-8(9)-en-3?-ol to lathos-
terol, and EBP maps to chromosome Xp11.23–p11.22
[22,23]. CHILD syndrome, or congenital hemidysplasia
with ichthyosiform erythroderma and limb defects
(MIM 308050) has been reported to be due to mutation
of either the NAD(P)H steroid dehydrogenase-like gene
(NSDHL)  or EBP . The involvement of EBP
mutations in CHILD syndrome is controversial.
NSDHL encodes a 3?-hydroxysterol dehydrogenase
that is involved in the demethylation of 4,4-dimethylcho-
lesta-8-en-3?-ol to yield cholesta-8(9)-en-3?-ol .
NSDHL maps to Xq28 .
Two additional human malformation syndromes are
due to genetic defects that cause a secondary abnormal-
ity in cholesterol synthesis. Kelley et al.  initially
showed an accumulation of lanosterol and dihydrol-
anosterol in a patient with Antley–Bixler Syndrome
(ABS, MIM 207410); however, they did not Wnd muta-
tions in the lanosterol-14-?-demethylase gene (CYP51),
as would have been predicted from the sterol proWle.
Cytochrome P450 reductase is a cofactor for both lanos-
terol-14-?-demethylase and enzymes involved in steroid
biogenesis. Abnormalities of steroid biogenesis have also
been reported in patients with ABS [29,30]. Recently,
Fig. 1. Terminal enzymatic reactions in cholesterol synthesis. DHCR7 reduces the C7–8 double of bond of both 7-dehydrocholesterol and 7-dehyd-
rodesmosterol to yield cholesterol and desmosterol, respectively. DHCR24 can reduce the C24–25 double bond in desmosterol to yield cholesterol.
NADPH is a cofactor for DHCR7. AY 9944, BM,766, and YM 9429 are inhibitors of DHCR7.
L.S. Correa-Cerro, F.D. Porter / Molecular Genetics and Metabolism 84 (2005) 112–126
Fluck et al.  reported Wnding mutations of the cyto-
chrome P450 reductase (POR) gene in some patients
with ABS. This gene is localized on 7q11.2 chromosome
. Hydrops-ectopic calciWcation-moth-eaten skeletal
dysplasia (HEM dysplasia, MIM 215140) was Wrst
described in 1988 by Greenberg et al. . While screen-
ing cases of skeletal dysplasia for cholesterol biosyn-
thetic defects, Kelley et al.  found increased levels of
cholesta-8,14-dien-3?-ol and cholesta-8,14,24-trien-3?-ol
in tissues from patients with HEM dysplasia. Cholesterol
levels were normal. Elevated levels of cholesta-8,14-dien-
3?-ol and cholesta-8,14,24-trien-3?-ol are consistent with
impaired sterol ?14-reductase activity; however, HEM
dysplasia is not due to mutation of the 3?-hydroxysterol
?14-reductase gene. Instead, Waterham et al.  found
that mutations of the lamin B receptor gene (LBR) cause
HEM dysplasia. The carboxyl end of the lamin B recep-
tor is homologous to other sterol reductase enzymes, and
the lamin B receptor has been shown to have sterol ?14-
reductase activity . The LBR gene is localized on
1q42.1 chromosome . HoVman et al.  reported
that a single heterozygous mutation of LBR causes the
Pelger–Huët anomaly (PHA). The Pelger–Huët anomaly
consists of hypolobulation of nuclei in leukocytes. Based
on a review of the literature, Oosterwijk et al.  sug-
gest that homozygosity for LBR mutations can give rise
to either a mild phenotype which includes the PHA or a
severe HEM dysplasia phenotype. This wide phenotypic
spectrum is presumably due to allelic heterogeneity;
however, this still needs to be conWrmed by molecular
characterization of LBR.
SLOS (MIM 270400) is an autosomal recessive, mul-
tiple malformation, mental retardation syndrome Wrst
described by Smith et al.  in 1964. Rutledge et al. 
later described a severe variant that became known as
type II SLOS (MIM 268670). SLOS was Wrst identiWed
as an inborn error of cholesterol synthesis in 1993
[41,42]. The biochemical Wndings of increased 7DHC
and decreased cholesterol levels suggested that the
underlying defect was due to impaired DHCR7 function.
Five years after the biochemical defect was identiWed,
DHCR7 was cloned , and mutations of DHCR7 were
identiWed in SLOS patients [44–46]. This review will
focus on what is known about the biochemistry, molecu-
lar biology, and mutation spectrum of DHCR7.
DHCR7 gene structure and mRNA
The DHCR7 cDNA (GeneID:1717, Accession: nc_00
0011) was cloned in 1998 by three independent groups
[43–46]. DHCR7 was mapped to chromosome 11q12–13
by radiation hybrid mapping , and chromosome
11q13 by FISH [45,46]. The human DHCR7 gene spans
14,100 base pairs (bp) of genomic DNA, consisting of
nine exons ranging in size from 64bp (exon 1) to 465bp
(exon 9) . The genomic structures of DHCR7 and the
corresponding rat and murine Dhcr7 are shown in Fig. 2.
The DHCR7 mRNA is 2786bp long, and has a 1425bp
open reading frame. The DHCR7 open reading frame is
encoded by exons three through nine. The 194 bp 5?-
untranslated region of DHCR7 is encoded by exons one,
two and part of three. The translation start codon is
encoded by exon three. Exon nine encodes the carboxyl
end of the DHCR7 protein, and a 961 bp 3?-untranslated
region. The genomic structure of the rat Dhcr7 gene is
similar to the human gene . Currently, only eight
exons have been reported for the murine Dhcr7 gene,
and there appears to be two alternative Wrst exons
encoding the 5?-untranslated sequence . Murine
Dhcr7 was mapped to chromosome 7F5 by FISH .
Rat Dhcr7 was mapped to chromosome 8q2.1 by FISH
; however, the NCBI database indicates that rat
Dhcr7 is localized on chromosome 1q41. Consistent with
the NCBI database localization, murine chromosome 7
is syntenic to rat chromosome 1.
As expected for an enzyme involved in cholesterol
synthesis, DHCR7 is ubiquitously expressed with the
highest mRNA levels detected in adrenal gland, liver,
testis, and brain tissue . DHCR7 expression is
induced by sterol deprivation . Kim et al.  charac-
terized the rat Dhcr7 promoter. This group showed that
the 179bp 5? of the transcription start site were neces-
sary for sterol-regulated transcription. No TATAA box
was identiWed in this region, which is consistent with
multiple transcription start sites reported for rat Dhcr7
. The DNA sequence immediately 5? of the rat Dhcr7
gene encodes a number of potential regulatory elements.
These include four SP1 sites, two NF-Y sites, and a sin-
gle sterol responsive element-1/E-box (SRE1/E-box)
binding site. DNase footprinting, electrophoretic mobil-
ity shift assays, and mutation analysis were used to dem-
onstrate that the SP1 site at ¡125, the NF-Y site at ¡88,
and the SRE1/E-box at ¡33/¡22 regulate Dhcr7 expres-
sion. NF-Y and SP1 are general transcription factors.
SRE1 elements bind sterol regulatory binding proteins
(SREBP), and regulate the expression of sterol respon-
sive genes [51,52]. The DNA sequence corresponding to
the 506bp immediately 5? of exon one of the human
DHCR7 gene is shown in Fig. 3. Similar to the rat gene,
the human gene does not appear to have a TATAA box.
This region contains three SP1 sites (¡54/¡59, ¡125/
¡130, and ¡146/¡151), and an inverted NF-Y site (¡84/
¡88). A potential partial SRE1/E-box element is located
at ¡307/¡312//¡301/¡306. A partial SRE1 element has
been shown to function in the human squalene synthase
promoter . Although it needs to be experimentally
demonstrated, these putative promoter regulatory
sequences may function to regulate the expression of the
L.S. Correa-Cerro, F.D. Porter / Molecular Genetics and Metabolism 84 (2005) 112–126
from gene/environment-induced cholesterol deWciency: further
evidence for a link to sonic hedgehog, Am. J. Med. Genet. 73
 M. Kolf-Clauw, F. Chevy, B. Siliart, C. Wolf, N. Mulliez, C.
Roux, Cholesterol biosynthesis inhibited by BM15.766 induces
holoprosencephaly in the rat, Teratology 56 (1997) 188–200.
 M. Shibata, A new potent teratogen in CD rats inducing cleft
palate, J. Toxicol. Sci. 18 (1993) 171–178.
 S.J. Fliesler, M.J. Richards, C.-Y. Miller, N.S. Peachey, Marked
alteration of sterol metabolism and composition without com-
promising retinal development or function, Invest. Ophthalmol.
Vis. Sci. 40 (1999) 1792–1801.
 R.K. Keller, T.P. Arnold, S.J. Fliesler, Formation of 7-dehydro-
cholesterol-containing membrane rafts in vitro and in vivo, with
relevance to the Smith–Lemli–Opitz syndrome, J. Lipid Res. 45
 L. Holmer, A. Pezhman, H.J. Worman, The human lamin B
receptor/sterol reductase multigene family, Genomics 54 (1998)
 E.C. Worman, H.J.G. Blobel, The lamin B receptor of the nuclear
envelope inner membrane: a polytopic protein with eight poten-
tial transmembrane domains, J. Cell Biol. 111 (1990) 1535–1542.
 I. Greeve, I. Hermans-Borgmeyer, C. Brellinger, D. Kasper, T.
Gomez-Isla, C. Behl, B. Levkau, R.M. Nitsch, The human
DIMINUTO/DWARF1 homolog seladin-1 confers resistance to
Alzheimer’s disease-associated neurodegeneration and oxidative
stress, J. Neurosci. 20 (2000) 7345–7352.
 E. Lecain, X. Chenivesse, R. Spagnoli, D. Pompon, Cloning by
metabolic interference in yeast and enzymatic characterization
of Arabidopsis thaliana sterol delta 7-reductase, J. Biol. Chem.
271 (1996) 10866–10873.
 G. Gil, J.R. Faust, D.J. Chin, J.L. Goldstein, M.S. Brown, Mem-
brane-bound domain of HMGCoA reductase is requiredfor ste-
rol-enhanced degradation of the enzyme, Cell 41 (1985) 249–258.
 X. Hua, A. NohturVt, J.L. Goldstein, M.S. Brown, Sterol resis-
tance in CHO cells traced to point mutation in SREBP cleavage-
activating protein, Cell 87 (1996) 415–426.
 A. NohturVt, M.S. Brown, J.L. Goldstein, Topology of SREBP
cleavage-activating protein, a polytopic membrane protein with
a sterol-sensing domain, J. Biol. Chem. 273 (1998) 17243–17250.
 E.D. Carstea, J.A. Morris, K.G. Coleman, S.K. Loftus, D. Zhang,
C. Cummings, J. Gu, M.A. Rosenfeld, W.J. Pavan, D.B. Krizman,
J. Nagle, M.H. Polymeropoulos, S.L. Sturley, Y.A. Loannou,
M.E. Higgins, M. Comly, A. Cooney, A. Brown, C.R. Kaneski,
E.J. Blanchette-Mackie, N.K. Dwyer, E.B. Neufeld, T.Y. Chang,
L. Liscum, J.F. Strauss 3rd, K. Ohno, M. Zeigler, R. Carmi, J.
Sokol, D. Markie, R.R. O’Neill, O.P. van Diggelen, M. Elleder,
M.C. Patterson, R.O. Brady, M.T. Vanier, P.G. Pentchev, D.A.
Tagle, Niemann–Pick C1 disease gene: homology to mediators
of cholesterol homeostasis, Science 277 (1997) 228–231.
 S.K. Loftus, J.A. Morris, E.D. Carstea, J.Z. Gu, C. Cummings, A.
Brown, J. Ellison, K. Ohno, M.A. Rosenfeld, D.A. Tagle, P.G.
Pentchev, W.J. Pavan, Murine model of Niemann–Pick C dis-
ease: mutation in a cholesterol homeostasis gene, Science 277
 R. Burke, D. Nellen, M. Bellotto, E. Hafen, K.A. Senti, B.J. Dick-
son, K. Basler, Dispatched, a novel sterol-sensing domain pro-
tein dedicated to the release of cholesterol-modiWed hedgehog
from signaling cells, Cell 99 (1999) 803–815.
 A. Radhakrishnan, L.P. Sun, J.J. Kwon, M.S. Brown, J.L. Gold-
stein, Direct binding of cholesterol to the puriWed membrane
region of SCAP: mechanism for a sterol-sensing domain, Mol.
Cell 15 (2) (2004) 259–268.
 N. Ohgami, D.C. Ko, M. Thomas, M.P. Scott, C.C. Chang, T.Y.
Chang, Binding between the Niemann–Pick C1 protein and a
photoactivatable cholesterol analog requires a functional sterol-
sensing domain, Proc. Natl. Acad. Sci. USA 101 (34) (2004)
 H.R. Waterham, R.J. Wanders, Biochemical and genetic aspects
of 7-dehydrocholesterol reductase and Smith–Lemli–Opitz syn-
drome, Biochim. Biophys. Acta 1529 (2000) 340–356.
 J.C. Jang, S. Fujioka, M. Tasaka, H. Seto, S. Takatsuto, A. Ishii,
M. Aida, S. Yoshida, J. Sheen, A critical role of sterols in embry-
onic patterning and meristem programming revealed by the fac-
kel mutants of Arabidopsis thaliana, Genes Dev. 14 (2000) 1485–
 M. Witsch-Baumgartner, B.U. Fitzky, M. Ogorelkova, H.G.
Kraft, F.F. Moebius, H. Glossmann, U. Seedorf, G. Gillessen-
Kaesbach, G.F. HoVmann, P. Clayton, R.I. Kelley, G. Utermann,
Mutational spectrum in the Delta 7-sterol reductase gene and
genotype–phenotype correlation in 84 patients with Smith–
Lemli–Opitz syndrome, Am. J. Hum. Genet. 66 (2000) 402–412.
 P.E. Jira, R.J. Wanders, J.A. Smeitink, J. De Jong, R.A. Wevers,
W. Oostheim, J.H. Tuerlings, R.C. Hennekam, R.C. Sengers,
H.R. Waterham, Novel mutations in the 7-dehydrocholesterol
reductase gene of 13 patients with Smith–Lemli–Opitz syn-
drome, Ann. Hum. Genet. 65 (2001) 229–236.
 M.J. Nowaczyk, S.A. Farrell, W.L. Sirkin, L. Velsher, P.A. Krak-
owiak, J.S. Waye, F.D. Porter, Smith–Lemli–Opitz (RHS) syn-
drome: holoprosencephaly and homozygous IVS8-1G–>C
genotype, Am. J. Med. Genet. 103 (2001) 75–80.
 A. Goldenberg, F. Chevy, C. Bernard, C. Wolf, V. Cormier-Daire,
Clinical characteristics and diagnosis of Smith–Lemli–Opitz syn-
drome and tentative phenotype-genotype correlation: report of
45 cases, Arch. Pediatr. 10 (2003) 4–10.
 M. Witsch-Baumgartner, E. Ciara, J. LoZer, H.J. Menzel, U. See-
dorf, J. Burn, G. Gillessen-Kaesbach, G.F. HoVmann, B.U.
Fitzky, H. Mundy, P. Clayton, R.I. Kelley, M. Krajewska-
Walasek, G. Utermann, Frequency gradients of DHCR7 muta-
tions in patients with Smith–Lemli–Opitz syndrome in Europe:
evidence for diVerent origins of common mutations, Eur. J. Hum.
Genet. 9 (2001) 45–50.
 J.S. Waye, L.M. Nakamura, B. Eng, L. Hunnisett, D. Chitayat, T.
Costa, M.J. Nowaczyk, Smith–Lemli–Opitz syndrome: carrier
frequency and spectrum of DHCR7 mutations in Canada, J.
Med. Genet. 39 (2002) E31.
 B.S. Wright, N.A. Nwokoro, C.A. Wassif, F.D. Porter, J.S. Waye,
B. Eng, M.J. Nowaczyk, Carrier frequency of the RSH/Smith–
Lemli–Opitz IVS8-1G>C mutation in African Americans, Am.
J. Med. Genet. 120A (2003) 139–141.
 H. Yu, G.S. Tint, G. Salen, S.B. Patel, Detection of a common
mutation in the RSH or Smith–Lemli–Opitz syndrome by a
PCR-RFLP assay: IVS8-G–>C is found in over sixty percent of
US propositi, Am. J. Med. Genet. 90 (2000) 347–350.
 K.P. Battaile, B.C. Battaile, L.S. Merkens, C.L. Maslen, R.D.
Steiner, Carrier frequency of the common mutation IVS8-
1G>C in DHCR7 and estimate of the expected incidence of
Smith–Lemli–Opitz syndrome, Mol. Genet. Metab. 72 (2001) 67–
 M.J. Nowaczyk, L.M. Nakamura, B. Eng, F.D. Porter, J.S. Waye,
Frequency and ethnic distribution of the common DHCR7
mutation in Smith–Lemli–Opitz syndrome, Am. J. Med. Genet.
102 (2001) 383–386.
 J.M. Opitz, E. Gilbert-Barness, J. Ackerman, A. Lowichik, Cho-
lesterol and development: the RSH (Smith–Lemli–Opitz) syn-
drome and related conditions, Pediatr. Pathol. Mol. Med. 21
 R.B. Lowry, S.L. Yong, Borderline normal intelligence in the
Smith–Lemli–Opitz (RSH) syndrome, Am. J. Med. Genet. 5
 J.M. Opitz, The RHS syndrome: paradigmatic metabolic malfor-
mation syndrome, in: M.I. New (Ed.), Diagnosis and Treatment
L.S. Correa-Cerro, F.D. Porter / Molecular Genetics and Metabolism 84 (2005) 112–126
of the Unborn Child, Idelson–Gnocchi, Nappoli, Italy, 1998, pp.
 L. Holmes, Prevalence of Smith–Lemli–Opitz (SLO), Am. J.
Med. Genet. 50 (1994) 334.
 V. Bzduch, D. Behulova, L. Kozak, J. Skodova, E. Veghova, A.
Dello Russo, G. Corso, F. Bauer, Smith–Lemli–Opitz syndrome
with extremely low plasma cholesterol, J. Inherit. Metab. Dis. 23
 R.I. Kelley, A new face for an old syndrome, Am. J. Med. Genet.
68 (1997) 251–256.
 A.K. Ryan, K. Bartlett, P. Clayton, S. Eaton, L. Mills, D. Donnai,
R.M. Winter, J. Burn, Smith–Lemli–Opitz syndrome: a variable
clinical and biochemical phenotype, J. Med. Genet. 35 (1998)
 M.J.M. Nowaczyk, J.D. Doukeits, J.S. Waye, Incidence of Smith–
Lemli–Opitz syndrome: results of a 3 year national surveillance
progam, J. Pediatr. 145 (2004) 530–535.
 R.I. Kelley, R.C. Hennekam, The Smith–Lemli–Opitz syndrome,
J. Med. Genet. 37 (2000) 321–335.
 F.D. Porter, RSH/Smith–Lemli–Opitz syndrome: a multiple con-
genital anomaly/mental retardation syndrome due to an inborn
error of cholesterol biosynthesis, Mol. Genet. Metab. 71 (2000)
 L.S. Correa-Cerro, C.A. Wassif, J.S. Waye, P.A. Krakowiak, D.
Cozma, N.R. Dobson, S.W. Levin, G. Anadiotis, R.D. Steiner, M.
Krajewska-Walasek, M.J.M. Nowaczyk, F.D. Porter, DHCR7
nonsense mutations and characterization of mRNA nonsense
mediated decay in Smith–Lemli–Opitz Syndrome, J. Med. Genet.
(2004), in press.
 D. De Brasi, T. Esposito, M. Rossi, G. Parenti, M.P. Sperandeo,
A. Zuppaldi, T. Bardaro, M.A. Ambruzzi, L. Zelante, A. Ciccodi-
cola, G. Sebastio, M. D’Urso, G. Andria, Smith–Lemli–Opitz
syndrome: evidence of T93M as a common mutation of delta7-
sterol reductase in Italy and report of three novel mutations, Eur.
J. Hum. Genet. 7 (1999) 937–940.
 M.J. Nowaczyk, D. Martin-Garcia, A. Aquino-Perna, M. Rodri-
guez-Vazquez, D. McCaughey, B. Eng, L.M. Nakamura, J.S.
Waye, Founder eVect for the T93M DHCR7 mutation in Smith–
Lemli–Opitz syndrome, Am. J. Med. Genet. 2 (2004) 173–176.
 D.N. Cooper, M. Krawczak, Cytosine methylation and the fate
of CpG dinucleotides in vertebrate genomes, Hum. Genet. 83
 P.A. Frischmeyer, A.C. Dietz, Nonsense-mediated mRNA decay
in health and disease, Hum. Mol. Genet. 8 (1999) 1893–1900.
 H. Yu, M.H. Lee, L. Starck, E.R. Elias, M. Irons, G. Salen, S.B.
Patel, G.S. Tint, Spectrum of Delta(7)-dehydrocholesterol reduc-
tase mutations in patients with the Smith–Lemli–Opitz (RSH)
syndrome, Hum. Mol. Genet. 9 (2000) 1385–1391.
 D.W. Neklason, K.M. Andrews, R.I. Kelley, J.E. Metherall, Bio-
chemical variants of Smith–Lemli–Opitz syndrome, Am. J. Med.
Genet. 85 (1999) 517–523.
 C.H. Shackleton, E. Roitman, R. Kelley, Neonatal urinary ste-
roids in Smith–Lemli–Opitz syndrome associated with 7-dehy-
drocholesterol reductase deWciency, Steroids 64 (1999) 481–490.
 C.H. Shackleton, E. Roitman, L.E. Kratz, R.I. Kelley, Midgesta-
tional maternal urine steroid markers of fetal Smith–Lemli–
Opitz (SLO) syndrome (7-dehydrocholesterol 7-reductase deW-
ciency), Steroids 64 (1999) 446–452.
 C.H. Shackleton, E. Roitman, L.E. Kratz, R.I. Kelley, Equine
type estrogens produced by a pregnant woman carrying a Smith–
Lemli–Opitz syndrome fetus, J. Clin. Endocrinol. Metab. 84
 C.A. Wassif, J. Yu, J. Cui, F.D. Porter, N.B. Javitt, 27-Hydroxyl-
ation of 7- and 8-dehydrocholesterol in Smith–Lemli–Opitz syn-
drome: a novel metabolic pathway, Steroids 68 (2003) 497–502.
 J. Marcos, L.W. Guo, W.K. Wilson, F.D. Porter, C. Shackleton,
The implications of 7-dehydrosterol-7-reductase deWciency
(Smith–Lemli–Opitz syndrome) to neurosteroid production, Ste-
roids 69 (2004) 51–60.
 M. Witsch-Baumgartner, M. Gruber, H.G. Kraft, M. Rossi, P.
Clayton, M. Giros, D. Haas, R.I. Kelley, M. Krajewska-
Walasek, G. Utermann, Maternal apo E genotype is a modiWer
of the Smith–Lemli–Opitz Syndrome, J. Med. Genet. 41 (2004)
 N. Blom, S. Gammeltoft, S. Brunak, Sequence and structure
based prediction of eukaryotic protein phosphorylation sites, J.
Mol. Biol. 294 (1999) 1351–1362.
 P.A. Krakowiak, N.A. Nwokoro, C.A. Wassif, K.P. Battaile, M.J.
Nowaczyk, W.E. Connor, C. Maslen, R.D. Steiner, F.D. Porter,
Mutation analysis and description of sixteen RSH/Smith–Lemli–
Opitz syndrome patients: polymerase chain reaction-based
assays to simplify genotyping, Am. J. Med. Genet. 94 (2000) 214–
 T. Evans, A. Poh, C. Webb, B. Wainwright, C. Wicking, I. Glass,
W.F. Carey, M. Fietz, Novel mutation in the Delta7-dehydrocho-
lesterol reductase gene in an Australian patient with Smith–
Lemli–Opitz syndrome, Am. J. Med. Genet. 103 (2001) 344–347.
 M. Witsch-Baumgartner, J. LoZer, G. Utermann, Mutations in
the human DHCR7 gene, Hum. Mutat. 17 (2001) 172–182.
 M.M. Nezarati, J. LoeZer, G. Yoon, L. MacLaren, E. Fung, F.
Snyder, G. Utermann, G.E. Graham, Novel mutation in the
Delta-sterol reductase gene in three Lebanese sibs with Smith–
Lemli–Opitz (RSH) syndrome, Am. J. Med. Genet. 110 (2002)
 C. Patrono, C. Dionisi-Vici, A. Giannotti, B. Bembi, M.C. Digilio,
C. Rizzo, C. PuriWcato, C. Martini, R. Pierini, F.M. Santorelli,
Two novel mutations of the human delta7-sterol reductase
(DHCR7) gene in children with Smith–Lemli–Opitz syndrome,
Mol. Cell. Probes 16 (2002) 315–318.
 C. Prasad, S. Marles, A.N. Prasad, S. Nikkel, S. LongstaVe, D.
Peabody, B. Eng, S. Wright, J.S. Waye, M.J. Nowaczyk, Smith–
Lemli–Opitz syndrome: new mutation with a mild phenotype,
Am. J. Med. Genet. 108 (2002) 64–68.
 F.A. Langius, H.R. Waterham, G.J. Romeijn, W. Oostheim,
M.M. de Barse, L. Dorland, M. Duran, F.A. Beemer, R.J. Wan-
ders, B.T. Poll-The, IdentiWcation of three patients with a very
mild form of Smith–Lemli–Opitz syndrome, Am. J. Med. Genet.
122A (2003) 24–29.
 M.J. Nowaczyk, B. Eng, J.S. Waye, S.A. Farrell, W.L. Sirkin,
Fetus with renal agenesis and Smith–Lemli–Opitz syndrome,
Am. J. Med. Genet. 120A (2003) 305–307.
 Y.H. Shim, S.H. Bae, J.H. Kim, K.R. Kim, C.J. Kim, Y.K. Paik, A
novel mutation of the human 7-dehydrocholesterol reductase
gene reduces enzyme activity in patients with holoprosencephaly,
Biochem. Biophys. Res. Commun. 315 (2004) 219–223.
 C. Patrono, C. Rizzo, A. Tessa, A. Giannotti, P. Borrelli, R. Car-
rozzo, F. Piemonte, E. Bertini, C. Dionisi-Vici, F.M. Santorelli,
Novel 7-DHCR mutation in a child with Smith–Lemli–Opitz
syndrome, Am. J. Med. Genet. 91 (2000) 138–140.
 C.E.M. De Die-Smulders, H.R. Waterham, J.P. Fryns, Unex-
pected molecular Wndings in 2 previously described brothers
with Smith–Lemli–Opitz syndrome, Genet. Couns. 10 (1999)
 C. Mueller, S. Patel, M. Irons, K. Antshel, G. Salen, G.S. Tint, C.
Bay, Normal cognition and behavior in a Smith–Lemli–Opitz
syndrome patient who presented with Hirschsprung disease, Am.
J. Med. Genet. 123A (2003) 100–106.
 V. Bzduch, L. Kozak, H. Francova, D. Behulova, Prenatal diag-
nosis of Smith–Lemli–Opitz syndrome by mutation analysis,
Am. J. Med. Genet. 95 (2000) 85.