Neuroscience Letters 424 (2007) 203–206
A study of the PEMT gene in schizophrenia
Yang Liua,d,1, Haiying Zhanga,1, Guizhi Jua, Xuan Zhanga, Qi Xub,
Shuzheng Liua, Yaqin Yua, Jieping Shia, Susanne Boylec,
Zhenqi Wanga, Yan Shenb, Jun Weie,∗
aResearch Center for Neuroscience and MH Radiobiology Research Unit,
Jilin University, Changchun 130021, China
bInstitute of Basic Medical Sciences, Chinese Academy of Medical Sciences (CAMS) and Peking
Union Medical College (PUMC), Beijing 100005, China
cThe School of Pharmacy, The Robert Gordon University, Schoolhill, Aberdeen AB10 1FR, UK
dThe First Unit of Surgery, The 209th Hospital of the PLA, China
eThe Ness Foundation, UHI Millennium Institute, Inverness IV3 8GY, UK
Received 30 May 2007; received in revised form 10 July 2007; accepted 29 July 2007
The phospholipid hypothesis of schizophrenia is becoming popular because of the findings from the niacin flush test, the treatment with
polyunsaturated fatty acids (PUFAs), biochemical studies for the phospholipid metabolism pathway and genetic studies of phospholipase A2. The
present study attempted to investigate the gene coding for phosphatidylethanolamine N-methyltransferase (PEMT), which is an important enzyme
for the synthesis of membrane phospholipids. We recruited 271 Chinese parent-offspring trios of Han descent and detected 3 single nucleotide
P=0.00001) and the rs464396-rs4244593 haplotypes (X2=17.3, d.f.=3, P=0.0006). The 3-SNP haplotype analysis also showed a haplotypic
association (X2=24.4, d.f.=7, P=0.0006). The present results suggest that the PEMT gene may contribute to the etiology of schizophrenia.
© 2007 Elsevier Ireland Ltd. All rights reserved.
Keywords: Membrane phospholipids; PEMT; Schizophrenia; Single nucleotide polymorphisms (SNPs)
phatidylethanolamine and polyunsaturated fatty acids (PUFAs)
in red blood cell (RBC) membranes of schizophrenic patients
[36,12,15,11,6,16,1]. Niacin-induced dermal flush has been
used as a non-invasive diagnostic approach to test for defi-
ciency of arachidonic acid (AA) and its derivatives such as
prostaglandins . Up to 80% of schizophrenic patients have
shown a poor skin response to niacin stimulation as compared
with 20% of healthy individuals [37,26,25,18,29,27,17].
∗Corresponding author. Tel.: +44 1463 248145; fax: +44 1463 861444.
E-mail addresses: email@example.com (Q. Xu), firstname.lastname@example.org
1These authors contributed equally to the work.
Increased phospholipase A2 (PLA2) activity was found in
schizophrenic patients with diminished niacin flush . These
findings suggest that abnormal niacin flush may represent a
functional deficit of the phospholipid metabolism pathway in
Because a genetic component is involved in schizophrenia,
the genes responsible for the phospholipid metabolism path-
way should be tested for a disease association. Although some
work on this field has been conducted in the past decade,
most of the studies reported to date have been focusing on
the genes responsible for the breakdown of phospholipids,
such as those coding for PLA2 and prostaglandin synthase
[13,20,41–43,38,28,14,19,34,33], whereas little attention has
been paid to those for the synthesis of membrane phos-
pholipids. Long-chain fatty acid-CoA ligase type 4 (FACL4)
is the enzyme, which selectively esterifies eicosapentaenoic
acid (EPA), docosahexaenoic acid (DHA) and AA with co-
enzyme A to form the acyl Co-A. The acyl Co-A can then be
0304-3940/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved.
Y. Liu et al. / Neuroscience Letters 424 (2007) 203–206
incorporated into membrane phospholipids. The gene coding
for FACL4 is located in the long arm of the X chromosome and
highly expressed in the developing and adult brain [2,3]. In a
ciation between the FACL4 gene and depression but they failed
to find such an association shown in schizophrenia. Wei and co-
workers  have also failed to identify a genetic association
between the FACL4 gene and the illness in British mother–son
Phosphatidylethanolamine N-methyltransferase (PEMT) is
the enzyme converting phosphatidylethanolamine into phos-
phatidylcholine. The PEMT pathway contributes about 30% of
that phosphatidylethanolamine contains much higher concen-
trations of AA than other phospholipids. The newly-formed
phosphatidylcholine through the PEMT pathway is rich in AA,
which is important for the AA signaling pathway and for the
was designed to see if the PEMT gene is associated with
A total of 271 Chinese parent-offspring trios of Han descent,
consisting of fathers, mothers and affected offspring with
schizophrenia, were recruited for the genetic analysis at the
Jilin University Research Center for Neuroscience, Changchun,
China. These family trios did not include those showing
Mendelian errors that had been rectified by genotyping more
than 10 highly informative SNPs (Heterozygosity is greater
than 0.25). These subjects originally came from the Northeast
area of China. The patients (174 males and 97 females), aged
26.1±6.6 years, were admitted to a psychiatric hospital dur-
ing the period between 2000 and 2004. They were diagnosed as
having a schizophrenic illness using the International Statistical
Classification of Diseases and Related Health Problems, Tenth
Revision (ICD-10). The diagnosis was made independently by
at least two psychiatrists following a clinical interview. All the
subjects gave written informed consent for the genetic anal-
ysis as approved by the ethics committee of Jilin University,
We detected 3 single nucleotide polymorphisms (SNPs)
using PCR-based restriction fragment length polymorphism
(RFLP) analysis based on the SNP map of the PEMT
genes (http://www.ncbi.nlm.nih.gov/LocusLink). These SNPs
included rs4244593 (Taq I), rs4646396 (Taq I) and rs936108
DNA used for PCR amplification was extracted from the whole
blood sample using a DNA extraction kit (Promega, Beijing,
China). The PCR amplification was performed in a 25-?L
reaction volume containing 10mM Tris–HCl (pH 8.3), 50mM
Genomic information of SNPs detected at the PEMT locus
SNPs RFLPInterval (kb) Numbera
aThe number of parents genotyped in this study.
The TDT for allelic association between the PEMT gene and schizophrenia
aThe number of alleles transmitted only by heterozygous parents.
bThe global P-value was 0.012 for 1000 permutation.
KCl, 1.5mM MgCl2, 0.001% (w/v) gelatin, 200?M of each
dNTP, 0.4?M of each primer, 1.0 unit of Taq DNA polymerase
conditions used for PCR amplification included an initial denat-
45s, 55–60◦C for 1min and 72◦C for 1min, and a final elonga-
tion at 72◦C for 10min. A 15-?L aliquot of the PCR products
was completely digested with 6–8 units of restriction enzymes
and then separated on ethidium bromide-stained agarose gels.
The genotyping data were analyzed with the UNPHASED
program . The transmission disequilibrium test (TDT) was
applied to test allelic association for a single locus and the
haplotype analysis was applied for haplotypic association. To
circumvent the multipoint analysis problem, we applied a per-
mutation test for the global null hypothesis that all the odds
ratios could be equal. The permutation test is a built-in program
of UNPHASED. It gives a significance level corrected for the 3
The TDT showed allelic association for rs464396 (X2=9.4,
P=0.002), but not for the other two (Table 2). As shown in
ciation for both the rs936108-rs464396 haplotypes (X2=25.7,
d.f.=3, P=0.00001) and the rs464396-rs4244593 haplotypes
test showed that the rs936108 (C)-rs464396 (C) haplotype was
P=0.0005). The 3-SNP haplotype analysis also revealed a
haplotypic association (X2=24.4, d.f.=7, P=0.0006) although
the major haplotype did not show an excess of transmission
Analysis of haplotypic association for the 2-SNP haplotypes at the PEMT locus
aThe d.f.=1 test.
bThe global P-value was 0.00001 (X2=25.7, d.f.=3).
cThe global P-value was 0.0006 (X2=17.3, d.f.=3).
Y. Liu et al. / Neuroscience Letters 424 (2007) 203–206
Analysis of haplotypic association for the rs936108-rs464396-rs4244593 hap-
lotypes at the PEMT locus
aThe global P-value was 0.0006 (X2=24.4, d.f.=7).
bThe d.f.=1 test.
The membrane phospholipid hypothesis for schizophrenia
has become increasingly popular since PUFAs showed a bene-
ficial effect on the treatment of schizophrenia and some other
to establish a genetic relationship between the genes responsi-
ble for phospholipid metabolism and schizophrenia. Although
a few publications suggest association of the cytosolic PLA2
only reason for abnormal niacin flush observed in schizophre-
nia. The dysfunction of phospholipid synthesis should also
be taken into account. Both FACL4 and PEMT are impor-
tant for the synthesis of membrane phospholipids containing
AA. PEMT can convert phosphatidylethanolamine into phos-
phatidylcholine. Because phosphatidylethanolamine is rich in
pathway and to the function of neuronal membranes. Possibly,
the PEMT gene polymorphisms contribute to both the etiology
of schizophrenia and the abnormal niacin flush.
of preliminary work, it is important to establish a genetic link
for abnormal niacin flushing in schizophrenia. Further study is
needed to replicate the initial finding in different populations
and to see the association between the PEMT gene and niacin
We thank the patients and families for their support and
participation. We also thank Changchun Kaixuan Hospital and
Siping Neuropsychiatric Hospital, Jilin Province, China, for
clinical interview with subjects and collection of blood sam-
ples. This work was supported by the National 863 program of
China (2004AA221070), the National Basic Research Program
of China (2004CB518601), the grants from the National Nat-
ural Science Foundation of China (30170343 and 30400263),
the Beijing Natural Science Foundation (5052021), the project
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