Analysis of the pseudoautosomal X-linked gene SYBL1in bipolar affective disorder: description of a new candidate allele for psychiatric disorders.
The absence of father-to-son transmission has been observed in a subset of families with bipolar disorder (BPD), suggestive of a susceptibility gene on the sex-linked portion of the X chromosome. This is supported by some genetic linkage studies that have provided evidence for a susceptibility locus near Xq28. We have analyzed one candidate gene on Xq28, SYBL1, which maps to the Xq pseudoautosomal region (PAR). SYBL1 encodes a member of the synaptobrevin family of proteins that is involved in synaptic vesicle docking and membrane transport. Genes in the PAR generally escape X-chromosome inactivation and have an active homolog on the Y chromosome, which would result in an increase in same-sex concordance in paternal transmitted traits. However, SYBL1 is neither expressed on the Y chromosome nor the inactive X chromosome and would therefore be expected to show typical sex-linked transmission. We have screened SYBL1 for mutations that could be tested as candidate alleles in the development of BPD. Following single-strand conformation polymorphism (SSCP) analysis and DNA sequencing, four single nucleotide polymorphisms were detected: a silent mutation at codon 108, two intron mutations without any obvious biological significance, and a G-->C transversion in the polypyrimidine tract at the 3' splice acceptor site preceding exon 8. This polymorphism, which creates a perfect 16/16 stretch of pyrimidines, was analyzed in 110 patients with BPD not selected for sex-linked transmission and 119 control subjects. The results show a statistical trend toward an increase in the frequency of the C allele in males with BPD but not females. Males: chi(2) = 3.46, 1 df, p =.06; Females: chi(2) =.20, 1 df, p =.66.
Saito
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T
Department of Psychiatry, Division of Psychiatry Research, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Parsia
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Papolos
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DF
Lachman
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HM
D000328:Adult; D000483:Alleles; D001714:Bipolar Disorder / Q000235:genetics*; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D005260:Female; D005787:Gene Frequency; D008040:Genetic Linkage; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D018807:Polymorphism, Single-Stranded Conformational; D050683:R-SNARE Proteins; D012737:Sex Factors; D018709:Statistics, Nonparametric; D014960:X Chromosome / Q000235:genetics*
D008565:Membrane Proteins; D050683:R-SNARE Proteins; C121241:VAMP7 protein, human