title: Characterisation of genetic variation in ST8SIA2 and its interaction region in NCAM1 in patients with bipolar disorder.
abstract: Alpha-2,8-sialyltransferase 2 (ST8SIA2) is an enzyme responsible for the transfer of polysialic acid (PSA) to glycoproteins, principally the neuronal cell adhesion molecule (NCAM1), and is involved in neuronal plasticity. Variants within ST8SIA2 have previously shown association with bipolar disorder, schizophrenia and autism. In addition, altered PSA-NCAM expression in brains of patients with schizophrenia or bipolar disorder indicates a functional dysregulation of glycosylation in mental illness. To explore the role of sequence variation affecting PSA-NCAM formation, we conducted a targeted re-sequencing study of a ∼ 100 kb region--including the entire ST8SIA2 gene and its region of interaction with NCAM1--in 48 Caucasian cases with bipolar disorder using the Roche 454 platform. We identified over 400 DNA variants, including 47 putative novel variants not described in dbSNP. Validation of a subset of variants via Sequenom showed high reliability of Roche 454 genotype calls (97% genotype concordance, with 80% of novel variants independently verified). We did not observe major loss-of-function mutations that would affect PSA-NCAM formation, either by ablating ST8SIA2 function or by affecting the ability of NCAM1 to be glycosylated. However, we identified 13 SNPs in the UTRs of ST8SIA2, a synonymous coding SNP in exon 5 (rs2305561, P207P) and many additional non-coding variants that may influence splicing or regulation of ST8SIA2 expression. We calculated nucleotide diversity within ST8SIA2 on specific haplotypes, finding that the diversity on the specific "risk" and "protective" haplotypes was lower than other non-disease-associated haplotypes, suggesting that putative functional variation may have arisen on a spectrum of haplotypes. We have identified common and novel variants (rs11074064, rs722645, 15:92961050) that exist on a spectrum of haplotypes, yet are plausible candidates for conferring the effect of risk and protective haplotypes via multiple enhancer elements. A Galaxy workflow/pipeline for sequence analysis used herein is available at: https://main.g2.bx.psu.edu/u/a-shaw-neura/p/next-generation-resources.
authors.affiliation: Neuroscience Research Australia, Sydney, New South Wales, Australia; Schizophrenia Research Institute, Sydney, New South Wales, Australia.
authors.forename: Alex D
authors.initials: AD
authors.lastname: Shaw
authors.affiliation: Neuroscience Research Australia, Sydney, New South Wales, Australia; Schizophrenia Research Institute, Sydney, New South Wales, Australia; School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Yash
authors.initials: Y
authors.lastname: Tiwari
authors.affiliation: Peter Wills Bioinformatic Centre, Garvan Institute, Sydney, New South Wales, Australia.
authors.forename: Warren
authors.initials: W
authors.lastname: Kaplan
authors.affiliation: Neuroscience Research Australia, Sydney, New South Wales, Australia.
authors.forename: Anna
authors.initials: A
authors.lastname: Heath
authors.affiliation: School of Psychiatry, University of New South Wales, Sydney, New South Wales, Australia; Black Dog Institute, Sydney, New South Wales, Australia.
authors.forename: Philip B
authors.initials: PB
authors.lastname: Mitchell
authors.affiliation: Neuroscience Research Australia, Sydney, New South Wales, Australia; Schizophrenia Research Institute, Sydney, New South Wales, Australia; School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Schofield
authors.affiliation: Neuroscience Research Australia, Sydney, New South Wales, Australia; Schizophrenia Research Institute, Sydney, New South Wales, Australia; School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Janice M
authors.initials: JM
authors.lastname: Fullerton
mesh_terms: D001714:Bipolar Disorder / Q000235:genetics*; D019002:CD56 Antigen / Q000235:genetics*; D002874:Chromosome Mapping; D016000:Cluster Analysis; D019295:Computational Biology; D004843:Epistasis, Genetic; D020869:Gene Expression Profiling; D023061:Gene Order; D056426:Genetic Loci; D014644:Genetic Variation; D005838:Genotype; D006239:Haplotypes; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D058977:Molecular Sequence Annotation; D020641:Polymorphism, Single Nucleotide; D015203:Reproducibility of Results; D012799:Sialyltransferases / Q000235:genetics*
chemical_list: D019002:CD56 Antigen; C522918:NCAM1 protein, human; C046778:CMP-N-acetylneuraminate-poly-alpha-2,8-sialosyl sialyltransferase; D012799:Sialyltransferases