Evidence for Association of Cell Adhesion Molecules Pathway and NLGN1 Polymorphisms with Schizophrenia in Chinese Han Population

Abstract

Multiple risk variants of schizophrenia have been identified by Genome-wide association studies (GWAS). As a complement for GWAS, previous pathway-based analysis has indicated that cell adhesion molecules (CAMs) pathway might be involved in the pathogenesis of schizophrenia. However, less replication studies have been reported. Our objective was to investigate the association between CAMs pathway and schizophrenia in the Chinese Han population. We first performed a pathway analysis utilizing our previous GWAS data. The CAMs pathway (hsa04514) was significantly associated with schizophrenia using hybrid gene set-based test (P = 1.03×10-10) and hypergeometric test (P = 5.04×10-6). Moreover, 12 genes (HLA-A, HLA-C, HLA-DOB, HLA-DPB1, HLA-DQA2, HLA-DRB1, MPZ, CD276, NLGN1, NRCAM, CLDN1 and ICAM3) were modestly significantly associated with schizophrenia (P<0.01). Then, we selected one promising gene neuroligin 1 (NLGN1) to further investigate the association between eight significant SNPs and schizophrenia in an independent sample (1814 schizophrenia cases and 1487 healthy controls). Our study showed that seven SNPs of NLGN1 and two haplotype blocks were significantly associated with schizophrenia. This association was confirmed by the results of combined analysis. Among them, SNP rs9835385 had the most significant association with schizophrenia (P = 2.83×10-7). Furthermore, in silico analysis we demonstrated that NLGN1 is preferentially expressed in human brain and SNP rs1488547 was related to the expression level. We validated the association of CAMs pathway with schizophrenia in pathway-level and identified one susceptibility gene NLGN1. Further investigation of the roles of CAMs pathway in the pathogenesis of schizophrenia is warranted.

Fig 1. Genes involved in ‘cell adhesion molecules’ pathway.

Color scheme: Red = significant genes (P<0.01). White = non-significant genes. See detail in (http://www.genome.jp/kegg-bin/show_pathway?hsa04514).

Fig 2. Linkage disequilibrium of the seven significant SNPs identified in this study.

The LD pattern was derived from the combined group (i.e., both case and healthy control subjects in our previous GWAS). The LD block was defined according to the criteria of Gabriel et al (38). The color scale ranges from red to white (color intensity decreases with decreasing r ² value). This plot was generated by Haploview (version 4.1).

Fig 3. Temporal-spatial expression profiling of NLGN1 in human brain tissues.

(a) Expression of NLGN1 is enriched in human brain tissues, the hippocampus, cerebellum, whole brain and frontal cortex have the highest enrichment scores. (b) Temporal expression pattern of NLGN1 in different human brain regions. AMY, amygdala; CBC, cerebellar cortex; HIP, hippocampus; MD, mediodorsal nucleus of the thalamus; NCX, neocortex; STR, striatum. Periods of human development and adulthood as defined in this figure: Embryonic (periods 1), Early fetal Early mid-fetal (periods 2–3), Early mid-fetal (periods 3–4), Late mid-fetal (periods 6), Late fetal (periods 7), Neonatal and early infancy (periods 8), Late infancy (periods 9), Early childhood (periods 10), Middle and late childhood (periods 11), Adolescence (periods 12), Young adulthood (periods 13), Middle adulthood (periods 14), Late adulthood (periods 15).

Fig 4. Effects of risk single-nucleotide polymorphisms on NLGN1 mRNA expression.

(a) Results in the lymphoblastoid cell lines of 75 healthy subjects. (b) Results in ten brain regions of 134 healthy subjects. SNIG, substantia nigra; MEDU, the inferior olivary nucleus (sub-dissected from the medulla); THAL, thalamus; WHMT, intralobular white matter; TCTX, temporal cortex; HIPP, hippocampus; PUTM, putamen; FCTX, frontal cortex; OCTX, occipital cortex; CRBL, cerebellar cortex.