Whole-exome sequencing in a family with a monozygotic twin pair concordant for schizophrenia and a follow-up case-control study of identified de-novo variants.

Whole-exome sequencing (WES) studies have shown that de-novo variants contribute to the genetic etiology of schizophrenia. WES studies of families with a monozygotic twin pair concordant or discordant for a disease may be fruitful for identifying de-novo pathogenic variants. Here, we performed WES in six individuals from one family (affected monozygotic twins, their unaffected parents, and two siblings) and identified three de-novo missense variants (CPT2 Ala283Thr, CPSF3 Val584Ile, and RNF148 Val210Ile) in the monozygotic twin pair concordant for schizophrenia. These three missense variants were not found in 1760 patients with schizophrenia or schizoaffective disorder or 1508 healthy controls. Our data do not support the role of the three missense variants in conferring risk for schizophrenia.

Comparative Analyses of Copy-Number Variation in Autism Spectrum Disorder and Schizophrenia Reveal Etiological Overlap and Biological Insights.

Compelling evidence in Caucasian populations suggests a role for copy-number variations (CNVs) in autism spectrum disorder (ASD) and schizophrenia (SCZ). We analyzed 1,108 ASD cases, 2,458 SCZ cases, and 2,095 controls in a Japanese population and confirmed an increased burden of rare exonic CNVs in both disorders. Clinically significant (or pathogenic) CNVs, including those at 29 loci common to both disorders, were found in about 8% of ASD and SCZ cases, which was significantly higher than in controls. Phenotypic analysis revealed an association between clinically significant CNVs and intellectual disability. Gene set analysis showed significant overlap of biological pathways in both disorders including oxidative stress response, lipid metabolism/modification, and genomic integrity. Finally, based on bioinformatics analysis, we identified multiple disease-relevant genes in eight well-known ASD/SCZ-associated CNV loci (e.g., 22q11.2, 3q29). Our findings suggest an etiological overlap of ASD and SCZ and provide biological insights into these disorders.

Rare PDCD11 variations are not associated with risk of schizophrenia in Japan.

AIM: Rare gene variations are thought to confer substantial risk for schizophrenia. We performed a three-stage study to identify rare variations that have a strong impact on the risk of developing schizophrenia. METHODS: In the first stage, we prioritized rare missense variations using whole-exome sequencing (WES) data from three families, consisting of a proband, an affected sibling, and parents. In the second stage, we performed targeted resequencing of the PDCD11 coding region in 96 patients. In the third stage, we conducted an association study of rare PDCD11 variations with schizophrenia in a total of 1357 patients and 1394 controls. RESULTS: Via WES, we identified two rare missense PDCD11 variations, p.(Asp961Asn) and p.(Val1240Leu), shared by two affected siblings within families. Targeted resequencing of the PDCD11 coding region identified three rare non-synonymous variations: p.(Asp961Asn), p.(Phe1835del), and p.(Arg1837His). The case-control study demonstrated no significant associations between schizophrenia and four rare PDCD11 variations: p.(Asp961Asn), p.(Val1240Leu), p.(Phe1835del), and p.(Arg1837His). CONCLUSION: Our data do not support the role of rare PDCD11 variations in conferring substantial risk for schizophrenia in the Japanese population.

Rare FBXO18 variations and risk of schizophrenia: Whole-exome sequencing in two parent-affected offspring trios followed by resequencing and case-control studies.

AIM: Rare variations are suggested to play a role in the genetic etiology of schizophrenia; to further investigate their role, we performed a three-stage study in a Japanese population. METHODS: In the first stage, we performed whole-exome sequencing (WES) of two parent-affected offspring trios. In the second stage, we resequenced the FBXO18 coding region in 96 patients. In the third stage, we tested rare non-synonymous FBXO18 variations for association with schizophrenia in two independent populations comprising a total of 1376 patients and 1496 controls. RESULTS: A rare frameshift variation (L116fsX) in the FBXO18 gene was recurrently identified by WES in both trios. Resequencing FBXO18 coding regions, we detected three rare non-synonymous variations (V15L, L116fsX, and V1006I). However, there were no significant associations between these rare FBXO18 variations and schizophrenia in the case-control study. CONCLUSION: Our present study does not provide evidence for the contribution of rare non-synonymous FBXO18 variations to the genetic etiology of schizophrenia in the Japanese population. However, to draw a definitive conclusion, further studies should be performed using sufficiently large sample sizes.

Rare UNC13B variations and risk of schizophrenia: Whole-exome sequencing in a multiplex family and follow-up resequencing and a case-control study.

Rare genomic variations inherited in multiplex schizophrenia families are suggested to play a role in the genetic etiology of the disease. To identify rare variations with large effects on the risk of developing schizophrenia, we performed whole-exome sequencing (WES) in two affected and one unaffected individual of a multiplex family with 10 affected individuals. We also performed follow-up resequencing of the unc-13 homolog B (Caenorhabditis elegans) (UNC13B) gene, a potential risk gene identified by WES, in the multiplex family and undertook a case-control study to investigate association between UNC13B and schizophrenia. UNC13B coding regions (39 exons) from 15 individuals of the multiplex family and 111 affected offspring for whom parental DNA samples were available were resequenced. Rare missense UNC13B variations identified by resequencing were further tested for association with schizophrenia in two independent case-control populations comprising a total of 1,753 patients and 1,602 controls. A rare missense variation (V1525M) in UNC13B was identified by WES in the multiplex family; this variation was present in five of six affected individuals, but not in eight unaffected individuals or one individual of unknown disease status. Resequencing UNC13B coding regions identified five rare missense variations (T103M, M813T, P1349T, I1362T, and V1525M). In the case-control study, there was no significant association between rare missense UNC13B variations and schizophrenia, although single-variant meta-analysis indicated that M813T was nominally associated with schizophrenia. These results do not support a contribution of rare missense UNC13B variations to the genetic etiology of schizophrenia in the Japanese population. © 2016 Wiley Periodicals, Inc.

Rare truncating variations and risk of schizophrenia: Whole-exome sequencing in three families with affected siblings and a three-stage follow-up study in a Japanese population.

Rare inherited variations in multiplex families with schizophrenia are suggested to play a role in the genetic etiology of schizophrenia. To further investigate the role of rare inherited variations, we performed whole-exome sequencing (WES) in three families, each with two affected siblings. We also performed a three-stage follow-up case-control study in a Japanese population with a total of 2617 patients and 2396 controls. WES identified 15 rare truncating variations that were variously present in the two affected siblings in each family. These variations did not necessarily segregate with schizophrenia within families, and they were different in each family. In the follow-up study, four variations (NWD1 W169X, LCORL R7fsX53, CAMK2B L497fsX497, and C9orf89 Q102X) had a higher mutant allele frequency in patients compared with controls, although these associations were not significant in the combined population, which comprised the first-, second- and third-stage populations. These results do not support a contribution of the rare truncating variations identified in the three families to the genetic etiology of schizophrenia.

Resequencing and Association Analysis of CLN8 with Autism Spectrum Disorder in a Japanese Population.

Rare variations contribute substantially to autism spectrum disorder (ASD) liability. We recently performed whole-exome sequencing in two families with affected siblings and then carried out a follow-up study and identified ceroid-lipofuscinosis neuronal 8 (epilepsy, progressive with mental retardation) (CLN8) as a potential genetic risk factor for ASD. To further investigate the role of CLN8 in the genetic etiology of ASD, we performed resequencing and association analysis of CLN8 with ASD in a Japanese population. Resequencing the CLN8 coding region in 256 ASD patients identified five rare missense variations: g.1719291G>A (R24H), rs201670636 (F39L), rs116605307 (R97H), rs143701028 (T108M) and rs138581191 (N152S). These variations were genotyped in 568 patients (including the resequenced 256 patients) and 1017 controls. However, no significant association between these variations and ASD was identified. This study does not support a contribution of rare missense CLN8 variations to ASD susceptibility in the Japanese population.

Whole-exome sequencing in a family with a monozygotic twin pair concordant for autism spectrum disorder and a follow-up study.

Two truncating variations (WDR90 V1125fs and EFCAB5 L1210fs), identified by whole-exome sequencing in a family with a monozygotic twin pair concordant for autism spectrum disorder (ASD), were not detected in 257 ASD patients, 677 schizophrenia patients or 667 controls in a follow-up study. Thus, these variations were exclusively identified in the family, suggesting that rare truncating variations may have a role in the genetic etiology of ASD, at least in a subset of ASD patients.

Association analysis of the Cadherin13 gene with schizophrenia in the Japanese population.

BACKGROUND: Cadherin13 (CDH13) is a glycosylphosphatidylinositol-anchored cell adhesion molecule that plays a crucial role in morphogenesis and the maintenance of neuronal circuitry. CDH13 has been implicated in the susceptibility to a variety of psychiatric diseases. A recent genome-wide association study using Danish samples showed, for the first time, the involvement of a single nucleotide polymorphism (SNP) of CDH13 (intronic SNP rs8057927) in schizophrenia. Here, we investigated the association between other SNPs of CDH13 and schizophrenia and tried to replicate the association for the SNP of rs8057927, in the Japanese population. METHODS: Using TaqMan(®) SNP genotyping assays, five tag SNPs (rs12925602, rs7193788, rs736719, rs6565051, and rs7204454) in the promoter region of CDH13 were examined for their association with schizophrenia in two independent samples. The first sample comprised 665 patients and 760 controls, and the second sample comprised 677 patients and 667 controls. One tag SNP for rs8057927 was also examined for the association with schizophrenia in the first sample set. RESULTS: A GACAG haplotype of the five SNPs in the promoter region of CDH13 was significantly associated with schizophrenia in the first sample set (P=0.016 and corrected P=0.098). A combined analysis of the GACAG haplotype with the second sample set enhanced the significance (P=0.0026 and corrected P=0.021). We found no association between rs8057927 and schizophrenia in the first sample set. CONCLUSION: Our results suggest that CDH13 may contribute to the genetic risk of schizophrenia. Further replication on the association of CDH13 with schizophrenia and functional studies are required to confirm the current findings.

Novel rare missense variations and risk of autism spectrum disorder: whole-exome sequencing in two families with affected siblings and a two-stage follow-up study in a Japanese population.

Rare inherited variations in multiplex families with autism spectrum disorder (ASD) are suggested to play a major role in the genetic etiology of ASD. To further investigate the role of rare inherited variations, we performed whole-exome sequencing (WES) in two families, each with three affected siblings. We also performed a two-stage follow-up case-control study in a Japanese population. WES of the six affected siblings identified six novel rare missense variations. Among these variations, CLN8 R24H was inherited in one family by three affected siblings from an affected father and thus co-segregated with ASD. In the first stage of the follow-up study, we genotyped the six novel rare missense variations identified by WES in 241 patients and 667 controls (the Niigata sample). Only CLN8 R24H had higher mutant allele frequencies in patients (1/482) compared with controls (1/1334). In the second stage, this variation was further genotyped, yet was not detected in a sample of 309 patients and 350 controls (the Nagoya sample). In the combined Niigata and Nagoya samples, there was no significant association (odds ratio = 1.8, 95% confidence interval = 0.1-29.6). These results suggest that CLN8 R24H plays a role in the genetic etiology of ASD, at least in a subset of ASD patients.

Rare heterozygous truncating variations and risk of autism spectrum disorder: Whole-exome sequencing of a multiplex family and follow-up study in a Japanese population.

AIMS: Rare heterozygous truncating variations in multiplex families with autism spectrum disorder (ASD) are suggested to play a major role in the genetic etiology of ASD. To further investigate the role of rare heterozygous truncating variations, we performed whole-exome sequencing (WES) in a multiplex ASD family with four affected individuals (two siblings and two maternal cousins), and a follow-up case-control study in a Japanese population. METHODS: WES was performed in four individuals (a proband, his affected and unaffected siblings, and their putative carrier mother) from the multiplex ASD family. Rare heterozygous truncating variations prioritized in WES were genotyped in 243 patients and 667 controls. RESULTS: By WES of the multiplex family, we prioritized two rare heterozygous truncating variations, RPS24 Q191X and CD300LF P261fsX266. However, we did not identify these variations in patients or controls in the follow-up study. CONCLUSIONS: Our findings suggest that two rare heterozygous truncating variations (RPS24 Q191X and CD300LF P261fsX266) are risk candidates for ASD.

Resequencing and association analysis of OXTR with autism spectrum disorder in a Japanese population.

AIMS: The oxytocin receptor (OXTR) is implicated in the pathophysiology of autism spectrum disorder (ASD). A recent study found a rare non-synonymous OXTR gene variation, rs35062132 (R376G), associated with ASD in a Japanese population. In order to investigate the association between rare non-synonymous OXTR variations and ASD, we resequenced OXTR and performed association analysis with ASD in a Japanese population. METHODS: We resequenced the OXTR coding region in 213 ASD patients. Rare non-synonymous OXTR variations detected by resequencing were genotyped in 213 patients and 667 controls. RESULTS: We detected three rare non-synonymous variations: rs35062132 (R376G/C), rs151257822 (G334D), and g.8809426G>T (R150S). However, there was no significant association between these rare non-synonymous variations and ASD. CONCLUSIONS: Our present study does not support the contribution of rare non-synonymous OXTR variations to ASD susceptibility in the Japanese population.

Association analysis of putative cis-acting polymorphisms of interleukin-19 gene with schizophrenia.

BACKGROUND: Genome-wide association studies (GWAS) and gene expression analyses have revealed that single nucleotide polymorphisms (SNPs) associated with multifactorial diseases, such as schizophrenia, are significantly more likely to be associated with expression quantitative trait loci (eQTL). It was recently suggested that an immune system imbalance plays an important role in the pathogenesis of schizophrenia. Interleukin-19 is a novel cytokine that may play multiple roles in immune regulation and various diseases. METHOD: We selected eight tag SNPs in the eQTL of the IL-19 gene. Seven of the SNPs are putative cis-acting SNPs. Then, we conducted a case-control study using two independent samples. The first sample comprised 567 schizophrenia patients and 710 controls, and the second sample comprised 677 schizophrenia patients and 667 controls. RESULT: We identified the TGAA haplotype as being significantly associated with schizophrenia (p=0.0036 and corrected p=0.0264), although a combined analysis of the TGAA haplotype with the replication samples exhibited a nominally significant difference (p=0.022 and corrected p=0.235). CONCLUSIONS: These results suggest that the IL-19 gene might slightly contribute to the genetic risk of schizophrenia. Thus, further research on the association of eQTL SNPs with schizophrenia is warranted.

Interleukin 1 beta gene and risk of schizophrenia: detailed case-control and family-based studies and an updated meta-analysis.

OBJECTIVE: Interleukin-1 beta (IL-1ß) has been implicated in the pathophysiology of schizophrenia. To assess whether the IL1B gene confers increased susceptibility to schizophrenia, we conducted case-control and family-based studies and an updated meta-analysis. METHODS: We tested the association between IL1B and schizophrenia in 1229 case-control and 112 trio samples using 12 markers, including common tagging single nucleotide variations (SNVs) and a rare non-synonymous variation detected by resequencing the coding regions. We also performed a meta-analysis of rs16944 using a total of 8724 case-control and 201 trio samples from 16 independent populations. RESULTS: We found no significant associations between any of the 12 SNVs examined and schizophrenia in either case-control or trio samples. Moreover, our meta-analysis results showed no significant association between the common SNV, rs16944, and schizophrenia. CONCLUSIONS: The present study does not support a role for IL1B in schizophrenia susceptibility.

An evaluation of association between a novel hippocampal biology related SNP (rs7294919) and schizophrenia.

Recent genetic analyses have implicated several candidate susceptibility variants for schizophrenia. The single nucleotide polymorphism (SNP) rs7294919 is likely a schizophrenia-susceptibility variant according to its significant association with hippocampal volume, hippocampus function, and cognitive performance as well as the nominal association with schizophrenia. However, all previous analyses were conducted only in Europeans, and whether rs7294919 is associated with schizophrenia in other populations are yet to be tested. Here, we conducted a case-control analysis of rs7294919 with schizophrenia in six independent Chinese (N = 3) and Japanese (N = 3) samples, including a total of 7,352 cases and 10,824 controls. The results of our association analysis were not able to confirm the association of rs7294919 with schizophrenia (p = 0.51 in total samples, odds ratio = 1.02 for allele[C]). The absence of rs7294919's association in Chinese and Japanese suggest a potential genetic heterogeneity in the susceptibility of schizophrenia on this locus and also demonstrate the difficulties in replicating associations of schizophrenia across different ethnic populations.

Resequencing and association analysis of MIR137 with schizophrenia in a Japanese population.

MicroRNA may play a role in the pathophysiology of schizophrenia. A recent meta-analysis of genome-wide association studies indicated a significant association between schizophrenia and a common intronic variation in MIR137HG (microRNA 137 host gene) encoding the primary microRNA-137. To explore additional risk variations for schizophrenia, we resequenced MIR137 and performed an association analysis in 1321 Japanese individuals. By resequencing, we detected four sequence variations in the 5' and 3' flanking regions. There were no significant associations between these variations and schizophrenia. Our resequencing and association analysis of MIR137 failed to find additional risk variations for schizophrenia.

Association of the BDNF†C270T polymorphism with schizophrenia: updated meta-analysis.

Brain-derived neurotrophic factor (BDNF) has been suggested to play a role in the pathophysiology of schizophrenia. The C270T polymorphism (rs56164415) in the BDNF 5'-non-coding region has been extensively investigated for an association with schizophrenia, but with conflicting results. An updated meta-analysis was therefore performed of 13 case-control association studies (3505 patients and 3992 controls). An association was found between the T allele and schizophrenia. The association was significant in the East Asian population, but not in the Caucasian population. It is suggested that the BDNF C270T polymorphism contributes to schizophrenia susceptibility, especially in East Asian subjects.