Regional heritability mapping identifies several novel loci (STAT4, ULK4, and KCNH5) for primary biliary cholangitis in the Japanese population.

While the advent of GWAS more than a decade ago has ushered in remarkable advances in our understanding of complex traits, the limitations of single-SNP analysis have also led to the development of several other approaches. Simulation studies have shown that the regional heritability mapping (RHM) method, which makes use of multiple adjacent SNPs jointly to estimate the genetic effect of a given region of the genome, generally has higher detection power than single-SNP GWAS. However, thus far its use has been mostly limited to agricultural settings, and its potential for the discovery of new genes in human diseases is yet to be fully exploited. In this study, by applying the RHM method to primary biliary cholangitis (PBC) in the Japanese population, we identified three novel loci (STAT4, ULK4, and KCNH5) at the genome-wide significance level, two of which (ULK4 and KCNH5) have not been found associated with PBC in any population previously. Notably, these genes could not be detected by using conventional single-SNP GWAS, highlighting the potential of the RHM method for the detection of new susceptibility loci in human diseases. These findings thereby provide strong empirical evidence that RHM is an effective and practical complementary approach to GWAS in this context. Also, liver tissue mRNA microarray analysis revealed higher gene expression levels in ULK4 in PBC patients (P < 0.01). Lastly, we estimated the common SNP heritability of PBC in the Japanese population (0.210 ± 0.026).

Analysis of whole Y-chromosome sequences reveals the Japanese population history in the Jomon period.

The Jomon and the Yayoi are considered to be the two major ancestral populations of the modern mainland Japanese. The Jomon people, who inhabited mainland Japan, admixed with Yayoi immigrants from the Asian continent. To investigate the population history in the Jomon period (14,500-2,300 years before present [YBP]), we analyzed whole Y-chromosome sequences of 345 Japanese males living in mainland Japan. A phylogenetic analysis of East Asian Y chromosomes identified a major clade (35.4% of mainland Japanese) consisting of only Japanese Y chromosomes, which seem to have originated from indigenous Jomon people. A Monte Carlo simulation indicated that ~70% of Jomon males had Y chromosomes in this clade. The Bayesian skyline plots of 122 Japanese Y chromosomes in the clade detected a marked decrease followed by a subsequent increase in the male population size from around the end of the Jomon period to the beginning of the Yayoi period (2,300 YBP). The colder climate in the Late to Final Jomon period may have resulted in critical shortages of food for the Jomon people, who were hunter-gatherers, and the rice farming introduced by Yayoi immigrants may have helped the population size of the Jomon people to recover.

Detection of Hereditary 1,25-Hydroxyvitamin D-Resistant Rickets Caused by Uniparental Disomy of Chromosome 12 Using Genome-Wide Single Nucleotide Polymorphism Array.

CONTEXT: Hereditary 1,25-dihydroxyvitamin D-resistant rickets (HVDRR) is an autosomal recessive disease caused by biallelic mutations in the vitamin D receptor (VDR) gene. No patients have been reported with uniparental disomy (UPD). OBJECTIVE: Using genome-wide single nucleotide polymorphism (SNP) array to confirm whether HVDRR was caused by UPD of chromosome 12. MATERIALS AND METHODS: A 2-year-old girl with alopecia and short stature and without any family history of consanguinity was diagnosed with HVDRR by typical laboratory data findings and clinical features of rickets. Sequence analysis of VDR was performed, and the origin of the homozygous mutation was investigated by target SNP sequencing, short tandem repeat analysis, and genome-wide SNP array. RESULTS: The patient had a homozygous p.Arg73Ter nonsense mutation. Her mother was heterozygous for the mutation, but her father was negative. We excluded gross deletion of the father's allele or paternal discordance. Genome-wide SNP array of the family (the patient and her parents) showed complete maternal isodisomy of chromosome 12. She was successfully treated with high-dose oral calcium. CONCLUSIONS: This is the first report of HVDRR caused by UPD, and the third case of complete UPD of chromosome 12, in the published literature. Genome-wide SNP array was useful for detecting isodisomy and the parental origin of the allele. Comprehensive examination of the homozygous state is essential for accurate genetic counseling of recurrence risk and appropriate monitoring for other chromosome 12 related disorders. Furthermore, oral calcium therapy was effective as an initial treatment for rickets in this instance.

The history of human populations in the Japanese Archipelago inferred from genome-wide SNP data with a special reference to the Ainu and the Ryukyuan populations.

The Japanese Archipelago stretches over 4000 km from north to south, and is the homeland of the three human populations; the Ainu, the Mainland Japanese and the Ryukyuan. The archeological evidence of human residence on this Archipelago goes back to >30 000 years, and various migration routes and root populations have been proposed. Here, we determined close to one million single-nucleotide polymorphisms (SNPs) for the Ainu and the Ryukyuan, and compared these with existing data sets. This is the first report of these genome-wide SNP data. Major findings are: (1) Recent admixture with the Mainland Japanese was observed for more than one third of the Ainu individuals from principal component analysis and frappe analyses; (2) The Ainu population seems to have experienced admixture with another population, and a combination of two types of admixtures is the unique characteristics of this population; (3) The Ainu and the Ryukyuan are tightly clustered with 100% bootstrap probability followed by the Mainland Japanese in the phylogenetic trees of East Eurasian populations. These results clearly support the dual structure model on the Japanese Archipelago populations, though the origins of the Jomon and the Yayoi people still remain to be solved.

Narcolepsy is strongly associated with the T-cell receptor alpha locus.

Narcolepsy with cataplexy, characterized by sleepiness and rapid onset into REM sleep, affects 1 in 2,000 individuals. Narcolepsy was first shown to be tightly associated with HLA-DR2 (ref. 3) and later sublocalized to DQB1*0602 (ref. 4). Following studies in dogs and mice, a 95% loss of hypocretin-producing cells in postmortem hypothalami from narcoleptic individuals was reported. Using genome-wide association (GWA) in Caucasians with replication in three ethnic groups, we found association between narcolepsy and polymorphisms in the TRA@ (T-cell receptor alpha) locus, with highest significance at rs1154155 (average allelic odds ratio 1.69, genotypic odds ratios 1.94 and 2.55, P < 10(-21), 1,830 cases, 2,164 controls). This is the first documented genetic involvement of the TRA@ locus, encoding the major receptor for HLA-peptide presentation, in any disease. It is still unclear how specific HLA alleles confer susceptibility to over 100 HLA-associated disorders; thus, narcolepsy will provide new insights on how HLA-TCR interactions contribute to organ-specific autoimmune targeting and may serve as a model for over 100 other HLA-associated disorders.