No abstract

To date, most genome-wide association studies (GWAS) and studies of fine-scale population structure have been conducted primarily on Europeans. Han Chinese, the largest ethnic group in the world, composing 20% of the entire global human population, is largely underrepresented in such studies. A well-recognized challenge is the fact that population structure can cause spurious associations in GWAS. In this study, we examined population substructures in a diverse set of over 1700 Han Chinese samples collected from 26 regions across China, each genotyped at approximately 160K single-nucleotide polymorphisms (SNPs). Our results showed that the Han Chinese population is intricately substructured, with the main observed clusters corresponding roughly to northern Han, central Han, and southern Han. However, simulated case-control studies showed that genetic differentiation among these clusters, although very small (F(ST) = 0.0002 approximately 0.0009), is sufficient to lead to an inflated rate of false-positive results even when the sample size is moderate. The top two SNPs with the greatest frequency differences between the northern Han and southern Han clusters (F(ST) > 0.06) were found in the FADS2 gene, which associates with the fatty acid composition in phospholipids, and in the HLA complex P5 gene (HCP5), which associates with HIV infection, psoriasis, and psoriatic arthritis. Ingenuity Pathway Analysis (IPA) showed that most differentiated genes among clusters are involved in cardiac arteriopathy (p < 10(-101)). These signals indicating significant differences among Han Chinese subpopulations should be carefully explained in case they are also detected in association studies, especially when sample sources are diverse.

Published reports of functional abnormalities in schizophrenia remain divergent due to lack of staging point-of-view and whole-brain analysis. To identify key functional-connectivity differences of first-episode (FE) and chronic patients from controls using resting-state functional MRI, and determine changes that are specifically associated with disease onset, a clinical staging model is adopted. We analyze functionalconnectivity differences in prodromal, FE (mostly drug naïve), and chronic patients from their matched controls from 6 independent datasets involving a total of 789 participants (343 patients). Brain-wide functional-connectivity analysis was performed in different datasets and the results from the datasets of the same stage were then integrated by meta-analysis, with Bonferroni correction for multiple comparisons. Prodromal patients differed from controls in their pattern of functionalconnectivity involving the inferior frontal gyri (Broca's area). In FE patients, 90% of the functional-connectivity changes involved the frontal lobes, mostly the inferior frontal gyrus including Broca's area, and these changes were correlated with delusions/blunted affect. For chronic patients, functionalconnectivity differences extended to wider areas of the brain, including reduced thalamo-frontal connectivity, and increased thalamo-temporal and thalamo-sensorimoter connectivity that were correlated with the positive, negative, and general symptoms, respectively. Thalamic changes became prominent at the chronic stage. These results provide evidence for distinct patterns of functional-dysconnectivity across FE and chronic stages of schizophrenia. Importantly, abnormalities in the frontal language networks appear early, at the time of disease onset. The identification of stage-specific pathological processes may help to understand the disease course of schizophrenia and identify neurobiological markers crucial for early diagnosis.

Autism is a pervasive neurodevelopmental disorder, with a significant role of genetic factors in its development. The neuropilin-2 (NRP2) gene is localized to 2q34, an autism susceptibility locus. NRP2 has been demonstrated to both guide axons and to control neuronal migration in the central nervous system. It has been reported that NRP2 may be required in vivo for sorting migrating cortical and striatal interneurons to their correct destination. We examine the association between the NRP2 gene and autism using a cohort of 169 Chinese Han family trios. Four single nucleotide polymorphisms (SNPs) were genotyped by the polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) analyses. The transmission disequilibrium tests (TDT) of SNPs and haplotype association were carried out using the TDTPHASE program. We found significant genetic association between autism and two of the SNPs of the NRP2 gene (rs849578: P = 0.017, rs849563: P = 0.027), as well as specific haplotypes, especially those formed by rs849563. Furthermore, haplotypes constructed with all markers showed significant excess transmission in both global and individual haplotype analyses (P = 0.004 and 0.017, respectively). The polymorphisms in the NRP2 gene are associated with autism, implying that the NRP2 gene may render individuals to be predisposed to autism.

Several genomewide screens indicated that chromosome 7q was linked to autistic disorder. FOXP2, located on 7q31, is a putative transcription factor containing a polyglutamine tract and a forkhead DNA binding domain. It is one member of the forkhead family who are known to be key regulators of embryogenesis. A point mutation at a highly conserved residue within the forkhead domain co-segregated with affected status in the KE family who was a unique three generation pedigree with a severe speech and language disorder and FOXP2 was directly disrupted by a translocation in an individual who had similar deficits as those of the KE family. Several studies have investigated the role of FOXP2 polymorphisms in autism and none of them found positive association. We performed a family-based association study of three single nucleotide polymorphisms (SNPs) of FOXP2 in 181 Chinese Han trios using the analyses of transmission/disequilibrium test (TDT) and haplotype. We found a significant association between autistic disorder and one SNP, as well as with specific haplotypes formed by this SNP with two other SNPs we investigated. Our findings suggest that the FOXP2 gene may be involved in the pathogenesis of autism in Chinese population.