Project description:A genome-wide association study in the Chinese Han population has identified several novel genetic variants of the serine racemase (SRR) gene in type 2 diabetes. Our purpose was to systematically evaluate the contribution of SRR variants in the Chinese Han population. rs391300 and rs4523957 in SRR were genotyped respectively in the two independent populations. A meta-analysis was used to estimate the effects of SRR in 21,305 Chinese Han individuals. Associations between single-nucleotide polymorphisms and diabetes-related phenotypes were analyzed among 2,615 newly diagnosed type 2 diabetes patients and 5,029 controls. Neither rs391300 nor rs4523957 were associated with type 2 diabetes in populations. Furthermore, meta-analysis did not confirm an association between type 2 diabetes and SRR. In the controls, rs391300-A and rs4523957-G were associated with higher 30-min plasma glucose in an oral glucose tolerance test. The present study did not confirm that SRR was associated with type 2 diabetes.
Project description:A mesiodens is a supernumerary tooth located in the midline of the premaxilla. To investigate the genetic cause of mesiodens, clinical and radiographic examination were performed on 23 family members of a two-generation Hmong family. Whole exome sequencing (WES) or Sanger sequencing were performed in 22 family members and two unrelated Thai patients with mesiodens. WES in the Hmong family revealed a missense mutation (c.1807G>A;p.Glu603Lys) in PTPN23 in seven affected members and six unaffected members. The mode of inheritance was autosomal dominance with incomplete penetrance (53.84%). Two additional mutations in PTPN23, c.2248C>G;p.Pro750Ala and c.3298C>T;p.Arg1100Cys were identified in two unrelated patients with mesiodens. PTPN23 is a regulator of endosomal trafficking functioning to move activated membrane receptors, such as EGFR, from the endosomal sorting complex towards the ESCRT-III complex for multivesicular body biogenesis, lysosomal degradation, and subsequent downregulation of receptor signaling. Immunohistochemical study and RNAscope on developing mouse embryos showed broad expression of PTPN23 in oral tissues, while immunofluorescence showed that EGFR was specifically concentrated in the midline epithelium. Importantly, PTPN23 mutant protein was shown to have reduced phosphatase activity. In conclusion, mesiodens were associated with genetic variants in PTPN23, suggesting that mesiodens may form due to defects in endosomal trafficking, leading to disrupted midline signaling.
Project description:Genetic variations were successfully associated among patients with coronary artery disease using Illumina Cardiometabochip containing 1,96,725 SNPs Illumina Cardio-metabochip is a custom designed SNP microarray containing 1,96,725 SNPs designed by several GWAS and consortia
Project description:Prevalence of diabetes and obesity in Mexican Pima Indians is low, while prevalence in US Pima Indians is high. Although lifestyle likely accounts for much of the difference, the role of genetic factors is not well explored. To examine this, we genotyped 359 single nucleotide polymorphisms, including established type 2 diabetes and obesity variants from genome-wide association studies (GWAS) and 96 random markers, in 342 Mexican Pimas. A multimarker risk score of obesity variants was associated with body mass index (BMI; β = 0.81 kg/m2 per SD, P = 0.0066). The mean value of the score was lower in Mexican Pimas than in US Pimas (P = 4.3 × 10-11 ), and differences in allele frequencies at established loci could account for approximately 7% of the population difference in BMI; however, the difference in risk scores was consistent with evolutionary neutrality given genetic distance. To identify loci potentially under recent natural selection, allele frequencies at 283 variants were compared between US and Mexican Pimas, accounting for genetic distance. The largest differences were seen at HLA markers (e.g., rs9271720, difference = 0.75, P = 8.7 × 10-9 ); genetic distances at HLA were greater than at random markers (P = 1.6 × 10-46 ). Analyses of GWAS data in 937 US Pimas also showed sharing of alleles identical by descent at HLA that exceeds its genomic expectation (P = 7.0 × 10-10 ). These results suggest that, in addition to the widely recognized balancing selection at HLA, recent directional selection may also occur, resulting in marked allelic differentiation between closely related populations.
Project description:AIMS AND HYPOTHESIS:Variants of the FTO (fat mass and obesity associated) gene are associated with obesity and type 2 diabetes in white Europeans, but these associations are not consistent in Asians. A recent study in Asian Indian Sikhs showed an association with type 2 diabetes that did not seem to be mediated through BMI. We studied the association of FTO variants with type 2 diabetes and measures of obesity in South Asian Indians in Pune. METHODS:We genotyped, by sequencing, two single nucleotide polymorphisms, rs9939609 and rs7191344, in the FTO gene in 1,453 type 2 diabetes patients and 1,361 controls from Pune, Western India and a further 961 population-based individuals from Mysore, South India. RESULTS:We observed a strong association of the minor allele A at rs9939609 with type 2 diabetes (OR per allele 1.26; 95% CI 1.13-1.40; p = 3 x 10(-5)). The variant was also associated with BMI but this association appeared to be weaker (0.06 SDs; 95% CI 0.01-0.10) than the previously reported effect in Europeans (0.10 SDs; 95% CI 0.09-0.12; heterogeneity p = 0.06). Unlike in the Europeans, the association with type 2 diabetes remained significant after adjusting for BMI (OR per allele for type 2 diabetes 1.21; 95% CI 1.06-1.37; p = 4.0 x 10(-3)), and also for waist circumference and other anthropometric variables. CONCLUSIONS:Our study replicates the strong association of FTO variants with type 2 diabetes and similar to the study in North Indians Sikhs, shows that this association may not be entirely mediated through BMI. This could imply underlying differences between Indians and Europeans in the mechanisms linking body size with type 2 diabetes.
Project description:BackgroundThe ABCC8 gene which encodes the sulfonylurea receptor plays a major role in insulin secretion and is a potential candidate for type 2 diabetes. The -3c → t (rs1799854) and Thr759Thr (C → T, rs1801261) single nucleotide polymorphisms (SNPs) of the ABCC8 gene have been associated with type 2 diabetes in many populations. The present study was designed to investigate the association of these two SNPs in an Asian Indian population from south India.Materials and methodsA total of 1,300 subjects, 663 normal glucose tolerant (NGT) and 637 type 2 diabetic subjects were randomly selected from the Chennai Urban Rural Epidemiology Study (CURES). The -3c → t and Thr759Thr were genotyped in these subjects using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and a few variants were confirmed by direct sequencing.ResultsThe frequency of the 't' allele of the -3c → t SNP was found to be 0.27 in NGT and 0.29 in type 2 diabetic subjects (P = 0.44). There was no significant difference in the genotypic frequency between the NGT and type 2 diabetic group (P = 0.18). Neither the genotypic frequency nor the allele frequency of the Thr759Thr polymorphism was found to differ significantly between the NGT and type 2 diabetic groups.ConclusionThe -3c → t and the Thr759Thr polymorphisms of the ABCC8 gene were not associated with type 2 diabetes in this study. However, an effect of these genetic variants on specific unidentified sub groups of type 2 diabetes cannot be excluded.
Project description:Abnormal N-methyl-D-aspartate receptor (NMDAR) function has been implicated in the pathophysiology of schizophrenia. D-serine is an important NMDAR modulator, and to elucidate the role of the D-serine synthesis enzyme serine racemase (Srr) in schizophrenia, we identified and characterized mice with an ENU-induced mutation that results in a complete loss of Srr activity and drastically reduced D-serine levels. Mutant mice displayed behaviors relevant to schizophrenia, including impairments in prepulse inhibition, sociability and spatial discrimination. Behavioral deficits were rescued by D-serine and the atypical antipsychotic clozapine, and were conversely, amplified by NMDAR inhibition. Expression profiling revealed that the Srr mutation influenced several genes that have been linked to schizophrenia and cognitive ability. Furthermore, analysis of Srr genetic variants in humans identified a robust association with schizophrenia. This study demonstrates that aberrant serine racemase function and diminished D-serine may contribute to schizophrenia pathogenesis, and that D-serine may be a beneficial form of treatment Keywords: genetic-mutant vs. wildtype comparison
Project description:ContextKrüppel-like factor 11 (KLF11) is a transcription factor of the zinc finger domain family that has been shown to regulate expression of the insulin gene. An initial study reported that a KLF11 variant predicting a Q62R was associated with type 2 diabetes (T2D) in French Caucasians; however, subsequent studies have failed to identify an association between this variant and T2D in subjects from a similar Northern-European ancestry.ObjectiveWe sought to determine whether the Q62R or other variants within KLF11 were associated with T2D in Pima Indians, a population with an extremely high prevalence of this disease.Design, setting, and subjectsKLF11 was sequenced in 24 Pima Indians to identify potentially novel variants. There were 18 variants genotyped in a family-based sample of 1337 Pima Indians to analyze the linkage disequilibrium pattern of this gene and identify representative variants. Four representative variants were further genotyped in a population-based sample of 3501 full-heritage Pima Indians for association analyses. Among these subjects, 413 had undergone metabolic studies when they were nondiabetic to measure traits that predict T2D.ResultsNeither the Q62R nor any other common variant in KLF11 was associated with T2D in the Pima population. In addition, no variant was associated with insulin secretion or insulin-stimulated glucose disposal rate.ConclusionsCommon variation in KLF11 variation does not appear to influence the population-based risk for developing T2D among full-heritage Pima Indians. Thus, KLF11 is unlikely to play a major role in the etiology of T2D among this Native American population.
Project description:BackgroundThere has been no systematic evaluation of the association between genetic variants of type 2 receptor for TNFα (TNFR2) and type 2 diabetes, despite strong biological evidence for the role of this receptor in the pathogenesis of this complex disorder. In view of this, we performed a comprehensive association analysis of TNFRSF1B variants with type 2 diabetes in 4,200 Indo-European subjects from North India.MethodsThe initial phase evaluated association of seven SNPs viz. rs652625, rs496888, rs6697733, rs945439, rs235249, rs17883432 and rs17884213 with type 2 diabetes in 2,115 participants (1,073 type 2 diabetes patients and 1,042 control subjects). Further, we conducted replication analysis of three associated SNPs in 2,085 subjects (1,047 type 2 diabetes patients and 1,038 control subjects).ResultsWe observed nominal association of rs945439, rs235249 and rs17884213 with type 2 diabetes (P < 0.05) in the initial phase. Haplotype CC of rs945439 and rs235249 conferred increased susceptibility for type 2 diabetes [OR = 1.19 (95%CI 1.03-1.37), P = 0.019/Pperm = 0.076] whereas, TG haplotype of rs235249 and rs17884213 provided protection against type 2 diabetes [OR = 0.83 (95%CI 0.72-0.95, P = 7.2 × 10-3/Pperm = 0.019]. We also observed suggestive association of rs496888 with plasma hsCRP levels [P = 0.042]. However, the association of rs945439, rs235249 and rs17884213 with type 2 diabetes was not replicated in the second study population. Meta-analysis of the two studies also failed to detect any association with type 2 diabetes.ConclusionsOur two-stage association analysis suggests that TNFRSF1B variants are not the determinants of genetic risk of type 2 diabetes in North Indians.
Project description:Human serine racemase (hSR) catalyses racemisation of L-serine to D-serine, the latter of which is a co-agonist of the NMDA subtype of glutamate receptors that are important in synaptic plasticity, learning and memory. In a 'closed' hSR structure containing the allosteric activator ATP, the inhibitor malonate is enclosed between the large and small domains while ATP is distal to the active site, residing at the dimer interface with the Tyr121 hydroxyl group contacting the α-phosphate of ATP. In contrast, in 'open' hSR structures, Tyr121 sits in the core of the small domain with its hydroxyl contacting the key catalytic residue Ser84. The ability to regulate SR activity by flipping Tyr121 from the core of the small domain to the dimer interface appears to have evolved in animals with a CNS. Multiple X-ray crystallographic enzyme-fragment structures show Tyr121 flipped out of its pocket in the core of the small domain. Data suggest that this ligandable pocket could be targeted by molecules that inhibit enzyme activity.