Identification of four novel mutations in the HNF-1A gene in Chinese early-onset and/or multiplex diabetes pedigrees:

Mutations in HNF1A Gene are not a Common Cause of Familial Young-Onset Diabetes in Iran

Mutations in hepatocyte nuclear factor-1 alpha (HNF1A) as a homeodomain transcription factor which regulates variety of genes, are the most common cause of maturity-onset diabetes of the young (MODY). Detection of HNF1A mutations not only classifies the subtype, but also predicts the likely clinical course and may alters the method of treatment from insulin to the oral sulphonylureas, which is shown to improve glycemic control. The coding and promoter regions of HNF1A gene were screened for mutations in 34 unrelated Iranian MODY patients. We identified one novel missense mutation (C49G) and two novel polymorphisms and 8 recently identified SNPs in the HNF1A gene. It is possible that in Iran, other yet to be identified genes are responsible for the familial young onset diabetes. Hence, there is a need for more extensive genetic analyses in Iranian patients with familial young onset diabetes.

Trans-ethnic fine mapping identifies a novel independent locus at the 3' end of CDKAL1 and novel variants of several susceptibility loci for type 2 diabetes in a Han Chinese population

AIMS/HYPOTHESIS

Candidate gene and genome-wide association studies have identified ∼60 susceptibility loci for type 2 diabetes. A majority of these loci have been discovered and tested only in European populations. The aim of this study was to assess the presence and extent of trans-ethnic effects of these loci in an East Asian population.

METHODS

A total of 9,335 unrelated Chinese Han individuals, including 4,535 with type 2 diabetes and 4,800 non-diabetic ethnically matched controls, were genotyped using the Illumina 200K Metabochip. We tested 50 established loci for type 2 diabetes and related traits (fasting glucose, fasting insulin, 2 h glucose). Disease association with the additive model of inheritance was analysed with logistic regression.

RESULTS

We found that 14 loci significantly transferred to the Chinese population, with two loci (p = 5.7 × 10(-12) for KCNQ1; p = 5.0 × 10(-8) for CDKN2A/B-CDKN2BAS) reaching independent genome-wide statistical significance. Five of these 14 loci had similar lead single-nucleotide polymorphisms (SNPs) as were found in the European studies while the other nine were different. Further stepwise conditional analysis identified a total of seven secondary signals and an independent novel locus at the 3' end of CDKAL1.

CONCLUSIONS/INTERPRETATION

These results suggest that many loci associated with type 2 diabetes are commonly shared between European and Chinese populations. Identification of population-specific SNPs may increase our understanding of the genetic architecture underlying type 2 diabetes in different ethnic populations.

Variants of the HNF1α gene: A molecular approach concerning diabetic patients from southern Brazil

Maturity Onset Diabetes of the Young (MODY) presents monogenic inheritance and mutation factors which have already been identified in six different genes. Given the wide molecular variation present in the hepatocyte nuclear factor-1α gene (HNF1α) MODY3, the aim of this study was to amplify and sequence the coding regions of this gene in seven patients from the Campos Gerais region, Paraná State, Brazil, presenting clinical MODY3 features. Besides the synonymous variations, A15A, L17L, Q141Q, G288G and T515T, two missense mutations, I27L and A98V, were also detected. Clinical and laboratory data obtained from patients were compared with the molecular findings, including the I27L polymorphism that was revealed in some overweight/obese diabetic patients of this study, this corroborating with the literature. We found certain DNA variations that could explain the hyperglycemic phenotype of the patients.

Gender-Dependent Penetrance of Small Heterodimer Partner (SHP) Gene Deficiency in Overweight/Obese Chinese Pedigrees

Mutations of the small heterodimer partner ( SHP) gene have been associated with mild obesity in Japanese subjects. This study was designed to investigate whether there was a similar association in 772 Chinese adults. A total of 272 subjects were normal weight, 423 were overweight and 77 were obese. Four non-synonymous mutations (R34X, H53fsdel10, G171A, G189E) were identified in 10 out of the 500 overweight/obese subjects, but were not seen in the normal weight controls (prevalence 2.00% versus 0.00%, respectively). The relatives of proband carriers, including 25 carriers and 33 non-carriers from three generations, were also screened for 10 multigenerational non-consanguineous pedigrees. A gender-dependent penetrance effect was observed in the pedigrees. Furthermore, the frequency of SHP gene mutations was significantly higher in those with type 2 diabetes compared with the non-diabetics (61.5% versus 28.1%, respectively). These data provide evidence of a gender-dependent effect on penetrance for SHP deficiency and suggest that SHP mutations increase susceptibility to type 2 diabetes.