Comprehensive genomic analysis identifies pathogenic variants in maturity-onset diabetes of the young (MODY) patients in South India.

BACKGROUND: Maturity-onset diabetes of the young (MODY) is an early-onset, autosomal dominant form of non-insulin dependent diabetes. Genetic diagnosis of MODY can transform patient management. Earlier data on the genetic predisposition to MODY have come primarily from familial studies in populations of European origin. METHODS: In this study, we carried out a comprehensive genomic analysis of 289 individuals from India that included 152 clinically diagnosed MODY cases to identify variants in known MODY genes. Further, we have analyzed exome data to identify putative MODY relevant variants in genes previously not implicated in MODY. Functional validation of MODY relevant variants was also performed. RESULTS: We found MODY 3 (HNF1A; 7.2%) to be most frequently mutated followed by MODY 12 (ABCC8; 3.3%). They together account for ~ 11% of the cases. In addition to known MODY genes, we report the identification of variants in RFX6, WFS1, AKT2, NKX6-1 that may contribute to development of MODY. Functional assessment of the NKX6-1 variants showed that they are functionally impaired. CONCLUSIONS: Our findings showed HNF1A and ABCC8 to be the most frequently mutated MODY genes in south India. Further we provide evidence for additional MODY relevant genes, such as NKX6-1, and these require further validation.

Novel ABCC8 (SUR1) gene mutations in Asian Indian children with congenital hyperinsulinemic hypoglycemia.

Congenital hyperinsulinemic hypoglycemia (HI) is a heterogeneous genetic disorder of insulin secretion characterized by persistent hypoglycemia, most commonly associated with inactivating mutations of the ß-cell ATP-sensitive K(+) channel (K(ATP) channel) genes ABCC8 (encoding SUR1) and KCNJ11(encoding Kir6.2). This study aimed to screen the mutations in the genes associated with congenital HI in Asian Indian children. Recessive mutations of these genes cause hyperinsulinism that is unresponsive to treatment with channel agonists like diazoxide. Dominant K(ATP) mutations have been associated with diazoxide-responsive disease. The KCNJ11, ABCC8, GCK, HNF4A, and GLUD1 genes were analyzed by sequence analysis in 22 children with congenital HI. We found 10 novel mutations (c.1delA, c.61delG, c.267delT, c.619-629delCCCGAGGACCT, Gln444*, Leu724Pro, Ala847Thr, Trp898*, IVS30-2A>C, and Leu1454Arg) and two known mutations (Gly111Arg and Arg598*) in the ABCC8 gene. This study describes novel and known ABCC8 gene mutations in children with congenital HI. This is the first large genetic screening study on HI in India and our results will help clinicians in providing optimal treatment for patients with hyperinsulinemia and in assisting affected families with genetic counseling.

Glucokinase gene mutations (MODY 2) in Asian Indians.

BACKGROUND AND AIM: Heterozygous inactivating mutations in the glucokinase (GCK) gene cause a hyperglycemic condition termed maturity-onset diabetes of the young (MODY) 2 or GCK-MODY. This is characterized by mild, stable, usually asymptomatic, fasting hyperglycemia that rarely requires pharmacological intervention. The aim of the present study was to screen for GCK gene mutations in Asian Indian subjects with mild hyperglycemia. SUBJECTS AND METHODS: Of the 1,517 children and adolescents of the population-based ORANGE study in Chennai, India, 49 were found to have hyperglycemia. These children along with the six patients referred to our center with mild hyperglycemia were screened for MODY 2 mutations. The GCK gene was bidirectionally sequenced using BigDye(®) Terminator v3.1 (Applied Biosystems, Foster City, CA) chemistry. In silico predictions of the pathogenicity were carried out using the online tools SIFT, Polyphen-2, and I-Mutant 2.0 software programs. RESULTS: Direct sequencing of the GCK gene in the patients referred to our Centre revealed one novel mutation, Thr206Ala (c.616A>G), in exon 6 and one previously described mutation, Met251Thr (c.752T>C), in exon 7. In silico analysis predicted the novel mutation to be pathogenic. The highly conserved nature and critical location of the residue Thr206 along with the clinical course suggests that the Thr206Ala is a MODY 2 mutation. However, we did not find any MODY 2 mutations in the 49 children selected from the population-based study. Hence prevalence of GCK mutations in Chennai is <1:1,517. CONCLUSIONS: This is the first study of MODY 2 mutations from India and confirms the importance of considering GCK gene mutation screening in patients with mild early-onset hyperglycemia who are negative for ß-cell antibodies.

EIF2AK3 mutations in South Indian children with permanent neonatal diabetes mellitus associated with Wolcott-Rallison syndrome.

OBJECTIVE: This study describes the clinical and genetic evaluation of permanent neonatal diabetes due to Wolcott-Rallison syndrome (WRS) in south Indian consanguineous families. We aimed to evaluate the genetic basis of the disease in eight children with WRS from five South Indian families. PATIENTS AND METHODS: We studied eight children who presented with permanent neonatal diabetes from five South Indian families. Follow up clinical evaluation revealed features (like liver disease, skeletal dysplasia, and thyroid dysfunction) suggestive of WRS. All the coding exons along with splice sites of KCNJ11, ABCC8, INS, GCK and EIF2AK3 genes were sequenced in all the probands. RESULTS: Two novel homozygous mutations (Trp658Ser, c.3150+1G>T) and one known homozygous mutation (Arg1065*, c.3193C>T) in EIF2AK3 gene were identified in children with WRS. Mutation Arg1065*was identified in four children. CONCLUSIONS: Our results in these families show that the mutations in homozygous state are likely to be causative. We suggest the screening for EIF2AK3 gene mutations as WRS is now recognized as the most frequent cause of neonatal diabetes in children with consanguineous parents. As the mode of inheritance is recessive, screening for genetic mutations becomes important to aid in risk prediction and clinical management.

Clinical profile and outcome of infantile onset diabetes mellitus in southern India.

OBJECTIVE: To study the etiology, clinical presentation and outcome of infantile onset diabetes mellitus (IODM). DESIGN: Descriptive cohort study. Retrospective study from 1999-2007 and prospective from 2008-2012. SETTING: The diabetic clinic at a Pediatric tertiary care referral institute in Chennai. METHODS: All infants diagnosed to have diabetes at less than one year of age were studied. Study variables were age at onset, gender, mode of presentation, birth weight, initial blood glucose, serum HbA1c, serum c peptide levels, outcome at initial presentation, insulin requirement, associated comorbid conditions, genetic analysis and outcome at the end of the study or until they were followed up. RESULTS: 40 infants with infantile onset diabetes were studied, constituting 8% of all children with onset of DM at less than 12 years of age. 67.5% of these children presented with diabetic keto acidosis (DKA), only 30% had a provisional diagnosis of DM or DKA at first physician contact. 63% of IODM with onset less than 6 months and 30% with onset more than 6 months were of low birth weight. Nearly 85% of the study group had low C-peptide levels. 84.5% of IODM with onset less than 6 months and 55% of those with onset more than 6 months were monogenic. Wolcott Rallison syndrome was the commonest type encountered. Genetic diagnosis aided switching over from insulin to oral sulphonylurea in 5 children with KCNJ11 and ABCC8 mutations. Missed diagnosis, recurrent admissions for metabolic instability and developmental delay were common problems in IODM. Mortality at 12.5 year follow up was 32.5%. CONCLUSIONS: IODM with onset at less than 6 months is predominantly monogenic and low birth weight is more common. 55% of IODM were misdiagnosed at onset. Developmental delay is the common co morbid condition in IODM. Genetic diagnosis aids change of therapy to oral sulphonylurea.