Spy1 Interacts with p27(Kip1) to Allow G(1)/S Progression

Progression through the G(1)/S transition commits cells to synthesize DNA. Cyclin dependent kinase 2 (CDK2) is the major kinase that allows progression through G(1)/S phase and subsequent replication events. p27 is a CDK inhibitor (CKI) that binds to CDK2 to prevent premature activation of this kinase. Speedy (Spy1), a novel cell cycle regulatory protein, has been found to prematurely activate CDK2 when microinjected into Xenopus oocytes and when expressed in mammalian cells. To determine the mechanism underlying Spy1-induced proliferation in mammalian cell cycle regulation, we used human Spy1 as bait in a yeast two-hybrid screen to identify interacting proteins. One of the proteins isolated was p27; this novel interaction was confirmed both in vitro, using bacterially expressed and in vitro translated proteins, and in vivo, through the examination of endogenous and transfected proteins in mammalian cells. We demonstrate that Spy1 expression can overcome a p27-induced cell cycle arrest to allow for DNA synthesis and CDK2 histone H1 kinase activity. In addition, we utilized p27-null cells to demonstrate that the proliferative effect of Spy1 depends on the presence of endogenous p27. Our data suggest that Spy1 associates with p27 to promote cell cycle progression through the G(1)/S transition

The tumor suppressor tuberin regulates mitotic onset through the cellular localization of cyclin B1

Tuberous sclerosis is a multi-organ disorder characterized by the formation of benign tumors, called hamartomas, which affect more than 1 million people worldwide. The syndrome is initiated by a mutation in one of two tumor suppressor genes, TSC1 or TSC2 which encode for the proteins hamartin and tuberin, respectively. Herein we demonstrate that tuberin binds and regulates the G(2)/M cyclin, cyclin B1. We have determined that this binding region encompasses a mutational hotspot within tuberin implicated in some of the most severe cases of TS. Mimicking a mutation found in a subset of patients with Tuberous sclerosis we found a significant reduction in the binding between tuberin and cyclin B1. Functionally, our data supports that tuberin plays a role in regulating the cellular localization of cyclin B1. These results demonstrate a novel and clinically relevant mechanism where tuberin functions in mitotic onset

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

Abstract 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

Additional file 1: Table S1a. of Comprehensive genomic analysis identifies pathogenic variants in maturity-onset diabetes of the young (MODY) patients in South India

Sample information and clinical characteristics. Table S1b. Summary of clinical characteristics of MODY patient samples. Table S2a. Sequencing statistics of combined exome and WGS. Table S2b. Sequencing statistics of targeted exome samples. Table S3. Targeted gene panel. Table S4. Candidate variants identified in MODY samples. Table S5. Differentially expressed genes - NKX6–1 (XLS 292 kb

Additional file 2: Figure S1. of Comprehensive genomic analysis identifies pathogenic variants in maturity-onset diabetes of the young (MODY) patients in South India

Box plot showing (a) fasting plasma glucose, (b) fasting insulin, (c) C-peptide fasting, (d) C-peptide stimulated and (e) creatinine in MODY and control samples. The median value is shown as a line with the whiskers extending from the highest value within 1.5 * IQR of the third quartile to the lowest value within 1.5 * IQR of the first quartile where IQR is the inter-quartile range. Figure S2. Heatmap depicting the genotype based identity of the discovery and validation MODY cohort and control samples. Genomic regions for which we obtained data for the validation cohort samples and corresponding regions from the discovery set samples using GATK joint-variant caller. The sample identity was computed based on the high-confidence set of single nucleotide variants (SNVs) that passed GATK Hard-Filtering criteria. Figure S3. Expression level of mouse Nkx6–1 (top) or human NKX6–1 (bottom) following induction in cells stably expressing the indicated variant or wildtype. Figure S4. Western blot showing the expression of NKX6–1 48 h post dox induction. Hsp90 was used as a loading control. (ZIP 5136 kb