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Articles by O Smirnova
Total Records ( 3 ) for O Smirnova
  R Bhandare , J Schug , J Le Lay , A Fox , O Smirnova , C Liu , A Naji and K. H. Kaestner
 

The global diabetes epidemic poses a major challenge. Epigenetic events contribute to the etiology of diabetes; however, the lack of epigenomic analysis has limited the elucidation of the mechanistic basis for this link. To determine the epigenetic architecture of human pancreatic islets we mapped the genome-wide locations of four histone marks: three associated with gene activation—H3K4me1, H3K4me2, and H3K4me3—and one associated with gene repression, H3K27me3. Interestingly, the promoters of the highly transcribed insulin and glucagon genes are occupied only sparsely by H3K4me2 and H3K4me3. Globally, we identified important relationships between promoter structure, histone modification, and gene expression. We demonstrated co-occurrences of histone modifications including bivalent marks in mature islets. Furthermore, we found a set of promoters that is differentially modified between islets and other cell types. We also use our histone marks to determine which of the known diabetes-associated single-nucleotide polymorphisms are likely to be part of regulatory elements. Our global map of histone marks will serve as an important resource for understanding the epigenetic basis of type 2 diabetes.

  S Rieck , P White , J Schug , A. J Fox , O Smirnova , N Gao , R. K Gupta , Z. V Wang , P. E Scherer , M. P Keller , A. D Attie and K. H. Kaestner
 

The inability of the ß-cell to meet the demand for insulin brought about by insulin resistance leads to type 2 diabetes. In adults, ß-cell replication is one of the mechanisms thought to cause the expansion of ß-cell mass. Efforts to treat diabetes require knowledge of the pathways that drive facultative ß-cell proliferation in vivo. A robust physiological stimulus of ß-cell expansion is pregnancy and identifying the mechanisms underlying this stimulus may provide therapeutic leads for the treatment of type 2 diabetes. The peak in ß-cell proliferation during pregnancy occurs on d 14.5 of gestation in mice. Using advanced genomic approaches, we globally characterize the gene expression signature of pancreatic islets on d 14.5 of gestation during pregnancy. We identify a total of 1907 genes as differentially expressed in the islet during pregnancy. The islet’s ability to compensate for relative insulin deficiency during metabolic stress is associated with the induction of both proliferative and survival pathways. A comparison of the genes induced in three different models of islet expansion suggests that diverse mechanisms can be recruited to expand islet mass. The identification of many novel genes involved in islet expansion during pregnancy provides an important resource for diabetes researchers to further investigate how these factors contribute to the maintenance of not only islet mass, but ultimately ß-cell mass.

  N Gao , J Le Lay , W Qin , N Doliba , J Schug , A. J Fox , O Smirnova , F. M Matschinsky and K. H. Kaestner
 

Foxa1 and Foxa2 play both redundant and distinct roles in early pancreas development. We demonstrate here that inducible ablation of both transcription factors in mature mouse β-cells leads to impaired glucose homeostasis and insulin secretion. The defects in both glucose-stimulated insulin secretion and intracellular calcium oscillation are more pronounced than those in β-cells lacking only Foxa2. Unexpectedly, in contrast to the severe reduction of β-cell-enriched factors contributing to metabolic and secretory pathways, expression of a large number of genes that are involved in neural differentiation and function is significantly elevated. We further demonstrate that expression of carbohydrate response element-binding protein (ChREBP or Mlxipl), an important transcriptional regulator of carbohydrate metabolism, is significantly affected in compound Foxa1/a2 mutant β-cells. ChREBP expression is directly controlled by Foxa1 and Foxa2 in both the fetal endocrine pancreas as well as mature islets. These data demonstrate that Foxa1 and Foxa2 play crucial roles in the development and maintenance of β-cell-specific secretory and metabolic pathways.

 
 
 
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