ß-Cell-Specific Mafk Overexpression Impairs Pancreatic Endocrine Cell Development.

The MAF family transcription factors are homologs of v-Maf, the oncogenic component of the avian retrovirus AS42. They are subdivided into 2 groups, small and large MAF proteins, according to their structure, function, and molecular size. MAFK is a member of the small MAF family and acts as a dominant negative form of large MAFs. In previous research we generated transgenic mice that overexpress MAFK in order to suppress the function of large MAF proteins in pancreatic ß-cells. These mice developed hyperglycemia in adulthood due to impairment of glucose-stimulated insulin secretion. The aim of the current study is to examine the effects of ß-cell-specific Mafk overexpression in endocrine cell development. The developing islets of Mafk-transgenic embryos appeared to be disorganized with an inversion of total numbers of insulin+ and glucagon+ cells due to reduced ß-cell proliferation. Gene expression analysis by quantitative RT-PCR revealed decreased levels of ß-cell-related genes whose expressions are known to be controlled by large MAF proteins. Additionally, these changes were accompanied with a significant increase in key ß-cell transcription factors likely due to compensatory mechanisms that might have been activated in response to the ß-cell loss. Finally, microarray comparison of gene expression profiles between wild-type and transgenic pancreata revealed alteration of some uncharacterized genes including Pcbd1, Fam132a, Cryba2, and Npy, which might play important roles during pancreatic endocrine development. Taken together, these results suggest that Mafk overexpression impairs endocrine development through a regulation of numerous ß-cell-related genes. The microarray analysis provided a unique data set of differentially expressed genes that might contribute to a better understanding of the molecular basis that governs the development and function of endocrine pancreas.

Localization of sugar residues in the stomach of three species of monkeys (Tupaiidae glis, Nycticebus cocang and Callithrix jacchus) by lectin histochemistry / Localización de los residuos de azúcar en el estómago de tres especies de monos (Tupaiidae glis, Nycticebus cocang y Callithrix jacchus) por histoquímica de lectina

The stomach of three species of non-human primates was investigated by lectin histochemistry to clarify the staining affinity and distribution patterns of their sugar residues. All gastric regions, with little differences between the deep and superficial parts of the same region, were rich in. in N-acetylglucosamine and/or neuraminic acid. Although, the superficial regions of the gastric mucosa were scanty in N-acetylgalactosamine, a- D-glucose and a -D-mannose, the deep parts of the gastric mucosa were rich in these sugars. In conclusion, there is a difference among the mucosubstances of surface and foveolar mucous cells, mucous neck cells, and gastric gland cells. This indicates heterogeneous composition of gastric mucus, or mucus molecules with variations in the degree of glycosylation of their oligosaccharide chains in the different cells which suggest that lectin binding affinity in the gastric mucosa correlated mostly to the degree of cellular differentiation.

El estómago de tres especies de primates no humanos fue investigado por histoquímica de lectinas para determinar la afinidad de tinción y los patrones de distribución de sus residuos de azúcar. Todas las regiones gástricas, con pequeñas diferencias entre las partes profundas y superficiales de la misma región, eran ricas en N-acetilglucosamina y/o ácido neuramínico. Si bien, las regiones superficiales de la mucosa gástrica eran escasas en N-acetilgalactosamina, a-D-glucosa y a-D-manosa, las partes profundas de la mucosa gástrica eran ricas en estos azúcares. En conclusión, existe una diferencia entre las mucosustancias de la superficie y células mucosas foveolares, células mucosas del cuello y células de las glándulas gástricas. Esto indica una composición heterogénea de la mucosa gástrica, o moléculas de moco con variaciones en el grado de glicosilación de sus cadenas de oligosacáridos en las diferentes células, sugieriendo que la afinidad de union de lectinas en la mucosa gástrica se relacionada principalmente con el grado de diferenciación celular.