Isolation of a cDNA Encoding Chicken Insulin Precursor

Hasegawa, Shin; Honda, Kazuhisa; Nata, Koji; Yonekura, Hideto; Okamoto, Hiroshi; Hikami, Yuzo

doi:10.2508/chikusan.62.867

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“…Surprisingly, none of these exons coincides with the previously predicted exon 1 based on the genomic sequence of the chicken preproinsulin 5Ј-flanking region (11). Thus far, only a partial chicken cDNA from pancreas had been reported (47). Moreover, we did not find the exon 1 A or 1 B sequences within the ϳ600 bp of the chicken 5Ј-flanking genomic preproinsulin provided by Soares et al (48), suggesting that both exons are located upstream from this region.…”

Section: Discussioncontrasting

confidence: 62%

Unprocessed Proinsulin Promotes Cell Survival During Neurulation in the Chick Embryo

et al. 2002

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We have chosen a vertebrate model accessible during neurulation, the chick, for analysis of endogenous insulin signaling and its contribution to early embryonic cell survival. Unlike rodents, humans and chickens have a single preproinsulin gene, facilitating its prepancreatic expression characterization. We show that in vivo interference with embryonic insulin signaling using antisense oligonucleotides against the insulin receptor increases apoptosis during neurulation. In contrast, high glucose administration does not increase the level of apoptosis in culture or in vivo. Exogenous insulin and, remarkably, proinsulin achieve similar survival protective effects at 10 ؊8 mol/l. The low abundant preproinsulin mRNA from the prepancreatic embryo is translated to a protein that remains as unprocessed proinsulin. This concurs with the absence of prohormone convertase 2 (PC2) in the embryo, whereas PC2 is present later in embryonic pancreas. A C-peptidespecific antibody stains proinsulin-containing neuroepithelial cells of the chick embryo in early neurulation, as well as other cells in mesoderm-and endoderm-derived structures in the 2.5-day embryo. We have determined by 5-RACE (rapid amplification of cDNA ends), and confirmed by RNase protection assay, that prepancreatic and pancreatic proinsulin mRNA differ in their first exon, suggesting differential transcriptional regulation. All these data support the role of endogenous proinsulin in cell survival in the chick embryo during important pathophysiologic periods of early development.

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Section: Discussioncontrasting

confidence: 62%