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Expression of homeobox genes, including an insulin promoting factor, in the murine yolk sac at the time of hematopoietic initiation
Author(s) -
McGrath Kathleen E.,
Palis James
Publication year - 1997
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/(sici)1098-2795(199710)48:2<145::aid-mrd1>3.0.co;2-s
Subject(s) - biology , homeobox , yolk sac , gene , haematopoiesis , hnf1b , microbiology and biotechnology , homeobox a1 , genetics , dlx5 , insulin , oocyte , embryo , gene expression , endocrinology , stem cell
The visceral yolk sac (YS), a simple bilayer structure formed during gastrulation, supplies blood cells and intestine‐ and liver‐like functions to support embryonic growth. To better understand gene regulation in extraembryonic tissues, we examined the early murine YS for expression of the homeobox family of developmental transcription regulators. We identified a subset of known homeobox sequences (Hox a1, b1, a9, c9, a7, b7, b8, a10, cdx‐1, and PDX‐1), as well as two novel homeodomains consisting of a fourth labial class Hox genes and one that matches the Antennapedia class on the amino acid level. The two most frequently isolated YS Hox genes, a9 and c9, are initially expressed only in the YS (E7.5) and subsequently expressed in both the embryo and YS (E8.5). Another of the identified genes, PDX‐1, is involved in pancreatic development and insulin regulation. Whereas the rodent YS is known to produce insulin from mid to late gestation, YS insulin expression had not been examined earlier in development. We detected insulin mRNA in the YS at both E7.5 and E8.5, prior to expression in the embryo proper or formation of the pancreas. However, other pancreatic products, such as glucagon, somatostatin, and carboxypeptidase A, are not expressed in the YS. In situ analysis indicates insulin is produced in YS mesothelial cells and endoderm cells, but not in blood cells. We hypothesize the early expression of insulin in the YS is required for the expansion of insulin responsive cells including primitive erythroblasts. Mol. Reprod. Dev. 48:145–153, 1997. © 1997 Wiley‐Liss, Inc.

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