Parker B Antin
Publications
PMID: 16273525;Abstract:
The 11th Annual Weinstein Cardiovascular Development Conference was held May 19-22, 2005 at the Westward Look Resort and Conference Center in Tucson, Arizona. The Westward Look was the site of the 6th Weinstein Meeting in 1999, and this year, 330 basic research scientists and research clinicians returned to Tucson for 3 days of meetings, Mariachis, and margaritas. The meeting was hosted by the cardiovascular research group at the University of Arizona and offered flavors of the desert southwest that included record temperatures, the Skopopelli conference logo modified from the Kokopelli of Native American mythology (Fig. 1), and liberal use of a cattle prod to encourage speaker timeliness. © 2005 Wiley-Liss, Inc.
PMID: 10096068;Abstract:
Whole mount in situ hybridization studies were performed to investigate the expression pattern of the homeobox gene Hex (also known as Prh) during early stages of chick embryogenesis. At the time of laying, cHex transcripts are detected in Koller's sickle and the forming hypoblast. During gastrulation (HH stage 4), chex is expressed in anteriorly-displaced hypoblast cells. At stage 6, cHex transcripts are observed within endoderm in an anterior arc that overlaps the cardiogenic region. Later chex expression is observed within pharyngeal endoderm immediately adjacent to the forming myocardium, in the endocardium and in the liver and thyroid gland primordia. cHex transcripts are also detected within blood islands beginning at stage 4, and in extraembryonic and intraembryonic vascular endothelial cells as vessels form.
PMID: 15063170;Abstract:
The vertebrate liver and heart arise from adjacent cell layers in the anterior lateral (AL) endoderm and mesoderm of late gastrula embryos, and the earliest stages of liver and heart development are interrelated through reciprocal tissue interactions. Although classical embryological studies performed several decades ago in chick and quail defined the timing of hepatogenic induction in birds and the important role for cardiogenic mesoderm in this process, almost nothing is known about the molecular aspects of avian liver development. Here we use in vivo and explantation assays to investigate tissue interactions and signaling pathways regulating Hex, a homeobox gene required for liver development, and the earliest stages of hepatogenesis in the chick embryo. We find that explants of late gastrula anterior lateral endoderm plus mesoderm, which have been used extensively for studies relating to heart development, also produce albumin-expressing hepatoblasts. Expression of Hex, the earliest known molecular marker for the hepatogenic endoderm, and albumin, indicative of early committed hepatoblasts, requires both autocrine Bmp signaling and a specific paracrine signal from the cardiogenic (anterior lateral) mesoderm. Endodermal expression of Fox2a, in contrast, requires the mesoderm but is independent of Bmp signaling. In vivo induction assays show that the ability of BMP2 to activate Hex expression in the endoderm is restricted to a region that is only slightly larger than the endogenous domain of Hex expression. Although Fgfs can substitute for the cardiogenic mesoderm to support the expression of Hex and albumin in the endoderm, several Fgf genes are expressed in the anterior lateral endoderm but an Fgf expressed predominantly in the mesoderm was not identified. Studies also showed that Fgf gene expression in the endoderm does not require a signal from the mesoderm. Mechanisms regulating endodermal signaling pathways activated by Fgfs may therefore be more complex than previously appreciated. © 2004 Elsevier Inc. All rights reserved.