Endoderm Patterning
Figure 1
In situ hybridization to serial sections of a Xenopus gastrula show that Hex and Cerberus are expressed only in the anterior endoderm, in contrast to Sox17, which is expressed in all of the endoderm tissue.
Sox17
Hex
Cerberus
Shortly after endoderm tissue is induced in the early embryo, it becomes patterned, so that some of it gives rise to the foregut while other regions of the endoderm gives rise to the hind gut. This process begins during gastrulation and continues during the period of development when the various organ primordia are induced, thus ensuring that the organs form in the correct position in the body. One of the first manifestations of this patterning can be seen during gastrulation with the asymmetric expression of genes such Hex and Cerberus in the anterior endoderm, which give rise to the future foregut (Fig. 1). Hex is a homeodomain transcription factor that is essential for anterior endoderm and liver development. And Cerberus is a secreted growth factor antagonist that participates in instructing cells that they are in the anterior part of the embryos.
We are trying to understand the molecular mechanisms that pattern the embryonic endoderm, in particular the foregut.
In order to address this we are characterizing the Hex promoter. Using Xenopus transgenics and a Green Fluorescent Protein (GFP), construct we are characterizing how growth factor signaling impacts the DNA sequences that control the transcription a Hex just in the anterior endoderm. We have recently discovered that Wnt growth factor signaling regulates organ fate in the early endoderm. In addition we have used various array screening techniques to identify novel genes that are expressed in spatially restricted regions of the endoderm.
These studies will provide essential information on the genetic pathways controlling the earliest steps in the formation of the liver, pancreas and lungs.
Zorn, AM, Butler, K and Gurdon, JB (1999) Anterior Endomesododerm Specification in Xenopus by Wnt/β-catenin and TGFβ Signaling Pathways. Dev Biol 209: 282-297.
Costa JMB, Mason J, Lee M, Amaya E and Zorn AM (2003) Novel gene expression domains reveal early patterning of the Xenopus endoderm. GEP 3: 509-519.
McLin VA, Rankin SA and Zorn AM (2007) Repression of Wnt/beta-catenin signaling in the anterior endoderm is essential for liver and pancreas development. Development 134: 2207-2217.
If you would like to join our research team, contact the Zorn Laboratory. The Zorn Lab is part of the Division of Developmental Biology at Cincinnati Children's Research Foundation. The lab is located in Location R (Research Foundation Building), Room 2509.
Division of Developmental Biology
Cincinnati Children's Research Foundation
Cincinnati, OH 45229-3039
E-mail Aaron.Zorn@chmcc.org
Phone 513-636-3770
Fax 513-636-4317 Interested in joining us as a student or a postdoc? Learn more about postdoctoral training and graduate student opportunities at Cincinnati Children's.
