Identification of Novel Genes Affecting Mesoderm Formation and Morphogenesis through an Enhanced Large Scale Functional Screen in Xenopus

J-A. Chen, J. Voigt, M. Gilchrist, N. Papalopulu and E. Amaya

Mechanisms of Development 122:307-331 (2005) (Full Article, 2400 Kb).

ABSTRACT

The formation of mesoderm is an important developmental process of vertebrate embryos, which can be broken down into several

steps; mesoderm induction, patterning, morphogenesis and differentiation. Although mesoderm formation in Xenopus has been

intensively studied, much remains to be learned about the molecular events responsible for each of these steps. Furthermore, the

interplay between mesoderm induction, patterning and morphogenesis remains obscure. Here, we describe an enhanced functional

screen in Xenopus designed for large-scale identification of genes controlling mesoderm formation. In order to improve the efficiency

of the screen, we used a Xenopus tropicalis unique set of cDNAs, highly enriched in full-length clones. The screening strategy

incorporates two mesodermal markers, Xbra and Xmyf-5, to assay for cell fate specification and patterning, respectively. In addition

we looked for phenotypes that would suggest effects in morphogenesis, such as gastrulation defects and shortened anterior-posterior

axis. Out of 1728 full-length clones we isolated 82 for their ability to alter the phenotype of tadpoles and/or the expression of Xbra

and Xmyf-5 . Many of the clones gave rise to similar misexpression phenotypes (synphenotypes) and many of the genes within each

synphenotype group appeared to be involved in similar pathways. We determined the expression pattern of the 82 genes and found

that most of the genes were regionalized and expressed in mesoderm. We expect that many of the genes identified in this screen will

be important in mesoderm formation.

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