The establishment and maintenance of cellular identity are ultimately dependent upon the accurate regulation of gene expression, the process by which genetic information is used to synthesize functional gene products. The post-transcriptional, pre-translational regulation of RNA constitutes RNA processing, which plays a prominent role in the modulation of gene expression in differentiated animal cells. The multi-protein Exon Junction Complex (EJC) serves as a critical signaling hub within the network that underlies many RNA processing events. Here, we identify a requirement for the EJC during early vertebrate embryogenesis. Knockdown of the EJC component Eukaryotic initiation factor 4a3 (Eif4a3) in embryos of the frog Xenopus laevis results in full-body paralysis, with defects in sensory neuron, pigment cell, and cardiac development; similar phenotypes are seen following knockdown of other ''core'' EJC protein constituents. Our studies point to an essential role for the EJC in the development of neural plate border derivatives.

Specification of the dorsoventral (DV) axis is critical for the subsequent differentiation of regional fate in the primary germ layers of the vertebrate embryo. We have identified a novel factor that is essential for dorsal development in embryos of the frog Xenopus laevis. Misexpression of Xenopus mab21-like 3 (Xmab21l3) dorsalizes gastrula-stage mesoderm and neurula-stage ectoderm, while morpholino-mediated knockdown of Xmab21l3 inhibits dorsal differentiation of these embryonic germ layers. Xmab21l3 is a member of a chordate-specific subclass of a recently characterized gene family, all members of which contain a conserved, but as yet ill-defined, Mab21 domain. Our studies suggest that Xmab21l3 functions to repress ventralizing activity in the early vertebrate embryo, via BMP/Smad and Ras/ERK signaling.

The establishment and maintenance of cellular identity are ultimately dependent upon the accurate regulation of gene expression, the process by which genetic information is used to synthesize functional gene products. The post-transcriptional, pre-translational regulation of RNA constitutes RNA processing, which plays a prominent role in the modulation of gene expression in differentiated animal cells. The multi-protein Exon Junction Complex (EJC) serves as a critical signaling hub within the network that underlies many RNA processing events. Here, we identify a requirement for the EJC during early vertebrate embryogenesis. Knockdown of the EJC component Eukaryotic initiation factor 4a3 (Eif4a3) in embryos of the frog Xenopus laevis results in full-body paralysis, with defects in sensory neuron, pigment cell, and cardiac development; similar phenotypes are seen following knockdown of other "core" EJC protein constituents. Our studies point to an essential role for the EJC in the development of neural plate border derivatives.

Apolipoprotein CI (ApoCI) belongs to the Apolipoprotein superfamily, members of which are involved in lipid transport, uptake and homeostasis. Excessive ApoCI has been implicated in atherosclerosis and Alzheimer’s disease in humans. In this study we report the isolation of Xenopus laevis apoCI and describe the expression pattern of this gene during early development, using reverse transcription polymerase chain reaction and whole mount in situ hybridization. Xenopus apoCI is enriched in the dorsal ectoderm during gastrulation, and is subsequently expressed in sensory placodes, neural tube and cranial neural crest. These data suggest as yet uncharacterized roles for ApoCI during early vertebrate embryogenesis.