The Function and Developmental Expression of Alternatively Spliced Isoforms of Amphioxus and Xenopus laevis Pax2/5/8 Genes: Revealing Divergence at the Invertebrate to Vertebrate Transition
Article first published online: 12 JUL 2012
Copyright © 2012 Wiley Periodicals, Inc.
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution
Volume 318, Issue 7, pages 555–571, November 2012
How to Cite
2012. The function and developmental expression of alternatively spliced isoforms of amphioxus and Xenopus laevis Pax2/5/8 genes: revealing divergence at the invertebrate to vertebrate transition. J. Exp. Zool. (Mol. Dev. Evol.) 318B:555–571., , .
- Issue published online: 18 OCT 2012
- Article first published online: 12 JUL 2012
- Manuscript Accepted: 28 MAY 2012
- Manuscript Revised: 7 MAY 2012
- Manuscript Received: 27 FEB 2012
- National Science Foundation. Grant Number: NSF MCB 06-20019
- GACR. Grant Number: P305/10/2141
- MSMT. Grant Number: LH12047
Pax genes encode highly conserved transcription factors vital for metazoan development. Pax transcripts, particularly those in Group II (Pax2/5/8), are extensively alternatively spliced. This study compares the transcriptional activation capacity and developmental stage-specific expression of major isoforms of Group II Pax proteins in amphioxus (Branchiostoma floridae) and in Xenopus laevis. The comparison reveals considerable divergence of splice forms between the lineages, with the X. laevis Group II Pax genes (Pax2, Pax5, and Pax8) possessing a greater repertoire of regulated and functionally distinct splice forms than the single amphioxus gene (Pax2/5/8). Surprisingly, some apparently conserved splice forms are expressed at quite different levels during development in the two organisms and present different capacities to activate transcription. However, despite this divergence, the combinatorial transcriptional activation capacity of the isoforms present in early X. laevis and amphioxus development are broadly similar. This suggests that the some of the conserved functional roles, implied by the expression of Group II Pax genes in homologous tissues of amphioxus and X. laevis embryos, may depend upon the combination of isoforms expressed in a particular tissue at a particular time in development. Thus, during early development, the evolutionary constraint on the net effect of several isoforms co-expressed in a given tissue may be more strict than that on specific isoforms. This flexibility may facilitate the appearance of new exons and splicing patterns in the vertebrate duplicates, leading to isoforms with subtly distinct functions critical to the subsequent development of vertebrate-specific cell types and structures. J. Exp. Zool. (Mol. Dev. Evol.) 318B:555–571, 2012. © 2012 Wiley Periodicals, Inc.