Apr 1, 2014

Evolutionary origin of gastrulation: insights from sponge development

BMC Biology
Nagayasu NakanishiBernard M Degnan

Abstract

The evolutionary origin of gastrulation--defined as a morphogenetic event that leads to the establishment of germ layers--remains a vexing question. Central to this debate is the evolutionary relationship between the cell layers of sponges (poriferans) and eumetazoan germ layers. Despite considerable attention, it remains unclear whether sponge cell layers undergo progressive fate determination akin to eumetazoan primary germ layer formation during gastrulation. Here we show by cell-labelling experiments in the demosponge Amphimedon queenslandica that the cell layers established during embryogenesis have no relationship to the cell layers of the juvenile. In addition, juvenile epithelial cells can transdifferentiate into a range of cell types and move between cell layers. Despite the apparent lack of cell layer and fate determination and stability in this sponge, the transcription factor GATA, a highly conserved eumetazoan endomesodermal marker, is expressed consistently in the inner layer of A. queenslandica larvae and juveniles. Our results are compatible with sponge cell layers not undergoing progressive fate determination and thus not being homologous to eumetazoan germ layers. Nonetheless, the expression of GATA in the spo...Continue Reading

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  • Citations21
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Mentioned in this Paper

Embryo
Endoderm
Mnemiopsis leidyi
Cell Movement
Uncinocarpus queenslandicus
Anatomical Layer
Delamination Process
Transdifferentiation
Apoptosis, Intrinsic Pathway
Halisarca dujardini

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