Diverse genes, expressed in distinct regions of the trunk epithelium define a monolayer cellular template for construction of the oikopleurid house

The filter-feeding house secreted by urochordate Appendicularians is among the most complex extracellular structures constructed by any organism. This structure allows the Appendicularia to exploit a wide range of food partic le sizes, including nanoplankton and submicrometer colloids, establishing t hem as an important and abundant component of marine zooplankton communitie s throughout the world. The oikoplastic epithelium, a monolayer of cells co vering the trunk of the animal, is responsible for secretion of the house. The epithelium has a fixed number of cells, organized in distinct fields, c haracterized by defined cell shapes and nuclear morphologies. Certain struc tures in the house appear to be spatially linked to these different fields of cells. Using cDNA representation difference analysis (cDNA RDA) on whole animals at two different developmental stages separated by the metamorphic tailshift event, we isolated four families of genes (oikosins) that are ex pressed only from specific subregions of the oikoplastic epithelium. The mo lecular patterns defined by oikosin gene expression establish the epitheliu m as an ideal and easily accessible monolayer cellular template for explori ng coordinate regulation of gene expression, cell-cell interactions involve d in pattern formation, gene/genome amplification, and the role of temporal changes in nuclear architecture in regulating gene expression. (C) 2001 Ac ademic Press.