A novel, tissue-specific integrin subunit, βν, expressed in the midgut of Drosophila melanogaster

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Abstract
The integrins are a family of cell surface receptors for extracellular matrix proteins and counter-receptors on other cells. We have used the polymerase chain reaction to identify a novel integrin receptor β subunit in Drosophila melanogaster. The deduced amino acid sequence of this subunit, which we have termed βν (betaneu), indicates that it has several unusual properties. The βν subunit is roughly 33% identical with each of the previously sequenced vertebrate and Drosophila β subunits and is lacking four of the 56 cysteine residues characteristic of most members of this protein family. The expression of the βν gene is strikingly restricted. It is temporally regulated, with maximal expression occurring at 12-15 hours of embryonic development. In situ hybridization analyses and antibody localization on whole-mount embryos reveal that βν expression is tissuespecific and confined to the developing midgut endoderm and its precursors during embryogenesis. Tissue specificity of expression is maintained through later stages of development as βν transcripts are found exclusively in the larval midgut. Within this structure, βν transcripts are especially concentrated in the cells of the midgut imaginal islands which give rise to the adult midgut.