Alternatively spliced forms of the Drosophila αPS2 subunit of integrin are sufficient for viability and can replace the function of the αPS1 subunit of integrin in the retina

The Drosophila inflated (if) gene encodes the αPS2 subunit of the PS family of integrins. The if transcript is spliced such that αPS2 is found in two alternative forms, αPS2(C) and αPS2(m8), which differ by 25 amino acid residues in a region shown to affect cation requirements and ligand specificity. In this study, we examine the functional significance of the protein isoforms of if by analyzing the ability of transgenes producing only one isoform to rescue developmental abnormalities associated with complete loss of PS2 integrin. We find that either form of αPS2 is sufficient to rescue if− animals to viability; however, the αPS2(C) form promotes higher survival of the organism. Furthermore, these studies suggest distinct roles for αPS2(C) and αPS2(m8) during development. When expressed in the developing wing, αPS2(m8) is more efficient at rescuing the if− wing blister phenotype than is αPS2(C). Expression of αPS2(C) in the eye produces dominant disruption of photoreceptor organization. We have also examined the ability of αPS2 and αPS1 to maintain photoreceptor organization in the Drosophila retina. Clonal analysis of sectioned eyes suggests a requirement for αPS1, but not αPS2. However, ectopic expression of if(m8) or if(C) shows that either splice form of αPS2 can functionally replace αPS1 and rescue the mew eye phenotype.