Interplay of βPS and βν integrins in Drosophila muscle functioning

Integrins are conserved cell-adhesion receptors implicated in development and disease, including joint disorders and osteoarthritis. Unlike humans, which encode 18 α- and 8 β-subunits, Drosophila melanogaster carries only 5 α- and 2 β-integrins, offering a simplified system to dissect their functions. While βPS is established as essential for embryonic muscle attachment, the roles of the less-characterised βν subunit, and the extent of overlap between the two, remain unresolved. Here, we combined βν null mutants with tissue-specific βPS knockdowns to systematically define their contributions to muscle function. We find that βν is required during early development, where its absence impairs larval body wall muscle performance, but becomes largely dispensable for adult survival, flight and other locomotory activities. By contrast, βPS is indispensable throughout Drosophila development, including the indirect flight muscle (IFM) integrity, where its depletion disrupts sarcomere organisation, precisely the H-zone width and downregulates thin filament genes. Notably, βν assumes supplementary roles in muscle development, with its transcript levels getting lowered when βPS is compromised. Again, in the functionally compromised larval muscles of βν nulls, βPS transcript levels are lowered, but gets upregulated in the functionally fit βν null adult muscle subsets. The results suggest, βν might function as a modulatory component of the integrin network rather than an essential determinant of IFM development. These findings uncover distinct yet cooperative functions of βPS and βν in Drosophila muscle development, providing a framework to understand how integrin diversity contributes to muscle performance.