Drosophila non-muscle α-actinin is localized in nurse cell actin bundles and ring canals, but is not required for fertility

Abstract

The single copy Drosophila alpha-actinin gene is alternatively spliced to generate three different isoforms that are expressed in larval muscle, adult muscle and non-muscle cells, respectively. We have generated novel alpha-actinin alleles, which specifically remove the non-muscle isoform. Homozygous mutant flies are viable and fertile with no obvious defects. Using a monoclonal antibody that recognizes all three splice variants, we compared alpha-actinin distribution in wild type and mutant embryos and ovaries. We found that non-muscle alpha-actinin was present in young embryos and in the embryonic central nervous system. In ovaries, non-muscle alpha-actinin was localized in the nurse cell subcortical cytoskeleton, cytoplasmic actin cables and ring canals. In the mutant, alpha-actinin expression remained in muscle tissues, but also in a subpopulation of epithelial cells in both embryos and ovaries. This suggests that various populations of non-muscle cells regulate alpha-actinin expression in different ways. We also show that ectopically expressed adult muscle-specific alpha-actinin localizes to all F-actin containing structures in the nurse cells in the absence of endogenous non-muscle alpha-actinin.

Tissue-autonomous EcR functions are required for concurrent organ morphogenesis in the Drosophila embryo

“…CG4325 appears not to be an essential gene, since a genomic deletion that removes moody and CG4325 (D18) is male semi-lethal and the lethality is rescued by a genomic fragment that contains moody, but not CG4325 (Bainton et al, 2005). Actn also appears to be non-essential since Actn mutant flies are normal and fertile (Wahlstrom et al, 2004). We find that usp ActD148 m À /z À embryos are rescued by l10 (which contains usp and CG4325, but not Actn), and that expression of usp from a heat-induced transgene rescues the usp ActD148 mutants (see Section 4), arguing that defects caused by the usp ActD148 allele are due to reduced Usp function.…”

Drosophila α-actinin in ovarian follicle cells is regulated by EGFR and Dpp signalling and required for cytoskeletal remodelling

“…This results in loss of a-actinin protein in most ovarian cells, except for the polar cells and the follicle cells at stages 10-14. On the mRNA level, however, non-muscle a-actinin is still expressed in the Actn D233 mutant (Wahlströ m et al, 2004). Since the antibody we have used does not distinguish between the different isoforms, we will refer to the population of a-actinin that is expressed in the Actn D233 follicle cells as FC-a-actinin (for follicle cell-a-actinin).…”

“…The deletion in the Actn D233 mutant does not remove the 5 0 -most part of the first exon, therefore the residual a-actinin protein detected in the follicle cells might result from correct splicing occurring further downstream (Wahlströ m et al, 2004). Therefore, we examined ovarian a-actinin protein expression in two other non-muscle a-actinin mutant lines, Actn D148 and usp 2 (Fig.…”

“…In wild-type embryos and ovaries, a-actinin is ubiquitously expressed (Wahlströ m et al, 2004). In the viable and fertile mutant Actn D233 , a small deletion disrupts the first untranslated exon of the non-muscle-specific transcript.…”

“…The Actn D233 mutant lacks detectable expression of a-actinin protein in early embryos, in the ovarian nurse cells and in follicle cells at early stages of oogenesis, yet both embryogenesis and oogenesis proceed normally. In Actn D233 mutant ovaries, polar cells and follicle cells from stage 10 onwards still express a-actinin, indicating that a-actinin expression is differently regulated in these cells (Wahlströ m et al, 2004). The aim of this study was to examine the population of a-actinin expressed in the Actn D233 mutant and to analyse its role in the follicle cells.…”