Transcripts of individual Drosophila actin genes are differentially distributed during embryogenesis

Abstract

The temporal and spatial patterns of accumulation of transcripts from individual actin genes during Drosophila embryogenesis have been determined by in situ hybridization. We describe the subcloning into transcription vectors of unique DNA fragments derived from the 3' transcribed, but nontranslated region of each actin gene. These fragments then served as templates for the synthesis in vitro of single-stranded, radio-active gene-specific RNA probes. Probe characterization and hybridization to developmental RNA blots are presented, demonstrated the independent developmental accumulation of actin transcripts from each gene. Each gene-specific probe has been hybridized in situ to the transcripts present in embryonic frozen sections. The results of these experiments have demonstrated that transcripts from each actin gene accumulate differentially in developing Drosophila tissues. The 5C and 42A actin genes are cytoplasmic actin genes, with transcripts distributed in all cells and tissues of the developing embryo. Therefore these genes presumably encode the cytoplasmic actins used for functions common to all cells. Transcripts from both cytoplasmic actin genes are evenly distributed in preblastoderm embryos, becoming localized to the periphery at blastoderm formation [5C: Burn et al.: Dev Biol 131:345-355, 1989]. Later in development, levels of these cytoplasmic transcripts vary in specific tissues. While the patterns of localization of 5C actin transcripts have been published [Burn et al.: Dev Biol 131:345-355, 1989], differential neurological localization is presented here; 42A transcripts are localized at higher concentrations in the midgut, the brain, nerve cord, and gonad. Both 87E and 57B transcripts accumulated in the developing larval body wall musculature, but at differing levels and in differing patterns. Transcripts of the 79B and the 88F actin genes were undetectable in embryos. The results of these experiments suggest dedicated contributions of individual actin genes to complex developmental processes.

Expression Profiling of a Hypercontraction-induced Myopathy in Drosophila Suggests a Compensatory Cytoskeletal Remodeling Response

“…The up-regulated muscle LIM proteins, for example, have peak expressions at the terminal stages of muscle development in the embryo and pupa (21). In addition, the strongly up-regulated Act57B is the predominant actin for larval somatic musculature, not adult muscles (54). Expression analysis of muscular dystrophies has also revealed a down-regulation of nuclear encoded mitochondrial genes (26,(55)(56)(57), similar to our observations in Drosophila.…”

Transcriptional regulation by Modulo integrates meiosis and spermatid differentiation in male germ line

“…The constitutive transcript of the ribosomal protein gene Rp49 (32) was used as the cDNA template-loading reference. The ubiquitous transcripts RpL9 (33) and Act5C (34) and the broadly expressed spermatogenesis-related genes des (31) and twe (35) were not significantly affected by the mod 07570 mutation.…”

One of the two cytoplasmic actin isoforms in Drosophila is essential

“…In Drosophila, cytoplasmic actin is supplied by Act5C and Act42A (9,10). There are only two amino acid differences between Act5C and Act42A (see Results).…”

“…Each substitution is conservative in nature (A261S and I331V), and neither is located in a region of the actin molecule known to interact with actinbinding proteins (11). mRNAs for both Act5C and Act42A are maternally loaded and initially, transcripts for both mRNAs are evenly distributed throughout the early embryo (10). Zygotic expression of both genes occurs throughout embryonic development in all cells.…”