Phenotypic analysis of EcR-A mutants suggests that EcR isoforms have unique functions during Drosophila development

Melissa B. Davis, Ginger E. Carney, Anne E. Robertson, Michael Bender

Research output: Contribution to journalArticle

72 Scopus citations

Abstract

The steroid hormone ecdysone triggers transitions between developmental stages in Drosophila by acting through a heterodimer consisting of the EcR and USP nuclear receptors. The EcR gene encodes three protein isoforms (EcR-A, EcR-B1, and EcR-B2) that have unique amino termini but that contain a common carboxy-terminal region including DNA-binding and ligand-binding domains. EcR-A and EcR-B1 are expressed in a spatially complementary pattern at the onset of metamorphosis, suggesting that specific responses to ecdysone involve distinct EcR isoforms. Here, we describe phenotypes of EcR-A specific deletion mutants isolated using transposon mutagenesis. Western blot analysis shows that each of these mutants completely lacks EcR-A protein, while the EcR-B1 protein is still present. The EcR112 strain has a deletion of EcR-A specific non-coding and regulatory sequences but retains the coding exons, while the EcR139 strain has a deletion of EcR-A specific protein coding exons but retains the regulatory region. In these mutants, the developmental progression of most internal tissues that normally express EcR-B1 is unaffected by the lack of EcR-A. Surprisingly, however, we found that one larval tissue, the salivary gland, fails to degenerate even though EcR-B1 is the predominant isoform. This result may indicate that the low levels of EcR-A in this tissue are in fact required. We identified yet another type of mutation, the EcR 94 deletion, that removes the EcR-A specific protein coding exons as well as the introns between the EcR-A and EcR-B transcription start sites. This deletion places the EcR-A regulatory region adjacent to the EcR-B transcription start site. While EcR112 and EcR139 mutant animals die during mid and late pupal development, respectively, EcR94 mutants arrest prior to pupariation. EcR-A mutant phenotypes and lethal phases differ from those of EcR-B mutants, suggesting that the EcR isoforms have distinct developmental functions.

Original languageEnglish (US)
Pages (from-to)385-396
Number of pages12
JournalDevelopmental Biology
Volume282
Issue number2
DOIs
StatePublished - Jun 15 2005

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Keywords

  • Drosophila
  • EcR-A
  • Ecdysone receptor
  • Metamorphosis

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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