TY - JOUR
T1 - Phenotypic analysis of EcR-A mutants suggests that EcR isoforms have unique functions during Drosophila development
AU - Davis, Melissa B.
AU - Carney, Ginger E.
AU - Robertson, Anne E.
AU - Bender, Michael
N1 - Funding Information:
We would like to thank the laboratories of Dr. Richard Meagher and Dr. Carl Thummel for the provision of antibody reagents. We thank Tong-Ruei Li and Heidi Weaver for help with Western blots, and Dave Brown for assistance with image processing. This work was supported by a grant from the National Institutes of Health (GM-053681) to M.B., an NIH pre-doctoral fellowship (GM-020095), and a Ford Foundation Dissertation fellowship to M.B.D. and by an NIH training grant (GM-07103) to G.E.C. Special thanks go to Drs. Judy Willis, Sue Wessler, Bob Ivarie, Mary Bedell, Claiborne Glover, and Kevin White for assistance and helpful comments in preparation of the manuscript.
PY - 2005/6/15
Y1 - 2005/6/15
N2 - 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.
AB - 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.
KW - Drosophila
KW - EcR-A
KW - Ecdysone receptor
KW - Metamorphosis
UR - http://www.scopus.com/inward/record.url?scp=20444372635&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=20444372635&partnerID=8YFLogxK
U2 - 10.1016/j.ydbio.2005.03.019
DO - 10.1016/j.ydbio.2005.03.019
M3 - Article
C2 - 15950604
AN - SCOPUS:20444372635
SN - 0012-1606
VL - 282
SP - 385
EP - 396
JO - Developmental Biology
JF - Developmental Biology
IS - 2
ER -