title: The transcription factors islet and Lim3 combinatorially regulate ion channel gene expression.
abstract: Expression of appropriate ion channels is essential to allow developing neurons to form functional networks. Our previous studies have identified LIM-homeodomain (HD) transcription factors (TFs), expressed by developing neurons, that are specifically able to regulate ion channel gene expression. In this study, we use the technique of DNA adenine methyltransferase identification (DamID) to identify putative gene targets of four such TFs that are differentially expressed in Drosophila motoneurons. Analysis of targets for Islet (Isl), Lim3, Hb9, and Even-skipped (Eve) identifies both ion channel genes and genes predicted to regulate aspects of dendritic and axonal morphology. Significantly, some ion channel genes are bound by more than one TF, consistent with the possibility of combinatorial regulation. One such gene is Shaker (Sh), which encodes a voltage-dependent fast K(+) channel (Kv1.1). DamID reveals that Sh is bound by both Isl and Lim3. We used body wall muscle as a test tissue because in conditions of low Ca(2+), the fast K(+) current is carried solely by Sh channels (unlike neurons in which a second fast K(+) current, Shal, also contributes). Ectopic expression of isl, but not Lim3, is sufficient to reduce both Sh transcript and Sh current level. By contrast, coexpression of both TFs is additive, resulting in a significantly greater reduction in both Sh transcript and current compared with isl expression alone. These observations provide evidence for combinatorial activity of Isl and Lim3 in regulating ion channel gene expression.
authors: Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom, The Gurdon Institute and Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 1QN, United Kingdom, and Department of Biology, Emory University, Atlanta, Georgia 30322.
authors: Verena
authors: V
authors: Wolfram
authors: Tony D
authors: TD
authors: Southall
authors: Cengiz
authors: C
authors: Günay
authors: Astrid A
authors: AA
authors: Prinz
authors: Andrea H
authors: AH
authors: Brand
authors: Richard A
authors: RA
authors: Baines
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D004330:Drosophila / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D007473:Ion Channels / Q000096:biosynthesis* / Q000235:genetics; D060850:LIM-Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D009046:Motor Neurons / Q000378:metabolism; D055495:Neurogenesis / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D007473:Ion Channels; D060850:LIM-Homeodomain Proteins; C494338:Lim3 protein, Drosophila; D014157:Transcription Factors; C494337:tup protein, Drosophila
keywords: Drosophila; RP3; Shaker; aCC; central nervous system; muscle