title: The Crumbs_C isoform ofDrosophilashows tissue- and stage-specific expression and prevents light-dependent retinal degeneration.
abstract: DrosophilaCrumbs (Crb) is a key regulator of epithelial polarity and fulfils a plethora of other functions, such as growth regulation, morphogenesis of photoreceptor cells and prevention of retinal degeneration. This raises the question how a single gene regulates such diverse functions, which in mammals are controlled by three different paralogs. Here, we show that inDrosophiladifferent Crb protein isoforms are differentially expressed as a result of alternative splicing. All isoforms are transmembrane proteins that differ by just one EGF-like repeat in their extracellular portion. Unlike Crb_A, which is expressed in most embryonic epithelia from early stages onward, Crb_C is expressed later and only in a subset of embryonic epithelia. Flies specifically lacking Crb_C are homozygous viable and fertile. Strikingly, these flies undergo light-dependent photoreceptor degeneration despite the fact that the other isoforms are expressed and properly localised at the stalk membrane. This allele now provides an ideal possibility to further unravel the molecular mechanisms by whichDrosophila crbprotects photoreceptor cells from the detrimental consequences of light-induced cell stress.
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, Dresden 01307, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Spannl
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, Dresden 01307, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Kumichel
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, Dresden 01307, Germany.
authors.forename: Sarita
authors.initials: S
authors.lastname: Hebbar
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, Dresden 01307, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Kapp
authors.affiliation: Department of Biochemistry, Sciences II, University of Geneva, 30 Quai Ernest-Ansermet, Geneva 4 1211, Switzerland.
authors.forename: Marcos
authors.initials: M
authors.lastname: Gonzalez-Gaitan
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, Dresden 01307, Germany.
authors.forename: Sylke
authors.initials: S
authors.lastname: Winkler
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, Dresden 01307, Germany.
authors.forename: Rosana
authors.initials: R
authors.lastname: Blawid
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, Dresden 01307, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Jessberger
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, Dresden 01307, Germany knust@mpi-cbg.de.
authors.forename: Elisabeth
authors.identifier: http://orcid.org/0000-0002-2732-9135
authors.initials: E
authors.lastname: Knust
keywords: Alternative splicing; EGF-like repeat; Epithelial polarity; Mutually exclusive exon