title: Drosophila Crumbs is a positional cue in photoreceptor adherens junctions and rhabdomeres.
abstract: Drosophila Crumbs (Crb) is required for apical-basal polarity and is an apical determinant in embryonic epithelia. Here, we describe properties of Crb that control the position and integrity of the photoreceptor adherens junction and photosensitive organ, or rhabdomere. In contrast to normal photoreceptor adherens junctions and rhabdomeres, which span the depth of the retina, adherens junctions and rhabdomeres of Crb-deficient photoreceptors initially accumulate at the top of the retina and fail to maintain their integrity as they stretch to the retinal floor. We show that Crb controls localization of the adherens junction through its intracellular domain containing a putative binding site for a protein 4.1 superfamily protein (FERM). Although loss of Crb or overexpression of the FERM binding domain causes mislocalization of adherens junctions, they do not result in a significant loss of photoreceptor polarity. Mutations in CRB1, a human homologue of crb, are associated with photoreceptor degeneration in retinitis pigmentosa 12 (RP12) and Leber congenital amaurosis (LCA). The intracellular domain of CRB1 behaves similarly to its Drosophila counterpart when overexpressed in the fly eye. Our studies may provide clues for mechanisms of photoreceptor degeneration in RP12 and LCA.
authors.affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA.
authors.forename: Shayan
authors.initials: S
authors.lastname: Izaddoost
authors.forename: Sang-Chul
authors.initials: SC
authors.lastname: Nam
authors.forename: Manzoor A
authors.initials: MA
authors.lastname: Bhat
authors.forename: Hugo J
authors.initials: HJ
authors.lastname: Bellen
authors.forename: Kwang-Wook
authors.initials: KW
authors.lastname: Choi
mesh_terms: D022005:Adherens Junctions / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D017124:Conserved Sequence; D003463:Cues; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000196:embryology* / Q000235:genetics / Q000648:ultrastructure; D005123:Eye / Q000166:cytology / Q000196:embryology / Q000378:metabolism / Q000648:ultrastructure; D005136:Eye Proteins; D006801:Humans; D019476:Insect Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009024:Morphogenesis; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins; D010641:Phenotype; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology* / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: C448939:CRB1 protein, human; D029721:Drosophila Proteins; D005136:Eye Proteins; D019476:Insect Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C064360:crb protein, Drosophila; C118488:dlt protein, Drosophila