title: Myosin 3A transgene expression produces abnormal actin filament bundles in transgenic Xenopus laevis rod photoreceptors.
abstract: Myo3A, a class III myosin, localizes to the distal (plus) ends of inner segment actin filament bundles that form the core of microvillus-like calycal processes encircling the base of the photoreceptor outer segment. To investigate Myo3A localization and function, we expressed green fluorescent protein-tagged bass Myo3A and related constructs in transgenic Xenopus rods using a modified opsin promoter. Tagged intact Myo3A localized to rod calycal processes, as previously reported for native bass Myo3A. Transgenic rods developed abnormally large calycal processes and subsequently degenerated. Modified Myo3A expression constructs demonstrated that calycal process localization required an active motor domain and the tail domain. Expressed tail domain alone localized to actin bundles along the entire inner segment length, rather than to the distal end. This tail domain localization required the conserved C-terminal domain (3THDII) previously shown to possess an actin-binding motif. Our findings suggest that Myo3A plays a role in the morphogenesis and maintenance of calycal processes of vertebrate photoreceptors.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA. linjones@berkeley.edu
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lin-Jones
authors.forename: Ed
authors.initials: E
authors.lastname: Parker
authors.forename: Mike
authors.initials: M
authors.lastname: Wu
authors.forename: Andréa
authors.initials: A
authors.lastname: Dosé
authors.forename: Beth
authors.initials: B
authors.lastname: Burnside
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D020816:Amino Acid Motifs; D000818:Animals; D030801:Animals, Genetically Modified; D001492:Bass; D003599:Cytoskeleton / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000235:genetics*; D025102:Myosin Type III; D009218:Myosins / Q000235:genetics*; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D017299:Rod Opsins / Q000235:genetics; D019076:Transgenes; D014982:Xenopus laevis
chemical_list: D000199:Actins; D017299:Rod Opsins; D049452:Green Fluorescent Proteins; C491724:MYO3A protein, human; D025102:Myosin Type III; D018995:Myosin Heavy Chains; D009218:Myosins