title: In vivo studies of the gamma subunit of retinal cGMP-phophodiesterase with a substitution of tyrosine-84.
abstract: The inhibitory rod cGMP phosphodiesterase gamma subunit (PDEgamma) is a major component of the photoresponse and is required to support rod integrity. Pdeg(tm1)/Pdeg(tm1) mice (which lack PDEgamma owing to a targeted disruption of the Pdeg gene) suffer from a very rapid and severe photoreceptor degeneration. The Y84G (Tyr(84)-->Gly) allele of PDEgamma has previously been shown in experiments carried out in vitro to reduce the regulatory control of the PDE catalytic core (PDEalphabeta) exerted by the wild-type gamma subunit. To determine the effects of this mutation on in vivo function, the murine opsin promoter was used to direct expression to the photoreceptors of +/Pdeg(tm1) mice of a mutant Y84G and a wild-type PDEgamma control transgene. The transgenic mice were crossed with Pdeg(tm1)/Pdeg(tm1) mice to generate animals able to synthesize only the transgenic PDEgamma. Our results showed that wild-type PDEgamma and Y84G transgenes could complement the Pdeg(tm1)/Pdeg(tm1) mutant for photoreceptor survival. The mutation caused a significant biochemical defect in PDE activation by transducin. However, the Y84G mutation did not fully eliminate the control of PDEgamma on the PDE catalytic core in vivo; the expression of the mutant subunit was associated with only a 10-fold reduction in the amplitude of the a-wave and a 1.5-fold decrease in the b-wave of the corneal electroretinogram. Unexpectedly, the mutation caused a much 'milder' phenotype in vivo than was predicted from the biochemical assays in vitro.
authors.affiliation: Jules Stein Eye Institute and Molecular Biology Institute, UCLA School of Medicine, 100 Stein Plaza, Los Angeles, CA 90095-7000, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Tsang
authors.forename: C K
authors.initials: CK
authors.lastname: Yamashita
authors.forename: K
authors.initials: K
authors.lastname: Doi
authors.forename: D J
authors.initials: DJ
authors.lastname: Salchow
authors.forename: N
authors.initials: N
authors.lastname: Bouvier
authors.forename: M
authors.initials: M
authors.lastname: Mendelsohn
authors.forename: P
authors.initials: P
authors.lastname: Gouras
authors.forename: D B
authors.initials: DB
authors.lastname: Farber
authors.forename: S P
authors.initials: SP
authors.lastname: Goff
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000737:chemistry / Q000378:metabolism*; D019943:Amino Acid Substitution; D000818:Animals; D003315:Cornea / Q000201:enzymology / Q000502:physiology; D004596:Electroretinography; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D014443:Tyrosine; D015106:3',5'-Cyclic-GMP Phosphodiesterases