Akhmedov N B, Piriev N I, Pearce-Kelling S, Acland G M, Aguirre G D, Farber D B
Jules Stein Eye Institute, University of California Los Angeles School of Medicine, 90095, USA.
Invest Ophthalmol Vis Sci. 1998 Sep;39(10):1775-81.
To characterize the cDNA and the organization of the gene encoding the cone-specific gamma subunit of transducin (Tgamma c) and to examine this gene as a candidate for the recessively inherited cone photoreceptor degeneration in the cd dog.
Canine Tgamma c cDNA was cloned and sequenced. Polymerase chain reaction (PCR) was used to define the Tgamma c gene structure, northern blot analysis to examine the level of expression of Tgamma c mRNA in control and cd-affected retinas, and immunocytochemistry to determine the presence and localization of Tgamma c in normal and cd retinas.
Immunocytochemical results showed Tgamma c localized to cone photoreceptor outer segments in the normal retina, whereas no Tgamma c immunoreactivity was observed in the cd retinas. However, the level of transcription and the primary structure of the cloned cDNA coding for the 69-amino acid protein were identical in retinas from wild-type and affected dogs.
Although Tgamma c immunoreactivity was specifically absent in the cd dog retina, no differences were detected between normal and cd retinas in the nucleotide sequence of Tgamma c mRNA or in its synthesis. These results indicate that a mutation in the Tgamma c gene may not be causally associated with the cd dog disease. These findings suggest that possible abnormalities in posttranslational modification of Tgamma c or defective assembly of the transducin alphabetagamma complex could lead to rapid degradation of Tgamma c.
