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Identification of two rds/peripherin homologs in the chick retina
J Weng1, T Belecky-Adams, R Adler
1Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas 75235-9111, USA.
Purpose:
To identify possible homologs of mammalian rds/peripherin in chick photoreceptors.
Methods:
An embryonic day-15 chick retinal library was screened by polymerase chain reaction with degenerate oligonucleotide primers derived from conserved segments of the mammalian retinal degeneration slow (rds) mRNA. The resultant amplification products were used to isolate cDNAs, containing complete coding regions. These clones were studied by nucleotide sequence, Northern blot, and in situ hybridization analyses.
Results:
Two new homologs of rds/peripherin were discovered: crds1 and crds2. The predicted crds1 protein is 78%, and the predicted crds2 protein is 54%, identical to mammalian rds/peripherin. The crds1 mRNA is an abundant 4.4-kb species present in photoreceptors. The crds2 mRNA is of similar size but is much rarer. No homologs of rom1 were identified in our screen. Developmentally, the crds1 mRNAs were first detectable at embryonic day 18.
Conclusions:
Crds1 likely represents the chick ortholog of mammalian rds/peripherin, whereas crds2 is a more distant homolog. Both share an elongated C-terminal domain, an unusual feature compared with other members of the rds family.