T. Kylma et al., THE INTRONS OF THE CANINE ROD OPSIN GENE SHOW HIGHER SEQUENCE HOMOLOGY TO THE HUMAN THAN TO THE RODENT INTRONS, DNA sequence, 8(1-2), 1997, pp. 99-104
Using genomic DNA from late-onset retinal degenerate and wild type Lab
rador Retrievers as templates and canine exon-specific oligonucleotide
s as primers in polymerase chain reaction, all four introns of opsin w
ere cloned and sequenced. Dot-matrix comparisons were made for human,
murine and canine introns. Selected sequences containing either intron
ic or coding sequences were aligned and used for phylogenetic relation
ship analysis. The opsin gene introns are conserved between the human,
the mouse and the dog with regards to number and length. In addition
there is an astonishingly high degree of sequence homology between the
second and fourth introns. Introns 2 (1277 bp in dog) and 4 (863 bp i
n dog) are 72% and 71% homologous to the human introns, and 57% and 52
% homologous to the mouse introns, respectively. The coding sequence (
CDS) of the dog shows 93% homology to human CDS and 88% homology to mo
use CDS. A phylogenetic analysis of the intronic sequences 2 and 4 con
firms the higher relatedness between dog and human than between mouse
and human opsin genes. As there are good reasons to believe that the p
rimate and rodent lineages are closer to each other than to the Canis
familiaris, there must be some functional constraints on the evolution
of human and dog opsins.