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M. Glosmann, L. Peichl, K. Neumann, R. Gattermann; Lack of a Functional Shortwave–Sensitive Cone Opsin is a Species Trait in the Golden Hamster . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2838.
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© ARVO (1962-2015); The Authors (2016-present)
All pet and laboratory golden hamsters (Mesocricetus auratus) originate from a single brother–sister pairing back in 1930. It is controversial to what extent different strains of hamster differ genetically and whether they are polymorphic with regard to the possession of a defect in the shortwave–sensitive (S) cone opsin. Here, we sought to evaluate the functional condition of the S cone visual pigment in wild and laboratory golden hamsters and in all three currently recognized congeneric hamster species.
Golden hamster retinal mRNA and genomic DNA were obtained from individuals of two outbred laboratory strains (CRL:LVG(SYR), Zoh:GOHA), from wild hamsters captured in Syria, and their descendents. The S cone opsin gene was amplified by PCR, cloned, and sequenced. Genomic DNA was extracted from three further Mesocricetus species (M. raddei, M. newtoni, and M. brandti) and used to obtain partial S cone opsin gene sequences. In golden hamster, cone opsin protein expression was evaluated by immunohistochemistry and Western blotting using opsin N–terminus–specific antibodies.
In all Mesocricetus species, the S cone opsin gene appears to be a pseudogene. We identified a single base deletion at position 264 in exon 1 in both laboratory golden hamster strains, confirming a previous preliminary report. This mutation results in a frame–shift and produces a preterminal stop codon, rendering the translation of a full–length protein impossible. Wild golden hamsters and M. raddei proved homozygous for the same deletion. In M. newtoni and M. brandti, several substitution and indel mutations were identified that similarly would prevent the translation of a functional S cone opsin. For the golden hamster, full–length S cone opsin cDNA was obtained from polyA–selected RNA. Our preliminary data provide no evidence for the translation of a truncated protein.
All four species of the genus Mesocricetus appear to lack a functional S cone visual pigment. The presence of the same S cone opsin deletion in two lineages, M. auratus and M. raddei, suggests this mutation is ancestral to M. auratus. Consequently, in the absence of reverse mutations, all laboratory and wild golden hamsters must lack a functional S cone visual pigment. In contrast to previous reports, S opsin mRNA appears to be transcribed but not translated in M. auratus.
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