Abstract
Purpose:
To characterize a novel mouse recessive mutation that develops retinal degeneration associated with the dysfunction of retinal pigment epithelium (RPE) and male infertility.
Methods:
Fundus examination, histology analysis, and immunostaining were performed to evaluate the molecular and cellular alterations in mutant mice.
Results:
Both heterozygous and homozygous mutant mice are viable with normal appearance. However, male homozygous mutant mice are infertile. Fundus examination reveals depigmented patches in the retinas of homozygous mutant mice. Disorganized and attenuated RPE layers are observed in histology sections and in flat-mount RPE staining from the homozygous mutant mice. At 3 weeks of age, although the photoreceptor cell layers remain relatively normal, mutant retinas display drastic abnormalities, including degenerated RPE cells and pigmented round structures in the subretinal space. Histology data show progressive retinal degeneration as mice age, evidenced by a loss of photoreceptor cells and the shortening of outer and inner segments. The progressive degeneration of retinal photoreceptors is likely a secondary effect to the RPE defects in mutant retinas. Interestingly, the testes of homozygous mutant mice are smaller than those of wild-type males; histology confirms that elongated spermatids are absent in degenerated seminiferous tubules of mutant testes. The causative gene has been mapped into a 6-Mb interval in mouse chromosome 2.
Conclusions:
Retinal degeneration and male infertility in the mutant mice resemble some of the phenotypes of human Bardet-Biedl Syndrome (BBS). However, none of the current BBS candidate genes is mapped into this locus. Thus, a mutation on an unknown candidate gene is responsible for the mutant phenotype. The identification of the causative gene mutation will be important for understanding the function of RPE cells and related retinal disorders.
Keywords: 701 retinal pigment epithelium •
688 retina •
695 retinal degenerations: cell biology