Wolfram syndrome 1 (Wfs1) gene expression in the normal mouse visual system

Wolfram syndrome (OMIM 222300) is a neurodegenerative disorder defined by insulin-dependent diabetes mellitus and progressive optic atrophy. This syndrome has been attributed to mutations in the WFS1 gene, which codes for a putative multi-spanning membrane glycoprotein of the endoplasmic reticulum. The function of WTS1 (wolframin), the distribution of this protein in the mammalian visual system, and the pathogenesis of optic atrophy in Wolfram syndrome are unclear. In this study we made a detailed analysis of the distribution of Wfs1 mRNA and protein in the normal mouse visual system by using in situ hybridization and immunohistochemistry. The mRNA and protein were observed in the retina, optic nerve, and brain. In the retina, Wfs1 expression was strong in amacrine and Muller cells, and moderate in photoreceptors and horizontal cells. In addition, it was detectable in bipolar and retinal ganglion cells. Interestingly, moderate Wfs1 expression was seen in the optic nerve, particularly in astrocytes, while little Wfs1 was expressed in the optic chiasm or optic tract. In the brain, moderate Wfs1 expression was observed in the zonal, superficial gray, and intermediate gray layers of the superior colliculus, in the dorsomedial part of the suprachiasmatic nucleus, and in layer II of the primary and secondary visual cortices. Thus, Wfs1 mRNA and protein were widely distributed in the normal mouse visual system. This evidence may provide clues as to the physiological role of Wfs1 protein in the biology of vision, and help to explain the selective vulnerability of the optic nerve to WFS1 loss-of-function.