Canine Model of Autosomal Recessive Complete-type Congenital Stationary Night Blindness

Abstract

Purpose: To report a dog pedigree with autosomal recessive, complete-type congenital stationary night blindness (CSNB). We performed comprehensive clinical, functional, morphological, and genetic analyses on this dog pedigree.

Methods: To determine the inheritance pattern, we crossed affected dogs with normal beagle dogs. Affected dogs were identified by “negative” type of electroretinograms (ERGs). In addition to routine clinical testing, retinal histology was determined by light and electron microscopy. Full-field scotopic and photopic ERGs were elicited by various stimulus intensities. Photopic long duration stimuli ERGs were also recorded to study the retinal function of the on- and off-pathways. Association between CSNB and GRM6, TRPM1, and GPR179 was studied.

Results: We found that inheritance pattern of our night blindness dog is autosomal recessive. Fundus testing and fluorescein angiography were normal. Retinal histology was also normal by both light and electron microscopy.Full-field ERGs showed no detectable rod response, “electro-negative” mixed rod and cone response, and relatively preserved cone response. Photopic long-flash ERGs showed normal off-response (d-wave) associated with severely reduced on-response (b-wave). These ERG findings did not change for five years. No mutation was found on GRM6, TRPM1, and GPR178 gene.

Conclusions: Conclusion. These results suggested that our dogs are autosomal recessive CSNB with selective retinal on-pathway dysfunction. These dogs can be an useful large animal model of complete-type CSNB.

Keywords: 688 retina • 696 retinal degenerations: hereditary • 509 electroretinography: clinical