Congenital stationary night blindness is associated with the leopard complex in the Miniature Horse

Department of Small Animal Clinical Sciences, University of Saskatchewan, Quill Lake, Saskatchewan, Canada.
Veterinary Ophthalmology (Impact Factor: 1.06). 04/2011; 15(1):18-22. DOI: 10.1111/j.1463-5224.2011.00903.x
Source: PubMed


  To determine if congenital stationary night blindness (CSNB) exists in the Miniature Horse in association with leopard complex spotting patterns (LP), and to investigate if CSNB in the Miniature Horse is associated with three single nucleotide polymorphisms (SNPs) in the region of TRPM1 that are highly associated with CSNB and LP in Appaloosas.
  Three groups of Miniature Horses were studied based on coat patterns suggestive of LP/LP (n=3), LP/lp (n=4), and lp/lp genotype (n=4).
  Horses were categorized based on phenotype as well as pedigree analysis as LP/LP, LP/lp, and lp/lp. Neurophthalmic examination, slit-lamp biomicroscopy, indirect ophthalmoscopy, and scotopic flash electroretinography were performed on all horses. Hair samples were processed for DNA analysis. Three SNPs identified and associated with LP and CSNB in the Appaloosa were investigated for association with LP and CSNB in these Miniature Horses.
  All horses in the LP/LP group were affected by CSNB, while none in the LP/lp or lp/lp groups were affected. All three SNPs were completely associated with LP genotype (χ(2) = 22, P < 0.0005) and CSNB status (χ(2) =11, P<0.0005).
  The Miniature Horse breed is affected by CSNB and it appears to be associated with LP as in the Appaloosa breed. The SNPs tested could be used as a DNA test for CSNB until the causative mutation is determined.

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    • "These include skeletal dysplasias, sensory neuropathies and spinal muscular atrophies (TRPV4, MIM 605427), kidney diseases (TRPC6, MIM 603652; TRPP1, MIM 601313), mucolipidosis type-IV (TRPML1, MIM 605248), familial episodic pain syndrome (TRPA1, MIM 604775), and Olmsted syndrome (TRPV3, MIM 607066). Within the melastatin sub-family, mutations have been implicated in Guamanian amyotropic lateral sclerosis-parkinsonism/dementia (TRPM7, MIM 605692), progressive familial heart block type-1B (TRPM4; MIM 604559), hypomagnesemia with secondary hypocalcemia (TRPM6; MIM 602014), and congenital stationary night blindness (CSNB) in humans (TRPM1, MIM 603576) and in horses homozygous for Leopard Complex (LP) coat spotting [18]–[22]. TRPM3 (melastatin-2), which is most phylogenetically conserved with TRPM1 (melastatin-1), has not been unambiguously linked with inherited human disease. Rare deletions involving TRPM3 have been reported in cases of Kabuki syndrome and autism, whereas, common non-coding variants in TRPM3 have been tentatively associated with longevity and elevated levels of low-density lipoprotein cholesterol and triglycerides [23]–[26]. "
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