Congenital stationary night blindness is associated with the leopard complex in the Miniature Horse.
ABSTRACT 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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ABSTRACT: Congenital stationary night blindness (CSNB) refers to a group of genetically and clinically heterogeneous retinal disorders. Seventeen different genes with more than 360 different mutations and more than 670 affected alleles have been associated with CSNB, including genes coding for proteins of the phototransduction cascade, those important for signal transmission from the photoreceptors to the bipolar cells or genes involved in retinoid recycling in the retinal pigment epithelium. This article describes the phenotypic characteristics of different forms of CSNB that are necessary for accurate diagnosis and to direct and improve genetic testing. An overview of classical and recent methods used to identify specific CSNB genotypes is provided and a meta-analysis of all previously published and novel data is performed to determine the prevalence of disease-causing mutations. Studies of the underlying molecular pathogenic mechanisms based on cell culture techniques and animal studies are outlined. The article highlights how the study of CSNB has increased understanding of the mechanisms of visual signalling in the retina, likely to prove important in developing future treatments for CSNB and other retinal disorders.Progress in Retinal and Eye Research 10/2014; 45. DOI:10.1016/j.preteyeres.2014.09.001 · 9.90 Impact Factor
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ABSTRACT: Toolara State Forest is the largest exotic commercial pine plantation located in the Sunshine Coast area of Queensland. Due to an abundant supply of resources, there is a significant population of feral horses (Equus caballus), which is facing an increased risk of overpopulation. Evidence from previous surveys suggests that over ten years the population has increased from 180 to 800 individuals, which could potentially lead to welfare issues. The objective of the study was to characterise population dynamics and growth in order to define the needs for long-term population control and management. The feral horse population was studied in the forest by direct observations from September 2011 through April 2012. Population composition, stability of harems, habitat preferences and foaling rate for 2011/2012 breeding season were estimated. Observations were performed over one week in each month. Horses were identified on the basis of body colour, natural head and leg markings, gender, age and group associations. The composition and location of horse groups was recorded at each observation. Detailed observations were made on a focal population of 319 horses, consisting of 54 breeding groups (277 horses), 15 bachelor groups (35 individuals) and 4 mares and their offspring groups (7 horses), which occupied the study area of 110 km2. Gender ratio of adult horses was slightly biased towards females; with the ratio being 1.0:0.85 females to males. The age structure of the focal population constituted of 68.3% adult horses, 10.3% juveniles (2-3 years old), and 6.89 yearlings. Foals made 14.42% of the total population in 2011/2012 breeding season. Based on observation of live foals present at foot (n=46), the foaling rate was calculated at 39%. The temporal trend indicated that reproduction in the focal population was seasonal, with the greater part of foaling events occurring between September and February; and reaching two foaling peaks in September (27%) and in January (23%), respectively. Estimated foal survival was 89% (n = 41), of which 60% (n=3) of recorded mortalities occurred in younger foals (age 0 to 1 month).The reproduction values for 2011/2012 breeding season reached 0.21 offspring per adult horse. Using finite rate of population increase, we estimated that the maximum rate for the focal population growth was 21.1% and was similar to estimates proposed for other feral horse populations. Based on our data, such as the female biased gender ratio, the large number of horses that are in reproductive age, and the potential of the population to grow per year at a rate of 21%, this population of feral horses in Toolara State Forest has the ability to increase considerably and will require active management to control numbers.Australian and New Zealand College of Veterinary Scientists, Gold Coast, Australia; 01/2012
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ABSTRACT: Leopard complex spotting is inherited by the incompletely dominant locus, LP, which also causes congenital stationary night blindness in homozygous horses. We investigated an associated single nucleotide polymorphism in the TRPM1 gene in 96 archaeological bones from 31 localities from Late Pleistocene (approx. 17 000 YBP) to medieval times. The first genetic evidence of LP spotting in Europe dates back to the Pleistocene. We tested for temporal changes in the LP associated allele frequency and estimated coefficients of selection by means of approximate Bayesian computation analyses. Our results show that at least some of the observed frequency changes are congruent with shifts in artificial selection pressure for the leopard complex spotting phenotype. In early domestic horses from Kirklareli–Kanligecit (Turkey) dating to 2700–2200 BC, a remarkably high number of leopard spotted horses (six of 10 individuals) was detected including one adult homozygote. However, LP seems to have largely disappeared during the late Bronze Age, suggesting selection against this phenotype in early domestic horses. During the Iron Age, LP reappeared, probably by reintroduction into the domestic gene pool from wild animals. This picture of alternating selective regimes might explain how genetic diversity was maintained in domestic animals despite selection for specific traits at different times.Philosophical Transactions of The Royal Society B Biological Sciences 12/2014; 370(1660). DOI:10.1098/rstb.2013.0386 · 6.31 Impact Factor