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: Archaeologists often argue whether Paleolithic works of art, cave paintings in particular, constitute reflections of the natural environment of humans at the time. They also debate the extent to which these paintings actually contain creative artistic expression, reflect the phenotypic variation of the surrounding environment, or focus on rare phenotypes. The famous paintings "The Dappled Horses of Pech-Merle," depicting spotted horses on the walls of a cave in Pech-Merle, France, date back ~25,000 y, but the coat pattern portrayed in these paintings is remarkably similar to a pattern known as "leopard" in modern horses. We have genotyped nine coat-color loci in 31 predomestic horses from Siberia, Eastern and Western Europe, and the Iberian Peninsula. Eighteen horses had bay coat color, seven were black, and six shared an allele associated with the leopard complex spotting (LP), representing the only spotted phenotype that has been discovered in wild, predomestic horses thus far. LP was detected in four Pleistocene and two Copper Age samples from Western and Eastern Europe, respectively. In contrast, this phenotype was absent from predomestic Siberian horses. Thus, all horse color phenotypes that seem to be distinguishable in cave paintings have now been found to exist in prehistoric horse populations, suggesting that cave paintings of this species represent remarkably realistic depictions of the animals shown. This finding lends support to hypotheses arguing that cave paintings might have contained less of a symbolic or transcendental connotation than often assumed.Proceedings of the National Academy of Sciences 11/2011; 108(46):18626-30. DOI:10.1073/pnas.1108982108 · 9.81 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; 06/2012
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ABSTRACT: Mutations in TRPM1, a calcium channel expressed in retinal bipolar cells and epidermal melanocytes, cause complete congenital stationary night blindness with no discernible skin phenotype. In the retina, TRPM1 activity is negatively coupled to metabotropic glutamate receptor 6 (mGluR6) signaling through Gαo and TRPM1 mutations result in the loss of responsiveness of TRPM1 to mGluR6 signaling. Here, we show that human melanocytes express mGluR6 and treatment of melanocytes with L-AP4, a type III mGluR-selective agonist, enhances Ca2+ uptake. Knockdown of TRPM1 or mGluR6 by shRNA abolished L-AP4-induced Ca2+ influx and TRPM1 currents showing that TRPM1 activity in melanocytes is positively coupled to mGluR6 signaling. Gαo protein is absent in melanocytes. However, forced expression of Gαo restored negative coupling of TRPM1 to mGluR6 signaling, but treatment with and pertussis toxin, an inhibitor of Gi /Go proteins, did not affect basal or mGluR6-induced Ca2+ uptake. Additionally, chronic stimulation of mGluR6 altered melanocyte morphology and increased melanin content. These data suggest differences in coupling of TRPM1 function to mGluR6 signaling explain different cellular responses to glutamate in the retina and the skin. © 2013 John Wiley & Sons A/S.Pigment Cell & Melanoma Research 03/2013; 26(3). DOI:10.1111/pcmr.12083 · 5.64 Impact Factor