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Kingsley NB, Sandmeyer L, Bellone RR. A review of investigated risk factors for developing equine recurrent uveitis. Vet Ophthalmol 2022; 26:86-100. [PMID: 35691017 DOI: 10.1111/vop.13002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 04/25/2022] [Accepted: 05/27/2022] [Indexed: 12/01/2022]
Abstract
Equine recurrent uveitis (ERU) is an ocular inflammatory disease that can be difficult to manage clinically. As such, it is the leading cause of bilateral blindness for horses. ERU is suspected to have a complex autoimmune etiology with both environmental and genetic risk factors contributing to onset and disease progression in some or all cases. Work in recent years has aimed at unraveling the primary triggers, such as infectious agents and inherited breed-specific risk factors, for disease onset, persistence, and progression. This review has aimed at encompassing those factors that have been associated, implicated, or substantiated as contributors to ERU, as well as identifying areas for which additional knowledge is needed to better understand risk for disease onset and progression. A greater understanding of the risk factors for ERU will enable earlier detection and better prognosis through prevention and new therapeutics.
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Affiliation(s)
- Nicole B Kingsley
- Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California - Davis, Davis, California, USA.,Department of Population Health and Reproduction, School of Veterinary Medicine, University of California - Davis, Davis, California, USA
| | - Lynne Sandmeyer
- Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Rebecca R Bellone
- Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California - Davis, Davis, California, USA.,Department of Population Health and Reproduction, School of Veterinary Medicine, University of California - Davis, Davis, California, USA
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Coat Color Roan Shows Association with KIT Variants and No Evidence of Lethality in Icelandic Horses. Genes (Basel) 2020; 11:genes11060680. [PMID: 32580410 PMCID: PMC7348759 DOI: 10.3390/genes11060680] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 06/18/2020] [Accepted: 06/19/2020] [Indexed: 11/26/2022] Open
Abstract
Roan (Rn) horses show a typical seasonal change of color. Their body is covered with colored and white hair. We performed a descriptive statistical analysis of breeding records of Icelandic horses to challenge the hypothesis of roan being lethal in utero under homozygous condition. The roan to non-roan ratio of foals from roan × roan matings revealed homozygous roan Icelandic horses to be viable. Even though roan is known to be inherited in a dominant mode and epistatic to other coat colors, the causative mutation is still unknown. Nevertheless, an association between roan phenotype and the KIT gene was shown for different horse breeds. In the present study, we identified KIT variants by Sanger sequencing, and show that KIT is also associated with roan in the Icelandic horse breed.
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Sandmeyer LS, Kingsley NB, Walder C, Archer S, Leis ML, Bellone RR, Bauer BS. Risk factors for equine recurrent uveitis in a population of Appaloosa horses in western Canada. Vet Ophthalmol 2020; 23:515-525. [PMID: 32086865 DOI: 10.1111/vop.12749] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 01/22/2020] [Accepted: 01/23/2020] [Indexed: 12/12/2022]
Abstract
OBJECTIVE To characterize clinical manifestations, measure frequency, and evaluate risk factors for equine recurrent uveitis (ERU) in Appaloosa horses in western Canada. ANIMALS 145 Appaloosa horses. PROCEDURES Ophthalmic examinations were completed and eyes were classified as having no or mild clinical signs, or moderate, or severe damage from ERU. Clinical signs, age, sex, base coat color, and pattern were recorded. Whole blood and/or mane hair follicles were collected for DNA extraction, and all horses were tested for the leopard complex (LP) spotting pattern allele. Pedigree analysis was completed on affected and unaffected horses, and coefficients of coancestry (CC) and inbreeding (COI) were determined. RESULTS Equine recurrent uveitis was confirmed in 20 (14%) horses. The mean age of affected horses was 12.3 years (±5.3; range 3-25). Age was a significant risk factor for ERU diagnosis (ORyear = 1.15) and classification (ORyear = 1.19). The fewspot coat pattern was significantly associated with increased risk for ERU compared to horses that were minimally patterned or true solids. The LP/LP genotype was at a significantly greater risk for ERU compared to lp/lp (OR = 19.4) and LP/lp (OR = 6.37). Classification of ERU was greater in the LP/LP genotype compared to LP/lp. Affected horses had an average CC of 0.066, and there was a significant difference in the distribution of CC for affected horses versus the control group (P = .021). One affected horse was the sire or grandsire of nine other affected. CONCLUSIONS Age, coat pattern, and genetics are major risk factors for the diagnosis and classification of ERU in the Appaloosa.
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Affiliation(s)
- Lynne S Sandmeyer
- Small Animal Clinical Sciences, University of Saskatchewan, Saskatoon, Sask, Canada
| | - Nicole B Kingsley
- Equine Research Unit, University of California Davis Veterinary Genetics Laboratory, Davis, CA, USA
| | - Cheryl Walder
- Large Animal Clinical Sciences, University of Saskatchewan College of Veterinary Medicine, Saskatoon, Sask, Canada
| | | | - Marina L Leis
- Small Animal Clinical Sciences, University of Saskatchewan, Saskatoon, Sask, Canada
| | - Rebecca R Bellone
- Veterinary Genetics Laboratory and the Department of Population Health and Reproduction, University of California-Davis, Davis, CA, USA
| | - Bianca S Bauer
- Small Animal Clinical Sciences, University of Saskatchewan, Saskatoon, Sask, Canada
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Some hematological and biochemical reference values of the thoroughbred Appaloosa horse breeds reared in Kyrgyzstan. ACTA ACUST UNITED AC 2019. [DOI: 10.1007/s00580-019-02991-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Druml T, Grilz-Seger G, Neuditschko M, Neuhauser B, Brem G. Phenotypic and Genetic Analysis of the Leopard Complex Spotting in Noriker Horses. J Hered 2017; 108:505-514. [PMID: 28453641 DOI: 10.1093/jhered/esx039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 04/21/2017] [Indexed: 11/14/2022] Open
Abstract
Genetic analyses of coat colors are frequently restricted to subjectively categorized phenotype information. The aim of this study was to develop a method to numerically quantify the variability of leopard complex (LP) spotting phenotypes introducing tools from image analysis. Generalized Procrustes analysis eliminates systematic errors due to imaging process. The binarization of normalized images and the application of principal component analysis (PCA) on the derived pixel matrices, transform pixel information into numerical data space. We applied these methods on 90 images to ascertain the specific leopard patterns within the Noriker breed. Furthermore, we genotyped a representative sample of 191 Noriker horses for the known LP spotting associated loci. Ninety-seven percentage of the genotyped leopard spotted horses were heterozygous for LP and had at least one copy of the PATN1 allele. However, the remaining pattern variation was great, indicating other genetic factors influencing the expression of LP spotting. Based upon this data, we estimated effect sizes of the modifier PATN1, and additional factors including sex, age, base color, and spotting phenotype of parents. The PCA of the pixel matrix resulted in 2 significant components accounting for 51% of the variation. Applying a linear model, we identified significant effects for age groups and base color on the first and second components, while for sex and parents' LP phenotype significant effects were found on 4 additional components.
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Affiliation(s)
- Thomas Druml
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1220 Vienna, Austria; Pöckau 41, Arnoldstein, Austria; and Agroscope, Swiss National Stud Farm, Les Longs Pres, Avenches, Switzerland
| | - Gertrud Grilz-Seger
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1220 Vienna, Austria; Pöckau 41, Arnoldstein, Austria; and Agroscope, Swiss National Stud Farm, Les Longs Pres, Avenches, Switzerland
| | - Markus Neuditschko
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1220 Vienna, Austria; Pöckau 41, Arnoldstein, Austria; and Agroscope, Swiss National Stud Farm, Les Longs Pres, Avenches, Switzerland
| | - Barbara Neuhauser
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1220 Vienna, Austria; Pöckau 41, Arnoldstein, Austria; and Agroscope, Swiss National Stud Farm, Les Longs Pres, Avenches, Switzerland
| | - Gottfried Brem
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1220 Vienna, Austria; Pöckau 41, Arnoldstein, Austria; and Agroscope, Swiss National Stud Farm, Les Longs Pres, Avenches, Switzerland
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Holl HM, Brooks SA, Archer S, Brown K, Malvick J, Penedo MCT, Bellone RR. Variant in theRFWD3gene associated withPATN1, a modifier of leopard complex spotting. Anim Genet 2015; 47:91-101. [DOI: 10.1111/age.12375] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/31/2015] [Indexed: 01/11/2023]
Affiliation(s)
- H. M. Holl
- Department of Animal Science; Cornell University; Ithaca NY 14853 USA
| | - S. A. Brooks
- Department of Animal Science; Cornell University; Ithaca NY 14853 USA
| | | | - K. Brown
- Department of Biology; University of Tampa; Tampa FL 33606 USA
| | - J. Malvick
- Veterinary Genetics Laboratory; School of Veterinary Medicine; University of California-Davis; Davis CA 95616 USA
| | - M. C. T. Penedo
- Veterinary Genetics Laboratory; School of Veterinary Medicine; University of California-Davis; Davis CA 95616 USA
| | - R. R. Bellone
- Department of Population Health and Reproduction; Veterinary Genetics Laboratory; School of Veterinary Medicine; University of California-Davis; Davis CA 95616 USA
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Abstract
Horses are valued for the beauty and variety of colouration and coat patterning. To date, eleven different genes have been characterized that contribute to the variation observed in the horse. Unfortunately, mutations involving pigmentation often lead to deleterious effects in other systems, some of which have been described in the horse. This review focuses on six such pleiotropic effects or associations with pigmentation genes. These include neurological defects (lethal white foal syndrome and lavender foal syndrome), hearing defects, eye disorders (congenital stationary night blindness and multiple congenital ocular anomalies), as well as horse-specific melanoma. The pigmentation phenotype, disorder phenotype, mode of inheritance, genetic or genomic methods utilized to identify the genes involved and, if known, the causative mutations, molecular interactions and other susceptibility loci are discussed. As our understanding of pigmentation in the horse increases, through the use of novel genomic tools, we are likely to unravel yet unknown pleiotropic effects and determine additional interactions between previously discovered loci.
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Affiliation(s)
- R R Bellone
- Department of Biology, University of Tampa, 401 W. Kennedy Blvd., Tampa, FL 33606, USA.
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Bellone RR, Holl H, Setaluri V, Devi S, Maddodi N, Archer S, Sandmeyer L, Ludwig A, Foerster D, Pruvost M, Reissmann M, Bortfeldt R, Adelson DL, Lim SL, Nelson J, Haase B, Engensteiner M, Leeb T, Forsyth G, Mienaltowski MJ, Mahadevan P, Hofreiter M, Paijmans JLA, Gonzalez-Fortes G, Grahn B, Brooks SA. Evidence for a retroviral insertion in TRPM1 as the cause of congenital stationary night blindness and leopard complex spotting in the horse. PLoS One 2013; 8:e78280. [PMID: 24167615 PMCID: PMC3805535 DOI: 10.1371/journal.pone.0078280] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 09/10/2013] [Indexed: 12/21/2022] Open
Abstract
Leopard complex spotting is a group of white spotting patterns in horses caused by an incompletely dominant gene (LP) where homozygotes (LP/LP) are also affected with congenital stationary night blindness. Previous studies implicated Transient Receptor Potential Cation Channel, Subfamily M, Member 1 (TRPM1) as the best candidate gene for both CSNB and LP. RNA-Seq data pinpointed a 1378 bp insertion in intron 1 of TRPM1 as the potential cause. This insertion, a long terminal repeat (LTR) of an endogenous retrovirus, was completely associated with LP, testing 511 horses (χ2=1022.00, p<<0.0005), and CSNB, testing 43 horses (χ2=43, p<<0.0005). The LTR was shown to disrupt TRPM1 transcription by premature poly-adenylation. Furthermore, while deleterious transposable element insertions should be quickly selected against the identification of this insertion in three ancient DNA samples suggests it has been maintained in the horse gene pool for at least 17,000 years. This study represents the first description of an LTR insertion being associated with both a pigmentation phenotype and an eye disorder.
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Affiliation(s)
- Rebecca R. Bellone
- Department of Biology, University of Tampa, Tampa, Florida, United States of America
- * E-mail:
| | - Heather Holl
- Department of Animal Science, Cornell University, Ithaca, New York, United States of America
| | - Vijayasaradhi Setaluri
- Department of Dermatology, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Sulochana Devi
- Department of Dermatology, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Nityanand Maddodi
- Department of Dermatology, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, United States of America
| | | | - Lynne Sandmeyer
- Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Arne Ludwig
- Department of Evolutionary Genetics, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
| | - Daniel Foerster
- Department of Evolutionary Genetics, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
| | - Melanie Pruvost
- Department of Evolutionary Genetics, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
- Epigenomic and Palaeogenomic Group, Institut Jacques Monod, Paris, France
| | - Monika Reissmann
- Department of Breeding Biology and Molecular Genetics, Humboldt University Berlin, Berlin, Germany
| | - Ralf Bortfeldt
- Department of Breeding Biology and Molecular Genetics, Humboldt University Berlin, Berlin, Germany
| | - David L. Adelson
- School of Molecular and Biomedical Science, the University of Adelaide, South Australia, Australia
| | - Sim Lin Lim
- School of Molecular and Biomedical Science, the University of Adelaide, South Australia, Australia
| | - Janelle Nelson
- Department of Biology, University of Tampa, Tampa, Florida, United States of America
| | - Bianca Haase
- Faculty of Veterinary Science, University of Sydney, Sydney, New South Wales, Australia
| | | | - Tosso Leeb
- Institute of Genetics, University of Bern, Bern, Switzerland
| | - George Forsyth
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Michael J. Mienaltowski
- Department of Molecular Pharmacology & Physiology, College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Padmanabhan Mahadevan
- Department of Biology, University of Tampa, Tampa, Florida, United States of America
| | | | | | | | - Bruce Grahn
- Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Samantha A. Brooks
- Department of Animal Science, Cornell University, Ithaca, New York, United States of America
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Genotypes of predomestic horses match phenotypes painted in Paleolithic works of cave art. Proc Natl Acad Sci U S A 2011; 108:18626-30. [PMID: 22065780 DOI: 10.1073/pnas.1108982108] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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.
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Bellone RR, Archer S, Wade CM, Cuka-Lawson C, Haase B, Leeb T, Forsyth G, Sandmeyer L, Grahn B. Association analysis of candidate SNPs in TRPM1 with leopard complex spotting (LP ) and congenital stationary night blindness (CSNB) in horses. Anim Genet 2010. [DOI: 10.1111/j.1365-2052.2010.02119.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bellone RR, Forsyth G, Leeb T, Archer S, Sigurdsson S, Imsland F, Mauceli E, Engensteiner M, Bailey E, Sandmeyer L, Grahn B, Lindblad-Toh K, Wade CM. Fine-mapping and mutation analysis of TRPM1: a candidate gene for leopard complex (LP) spotting and congenital stationary night blindness in horses. Brief Funct Genomics 2010; 9:193-207. [PMID: 20353955 DOI: 10.1093/bfgp/elq002] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Leopard Complex spotting occurs in several breeds of horses and is caused by an incompletely dominant allele (LP). Homozygosity for LP is also associated with congenital stationary night blindness (CSNB) in Appaloosa horses. Previously, LP was mapped to a 6 cm region on ECA1 containing the candidate gene TRPM1 (Transient Receptor Potential Cation Channel, Subfamily M, Member 1) and decreased expression of this gene, measured by qRT-PCR, was identified as the likely cause of both spotting and ocular phenotypes. This study describes investigations for a mutation causing or associated with the Leopard Complex and CSNB phenotype in horses. Re-sequencing of the gene and associated splice sites within the 105 624 bp genomic region of TRPM1 led to the discovery of 18 SNPs. Most of the SNPs did not have a predictive value for the presence of LP. However, one SNP (ECA1:108,249,293 C>T) found within intron 11 had a strong (P < 0.0005), but not complete, association with LP and CSNB and thus is a good marker but unlikely to be causative. To further localize the association, 70 SNPs spanning over two Mb including the TRPM1 gene were genotyped in 192 horses from three different breeds segregating for LP. A single 173 kb haplotype associated with LP and CSNB (ECA1: 108,197,355- 108,370,150) was identified. Illumina sequencing of 300 kb surrounding this haplotype revealed 57 SNP variants. Based on their localization within expressed sequences or regions of high sequence conservation across mammals, six of these SNPs were considered to be the most likely candidate mutations. While the precise function of TRPM1 remains to be elucidated, this work solidifies its functional role in both pigmentation and night vision. Further, this work has identified several potential regulatory elements of the TRPM1 gene that should be investigated further in this and other species.
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Differential gene expression of TRPM1, the potential cause of congenital stationary night blindness and coat spotting patterns (LP) in the Appaloosa horse (Equus caballus). Genetics 2008; 179:1861-70. [PMID: 18660533 DOI: 10.1534/genetics.108.088807] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The appaloosa coat spotting pattern in horses is caused by a single incomplete dominant gene (LP). Homozygosity for LP (LP/LP) is directly associated with congenital stationary night blindness (CSNB) in Appaloosa horses. LP maps to a 6-cM region on ECA1. We investigated the relative expression of two functional candidate genes located in this LP candidate region (TRPM1 and OCA2), as well as three other linked loci (TJP1, MTMR10, and OTUD7A) by quantitative real-time RT-PCR. No large differences were found for expression levels of TJP1, MTMR10, OTUD7A, and OCA2. However, TRPM1 (Transient Receptor Potential Cation Channel, Subfamily M, Member 1) expression in the retina of homozygous appaloosa horses was 0.05% the level found in non-appaloosa horses (R = 0.0005). This constitutes a >1800-fold change (FC) decrease in TRPM1 gene expression in the retina (FC = -1870.637, P = 0.001) of CSNB-affected (LP/LP) horses. TRPM1 was also downregulated in LP/LP pigmented skin (R = 0.005, FC = -193.963, P = 0.001) and in LP/LP unpigmented skin (R = 0.003, FC = -288.686, P = 0.001) and was downregulated to a lesser extent in LP/lp unpigmented skin (R = 0.027, FC = -36.583, P = 0.001). TRP proteins are thought to have a role in controlling intracellular Ca(2+) concentration. Decreased expression of TRPM1 in the eye and the skin may alter bipolar cell signaling as well as melanocyte function, thus causing both CSNB and LP in horses.
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Sandmeyer LS, Breaux CB, Archer S, Grahn BH. Clinical and electroretinographic characteristics of congenital stationary night blindness in the Appaloosa and the association with the leopard complex. Vet Ophthalmol 2007; 10:368-75. [PMID: 17970998 DOI: 10.1111/j.1463-5224.2007.00572.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To determine the prevalence of congenital stationary night blindness (CSNB) in Appaloosa horses in western Canada, investigate the association with the leopard complex of white spotting patterns, and further characterize the clinical and electroretinographic aspects of CSNB in the Appaloosa. ANIMALS STUDIED Three groups of 10 Appaloosas were studied based on coat patterns suggestive of LpLp, Lplp, and lplp genotype. PROCEDURES Neurophthalmic examination, slit-lamp biomicroscopy, indirect ophthalmoscopy, measurement of corneal diameter, streak retinoscopy, scotopic and photopic full-field and flicker ERGs and oscillatory potentials (OPs) were completed bilaterally. RESULTS All horses in the LpLp group were affected by CSNB, while none in the Lplp or lplp groups was affected. The LpLp and Lplp groups had significantly smaller vertical and horizontal corneal diameters than the lplp group had. Median refractive error was zero for all groups. Scotopic ERGs in the LpLp (CSNB-affected) group were consistent with previous descriptions. The CSNB-affected horses had significantly longer photopic a-wave implicit times, greater a-wave amplitudes, and lower b-wave amplitudes than the Lplp and lplp (normal) groups did. No differences were present in photopic flicker amplitude or implicit times. Scotopic flickers in the CSNB-affected horses were markedly reduced in amplitude and abnormal in appearance. No differences were noted in OP implicit times; however, amplitudes of some OPs were reduced in CSNB-affected horses. There were no differences in scotopic and photopic or flicker ERGs or OPs between the normal groups. CONCLUSIONS CSNB was present in one-third of horses studied and there was a significant association between CSNB and the inheritance of two Lp alleles. ERG abnormalities support the hypothesis that CSNB is caused by a defect in neural transmission through the rod pathway involving the inner nuclear layer.
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Affiliation(s)
- Lynne S Sandmeyer
- Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 584.
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Bellone R, Lawson S, Hunter N, Archer S, Bailey E. Analysis of a SNP in exon 7 of equine OCA2 and its exclusion as a cause for appaloosa spotting. Anim Genet 2006; 37:525. [PMID: 16978190 DOI: 10.1111/j.1365-2052.2006.01505.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- R Bellone
- Department of Biology, University of Tampa, Tampa, FL 33606, USA
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Terry RB, Archer S, Brooks S, Bernoco D, Bailey E. Assignment of the appaloosa coat colour gene (LP) to equine chromosome 1. Anim Genet 2004; 35:134-7. [PMID: 15025575 DOI: 10.1111/j.1365-2052.2004.01113.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A single autosomal dominant locus, leopard complex (LP) controls the presence of appaloosa pigmentation patterns in the horse. The causative gene for LP is unknown. This study was undertaken to map LP in the horse. Two paternal half sib families segregating for the LP locus and including a total of 47 offspring were used to perform a genome scan which localized LP to horse chromosome 1 (ECA1). LP was linked to ASB08 (LOD = 9.99 at Theta = 0.02) and AHT21 (LOD = 5.03 at Theta = 0.14). To refine the map position of LP, eight microsatellite markers on ECA1 (UM041, LEX77, 1CA41, TKY374, COR046, 1CA32, 1CA43, and TKY002) were analysed in the two half sib families. Results from this linkage analysis showed LP was located in the interval between ASB08 and 1CA43. Tight junction protein (TJP1), which lies within the LP interval on ECA1, was used to determine the homologous chromosomes in humans (HSA15) and mice (mouse chromosome 7). We propose that the pink eyed dilution (p) gene and transient receptor potential cation channel subfamily M, member 1 (TRPM1) are positional candidate genes for LP.
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Affiliation(s)
- R B Terry
- Department of Biology, University of Tampa, Tampa, FL 33606, USA.
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Terry RB, Bailey E, Lear T, Cothran EG. Rejection of MITF and MGF as the genes responsible for appaloosa coat colour patterns in horses. Anim Genet 2002; 33:82-4. [PMID: 11849149 DOI: 10.1046/j.1365-2052.2002.0742h.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- R B Terry
- Department of Veterinary Science, University of Kentucky, Lexington, KY, USA
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Terry RR, Bailey E, Bernoco D, Cothran EG. Linked markers exclude KIT as the gene responsible for appaloosa coat colour spotting patterns in horses. Anim Genet 2001; 32:98-101. [PMID: 11421946 DOI: 10.1046/j.1365-2052.2001.00737.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The appaloosa coat colour pattern of the horse is similar to that caused by the rump-white (Rw) gene in the mouse. In the mouse Rw colour pattern is the result of an inversion involving the proto-oncogene c-kit (KIT). Therefore, we investigated KIT as a candidate gene that encodes the appaloosa coat colour gene (Lp) in horses. KIT plays a critical role in haematopoiesis, gametogenesis, and melanogenesis and encodes a transmembrane tyrosine kinase receptor that belongs to the PDGF/CSF-1/c-KIT receptor subfamily. Half-sib families segregating for Lp were uninformative for a reported polymorphism in KIT. However, KIT is located on horse chromosome 3 close to albumin (ALB), serum carboxylesterase (ES), vitamin D-binding protein (GC) and microsatellite markers ASB23, LEX007, LEX57, and UCDEQ437. Indeed, KIT and ASB23 were localized to ECA3q21-22.1 and 3q22.1-22.3, respectively, by fluorescent in situ hybridization. Family studies were conducted to investigate linkage of Lp to these markers using eight half-sib families in which Appaloosa stallions were mated to solid coloured mares. Linkage of Lp to the chromosome region containing ES, ALB, GC, ASB23, UCDEQ437, LEX57, and LEX007 was investigated by a multipoint linkage analysis using the computer program GENEHUNTER. LOD scores over the interval under investigation ranged from -4.28 to -12.48, with a score of -12.48 at the location for ASB23. Therefore, it was concluded that appaloosa (Lp) is not linked to any of the tested markers on ECA3, and thus Lp is unlikely to be the product of KIT.
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Affiliation(s)
- R R Terry
- Department of Veterinary Science, University of Kentucky, Lexington, KY 40524, USA. Stormont Laboratories, Woodland, CA 95776, USA.
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