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Targeted analysis of four breeds narrows equine Multiple Congenital Ocular Anomalies locus to 208 kilobases.

ABSTRACT: The syndrome Multiple Congenital Ocular Anomalies (MCOA) is the collective name ascribed to heritable congenital eye defects in horses. Individuals homozygous for the disease allele (MCOA phenotype) have a wide range of eye anomalies, while heterozygous horses (Cyst phenotype) predominantly have cysts that originate from the temporal ciliary body, iris, and/or peripheral retina. MCOA syndrome is highly prevalent in the Rocky Mountain Horse but the disease is not limited to this breed. Affected horses most often have a Silver coat color; however, a pleiotropic link between these phenotypes is yet to be proven. Locating and possibly isolating these traits would provide invaluable knowledge to scientists and breeders. This would favor maintenance of a desirable coat color while addressing the health concerns of the affected breeds, and would also provide insight into the genetic basis of the disease. Identical-by-descent mapping was used to narrow the previous 4.6-Mb region to a 264-kb interval for the MCOA locus. One haplotype common to four breeds showed complete association to the disease (Cyst phenotype, n = 246; MCOA phenotype, n = 83). Candidate genes from the interval, SMARCC2 and IKZF4, were screened for polymorphisms and genotyped, and segregation analysis allowed the MCOA syndrome region to be shortened to 208 kb. This interval also harbors PMEL17, the gene causative for Silver coat color. However, by shortening the MCOA locus by a factor of 20, 176 other genes have been unlinked from the disease and only 15 genes remain.

SUBMITTER: Andersson LS

PROVIDER: S-EPMC3098992 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND: Equine Multiple Congenital Ocular Anomalies (MCOA) syndrome consists of a diverse set of abnormalities predominantly localized to the frontal part of the eye. The disease is in agreement with a codominant mode of inheritance in our horse material. Animals presumed to be heterozygous for the mutant allele have cysts originating from the temporal ciliary body, peripheral retina and/or iris. In contrast, animals predicted to be homozygous for the disease-causing allele possess a wide range of multiple abnormalities, including iridociliary and/or peripheral retinal cysts, iridocorneal angle abnormalities, cornea globosa, iris hypoplasia and congenital cataracts. MCOA is most common in the Rocky Mountain horse breed where it occurs at a high frequency among Silver colored horses. The Silver coat color is associated with mutations in PMEL17 that resides on ECA6q23. To map the MCOA locus we analyzed 11 genetic markers on ECA6q and herein describe a chromosome interval for the MCOA locus. RESULTS: We performed linkage analysis within 17 paternal half-sib families of the Rocky Mountain horse breed. More than half of the 131 offspring had the Cyst phenotype and about one third had MCOA. Segregation data were obtained by genotyping 10 microsatellite markers most of which are positioned on ECA6q22-23, as well as the missense mutation for the Silver phenotype in PMEL17. Significant linkage was found between the MCOA locus and eight of the genetic markers, where marker UPP5 (Theta = 0, z = 12.3), PMEL17ex11 (Theta = 0, z = 19.0) and UPP6 (Theta = 0, z = 17.5) showed complete linkage with the MCOA locus. DNA sequencing of PMEL17 in affected and healthy control individuals did not reveal any additional mutations than the two mutations associated with the Silver coat color. CONCLUSION: The MCOA locus can with high confidence be positioned within a 4.9 megabase (Mb) interval on ECA6q. The genotype data on UPP5, PMEL17ex11 and UPP6 strongly support the hypothesis that horses with the Cyst phenotype are heterozygous for the mutant allele and that horses with the MCOA phenotype are homozygous for the mutant allele.

Project description:Background and objectiveImpact of appearance of congenital hand anomalies has not previously been reported. The purpose of this study was to describe the common perception about how different congenitally malformed hands look.MethodsWe developed a questionnaire in a game format to evaluate the appearance of different hands. Altogether 1450 (954 females) 4- to 84-year-old residents (296 children) of two European and one Asian (n = 102) country were asked to rate the appearance of different looking hands on a five-point pictorial Likert-type scale. Standardized photographs of the dorsal aspect of 17 different congenitally malformed non-operated hands and a normal hand were presented to respondents. Significance of age, gender, nationality, and profession of the respondents was assessed.ResultsThe respondents' ranking order of the hands was nearly consistent. The normal hand (mean = 4.43, standard deviation = 0.85, Md = 5) and clinodactyly (mean = 4.37, standard deviation = 0.86, Md = 5) were perceived to have the best appearance. Symbrachydactyly (mean = 1.42, standard deviation = 0.68, Md = 1) and radial club hand (mean = 1.40, standard deviation = 0.68, Md = 1) received the lowest scores. Adults rated the appearance of hands higher than children regarding 14 hands, females higher than men regarding 15 hands, and Europeans higher than Asians in 4 hands (p < 0.05, respectively). Europeans rated four-finger hand (mean = 3.21, standard deviation = 1.18, Md = 3) better looking than six-finger hand (mean = 2.92, standard deviation = 1.18, Md = 3, p < 0.005), whereas Asians gave higher scores to six-finger hand (mean = 2.66, standard deviation = 1.26, Md = 3) compared to four-finger hand (mean = 2.51, standard deviation = 1.14, Md = 2). Medical doctors and nurses gave higher scores compared to the other profession groups, school children, and high school students in five hands (p < 0.05).ConclusionsA normal hand is perceived distinctly better looking than most congenitally different hands. Different malformations' appearance was ranked very coherently in the same order despite of participants' age, gender, nationality, or profession. Asians seem to prefer an additional digit to a four-finger hand.

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Targeted analysis of four breeds narrows equine Multiple Congenital Ocular Anomalies locus to 208 kilobases.

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