title: The KIT gene is associated with the english spotting coat color locus and congenital megacolon in Checkered Giant rabbits (Oryctolagus cuniculus).
abstract: The English spotting coat color locus in rabbits, also known as Dominant white spotting locus, is determined by an incompletely dominant allele (En). Rabbits homozygous for the recessive wild-type allele (en/en) are self-colored, heterozygous En/en rabbits are normally spotted, and homozygous En/En animals are almost completely white. Compared to vital en/en and En/en rabbits, En/En animals are subvital because of a dilated ("mega") cecum and ascending colon. In this study, we investigated the role of the KIT gene as a candidate for the English spotting locus in Checkered Giant rabbits and characterized the abnormalities affecting enteric neurons and c-kit positive interstitial cells of Cajal (ICC) in the megacolon of En/En rabbits. Twenty-one litters were obtained by crossing three Checkered Giant bucks (En/en) with nine Checkered Giant (En/en) and two en/en does, producing a total of 138 F1 and backcrossed rabbits. Resequencing all coding exons and portions of non-coding regions of the KIT gene in 28 rabbits of different breeds identified 98 polymorphisms. A single nucleotide polymorphism genotyped in all F1 families showed complete cosegregation with the English spotting coat color phenotype (θ=0.00 LOD  =75.56). KIT gene expression in cecum and colon specimens of En/En (pathological) rabbits was 5-10% of that of en/en (control) rabbits. En/En rabbits showed reduced and altered c-kit immunolabelled ICC compared to en/en controls. Morphometric data on whole mounts of the ascending colon showed a significant decrease of HuC/D (P<0.05) and substance P (P<0.01) immunoreactive neurons in En/En vs. en/en. Electron microscopy analysis showed neuronal and ICC abnormalities in En/En tissues. The En/En rabbit model shows neuro-ICC changes reminiscent of the human non-aganglionic megacolon. This rabbit model may provide a better understanding of the molecular abnormalities underlying conditions associated with non-aganglionic megacolon.
authors.affiliation: Department of Agricultural and Food Sciences, Division of Animal Sciences, Laboratory of Livestock Genomics, University of Bologna, Bologna, Italy; Centre for Genome Biology, University of Bologna, Bologna, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Fontanesi
authors.affiliation: Health Sciences and Technologies-Interdepartmental Center for Industrial Research, University of Bologna, Bologna, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Vargiolu
authors.affiliation: Department of Agricultural and Food Sciences, Division of Animal Sciences, Laboratory of Livestock Genomics, University of Bologna, Bologna, Italy.
authors.forename: Emilio
authors.initials: E
authors.lastname: Scotti
authors.affiliation: Department of Veterinary Medical Science, University of Bologna, Bologna, Italy; Department of Medical and Surgical Sciences, Centro Unificato di Ricerca Biomedica Applicata (C.R.B.A.), St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
authors.forename: Rocco
authors.initials: R
authors.lastname: Latorre
authors.affiliation: Department of Experimental and Clinical Medicine, Section of Anatomy and Histology, University of Florence, Florence, Italy.
authors.forename: Maria Simonetta
authors.initials: MS
authors.lastname: Faussone Pellegrini
authors.affiliation: Department of Veterinary Medical Science, University of Bologna, Bologna, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Mazzoni
authors.affiliation: Department of Veterinary Medical Science, University of Bologna, Bologna, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Asti
authors.affiliation: Department of Veterinary Medical Science, University of Bologna, Bologna, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Chiocchetti
authors.affiliation: Department of Medical and Surgical Sciences, Medical Genetics Unit, St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Romeo
authors.affiliation: Department of Veterinary Medical Science, University of Bologna, Bologna, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Clavenzani
authors.affiliation: Department of Medical and Surgical Sciences, Centro Unificato di Ricerca Biomedica Applicata (C.R.B.A.), St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: De Giorgio
mesh_terms: D000818:Animals; D003433:Crosses, Genetic; D004195:Disease Models, Animal; D005260:Female; D015870:Gene Expression; D056726:Genetic Association Studies; D008040:Genetic Linkage; D005838:Genotype; D006200:Hair Color / Q000235:genetics*; D006627:Hirschsprung Disease / Q000235:genetics* / Q000378:metabolism; D056885:Interstitial Cells of Cajal / Q000378:metabolism / Q000648:ultrastructure; D008297:Male; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D010641:Phenotype; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000378:metabolism; D011817:Rabbits
chemical_list: D019009:Proto-Oncogene Proteins c-kit
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