Single nucleotide polymorphisms concordant with the horned/polled trait in Holsteins.

BACKGROUND: Cattle that naturally do not grow horns are referred to as polled, a trait inherited in a dominant Mendelian fashion. Previous studies have localized the polled mutation (which is unknown) to the proximal end of bovine chromosome 1 in a region approximately 3 Mb in size. While a polled genetic test, Tru-Polledtrade mark, is commercially available from MetaMorphix Inc., Holsteins are not a validated breed for this test. FINDINGS: Approximately 160 kb were sequenced within the known polled region from 12 polled and 12 horned Holsteins. Analysis of the polymorphisms identified 13 novel single nucleotide polymorphisms (SNPs) that are concordant with the horned/polled trait. Three of the 13 SNPs are located in gene coding or regulatory regions (e.g., the untranslated region, or UTR) where one is located in the 3'UTR of a gene and the other two are located in the 5'UTR and coding region (synonymous SNP) of another gene. The 3'UTR of genes have been shown to be targets of microRNAs regulating gene expression. In silico analysis indicates the 3'UTR SNP may disrupt a microRNA target site. CONCLUSION: These 13 novel SNPs concordant with the horned/polled trait in Holsteins represent a test panel for the breed and this is the first report to the authors' knowledge of SNPs within gene coding or regulatory regions concordant with the horned/polled trait in cattle. These SNPs will require further testing for verification and further study to determine if the 3'UTR SNP may have a functional effect on the polled trait in Holsteins.

Heritability and complex segregation analysis of deafness in Jack Russell Terriers.

BACKGROUND: The association between patterns of pigmentation and deafness in the dog has a long-documented history, with reports dating back over one hundred years. Long suspected of having a genetic basis, the search for loci with a pronounced influence in the expression of hearing loss in the dog has yet to be successful. No studies in the dog to date have found a possible influence of a specific colour locus associated with deafness. The present study is intended to evaluate the heritability of deafness in the Jack Russell Terrier (JRT), characterize the mode of inheritance, and evaluate the existence of a sex, coat colour, or coat texture influence on the expression of sensorineural deafness. RESULTS: The estimation of heritability of deafness in the JRT was 0.22 when deafness was considered a binary (normal/deaf) trait and 0.31 when deafness was considered a three-category (normal/unilateral/bilateral deafness). The influence of coat colour in the incidence of JRT deafness was statistically significant, indicating that dogs with more white are more likely to be deaf. The influence of sex or coat texture was not statistically significant in the incidence of JRT deafness. Complex segregation analysis revealed a model of a single locus with a large effect on the binary measure of hearing loss is not supported. CONCLUSION: This is the first attempt, to our knowledge, to characterize a genetic component responsible for deafness in the JRT. The heritability of deafness in the JRT was found to be 0.22 and 0.31 considering deafness to be a two-category or three-category trait, respectively. There appears to be an influence of coat colour on the expression of deafness. In an attempt to characterize the mode of inheritance of deafness in the JRT, a model of a single locus with a large effect on hearing loss is not supported with this data. Further study is needed to determine if a single locus may be influencing deafness in the JRT. While the absence of a clear mode of inheritance complicates genetic dissection of deafness in the JRT, the assembling of this pedigree provides a tool for eventually defining the genetic bases of this disorder.

Linkage and segregation analysis of black and brindle coat color in domestic dogs.

Mutations of pigment type switching have provided basic insight into melanocortin physiology and evolutionary adaptation. In all vertebrates that have been studied to date, two key genes, Agouti and Melanocortin 1 receptor (Mc1r), encode a ligand-receptor system that controls the switch between synthesis of red-yellow pheomelanin vs. black-brown eumelanin. However, in domestic dogs, historical studies based on pedigree and segregation analysis have suggested that the pigment type-switching system is more complicated and fundamentally different from other mammals. Using a genomewide linkage scan on a Labrador x greyhound cross segregating for black, yellow, and brindle coat colors, we demonstrate that pigment type switching is controlled by an additional gene, the K locus. Our results reveal three alleles with a dominance order of black (K(B)) > brindle (k(br)) > yellow (k(y)), whose genetic map position on dog chromosome 16 is distinct from the predicted location of other pigmentation genes. Interaction studies reveal that Mc1r is epistatic to variation at Agouti or K and that the epistatic relationship between Agouti and K depends on the alleles being tested. These findings suggest a molecular model for a new component of the melanocortin signaling pathway and reveal how coat-color patterns and pigmentary diversity have been shaped by recent selection.

Radiation hybrid mapping and comparative sequence analysis of bovine RIG-I and MAVS genes.

Retinoic acid inducible gene I (RIG-I) and mitochondrial antiviral signaling (MAVS) proteins have recently been found to operate in a pathway for the detection and subsequent elimination of replicating viral genomes. Because of this innate immunity role, RIG-I and MAVS are candidates for studies of disease resistance. The objectives of this work were to (1) radiation hybrid (RH) map bovine RIG-I and MAVS and (2) perform comparative sequence analysis of partial genomic sequence from each gene. Using a bovine 5000(rad) RH panel, RIG-I was localized to BTA08 (LOD > 12) and MAVS was localized to BTA13 (LOD > 12). RIG-I exon 14 and partial MAVS exon five were sequenced in nine breeds and compared with available sequence from the Bovine Genome Project. RIG-I exon 14 and partial MAYS exon five were conserved in all samples examined. One T-A transversion SNP was found in intronic sequence downstream of RIG-I exon 14.

The color of a Dalmatian's spots: linkage evidence to support the TYRP1 gene.

BACKGROUND: The distinctive coat pattern of a Dalmatian is the result of the interaction of several loci. While the encoded function of these genes is not fully understood, it is known the Piebald, Ticking, and Flecking loci interact to produce the Dalmatian's classic pigmented spots on a white background. The color of the pigmented spots in purebred Dalmatians can either be black or liver, but the locus responsible for color determination is unknown. Studies have been conducted to determine the underlying genes involved in coat color determination in the dog, e.g., in the Labrador Retriever, but none to date have addressed black versus liver in the Dalmatian. RESULTS: A genome scan was conducted in a multi-generational kindred of Dalmatians segregating black and liver spot color. Linkage analysis was performed using a total of 113 polymorphic microsatellite markers from the kindred. Linkage was found between spot color and a single microsatellite marker, FH2319 (LOD = 12.5) on chromosome 11. CONCLUSION: The TYRP1 (Brown) locus is located at position 50.1 Mb on chromosome 11, which is approximately 0.4 Mb from marker FH2319. Given the recent characterization of TYRP1 genetic variations in the dog and the linkage evidence reported here, TYRP1 is likely responsible for the spot color variation of black versus liver seen in the Dalmatian.

Multiplexing of canine microsatellite markers for whole-genome screens.

A set of 172 canine microsatellite markers, termed minimal screening set 1 (MSS1), was recently characterized for use in whole-genome screens. We report here the multiplexing of 155 MSS1 markers into 48 multiplex sets. Amplification of the multiplex sets is achieved using a single thermal cycling program. The markers are labeled with fluorescent dyes and optimized for resolution on an ABI 310 Genetic Analyzer or ABI 377 Sequencer. The multiplexing strategy involves amplifying combinations of markers so that no two markers with the same dye and product size overlap. Multiplexing the MSS1 provides an efficient tool for the collection of genotypes and streamlines whole-genome screens. Screening the canine genome for linkage of markers with various hereditary diseases facilitates identification of affected and carrier individuals, thereby providing researchers and clinicians with an additional diagnostic tool.