Heritable syndrome of skeletal defects in a family of Australian shepherd dogs

A syndrome of multiple defects including cleft palate, polydactyly, and often syndactyly, shortened tibia-fibula, brachygnathism and scoliosis lethal to males is described in a family of Australian shepherd dogs. Female pups lack the cleft palate and survive, but may exhibit the other defects to a lesser degree than do males. Litter data suggest that the trait is inherited as an X-linked lethal gene, but the possibility of a sex-influenced autosomal allele cannot be ruled out. The syndrome may have arisen in conjunction with instability of the merle locus.     

Inheritance of tweed, a modification of merle, in Australian shepherd dogs

An autosomal mutation is responsible for the modification of merle coat color (previously indicated to be due to a transposable DNA element) to the tweed merle pattern in the Australian shepherd dog. The tweed merle pattern consists of color patches that have a greater range in the intensity of the dilute patches and tend to be larger than the patches of nontweed merle. It has no action on nonmerle dogs. The symbol Tw is proposed for this gene.     

Heritability and phenotypic variation of canine hip dysplasia radiographic traits in a cohort of Australian German shepherd dogs

Canine Hip Dysplasia (CHD) is a common, painful and debilitating orthopaedic disorder of dogs with a partly genetic, multifactorial aetiology. Worldwide, potential breeding dogs are evaluated for CHD using radiographically based screening schemes such as the nine ordinally-scored British Veterinary Association Hip Traits (BVAHTs). The effectiveness of selective breeding based on screening results requires that a significant proportion of the phenotypic variation is caused by the presence of favourable alleles segregating in the population. This proportion, heritability, was measured in a cohort of 13,124 Australian German Shepherd Dogs born between 1976 and 2005, displaying phenotypic variation for BVAHTs, using ordinal, linear and binary mixed models fitted by a Restricted Maximum Likelihood method. Heritability estimates for the nine BVAHTs ranged from 0.14-0.24 (ordinal models), 0.14-0.25 (linear models) and 0.12-0.40 (binary models). Heritability for the summed BVAHT phenotype was 0.30 ± 0.02. The presence of heritable variation demonstrates that selection based on BVAHTs has the potential to improve BVAHT scores in the population. Assuming a genetic correlation between BVAHT scores and CHD-related pain and dysfunction, the welfare of Australian German Shepherds can be improved by continuing to consider BVAHT scores in the selection of breeding dogs, but that as heritability values are only moderate in magnitude the accuracy, and effectiveness, of selection could be improved by the use of Estimated Breeding Values in preference to solely phenotype based selection of breeding animals.     

Towards interbreed IBD fine mapping of the mh locus: Double-muscling in the Asturiana de los Valles breed involves the same locus as in the Belgian Blue cattle breed

The Spanish ``Asturiana' cattle breed is characterized by the segregation of a genetically determined muscular hypertrophy referred to as double-muscling or ``culones'. We demonstrate by linkage analysis that this muscular hypertrophy involves the mh locus previously shown to cause double-muscling in the Belgian Blue cattle breed, pointing towards locus homogeneity of this trait across both breeds. Moreover, using a twopoint and multipoint maximum likelihood approach, we show that flanking microsatellite markers are in linkage disequilibrium with the mh locus in both breeds albeit with different alleles. Finally, we discuss how allelic homogeneity across breeds might be exploited to achieve efficient genetic fine-mapping of the mh locus. Received: 13 September 1996 / Accepted: 20 January 1997     

Complex segregation analysis of canine hip dysplasia in German shepherd dogs

Complex segregation analyses were carried out to clarify the mode of inheritance of canine hip dysplasia (CHD) in German shepherd dogs. Data were used from 8,567 animals examined for CHD from 20 families with three to four generations. The existence of a major gene in addition to polygenic gene effects was detected. In the present study, a mixed model with a dominant major gene effect seemed to be most probable for dichotomous encoding (0: dogs without signs of CHD; 1: dogs with borderline/slight to severe CHD). In addition, mixed major gene inheritance was shown for a binary trait where borderline was assigned to dogs scored free from CHD and for a trichotomously encoded trait (0: dogs without signs of CHD; 1: borderline CHD; 2: mild to severe CHD). Although only small frequencies were found for the unfavorable homozygotic genotype AA, the probability of the AB genotype was high in affected animals. Selection schemes to reduce the frequency of the allele A should therefore efficiently improve existing breeding programmes in German shepherd dogs.     

Coat colour inheritance in Soay, Orkney and Shetland sheep

Analysis of the numerical proportions of Soay, Orkney and Shetland sheep of different colours together with test matings, produced results compatible with the hypothesis that these breeds have a multiple allelic series at locus A , white ( A ₁) being dominant to grey ( A ₂) and both being dominant to the gene for self-colour ( A ₅). The alleles at the A locus are epistatic to the alleles for pigment production at locus B , black ( B ₁) being dominant to brown ( B ₂).     

Extent of linkage disequilibrium in large-breed dogs: chromosomal and breed variation

The aim of this study was to better define the extent of linkage disequilibrium (LD) in populations of large-breed dogs and its variation by breed and chromosomal region. Understanding the extent of LD is a crucial component for successful utilization of genome-wide association studies and allows researchers to better define regions of interest and target candidate genes. Twenty-four Golden Retriever dogs, 28 Rottweiler dogs, and 24 Newfoundland dogs were genotyped for single-nucleotide polymorphism (SNP) data using a high-density SNP array. LD was calculated for all autosomes using Haploview. Decay of the squared correlation coefficient (r ²) was plotted on a per-breed and per-chromosome basis as well as in a genome-wide fashion. The point of 50 % decay of r ² was used to estimate the difference in extent of LD between breeds. Extent of LD was significantly shorter for Newfoundland dogs based upon 50 % decay of r ² data at a mean of 344 kb compared to Golden Retriever and Rottweiler dogs at 715 and 834 kb, respectively (P < 0.0001). Notable differences in LD by chromosome were present within each breed and not strictly related to the length of the corresponding chromosome. Extent of LD is breed and chromosome dependent. To our knowledge, this is the first report of SNP-based LD for Newfoundland dogs, the first report based on genome-wide SNPs for Rottweilers, and an almost tenfold improvement in marker density over previous genome-wide studies of LD in Golden Retrievers.     

Mapping and characterization of the dominant black colour locus in sheep

Dominant black pigment synthesis in sheep is caused by alterations of the melanocortin-1 receptor (MC1-R) coding sequence. Using five bovine microsatellite markers we have mapped the sheep MC1-R gene to chromosome 14, corresponding to the location in other mammalian species. The existence of two independent mutations, both causing an amino acid substitution, in distantly related breeds of sheep, support the hypothesis that the observed black pigment synthesis is caused by a mutual effect of the two mutations. As similar mutations are found separately at both locations in dominant black variants of other animal species, it is also possible that any of the two mutations could be sufficient for a partial pigment switch.     

Dichromatic colour vision in an Australian marsupial, the tammar wallaby

Despite earlier assertions that most mammals are colour blind, colour vision has in recent years been demonstrated in a variety of eutherian mammals from a wide range of different orders. This paper presents the first behavioural evidence from colour discrimination experiments, that an Australian marsupial, the tammar wallaby (Macropus eugenii), has dichromatic colour vision. In addition, the experiments show that the wallabies readily learn the relationship between the presented colours rather than the absolute hues. This provides a sensitive method to measure the location of the neutral-point, which is the wavelength of monochromatic light that is indistinguishable from white. This point is a diagnostic feature for dichromats. The spectral sensitivity of the wallabies' middle-wavelength-sensitive photoreceptor is known (peak: 539 nm) and the behavioural results imply that the sensitivity of the short-wavelength-sensitive receptor must be near 420 nm. These spectral sensitivities are similar to those found in eutherian mammals, supporting the view that the earliest mammals had dichromatic colour vision. Accepted: 18 July 1999     

Insect colour preference compared to flower colours in the Australian Alps

An apparent predominance of plant taxa with pale flowers in the alpine floras of Australia and New Zealand may be due to the prevalence of insects, such as flies, that prefer pale colours and the absence of other types of potential pollinators that are attracted to bright colours such as social bees and birds. In this study, the diversity of flower colours, and the preference of insects for different colours were examined for the largest contiguous alpine area in Australia, around Mt Kosciuszko. Out of an alpine flora of 204 taxa, 127 species were found to have large showy flowers. The most common flower colour among these taxa was white (53.5%), then yellow (21.3%), followed by pink (6.3%), and cream (6.3%). Only a handful of taxa had red, blue, brown, green, orange or purple flowers. When the colour preference of insects was tested using five different coloured traps (white, yellow, orange, red and purple), the most successful traps were white then yellow, with these two colours accounting for 66% of all individual insects collected. Diptera were the most common insects caught (576 insects greater than 4 mm in length, 31 morphotaxa) showing an apparent preference for white and yellow coloured traps over others. Therefore, the results add some support to the proposition that the 'white' flora of the Australian Alps may be associated with the colour preference of flies, which have previously been found to be the most common type of pollinators in the Kosciuszko alpine zone.     

Multiple loci associated with canine hip dysplasia (CHD) in German shepherd dogs

Canine hip dysplasia (CHD) is the most common hereditary skeletal disorder in dogs. To identify common alleles associated with CHD, we developed 37 informative single nucleotide polymorphisms (SNPs) within 13 quantitative trait loci (QTL) previously identified for German shepherd dogs. These SNPs were genotyped in 95 German shepherd dogs affected by CHD and 95 breed, sex, and birth year-matched controls. A total of ten SNPs significant at a nominal P value of 0.05 were validated in 843 German shepherd dogs including 277 unaffected dogs and 566 CHD-affected dogs. Cases and controls were sampled from the whole German shepherd dog population in Germany in such a way that mean coancestry coefficients were below 0.1 % within cases and controls as well as among cases and controls. We identified nine SNPs significantly associated with CHD within five QTL on dog chromosomes (CFA) 3, 9, 26, 33, and 34. Genotype effects of these nine SNPs explained between 22 and 34 % of the phenotypic variance of hip dysplasia in German shepherd dogs. The strongest associated SNPs were located on CFA33 and 34 within the candidate genes PNCP, TRIO, and SLC6A3. Thus, the present study validated positional candidate genes within five QTL for CHD.     

Coat colour variation in the banded palm civet Hemigalus derbyanus and in Owston's civet Chrotogale owstoni

1. Coat colour variation was studied in two viverrid species belonging to the subfamily Hemigalinae, on the basis of museum specimens and observations of live animals. 2. In both species, polymorphism and ontogenetic colour change occur, and in the Owston's civet, sexual dimorphism in coat colour was identified.