Genetic diversity of Swiss sheep breeds in the focus of conservation research

There is constant pressure to improve evaluation of animal genetic resources in order to prevent their erosion. Maintaining the integrity of livestock species as well as their genetic diversity is of paramount interest for long-term agricultural policies. One major use of DNA techniques in conservation is to reveal genetic diversity within and between populations. Forty-one microsatellites were analysed to assess genetic diversity in nine Swiss sheep breeds and to measure the loss of the overall diversity when one breed would become extinct. The expected heterozygosities varied from 0.65 to 0.74 and 10.8% of the total genetic diversity can be explained by the variation among breeds. Based on the proportion of shared alleles, each of the nine breeds were clearly defined in their own cluster in the neighbour-joining tree describing the relationships among the breeds. Bayesian clustering methods assign individuals to groups based on their genetic similarity and infer the number of populations. In STRUCTURE, this approach pooled the Valais Blacknose and the Valais Red. With BAPS method the two Valais sheep breeds could be separated. Caballero & Toro approach (2002) was used to calculate the loss or gain of genetic diversity when each of the breeds would be removed from the set. The changes in diversity based on between-breed variation ranged from -12.2% (Valais Blacknose) to 0% (Swiss Black Brown Mountain and Mirror Sheep); based on within-breed diversity the removal of a breed could also produce an increase in diversity (-0.6% to + 0.6%). Allelic richness ranged from 4.9 (Valais Red) to 6.7 (Brown Headed Meat sheep and Red Engadine Sheep). Breed conservation decisions cannot be limited to genetic diversity alone. In Switzerland, conservation goals are embedded in the desire to carry the cultural legacy over to future generations

Arachnomelia in Brown Swiss cattle maps to chromosome 5

Arachnomelia in Brown Swiss cattle is a monogenic autosomal recessive inherited congenital disorder of the skeletal system giving affected calves a spidery look (OMIA ID 000059). Over a period of 20 years 15 cases were sampled in the Swiss and Italian Brown cattle population. Pedigree data revealed that all affected individuals trace back to a single acknowledged carrier founder sire. A genome scan using 240 microsatellites spanning the 29 bovine autosomes showed homozygosity at three adjacent microsatellite markers on bovine Chr 5 in all cases. Linkage analysis confirmed the localization of the arachnomelia mutation in the region of the marker ETH10. Fine-mapping and haplotype analysis using a total of 34 markers in this region refined the critical region of the arachnomelia locus to a 7.19-Mb interval on bovine Chr 5. The disease-associated IBD haplotype was shared by 36 proven carrier animals and allows marker-assisted selection. As the corresponding human and mouse chromosome segments do not contain any clear functional candidate genes for this disorder, the mutation causing arachnomelia in the Brown Swiss cattle might help to identify an unknown gene in bone development

Homozygosity mapping of Arachnomelia in Brown cattle"

Fifteen calves affected with arachnomelia were sampled in the Swiss and Italian Brown cattle population. Analysis of the pedigree data confirmed monogenic autosomal recessive inheritance and revealed that all affected individuals traced back to a single acknowledged carrier founder sire. Eight affected offspring and 10 available relatives were genotyped for a panel of 240 microsatellites spanning the 29 bovine autosomes. Homozygosity mapping showed homozygosity of all cases at two adjacent microsatellite markers on BTA5. For fine mapping purposes 14 additional BTA5 microsatellites were genotyped in all available cases and indicated shared homozygous haplotypes across 20 Mb among affected individuals. A second pedigree with 23 acknowledged carriers among 34 sires in total related to the founder were genotyped for these markers. Linkage and haplotype analysis showed that the arachnomelia mutation could be assigned to a 7.2 Mb candidate region (LOD score >6). The linked markers can be used for indirect determination of the arachnomelia genotype in offspring of related carrier sires. This bovine chromosome segment corresponds to an ortholog segment of HSA12q containing more than 140 annotated genes and loci. The only obvious functional candidate gene of this region GDF11 is probably not responsible for this fatal bovine disorder

Diversidade genética e eficiência de DNA microssatélites para o controle genealógico da raça Nelore Genetic diversity and efficiency of DNA microsatellites for genealogic control in Nelore breed

Foram estimados na raça Nelore a variabilidade genética e os valores de determinação de paternidade usando-se 11 marcadores microssatélites do painel ISAG/FAO. Estes foram organizados em quatro conjuntos de amplificação para genotipagem semi-automática por fluorescência. Todos os marcadores apresentaram-se altamente polimórficos, com média de 8,2 alelos por loco. A heterozigosidade observada, com média de 0,48, foi menor que a esperada em 10 locos. Foram observadas deficiências de heterozigotos em nove locos, o que resultou no desequilíbrio de Hardy-Weinberg para a população estudada. O conteúdo polimórfico informativo foi superior a 0,5 em 10 locos. O poder de discriminação foi >0,999 e as probabilidades de exclusão de paternidade quando são conhecidos os genótipos de um bezerro, sua mãe e um pai alegado, ou quando um ou outro genótipo parental não está disponível, para o conjunto de marcadores foram >0,999 e >0,989, respectivamente. O conjunto de 11 marcadores constitui método eficiente para a determinação de paternidade na raça Nelore.<br>The genetic variability and paternity testing values in Nelore breed were estimated using 11 ISAG/FAO microsatellites. The markers were organized into 4 amplification groups for semi-automated fluorescence genotyping. All markers were highly polymorphic, with an average of 8.2 alleles per locus. With a mean value of 0.48, the observed heterozygosity was lower than the expected for 10 of the loci. A significant deficit of heterozygotes was observed for 9 loci, resulting in a lack of Hardy-Weinberg equilibrium in the studied population. Polymorphism information content values exceeded 0.5 for 10 loci. The power of discrimination was >0.999 and paternity exclusion probabilities when a mother, her offspring and a putative sire are compared or when one or other parental genotype is unavailable for the combined set of markers were, respectively, >0.999 and >0.989. The set of 11 microsatellite markers proved to be an efficient tool for paternity testing in Nelore cattle