ABSTRACT
In the course of evolution, pecorans (i.e., higher ruminants) developed a remarkable diversity of osseous cranial appendages, collectively referred to as "headgear," which likely share the same origin and genetic basis. However, the nature and function of the genetic determinants underlying their number and position remain elusive. Jacob and other rare populations of sheep and goats are characterized by polyceraty, the presence of more than two horns. Here, we characterize distinct POLYCERATE alleles in each species, both associated with defective HOXD1 function. We show that haploinsufficiency at this locus results in the splitting of horn bud primordia, likely following the abnormal extension of an initial morphogenetic field. These results highlight the key role played by this gene in headgear patterning and illustrate the evolutionary co-option of a gene involved in the early development of bilateria to properly fix the position and number of these distinctive organs of Bovidae.
Subject(s)
Biological Evolution , Goats/genetics , Homeodomain Proteins/genetics , Horns , Sheep/genetics , Animals , Biometry , Gene Expression Regulation, Developmental , Goats/embryology , Goats/metabolism , Homeodomain Proteins/metabolism , Male , Mice, Transgenic , Mutation , Sheep/embryology , Sheep/metabolismABSTRACT
Preservation of genetic diversity is one of the most pressing challenges in the planetary boundaries concept. Within this context, we focused on genetic diversity in a native, unselected and highly admixed domesticated metapopulation. A set of 1,828 individuals from 60 different cattle breeds was analysed using a medium density SNP chip. Among these breeds, 14 Busa strains formed a metapopulation represented by 350 individuals, while the remaining 46 breeds represented the global cattle population. Genetic analyses showed that the scarcely selected and less differentiated Busa metapopulation contributed a substantial proportion (52.6%) of the neutral allelic diversity to this global taurine population. Consequently, there is an urgent need for synchronized maintenance of this highly fragmented domestic metapopulation, which is distributed over several countries without sophisticated infrastructure and highly endangered by continuous replacement crossing as part of the global genetic homogenization process. This study collected and evaluated samples, data and genomewide information and developed genome-assisted cross-border conservation concepts. To detect and maintain genetic integrity of the metapopulation strains, we designed and applied a composite test that combines six metrics based on additive genetic relationships, a nearest neighbour graph and the distribution of semiprivate alleles. Each metric provides distinct information components about past admixture events and offers an objective and powerful tool for the detection of admixed outliers. The here developed conservation methods and presented experiences could easily be adapted to comparable conservation programmes of domesticated or other metapopulations bred and kept in captivity or under some other sort of human control.