Evolutionary, Clinical and Molecular Cytogenetics in Water Buffalo: an update

Cytogenetics represents one of the modern biotechnologies applied to the genetic improvement of livestock, including the water buffalo (Bubalus bubalis ), one of the most important economic species raised in the world, especially in the East Countries. Cytogenetics covers several aspects of the genetic improvement. In the present paper, an update on the evolutionary, clinical and molecular cytogenetics of the water buffalo is reported. Evoluzionary cytogenetics: Two main types of buffaloes are present in the world: the African buffalo (Syncerus caffer) and the Asiatic buffalo (Bubalus bubalis). The latter has two subspecies: the river type (2n=50) and the swamp type (2n=48). These two species diverged by a tandem fusion translocation involving river buffalo chromosomes 4 and 9 (telomere of 4p and centromere of 9). This fusion was accompanied by loss of the nucleolus organizer regions (NORs) present in river buffalo chromosome 4p, and large portions of constitutive heterochromatin (HC) present in river buffalo chromosome 9. River and swamp buffaloes are normally crossbreed, especially to increase milk production in swamp buffaloes. The hybrid (2n=49) could have a lower fertility due to unbalanced chromosome embryos. Further informations differentiating tribe bovinae (cattle and water buffalo) from the remaining ones belonging to bovidae family will be given. Clinical cytogenetics:The study of water buffalo karyotype is very important because several studies have demonstrated that about 20% of females with reproductive problems (lack of oestrus in fertility age or large delay in the return in oestrus) show sex chromosome abnormalities and almost of them have been found to be sterile for serious damages occurring in internal sex adducts.In Italy, in collaboration with the National Buffalo Breeder Association (ANASB), cytogenetic controls of bulls and males addressed to the reproduction, as well a s on some females with reproductive problems, have been performed to eliminate the carriers of chromosome abnormalities, adding economic value to river buffalo breeding. These studies are routinely performed by using both CBA- and RBA- banding techniques. Specific cases are also studied by fluorescence in situ hybridization (FISH) technique and specific molecular markers (generally bovine BAC-clones).Molecular cytogenetics:The availability of specific molecular markers containing coding sequences (generally bovine or ovine BAC-clones) and the use of the FISH-technique have opened the door to the molecular cytogenetics also for water buffalo. Indeed, cytogenetic maps with specific and detailed location of loci containing expressed coding (and no-coding) sequences along the chromosomes, have been performed for this species, although these maps are not particularly dense. However, they are useful: (a) to increase our knowledge on water buffalo genome by detailed physical description of mapped loci per single chromosome and chromosome band; (b) to study such chromosome abnormalities; (c) to anchor genetic maps (linkage, RH-maps) to specific chromosome regions; (d) to delineate the karyotype evolution of river buffalo versus cattle, sheep and related bovids, as well as between bovids and humans, especially to transfer useful information from human to animal genomes.