The cytogenetic map in the genetic improvement of domestic river buffalo (Bubalus bubalis, 2n=50)

Since the construction and publication of river buffalo standard karyotype with six different chromosome banding techniques, the laboratory of Animal Cytogenetics and Gene Mapping of the ISPAAM has been focalised part of its scientific activity in the genetic improvement of river buffalo, a species of great economic importance in the world, with about 130,000 million of heads, and in Italy, with about 220,000, mostly in Campania region (Southern Italy).
Our studies have been addressed to both clinical cytogenetics on female river buffaloes with reproductive disturbances (25% of these females showed sex chromosome abnormalities) and molecular cytogenetics by physical mapping of various loci by means fluorescence in situ hybridization (FISH) techniques and probe DNA containing both type I markers (expressed genes) and type II markers (microsatellites). A cytogenetic map with 293 loci of all 31 cattle syntenic groups has been published: 171 loci were of type I and 122 of type II. This maps extends our knowledge on the physical organization of river buffalo genome and is a useful tool for:
(a) comparative genome studies with other species (human, cattle) with richer genetic and cytogenetic maps and with all genes sequenced;
(b) assisted selection of reproducers with molecular markers;
(c) detection of chromosome abnormalities;
(d) selection of chromosome regions containing genes of interest (animal production and disease resistances).
In particular, the order of loci found in some homologous chromosomes of bovids allowed to reveal the first autosomal mutation which differentiated the autosomes of bovids. Indeed, a proximal region of chromosome 9 of cattle and river buffalo (subfamily Bovinae) has been translocated in the proximale region of chromosome 14 of goata e sheep (subfamily Caprinae) (Iannuzzi et al. 2001). Furthermore, the comparative cytogenetic maps of X-chromosomes of river buffalo (acrocentric), cattle (submetacentric) and sheep (acrocentric with visible short arms) have demonstrated that this chromosome had a more complex evolution by the use of centromeric transpositions (between river buffalo and cattle) and transpositions of at least 4 chromosome regions between subfamilies Bovinae and Caprinae(Iannuzzi et al. 2000).

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