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In goats, k-casein (CSN3) locus is highly polymorphic with up to 16 allele currently characterized. They produce 13 protein variants (CSN3) that were classified in two groups (AIEF and BIEF), according to their isoelectric point. Isoelectric focusing (IEF) of milk samples allows the detection of these two CSN3 groups, but for correct identification of CSN3 alleles DNA based genotyping methods are needed. Therefore the objective of this study was to identify the types of alleles occurring at the CSN3 locus in Carpathian goat breed by using a combined IEF and DNA sequencing approach. IEF analysis of milk samples collected from two Carpathian goat populations reared in Romania revealed two distinct CSN3 patterns. Amplification and sequencing of CSN3 cDNA obtained from these goats revealed four polymorphic sites located in the exon 4 that are responsible for amino acids substitutions, as compared with the reference sequence of A allele. By comparative analysis of IEF and cDNA sequencing data obtained from the two populations, we shown that AIEF alleles are represented by B allele, while BIEF alleles are represented by D allele. However, the variation of CSN3 locus in Carpathian goat breed could be more complex, therefore further studies are needed to characterize it.

The development and function of mammary gland is mainly controlled by growth hormone and prolactin, two protein hormones secreted by the anterior pituitary gland. Their synthesis is under regulatory influence of pituitary factor 1 (PIT1 or POU1F1), a protein factor produced in hypothalamic nuclei. In cattle, it was shown that a HinfI polymorphism located in exon 6 of PIT1 gene may have significant influence on milk quantity. In particular A allele was associated with a higher milk yield and could be a valuable genetic marker for improving milk quantity in cattle. In an effort to better understand the possible influence of this polymorphism on mammary gland development and function in cattle, we have studied the frequency this polymorphism in Romanian Black and White breed, a high milk production cattle breed versus Romanian Grey Steppe breed, a primitive breed with very low milk production. In both breeds the frequency of B allele is much higher as compared with the frequency of A allele. The study of PIT1 polymorphism in Romanian cattle breeds is a part of a more complex study targeting several key genes involved in mammary gland function