Polimorfismo nos genes IGF-1 e NF1-C2 e sua associação com características produtivas em caprinos leiteiros

Abstract

Several physiological and metabolic processes have the participation of the growth factor insulin-like 1 (IGF-1). During the breast enlargement process and pregnancy, this factor works in the local action of steroid hormones, growth hormone and prolactin, the primary regulators of differentiation. Besides is required for the development of mammary gland lobuloalveolar. The NF1-C2 is the gene encoding the nuclear transcription factor 1-C2, which mediates the action of prolactin in the mammary gland and plays an important role in the activation of several specific genes of this gland, participating both from its establishment as protect against tumors during proliferation. Therefore, we aim with this study: evaluate the variations found in IGF-1 and NF1-C2 genes in breeds of dairy goats cashmere Xinjiang and Nanjiang (IGF-1) and white cashmere Xinong Saanen Guanzhong Xinjiang (NF1-C2) are present in an experimental population of goats of Saanen and Alpine, relating them to milk production , lactation period, somatic cell count and milk constituents content (fat, protein, lactose, and total solids) and detect molecular markers that may be used in animal breeding and selection. A herd of goats (Capra hircus) in reproductive age, composed of animals of Saanen and Alpine breeds, considered as a single population, genotyped for polymorphisms of IGF-1 and NF1-C2 genes was used. The collected blood of peripheral circulation (approximately 10 mL) was used for genomic DNA extraction through the white blood cells and the amplification of the fragments was carried out by polymerase chain reaction (PCR). The amplified fragments were assessed for polymorphism by restriction fragment length (PCR-RFLP), identified via polyacrylamide gel electrophoresis 5%, stained with silver nitrate. PCR products showed approximate size as expected, 363 bp (IGF-1) and 233 bp (NF1-C2), with a total of 168 and 197 evaluated animals, respectively. In intron 4 of IGF-1, the single base polymorphism gene (SNP) refers to transversion G>C in position 5752 was identified by HaeIII endonuclease, but allele A had a very low frequency (0.09) and there was no significant association with neither of the productive characteristics (P>0.05). Therefore, its use as a marker for these traits is not recommended. In NF1-C2 gene, the SNP located in exon 5 (G>A), in position 44654 of the nucleotide sequence, was identified by BstNI restriction enzyme and frequencies of A and G alleles are 0.43 and 0.57, respectively. It was found association of this polymorphism with the percentage of milk protein (P <0.01), with AA genotype associated to greater content of protein than GG, while the heterozygous genotype did not differ from homozygotes. Therefore, this polymorphism may help select animals that produce milk with higher protein content.