The folicular development in bovines happens in a wave pattern. Each follicular wave is characterized by a group of small follicles that are recruted and start a growing phase wich is commom to all follicles. There are evidencies that zebu females (Bos indicus) have more follicles per wave than taurine females (Bos taurus). Some authors have described that the follicle population is related to the animal fertility. Furthermore, it can be associated to hormonal profiles and expression of genes that control follicle development. This project is part of a larger FAPESP grant (11/50964-0) and has the specific objectives: 1) to identify single nucleotide polimorfisms (SNPS) in Nelore cows (Bos indicus) and Aberdeen Angus (Bos taurus) cows whithin breeds and in the same breed and 2) to compare the transcriptome of ovarian follicles through microarray analysis in cows with high (APF) or low (BPF) follicle count, whithin the same breed and between breeds (Nellore and Aberdeen Angus). One hundred animals of each breed will be used in the beginning of the experiment. The follicle count of each animal will be followed for two estral cycles. Animals that present the number of follicles outside the average of the total number of folicles for each animal plus or minus the standart deviation will be selected for the experiments. For the SNP analysis we will select 30 animals with APF and BPF from each breed. The animals will have their estral cycle synchronized with prostaglandin and the blood collected in the first day of the follicular wave. The DNA will be extracted from the white cells of the serum and the DNA analysed using 777 HD bovine Illumina® chip. Ten animals of each breed with APF and ten animals of each breed with BPF will be sellected for the transcriptome analysis. The animals will be slaughter in the first day of the second folicular wave and the ovaries collected for follicle dissection. The RNA will be extracted from a pool of five folicles with 2 to 3 mm of diameter. The extracted RNA will be used for the microarray analysis. Differentially expressed genes will be identified between groups ( APF x BPF) within the same breed and between breeds. Microarray results will be confirmed with RT-PCR. SNPs results will be analysed to identify SNPs that are commom in animals of the same breed and between breeds. Adicionally, we will identify SNPs that are related to the genes differentialy expressed by the microarray and to the hormonal profile (testosterone, FSH, estradiol, anti-mullerian hormone and progesternone) of these animals.
News published in Agência FAPESP Newsletter about the scholarship: