Anàlisi genòmica de caràcters lleters i de la pigmentació en cabres de la raça murciano-granadina
- Autores: Dailu Guan
- Directores de la Tesis: M. Amills (dir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2020
- Idioma: español
- Tribunal Calificador de la Tesis: Raquel Quintanilla Aguado (presid.), Alejandro Clop Ponte (secret.), Yuliaxis Ramayo Caldas (voc.)
- Programa de doctorado: Programa de Doctorado en Producción Animal por la Universidad Autónoma de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
In order to obtain new insights into the molecular basis of lactation in Murciano-Granadina (MUG) goats, we carried out a RNA-Seq analysis of mammary gland samples (N = 7) obtained in three different time points, that is, 78 days (T1, early lactation), 216 days (T2, late lactation) and 285 days (T3, dry period) after parturition. This experiment allowed the identification of 1654 differentially expressed (DE) genes, the functions of which were mainly related to protein, lipid and carbohydrate metabolism, calcium homeostasis, programmed cell death, tissue remodeling and immunity. In order to help elucidate the genomic architecture of milk production and composition, we also carried out a genome-wide association study (GWAS) including 822 goats with records for seven dairy phenotypes measured during the first lactation. This study allowed the detection of 24 quantitative trait loci (QTL). However, only three QTL showed statistical significance at the genome-wide level, that is, QTL1 (chromosome 2, 130.72-131.01 Mb) for the percentage of lactose in milk, QTL6 (chromosome 6, 78.90-93, 48) Mb) for the percentage of protein and QTL17 (chromosome 17, 11.20 Mb) for the percentages of protein and dry matter.
By analyzing the segregation patterns of single nucleotide polymorphisms (SNPs) mapping to the casein genes in bezoars (ancestor of the domestic goat) and domestic goats of Europe, Africa, the Near East and the Far East, it was determined that about 36.1% (CSN2) to 55.1% (CSN1S2) of casein SNPs are shared between bezoars and domestic goats. Besides, more than 50% of the SNPs of the casein genes were shared by 2 or more domestic goat populations located on different continents, and 18 to 44% of the SNPs were shared by the four previously mentioned domestic populations. These results allow us to conclude that an important part of the diversity existing in the caprine casein genes emerged before the domestication of goats.
Another objective of the Thesis consisted of characterizing copy number variation (CNV) in a population of 1036 MUG goats. Using the PennCNV and QuantiSNP software, we identified 4617 and 7750 autosomal CNVs, respectively, which were subsequently assembled into 486 CNV regions (CNVR). Genes located within CNV show an enrichment of functions related to olfactory transduction, ABC transporters and embryonic development. Interestingly, one of the CNVR identified in our study coincides with the position of the agouti signaling protein (ASIP) gene, which favors the synthesis of yellow/red pheomelanin. In several studies, increased copy number of the ASIP gene was associated with a white pigmentation in goats. However, when conducting a qPCR experiment with the objective of quantifying the number of copies of the ASIP gene in goat populations with different coat colors, we found that the ASIP CNV not only segregates in Saanen (white) goats, but also in MUG (black/brown) and Malagueñas goats (brown/blond). This result indicates the absence of a simple and linear relationship between the number of copies of the goat ASIP gene and the dilution of pigmentation. Finally, we have investigated the genomic architecture of coat color in MUG goats by combining different experimental techniques. This analysis revealed the existence of a close association between a missense mutation (c.801C>G, p.Cys267Trp) in the melanocortin receptor 1 (MC1R) gene and the black/brown color of MUG goats, which implies that the inheritance of pigmentation in this breed is monogenic.
