Analysis of epigenomic profiles in nucleated blood cells during exposure to heat in Angus and Nelore cattle

Author(s)

Ludmilla Balbo Zavarez

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2018-12-04.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2018-10-26
• Advisor: José Fernando Garcia

Abstract

One of the most interesting questions that could be solved using genome-wide methylation analysis is how it affects the regulation of body temperature in domestic animals. The answer to this question becomes imperative, particularly in the case of dairy and beef cattle, since modern breeds more frequently descended from a common ancestor, derived in two subspecies (Bos taurus and Bos indicus), which respond to environmental stimuli of different forms (breeds of temperate zones and adapted to tropical regions, respectively). Genomic maps were originated using RRBS DNA methylation data from nucleated blood cells of a group of pure Angus and Nelore cattle exposed to environmental heat strees. Methylation data distributed along the bovine chromosomes could be represented graphically, emphasizing a highly homogeneous pattern between the analyzed samples and the robustness of the method. The sequencing coverage used was sufficiently deep (in all cases higher than 20 times the genome size) leading to the identification of DNA methylation events possibly associated with physiological changes caused by heat stress. The DNA methylation analysis showed a total of 4,662 differentially methylated windows (each with 1,000 base pairs), most of them (2,695) related to differences between breeds and not to the response to heat stress. Analysis of the 214 common windows (comprising 103 genes) revealed epigenetic signals related to the heat stress response and recovery, which were mainly breed-specific. Comparison of DNA methylation patterns in nucleated cells, pointed to genomic regions and differentially methylated specific genes (ACTL8, PNOC e FGFR2) that could be the result of epigenic changes occuring during acute adaptation to drastic climate changes. It was evident the presence of DNA methylation sites in the genome of these bovine breeds, which should interfere in the regulation of metabolic processes, such as rumination, digestion, heat dissipation capacity, among others, and which directly affect the economic performance of livestock production. Deeper investigation of the mechanisms these candidate methylated genes use to interact and perform their functions is necessary to improve understanding of this adaptive behavior in cattle. (AU)

• FAPESP's process: 15/08553-4 - Analysis of DNA methylation patterns associated with cattle submitted adaptation to stress heat
• Grantee: Ludmilla Balbo Zavarez
• Support Opportunities: Scholarships in Brazil - Doctorate