Análise de perfis epigenômicos em células nucleadas do sangue durante a exposição ao calor em bovinos das raças Angus e Nelore
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Data
2018-10-26
Autores
Zavarez, Ludmilla Balbo [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Uma das questões mais interessantes que poderiam ser elucidadas empregando a análise de metilação em todo o genoma é como ela afeta a regulação da temperatura corporal em animais domésticos. A resposta a esta questão torna-se imperativa, particularmente no caso de bovinos de leite e corte, uma vez que as raças modernas mais populares descendem de ancestral comum, que derivou em duas subespécies (Bos taurus e Bos indicus) as quais respondem aos estímulos ambientais de formas opostas (raças de zonas temperadas ou adaptadas a regiões tropicais, respectivamente). Mapas de metilação do DNA genômico foram originados usando a técnica de RRBS à partir de células nucleadas do sangue de um grupo de bovinos Angus e Nelore puros, expostos ao estresse ambiental condicionado pelo calor. Os dados de metilação distribuídos ao longo dos cromossomos bovinos puderam ser representados graficamente, enfatizando padrão altamente homogêneo entre as amostras analisadas e a robustez do método. A cobertura de sequenciamento empregada foi suficientemente profunda (em todos os casos superior a 20 vezes o tamanho do genoma), permitindo concluir sobre a ocorrência de eventos de metilação do DNA possivelmente associados a alterações fisiológicas causadas pelo estresse térmico. A análise da metilação do DNA revelou 4.662 janelas metiladas diferencialmente (cada uma com 1.000 pares de bases), sendo a maioria (2.695) relacionada a diferenças entre as raças e não diretamente à resposta ao estresse térmico. A análise das 214 janelas comuns (compreendendo 103 genes) revelou sinais epigenéticos relacionados à resposta ao estresse por calor e à recuperação deste, que foram principalmente específicos da raça. A comparação dos padrões de metilação do DNA em células nucleadas, apontou para genes específicos diferencialmente metilados (ACTL8, PNOC e FGFR2) que poderiam ser o resultado de mudanças epigenômicas que ocorrem durante adaptação às mudanças climáticas drásticas. Ficou evidente a presença de sítios de metilação do DNA no genoma nessas raças bovinas que devem interferir na regulação de processos metabólicos, tais como ruminação, digestão, capacidade de dissipação do calor, entre outros, e que afetam diretamente o desempenho econômico da produção pecuária. Exploração mais profunda dos mecanismos que os genes candidatos metilados usam para interagir e desempenhar suas funções faz-se necessária para melhorar o entendimento sobre esse comportamento adaptativo dos bovinos.
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.
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.
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Palavras-chave
Bovino, Epigenética, Estresse Térmico, Metilação do DNA, RRBS, Bovine, DNA Methylation, Epigenetics, Heat Stress, RRBS