Caracterização de polimorfismos do gene AMH e sua associação com características indicadoras de precocidade sexual em novilhas da raça Nelore
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Data
2017-04-25
Autores
Pierucci, Julia Cestari [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O hormônio anti-Mülleriano (AMH) é uma glicoproteína de 140 kDa exclusivamente expressa nas gônadas e que pertence à família de fatores de crescimento transformantes (TGF)-ß e está relacionada ao desenvolvimento folicular ovariano. O AMH possui a importante função de evitar a depleção prematura da reserva folicular por meio do equilíbrio entre a inibição e a promoção do crescimento e desenvolvimento de folículos. Em bovinos, o gene do hormônio anti-Mülleriano está localizado no cromossomo 7 e é composto por cinco éxons. Considerando esse contexto, este trabalho inclui dois capítulos: o primeiro com uma revisão das caraterísticas ocorrência de prenhez precoce (OPP) e idade ao primeiro parto (IPP), assim como a apresentação detalhada do AMH, citando suas principais funções no aparelho reprodutor feminino e de seu respectivo gene e suas variantes em humanos e animais. No segundo capítulo, o objetivo foi caracterizar a presença de polimorfismos nas regiões codificantes do gene AMH, analisar a constituição genética da população para o gene e estudar a associação entre os polimorfismos e as características OPP e IPP em 197 novilhas da raça Nelore, com idade de 16-18 meses. Quatro polimorfismos do tipo SNP foram detectados no presente estudo, sendo um deles no íntron 2 (rs132972253) e três no éxon 5 (rs527023314, rs722016629 e rs134387246), sendo que somente o SNP rs134387246 exibiu valor significativo (p<0,1) para ambas características (OPP e IPP). A análise demonstrou superioridade do alelo A, sendo que o genótipo GA apresentou valor de IPP 75 dias menor do que o homozigoto GG, apresentando ação melhoradora nessa característica. Ademais, efeito de sobredominância dos animais heterozigotos (p=0,056) e ausência de ação gênica aditiva (p=0,67) foram revelados neste estudo. Pela primeira vez na literatura, polimorfismos do gene AMH foram descritos em novilhas da raça Nelore e associados às características OPP e IPP, sendo que um dos SNPs influenciou positivamente nas mesmas e poderá futuramente ser utilizado como ferramenta de seleção em fêmeas Nelore.
Anti-Müllerian Hormone (AMH) is a 140 kDa glycoprotein exclusively expressed in the gonads, which belongs to the transforming growth factor (TGF)- ß family and is related to ovarian follicular development. AMH plays an important role to prevent premature depletion of the follicular reserve, by promoting balance between inhibition and promotion of follicular growth and development. In bovines, the AMH gene is located in chromosome seven and contains five exonic regions. Considering this context, the content of this work includes two chapters: the first with a review of early pregnancy occurence (EPO) and age at first calving (AFC) traits, as well as the detailed presentation of AMH, citing its main functions in the reproductive system and also its related gene and variants in both humans and animals. In the second chapter, the aim was to characterize the presence of polymorphisms in the coding region of the AMH gene, analyze the genetic constitution of the population for this gene and study the association between the polymorphisms and OPP and IPP traits in 197 Nelore heifers, aging 16 to 18 months. A total of four single nucleotide polymorphisms (SNP) were detected in the present study, being one in intron two (rs132972253) and three in exon five (rs527023314, rs722016629 and rs134387246), wherein only SNP rs134387246 showed significant value (p <0.1) for both phenotypes. The analysis revealed superiority of the A allele, and the GA genotype presented AFC 75 days lower than the GG homozygote, showing an improvement action in this trait. In addition, an overdominance effect of heterozygous animals (p = 0.056), and absence of additive gene action (p = 0.67) were revealed in this study. Polymorphisms of AMH gene were described in Nelore heifers and associated to EPO and AFC traits for the first time, wherein one of the SNPs had a positive influence on them and could be further used as a tool for selection of Nelore females.
Anti-Müllerian Hormone (AMH) is a 140 kDa glycoprotein exclusively expressed in the gonads, which belongs to the transforming growth factor (TGF)- ß family and is related to ovarian follicular development. AMH plays an important role to prevent premature depletion of the follicular reserve, by promoting balance between inhibition and promotion of follicular growth and development. In bovines, the AMH gene is located in chromosome seven and contains five exonic regions. Considering this context, the content of this work includes two chapters: the first with a review of early pregnancy occurence (EPO) and age at first calving (AFC) traits, as well as the detailed presentation of AMH, citing its main functions in the reproductive system and also its related gene and variants in both humans and animals. In the second chapter, the aim was to characterize the presence of polymorphisms in the coding region of the AMH gene, analyze the genetic constitution of the population for this gene and study the association between the polymorphisms and OPP and IPP traits in 197 Nelore heifers, aging 16 to 18 months. A total of four single nucleotide polymorphisms (SNP) were detected in the present study, being one in intron two (rs132972253) and three in exon five (rs527023314, rs722016629 and rs134387246), wherein only SNP rs134387246 showed significant value (p <0.1) for both phenotypes. The analysis revealed superiority of the A allele, and the GA genotype presented AFC 75 days lower than the GG homozygote, showing an improvement action in this trait. In addition, an overdominance effect of heterozygous animals (p = 0.056), and absence of additive gene action (p = 0.67) were revealed in this study. Polymorphisms of AMH gene were described in Nelore heifers and associated to EPO and AFC traits for the first time, wherein one of the SNPs had a positive influence on them and could be further used as a tool for selection of Nelore females.
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Palavras-chave
Bos indicus, Fertilidade, Gene do Hormônio Anti-Mülleriano, Puberdade precoce