Mutações causadoras do nanismo do tipo condrodisplásico em equinos da raça Mini-Horse no Brasil
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Data
2020-08-13
Autores
Andrade, Danilo Giorgi Abranches de
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Universidade Estadual Paulista (Unesp)
Resumo
Em equinos da raça Mini-Horse, o nanismo condrodisplásico possui padrão de herança autossômico recessivo e já foram descritas quatro variantes causais (D1, D2, D3* e D4) no gene aggrecan (ACAN). Animais homozigotos ou heterozigotos compostos para essas variantes apresentam a doença. Os objetivos gerais desse estudo foram verificar as mutações já descritas anteriormente e investigar outra(s) possível(is) mutação(ões) relacionada(s) com o nanismo do tipo condrodisplásico em equinos da raça Mini-Horse, além de estimar suas frequências alélicas. O RNAm do gene ACAN foi sequenciado e, após a comparação entre animais afetados e seus pais, sugeriu-se que o polimorfismo de nucleotídeo único (SNP) c.6465A>T (g.95271115A>T; p.L2155F – RefSeq XM_005602799.2; XP_005602856.2 – EquCab3.0) fosse uma variante potencialmente associada ao nanismo condrodisplásico ainda não descrita na literatura consultada. Teste genético, baseado em reação em cadeia da polimerase (PCR) seguida de sequenciamento Sanger, para as cinco variantes em 347 equinos da raça Mini-Horse fenotipicamente normais, assim como o estudo in silico da estrutura proteica potencialmente associaram c.6465A>T com a enfermidade. Estudos em equinos de raças grandes demonstraram a presença do SNP c.6465A>T em heterozigose e dois cavalos Mangalarga Marchador fenotipicamente normais apresentaram-no em homozigose. Na população estudada de equinos da raça Mini-Horse fenotipicamente normais (n=347), a frequência alélica combinada de D1, D2, D3*, D4 e c.6465A>T foi de 0,392, o que sugere uma taxa de heterozigotos de 47,7%. Interações complexas no genoma de Mini-Horses possivelmente contribuem para a associação de c.6465A>T com o nanismo condrodisplásico ou este é um marcador em desequilíbrio ligado com uma variante causal ainda não identificada.
In Miniature horses, chondrodysplastic dwarfism has an autosomal recessive inheritance pattern and four causative variants (D1, D2, D3* and D4) in the aggrecan (ACAN) gene have been described previously. Homozygous or compound heterozygotes animals for these variants present the disorder. The general aims of this study were to verify the mutations already described and to investigate other possible variant(s) related to chondrodysplastic dwarfism in Miniature horses; in addition, to estimate the allelic frequency of the mutations. The mRNA of the ACAN gene was sequenced, and after comparing the affected animals and their parents, it was suggested that the single nucleotide polymorphism (SNP) c.6465A>T (g.95271115A>T; p.L2155F – RefSeq XM_005602799.2; XP_005602856.2 – EquCab3.0) could be potentially associated with dwarfism not yet described in the literature. Genetic test based in polymerase chain reaction (PCR) and Sanger sequencing for the five variants in 347 phenotypically normal Miniature horses, as well as the in silico protein structure study potentially associated c.6465A>T with dwarfism. Study in large sized horses showed the presence of the SNP in heterozygosis and two Mangalarga Marchador horses presented it in homozygosis. In the studied population of phenotypically normal Miniature horses (n=347), the combined frequency of D1, D2, D3*, D4 and c.6465A>T was 0.392, suggesting a heterozygous rate of 47.7%. Complex interactions in the Miniature horse genome could contribute to association of c.6465A>T with chondrodysplastic dwarfism or it could be a marker in linkage disequilibrium with a causative variant not yet identified.
In Miniature horses, chondrodysplastic dwarfism has an autosomal recessive inheritance pattern and four causative variants (D1, D2, D3* and D4) in the aggrecan (ACAN) gene have been described previously. Homozygous or compound heterozygotes animals for these variants present the disorder. The general aims of this study were to verify the mutations already described and to investigate other possible variant(s) related to chondrodysplastic dwarfism in Miniature horses; in addition, to estimate the allelic frequency of the mutations. The mRNA of the ACAN gene was sequenced, and after comparing the affected animals and their parents, it was suggested that the single nucleotide polymorphism (SNP) c.6465A>T (g.95271115A>T; p.L2155F – RefSeq XM_005602799.2; XP_005602856.2 – EquCab3.0) could be potentially associated with dwarfism not yet described in the literature. Genetic test based in polymerase chain reaction (PCR) and Sanger sequencing for the five variants in 347 phenotypically normal Miniature horses, as well as the in silico protein structure study potentially associated c.6465A>T with dwarfism. Study in large sized horses showed the presence of the SNP in heterozygosis and two Mangalarga Marchador horses presented it in homozygosis. In the studied population of phenotypically normal Miniature horses (n=347), the combined frequency of D1, D2, D3*, D4 and c.6465A>T was 0.392, suggesting a heterozygous rate of 47.7%. Complex interactions in the Miniature horse genome could contribute to association of c.6465A>T with chondrodysplastic dwarfism or it could be a marker in linkage disequilibrium with a causative variant not yet identified.
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Palavras-chave
Agrecano, Análise de sequência de DNA, Condrodisplasia, Doenças genéticas, Neonatologia equina, Aggrecan, Chondrodysplasia, Equine neonatology, Genetic diseases, Sequence analysis