ABSTRACT
Resumen El síndrome de braquiespina es una condición genética de la raza Holstein, detectada en el año 2006. Es causado por una deleción de 3.3 Kb en el gen FANCI localizado en el cromosoma bovino 21. La mutación fue identificada en poblaciones de Holstein de Europa, América del Norte y Asia. Dada la importancia económica del defecto y su amplia distribución mundial, el objetivo de este trabajo ha sido la identificación de animales portadores en el núcleo de selección genética de la raza en Uruguay y el diagnóstico molecular del alelo deletéreo en animales del rodeo nacional. En el presente estudio se analizaron 2598 registros de toros Holstein del catálogo de padres del sistema de evaluación genética lechera, los registros de toros pertenecientes a los catálogos de semen Holstein disponible para Uruguay de los años 2014 al 2018; y 71 vacas pertenecientes al rodeo general. Se encontraron 28 toros portadores de braquiespina de un total de 377 toros con información genética del catálogo de padres y cuatro vacas portadoras de un total de 71 genotipificadas en nuestro laboratorio. Se demostró una disminución en el ingreso de semen de animales portadores al país entre los años 2014 y 2018. La frecuencia significativa de animales portadores en Uruguay evidencia la necesidad de implementar estrategias que permitan eliminar gradualmente el defecto de la población.
Abstract Brachyspina syndrome is a hereditary recessive disease of recent identification in the Holstein breed. It is caused by a deletion of 3.3Kb in the FANCI gene located in the bovine chromosome 21. The mutation was identified in Holstein populations of Europe, North America and Asia. Given the economic importance of the defect and its wide distribution, the objective of this work was the identification of carrier animals in the genetic selection nucleus of the breed in Uruguay and the molecular verification of the deleterious allele in animals of the national herd. In the present study, 2598 records of Holstein bulls were analyzed from the list of parents of the dairy genetic evaluation system, records of bulls belonging to the Holstein semen catalogs available for Uruguay from 2014 to 2018; and 71 cows belonging to the general herd. Twenty-eight brachyspina carrier bulls were found of a total of 377 bulls with genetic information from the list of parents and four carrier cows of a total of 71 genotyped in our laboratory. A decrease in the income of semen from carrier animals to the country between 2014 and 2018 was demonstrated. The significant frequency of carrier animals in Uruguay evidences the need to implement strategies to gradually eliminate the population defect.
ABSTRACT
Fragile sites (FS) are chromosomal regions where the normal compactation of chromatine is not observed. FRAXA (Fra Xq27.3, X sexual chromosome) is one of the most studied FS in humans. FRAXA is an expansion of the trinucleotide CGG located in the gene FMR-1. In cattle, sites of chromosomal fragility were reported in BTAX, associated with different pathologies and fertility impairment. Chromosomal microdissection has became a valuable tool for isolating chromatine fragments. In this work, it was combined the chromosomal microdissection technique with DOP-PCR in order to carry out a molecular analysis of the fragile chromosomal region BTAXq31-34. In that region, polymorphic DNA-RAPD sequences (GC rich) are present and sequences of the gene FMR-1 are missing. The results showed the usefulness of the microdissection-DOP-PCR technique for molecular characterization of fragile chromosomal sites in cattle.
Os sítios frágeis (FS) são regiões de cromossomo onde a compactação normal da cromatina não é realizada. O FRAXA (Fra Xq27.3, cromossomo sexual X) é um dos FS mais estudados em seres humanos. O FRAXA apresenta expansão do trinucleotídeo CGG localizado no gene FMR-1. Em bovinos, existem estudos informando sobre fragilidade cromossômica em BTAX associada com diversas patologias e alterações na fertilidade. A microdissecação cromossômica é uma valiosa técnica para isolar fragmentos de cromatina. Neste trabalho, combinou-se a técnica de microdissecação de cromossomo com DOP-PCR para executar a análise molecular da região do sitio frágil cromossômico BTAXq31-34. Naquela região estão presentes seqüências do polimorfo DNA-RAPD (rico em GC), em que as seqüências do gene FMR-1 estão ausentes. Os resultados mostram a utilidade da técnica de microdissecação-DOP-PCR para a caracterização molecular de sítios frágeis cromossômicos em bovinos.