Alicia Postiglioni

Microsatellite analysis of a sample of Uruguayan Creole bulls (Bos taurus)

The Uruguayan Creole cattle genetic reserve consists of a herd of about 600 animals (bulls, cows and calves) located in an indigenous habitat of 650 hectares. In a previous study, a random sample from this herd showed high heterozygosity and a Hardy-Weinberg equilibrium for markers of major genes related to milk production. To study its genetic diversity we genotyped a sample of bulls (N = 19 out of 23 for the whole herd) using the PCR reaction with a set of 17 microsatellite markers. Between two and seven different alleles were identified per microsatellite in a total of 73 alleles. The expected mean heterozygosity (He) per locus was between 0.465 and 0.801, except for microsatellite HEL13 which gave a He value of 0.288. The expected mean heterozygosity was 0.623 and the polymorphic information content (PIC) was between 0.266 for HEL13 and 0.794 for CSSM66. The genetic diversity found in polymorphic markers in the breeding bulls of this Creole cattle population supports previous genetic analyses using major production genes and indicate that further studies should be carried out on this population to provide data of interest to cattle production.

Localisation of aphidicolin-induced break points in Holstein-Friesian cattle (Bos taurus) using RBG-banding

Fragile sites (FS) seem to play a role in genome instability and may be involved in karyotype evolution and chromosome aberrations. The majority of common fragile sites are induced by aphidicolin. Aphidicolin was used at two different concentrations (0.15 and 0.30 μM) to study the occurrence of FS in the cattle karyotype. In this paper, a map of aphidicolin induced break points and fragile sites in cattle chromosomes was constructed. The statistical analysis indicated that any band with three or more breaks was significantly damaged (P < 0.05). According to this result, 30 of the 72 different break points observed were scored as fragile sites. The Pearson correlation test showed a positive association between chromosome length and the number of fragile sites (r = 0.54). On the contrary, 21 FS were identified on negative R bands while 9 FS were located on positive R bands.

Analysis of the population structure of Uruguayan Creole cattle as inferred from milk major gene polymorphisms

The ancestors of Uruguayan Creole cattle were introduced by the Spanish conquerors in the XVII century, following which the population grew extensively and became semi-feral before the introduction of selected breeds. Today the Uruguayan Creole cattle genetic reserve consists of 575 animals. We used the tetra primer amplification refractory mutation system polymerase chain reaction (ARMS-PCR) to analyze the k-casein, b-casein, aS1-casein and a-lactoalbumin gene polymorphisms and restriction fragment length polymorphism PCR (RFLP-PCR) for the b-lactoglobulin and the acylCoA:diacyl glycerol acyltransferase 1 (DGAT1) genes. The k-casein and b-lactoglobulin genes presented very similar A and B allele frequencies, while the as1-casein and a-lactoalbumin gene B alleles showed much higher frequencies than the corresponding A alleles. The b-casein B allele was not found in the population sampled. There was a very high frequency of the DGAT1 gene A allele which is associated with low milk fat content and high milk yield. All loci were in Hardy-Weinberg equilibrium and the level of heterozygosity agreed with the high genetic diversity observed in a previous analysis of this population. Preservation of the allelic richness observed in the Uruguayan Creole cattle should be considered for future dairy management and livestock genetic improvement. The results also emphasize the value of the tetra primers ARMS-PCR technique as a rapid, easy and economical way of genotyping cattle breeds for milk gene single nucleotide polymorphisms.

Could Tissue-Specific Genes be Silenced in Cattle Carrying the Rob(1;29) Robertsonian Translocation?

Robertsonian translocations (rob) are frequent chromosome rearrangements observed in human (Nielsen & Wohlert, 1991), plants (Friebe et al., 2005), mice (Saferali et al., 2010) and domestic animals (Fries & Popescu, 1999), that are considered in arthropods classical mechanisms of chromosome evolution (Robertson, 1916). In cattle, this type of translocation is the most widespread chromosomal abnormality in European and American Creole cattle breeds. In Uruguayan Creole cattle the monocentric Robertsonian translocation rob(1;29) presents a frequency of 4%, whereas a frequency between 4 to 10% is described in beef and dairy cattle breeds (King, 1991; Postiglioni et al., 1996). In these populations there is a high incidence of heterozygous carriers and a very small number or even absence of homozygous individuals (Kastelic & Mapletoft, 2003). This situation has also been observed in the majority of cattle populations in which rob(1;29) has been detected (Ducos et al., 2008).

Bovinos y ovinos Criollos del Uruguay. Estudios y perspectivas

Los bovinos y ovinos Criollos de America descienden del ganado introducido por los conquistadores espanoles y portugueses en los Siglos XVI y XVII. En Uruguay existe una reserva de bovinos Criollos y otra de ovinos Criollos en el Parque de San Miguel, Rocha, ademas de varias poblaciones de Criollos con diversos grados de pureza en otras partes del pais. El Departamento de Genetica y Mejora Animal de la Facultad de Veterinaria (UdelaR) se ha dedicado al estudio y caracterizacion de estos animales desde el ano 1996. Se han llevado a cabo estudios morfologicos, citogeneticos y con marcadores moleculares de ADN, entre los cuales se destacan genes relacionados a produccion de leche, carne, enfermedades hereditarias y marcadores de diversidad genetica. Los bovinos Criollos constituyen, ademas, una herramienta de gran valor para el analisis de rearreglos cromosomicos y su relacion con aspectos reproductivos y epigeneticos. Los estudios demuestran la gran variabilidad genetica de los Criollos debido a su adaptacion al medio natural y a que no fueron sometidos a seleccion con fines productivos. Por otro lado, cierta homogeneidad morfologica y estudios de relaciones filogeneticas con otras poblaciones apoyan su concepcion como raza, en especial del bovino Criollo Uruguayo, que ha sido mas estudiado. Estudios de aptitud productiva, de habilidad materna y reproduccion, de resistencia a parasitos y a otros patogenos contribuiran a evaluar el potencial de los Criollos y su posible inclusion en sistemas productivos sustentables.

Marcadores moleculares asociados a la terneza de la carne: análisis del gen de la calpastatina en Aberdeen Angus, Hereford y bovino Criollo del Uruguay

Actualmente la ganaderia se enfrenta al desafio de poner en practica una nueva biotecnologia: los marcadores moleculares. La seleccion asistida por marcadores es un apoyo a los sistemas tradicionales de seleccion que posibilita una mayor precision en la estimacion del valor de cria de los reproductores, accion certera por parte del productor, que asi podra seleccionar animales geneticamente superiores en la caracteristica de interes. Un ejemplo es la terneza de la carne, de evidente importancia en la industria carnica y dificil de incluir como objetivo de seleccion en los programas de mejoramiento genetico clasico. El gen de la Calpastatina (CAST), asociado a la terneza, presenta un polimorfismo de nucleotido simple (SNP) con los alelos G y C. Los animales con el genotipo CC presentan carne de mayor terneza que los que poseen el genotipo GG (Schenkel et al., 2006). El objetivo de este trabajo fue estimar el potencial genetico para la produccion de carne tierna de las razas Hereford, Aberdeen Angus y bovino Criollo Uruguayo mediante el analisis del gen CAST.