Identification of the e allele at the Extension locus (MC1R) in Brazilian Creole sheep and its role in wool color variation.

The melanocortin 1 receptor (MC1R) gene has been described as responsible for the black color in some breeds of sheep, but little is known about its function in many colored breeds, particularly those with a wide range of pigmentation phenotypes. The Brazilian Creole is a local breed of sheep from southern Brazil that has a wide variety of wool colors. We examined the MC1R gene (Extension locus) to search for the e allele and determine its role in controlling wool color variation in this breed. One hundred and twenty-five animals, covering the most common Creole sheep phenotypes (black, brown, dark gray, light gray, and white), were sequenced to detect the mutations p.M73K and p.D121N. Besides these two mutations, three other synonymous sites (429, 600, and 725) were found. The dominant allele (E(D): p.73K, and p.121N) was found only in colored animals, whereas the recessive allele (E⁺: p.73M, and p.121D) was homozygous only in white individuals. We concluded that MC1R is involved in the control of wool color in Brazilian Creole sheep, particularly the dark phenotypes, although a second gene may be involved in the expression of the white phenotype in this breed.

Mitochondrial and nuclear DNA analyses reveal population differentiation in Brazilian Creole sheep.

Using ND5 sequences from mtDNA and 10 nuclear markers, we investigated the genetic differentiation of two South American Creole sheep phenotypes that historically have been bred in different biomes in southern Brazil. In total, 18 unique mtDNA haplotypes were detected, none of which was shared between the two phenotypes. Bayesian analysis also indicated two different groups (k = 2). Thus, these varieties are supported as being genotypically distinct. This situation could have resulted either from geographical isolation, associated with differences in the cultural habits of sheep farmers and in the way that flocks were managed, or more likely, from the introduction of different stocks four centuries ago.

Effect of polymorphisms linked to LEP gene on its expression on adipose tissues in beef cattle.

In cattle, genetic markers at the leptin (LEP) gene and at those linked to the gene have been described as affecting calving interval (markers LEPSau3AI and IDVGA51), or daily weight gain (BMS1074 and BM1500). This work investigated the effect of these alleles on LEP mRNA levels in cattle subcutaneous and omental adipose tissues. A sample of 137 females of a Brangus-Ibage beef cattle herd was analysed to evaluate the distribution of the polymorphisms; then, animals having at least one of the IDVGA51*181 (allele 181 at marker IDVGA51; six animals), LEPSau3AI*2 (four), BMS1074*151 (13), BM1500*135 (six) alleles and a control group composed of animals without any of these alleles (four animals) were submitted to surgery to obtain omental and subcutaneous adipose tissues. Leptin mRNA expression was quantified by TaqMan RT-PCR, using 18S rRNA as internal control and adjusted for the effect of body condition score, through regression analysis. Omental fat had LEP gene expression 33% lower than the subcutaneous tissue. Carriers of IDVGA*181 and BMS1074*151 showed subcutaneous fat leptin mRNA levels higher than the controls. Leptin controls feed intake and coordinates reproduction; therefore, animals with higher LEP gene expression will probably have lower daily weight gain than others with similar forage offer and nutritional condition and probably will also have longer calving interval.

Detection of genomic variability in different populations of the cattle tick Boophilus microplus in southern Brazil.

DNA from seven isolates of the cattle tick Boophilus microplus was analyzed by restriction fragment length polymorphism (RFLP). Three different cDNA clones, named P-9, P-25 and CP-12, isolated from a B. microplus cDNA library, were used as DNA probes. DNA sequences of P-9 have high similarity to ribosomal genes, whereas P-25 does not show significant homology with known sequences within databases. CP-12 is a cDNA clone encoding a cysteine endopeptidase gene. A limited degree of polymorphism was detected with P-9 and P-25, while CP-12 showed a different pattern of bands for each tick isolate. These findings suggest the existence of a complex genotypic diversity of the tick B. microplus population in endemic regions.