Polymorphism of three milk protein genes in Mexican Jersey cattle

The objective was to estimate the allelic and genotypic frequencies, genetic diversity and polymorphic information content for the β-casein, κ-casein and β-lactoglobulin genes. Blood and frozen semen samples were collected from 453 Jersey individuals registered by the Mexican Jersey Cattle Association. Twenty eight breed specific SNP primers for whole genes were used. The B allele of κ-casein had higher frequency (0.69) than the A (0.26) and E (0.05). For β-lactoglobulin, the highest frequency was for B (0.72), followed by A and C alleles (0.26 and 0.02, respectively). The β-casein allele with the highest frequency was A² (0.71), followed by A¹ (0.19), A³ (0.05), B (0.04) and C (0.01). The average genetic diversity (He) was 0.53. The average locus effective allele number was 1.79. These results indicate a high allelic diversity for κ-caseín, β-casein and β-lactoglobulin that could be included in breeding programs in the population studied, aimed to improve the milk quality traits of economic importance.

Convenient genotyping of nine bovine K-casein variants

K-casein gene polymorphisms are of major importance in the dairy industry due to their association with different quality and productive traits (i.e., milk protein). Several methods for genotyping this gene have been proposed; however, none are focused on the simultaneous discrimination of nine K-casein variants. A strategy based on PCR-RFLP was designed to characterize nine K-casein variants (A, B, C, E, F², G, H, I and J) and used to genotype three cattle populations: Gyrholando (3/8 Gyr x 5/8 Holstein), Charolais and Carora. The B variant was the most frequent in the Charolais and Carora breeds, with allelic frequencies of 0.60 and 0.59, respectively. In the Gyrholando breed, four variants were found, with the A variant being the most frequent and E and H the least. The genotyping strategy was effective in detection and differentiation of K-casein variants, and it is proposed for use in laboratories with minimal molecular biology equipment for genotyping and evaluation of the phenotypic effects of nine K-casein variants on milk production and quality.

Polimorfismo genético de la kappa-caseína en ganado criollo limonero / Genetic polymorphism of kappa-casein in creole limonero bovine

Con el objeto de estudiar el polimorfismo del gen CSN3 en la raza bovina Criollo Limonero, se extrajeron muestras séricas de 163 individuos (machos y hembras), los cuales fueron caracterizados mediante la técnica PCR-RFLP. Los resultados obtenidos indican que las frecuencias encontradas correspondieron a 0,11; 0,56 y 0,33 para los AA, AB y BB, respectivamente, correspondiendo a frecuencias alélicas de 0,39 para el alelo A y 0,61 para el B, respectivamente. Cabe destacar que a partir de esta información de la CSN3 y su relación con caracteres, tales como la producción de leche y rendimiento quesero, se pueden llevar a cabo planes de mejoramiento asistido por marcadores, garantizando el mantenimiento de la variabilidad genética de estas poblaciones locales que se caracterizan por censos reducidos y la amenaza constante por cruzamientos con razas mejoradoras o comerciales, que buscan incrementar el volumen de producción de leche en detrimento de la calidad del producto; así mismo, se indica la ventaja potencial que presenta la leche del ganado Criollo Limonero en la producción de quesos, por mostrar mayoritariamente alelos del tipo B de la CSN3.

In order to assess the polymorphism of CSN3 gen in Limonero Creole breed, blood samples were collected from 163 male and female individuals, with which characterization through RFLP-PCR was conducted. Results showed that genotypic frequencies were 0.11, 0.56 and 0.33 for AA, AB and BB, respectively. Allelic frequencies were 0.39 and 0.61 for allele A and B, accordingly. It is important to mention that with this information of CSN3 and its relationship with some traits such as milk production and cheese productivity, markers-assisted genetic improvement plans can be undertaken, which would maintain genetic variability of these local populations characterized by small numbers of animals and by the constant threat of crossbreeding with improved or commercial breeds, with the objective of increasing milk production over product quality; moreover, a potential advantage of Limonero Creole breed in milk production by its having mainly B-type alleles in CSN3 is shown.

Hypoxia activates signal transducers and activators of transcription 5 (STAT5) and increases its binding activity to the GAS element in mammary epithelial cells

STATs (signal transducers and activators of transcription) are proteins with dual functions: signal transducers in the cytoplasm and transcriptional activators in the nucleus. STAT proteins act as transcription factors activated by phosphorylation on its tyrosine residues upon stimulation by various cytokines. The phosphorylated STAT molecules then form homo- or heterodimers through SH2-mediated interaction and translocate into the nucleus to activate the transcription of various target genes. STAT5 recognizes the interferon-gamma activated site TTCNNNGAA (GAS sequence) in the promoter region of the beta-casein gene. Except for prolactin-dependent beta-casein production in mammary gland cells, the biological consequences of STAT5a activation in various systems are not clear. Here we showed that STAT5a was phosphorylated 10 min after desferrioxamine (DFO) treatment, and reached a maximum induction at 4 h in mammary epithelial cells (HC11) and transfected COS-7 cells. Under hypoxic conditions (2% O2), a maximal phosphorylation of STAT5a was observed within 6 h. EMSA (electrophoretic mobility shift assay) showed that DFO or hypoxia enhanced the binding activities of STAT5a DNA to beta-casein gene promoter in mammary epithelial cells (HC11) and transfected COS-7 cells. These results showed that DFO or hypoxia induces tyrosine phosphorylation of STAT5a and also increases the binding activity of STAT5a DNA in mammary epithelial cells. Our data suggest that the STAT5 may act as a mediator in hypoxia-mediated gene expression.

Non-coordinate expression of closely linked mouse casein genes.

Expression levels of five mouse casein genes were analysed in the mammary gland of virgin, pregnant and lactating mice. We have already shown that the five murine casein genes are arranged in the order, alpha-beta-gamma-epsilon-kappa in a tandem array, very close to each other in a 250 kb DNA fragment of mouse genome. Northern blot analysis showed that, of the calcium-sensitive casein genes, the epsilon casein gene is expressed only during lactation unlike the alpha, beta and gamma casein genes which are expressed during pregnancy and lactation. Even though the alpha, beta and gamma genes exhibited a co-ordinated expression pattern from mid to the later stages of pregnancy, the mRNA levels varied considerably (60, 90 and 100% respectively) by the onset of lactation. The mRNA level of the calcium-insensitive kappa casein gene increased from mid-pregnancy but at a lower rate and reached approximately 60% by the first day of lactation. Considering the locations and closeness of the casein genes, a non-coordinate expression profile is exhibited by the mouse casein genes, particularly the epsilon casein gene.