Caseins (Alpha-S1/k)

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Caseins (Alpha-S1/k)

Interpretation of the results of the polymorphism analyzes of the genes encoding αS1-casein (CSN1S1) and κ-casein (CSN3) Introduction In goats, casein milk proteins are encoded by a group of four genes located on chromosome VI that represent a ligament group (Hayes, et al., 1993): αS1-casein (alphaS1), αs2-casein (alphaS2), β-casein (beta) and κ-casein (kappa). So far they have identified several polymorphisms (SNPs) in these genes that are related to the type and amount of protein produced (Caroli et al. 2006). The effect of these mutations is currently being studied as a haplotype, that is, as a single gene with a multiple effect (Finocchiaro et al. 2008; Hayes et al. 2006). Practically all of the milk production of the Murciano-Granadina goat breed is destined for technological transformation into cheese, although there is currently a certain interest in the marketing of fresh milk or other processed products such as yogurt. Caseins have an important effect on curd production, in addition to having a very varied effect on the organoleptic characteristics and technologies of milk. Knowledge at the molecular level of the different allelic forms present can be of great help to improve the calculation of the genetic value of the breeders and, above all, to guide the improvement and genetic selection of milk-producing animals with proteins more suitable for the different uses to which they are used. that dairy production is intended for (fresh milk, curds, fermentation, etc.). tdesc_22 In the Applied Molecular Genetics Laboratory of the technology-based company of the University of Córdoba Animal Breeding Consulting S.L. (ABC) the polymorphisms of the gene that encodes αS1-casein and the gene that encodes κ-casein are studied and characterized. In general, αS1-casein is associated with a higher proportion of total protein in milk and a higher amount of fat. κ-casein is related to cheese yield, its effect on the coagulation speed and size of curd granules being demonstrated, especially in cattle. Genotyping of these two genes is done routinely in the laboratory and their genotypes have been introduced as another piece of information in the breed selection scheme. The technology necessary to analyze the genes that code for αs2-casein and β-casein is currently being developed. β-casein is the most present protein, in percentage, in goat milk, but the mechanisms of iteration with the other caseins are not yet known. Results analysis αS1-casein The gene that codes for αS1-casein is the most polymorphic of the 4 genes in the complex. In different studies in various goat breeds around the world, more than 17 main alleles have been found that are associated with variations in the protein expressed in milk. Strong, medium, low and null alleles (absence of αS1-casein in milk) have been described. According to published data, the effect of these alleles on the production of αS1-dairy casein protein is (Ramunno et al. 2005; Maga et al. 2009; Caravaca et al. 2011): - Alleles A, B, C, H, L and M are considered "strong" alleles and are associated with the highest amount of αS1-casein in milk. - Alleles E and I are considered “intermediate expression”. - Alleles D, F and G are considered “low expression”. - Alleles 01, 02 and N are described as "null" and are associated with no expression of αS1-casein in milk or with residual expression. In the case of the Murciano-Granadina goat breed, taking as reference the data published in the scientific literature (Martin et al. 1999; Caravaca et al. 2009), the estimate of the effect of the different genotypes is reported in the following table. It must be taken into account that these are statistical data that have been observed in a specific sample of individuals and that therefore variations may occur. Genotype Estimated mean αS1-casein production AA or BB 7,20 g/l EE 2,50 g/l FF 0,80 g/l NN Absence or traces AE or BE 4,70 g/l AF or BF 3,95 g/l AN or BN 3,50 g/l EN 1,10 g/l FN 0,45 g/l   κ-casein The gene encoding κ-casein is the second most polymorphic gene in the complex. In the goat species, 17 allelic variants of this gene are known that affect the functionality, and as a consequence, the effectiveness of κ-casein to produce more or less firm curd globules, reaching the extreme case of not producing any amount of κ-casein in milk. However, only variants A, B and C have been found in Central European and Iberian goat breeds (Yahyaoui et al. 2001). The following variants have been found in the Murciano-Granadina breed: - The B or “improving” allele. According to published data, this variant would be associated with a better technical quality of the curd produced and a greater amount of protein and fat in the milk, although these effects have not been quantified so far. The effect that has been demonstrated, both in goats and cattle, is the positive effect on coagulation capacity quantified according to the Rennet coagulation time (Caravaca et al. 2009; Caravaca et al. 2011). - The A or “normal” allele - The C allele or “low expression”. It is present although with very low frequency, it has probably been disappearing due to the effect of selection. Genotype Rennet coagulation time AA 11±1.48 BB 13±1,35 AB 12±1,19   Bibliography - Caravaca F., Ares J.L., Carrizosa J., Urrutia B., Baena F., Jordana J., Badaoui B., Sanchez A., Angiolillo A., Amills M. & Serradilla J.M. (2011) Effects of alpha s1-casein (CSN1S1) and kappa-casein (CSN3) genotypes on milk coagulation properties in Murciano-Granadina goats. J Dairy Res 78, 32-7. - Caravaca F., Carrizosa J., Urrutia B., Baena F., Jordana J., Amills M., Badaoui B., Sánchez A., Angiolillo A. & Serradilla J.M. (2009) Effect of αS1casein (CSN1S1) and κ casein (CSN3) genotypes on milk composition in Murciano"Granadina goats. J Dairy Res 92, 2960-4. - Caroli A, Chiatti F, Chessa S, Rignanese D, Bolla P, Pagnacco G. 2006. Focusing on the goat casein complex, J Dairy Sci, 89:3178-3187. - Finocchiaro R, Hayes BJ, Siwek M, Spelman RJ, van Kaam JB, Adnoy T, Portolano B. 2008. Comparison of casein haplotypes between two geographically distant European dairy goat breeds, J Anim Breed Genet, 125:68-72. - Hayes B, Hagesaether N, Adnoy T, Pellerud G, Berg PR, Lien S. 2006. Effects on production traits of haplotypes among casein genes in Norwegian goats and evidence for a site of preferential recombination, Genetics, 174:455-464. - Maga E.A., Daftari P., Kultz D. & Penedo M.C. (2009) Prevalence of alphas1-casein genotypes in American dairy goats. J Anim Sci 87, 3464-9. - Martin P., Ollivier-Bousquet M. & Grosclaude F. (1999) Genetic polymorphism of caseins: a tool to investigate casein micelle organization. International Dairy Journal 9, 163-71. - Ramunno L., Cosenza G., Rando A., Pauciullo A., Illario R., Gallo D., Di Berardino D. & Masina P. (2005) Comparative analysis of gene sequence of goat CSN1S1 F and N alleles and characterization of CSN1S1 transcript variants in mammary gland. Gene 345, 289-99. - Yahyaoui M.H., Coll A., Sanchez A. & Folch J.M. (2001) Genetic polymorphism of the caprine kappa casein gene. J Dairy Res 68, 209-16.
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