Effect of κ-Casein Polymorphism on Milk Composition in the Orobica Goat

The aim of this work was to study the effects of isoelectrofocusing (IEF) milk protein variants on milk composition in the Italian Orobica goat breed, which is characterized by a rather high frequency of the kappa-casein (CSN3) B(IEF) allele. Significant associations were found between the IEF phenotype and protein and casein percentages. A favorable effect of the CSN3 B(IEF) variant was found for both protein and casein percentages, with a codominance trend for the 3 phenotypes: BB > AB > AA. Depending on the selection purpose, emphasis could be given to different kappa-casein variants in breeding. The high frequency of B(IEF) could be exploited in breeding strategies to improve the protein and casein percentages when cheese making is a selection objective.

Focusing on the Goat Casein Complex

The analysis of casein polymorphisms in goat species is rather difficult, because of a large number of mutations at each locus, and the tight linkage involving the 4 casein genes. Three goat breeds from Northern Italy, Orobica, Verzasca, and Frisa, were analyzed at the casein complex by milk isoelectrofocusing and analyses at the DNA level to identify the majority of all known polymorphisms. The casein gene structure of the 3 local breeds at alpha(S1)-casein (CSN1S1), beta-casein (CSN2), alpha(S2)-casein (CSN1S2), and kappa-casein (CSN3) was compared with that of Camosciata, a more widely distributed breed. A new allele was identified and characterized at CSN2 gene, which seemed to be specific to the Frisa breed. It was named CSN2*E, and was characterized by a transversion TCT --> TAT responsible for the amino acid exchange Ser(166) --> Tyr(166) in the mature protein. The casein haplotype structure is highly different among breeds. A total of 26 haplotypes showed a frequency higher than 0.01 in at least 1 of the 4 breeds considered, with 12, 3, 5, and 19 haplotypes in Frisa, Orobica, Verzasca, and Camosciata breeds, respectively. Only 13 haplotypes occurred at a frequency higher than 0.05 in at least 1 breed. With the molecular knowledge of each locus, the ancestral haplotype coding for CSN1S1*B, CSN2*A, CSN1S2*A, and CSN3*B protein variants can be postulated. A protein evolutionary model considering the whole casein haplotype is proposed.

Short Communication: Predominance of β-Casein (CSN2) C Allele in Goat Breeds Reared in Italy

A protocol for the rapid and simultaneous genotyping of A, C, and 0 'CSN2 alleles in goat was developed by single strand conformational polymorphism polymerase chain reaction (SSCP-PCR) technique. Screening the CSN2 variability in 7 goat breeds reared in Italy validated the genotyping test. The SSCP-PCR technique was also suitable for monitoring CSN2 polymorphism. In particular, the discrimination between CSN2*A and CSN2*C is important because the 2 corresponding protein variants cannot be separated by standard typing techniques. The monitoring of CSN2 variability in the goat breeds indicates the predominance of the C allele. In most breeds, CSN2*C occurred with the highest frequency, except in Saanen where CSN2*A and CSN2*C showed similar frequencies. Variant CSN2*C occurred with a frequency of 0.68 (Camosciata), 0.70 (Jonica), 0.71 (Garganica), 0.82 (Maltese), 0.87 (Cilentana), and 0.97 (Orobica). The alignment among the mature CSN2 sequences of different species suggests that CSN2*A is the ancestral allele compared with CSN2*C. Interestingly, the CSN2*A goat variant showed higher frequencies in selected breeds (Saanen and Camosciata).

Casein Haplotype Structure in Five Italian Goat Breeds

The aim of this work was to investigate the genetic structure of the casein gene cluster in 5 Italian goat breeds and to evaluate the haplotype variability within and among populations. A total of 430 goats from Vallesana, Roccaverano, Jonica, Garganica, and Maltese breeds were genotyped at alphas1-casein (CSN1S1), alphas2-casein, (CSN1S2), beta-casein (CSN2), and kappa-casein (CSN3) loci using several genomic techniques and milk protein analysis. Casein haplotype frequencies were estimated for each breed. Principal component analysis was carried out to highlight the relationship among breeds. Allele and haplotype distributions indicated considerable differences among breeds. The haplotype CSN1S1*F- CSN1S2*F-CSN3*D occurred in all breeds with frequencies >0.100 and was the most common haplotype in the Southern breeds. A high frequency of CSN1S1*0-CSN1S2*C-CSN3*A haplotype was found in Vallesana population (0.162). Principal component analysis clearly separated the Northern and Southern breeds by the first component. The variability of the caprine casein loci and variety of resulting haplotypes should be exploited in the future using specific breeding programs aiming to preserve biodiversity and to select goat genetic lines for specific protein production.

Single nucleotide polymorphisms in the ovine casein genes detected by polymerase chain reaction-single strand conformation polymorphism

Casein genetic polymorphisms are important and well known due to their effects on quantitative traits and technological properties of milk. At the DNA level, polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) allows for the simultaneous typing of several alleles at casein loci, as well as the detection of unknown polymorphisms. Here we describe the usefulness of the PCR-SSCP technique for casein typing in sheep. In particular, three single-nucleotide polymorphisms (SNP) are described at CSN1S1, CSN2, and CSN3, all resulting in amino acid exchanges. At CSN1S1, a transition T-->C was found, resulting in the deduced amino acid exchange Ile186-->Thr186. A transition A-->G resulting in the deduced amino acid exchange Met183-->Val183 was identified at CSN2. The 2 SNP showed a rather high frequency (ranging from 0.12 to 0.26) in 3 Italian breeds (Sarda, Comisana, Sopravissana). Another transition C-->T (Ser104-->Leu104) was found at CSN3 in one heterozygous animal.

Genetic polymorphism of goat kappa-casein (CSN3) in different breeds and characterization at DNA level

Data on genetic differences at CSN3 in goat breeds including a DNA based typing method and the mutations responsible for variation on protein and DNA level are presented here. Isoelectric focusing (IEF) in ultrathin polyacrylamide gels with carrier ampholytes was used to demonstrate CSN3 polymorphism in milk samples of Italian (Orobica n=88; Ionica n=68) and German goat breeds (Bunte Deutsche Edelziege n=244; Weisse Deutsche Edelziege n=134; Toggenburger n=25; Thüringer Waldziege n=70). A further CSN3 band was found presenting a more cathodic migration than CSN A. After chymosin action, the genetic polymorphism was also observed in the para-kappa-casein fraction. The new allele CSN3(B) was spread mainly in Orobica (37%), Bunte Deutsche Edelziege (11%) and Ionica (10%). CSN3(B) occurred in low frequency (<3%) in Thüringer Waldziege and in Weisse Deutsche Edelziege, and could not be demonstrated in milk samples of Toggenburger. The populations were in Hardy-Weinberg equilibrium at CSN3. The codominant genetic control of CSN3(B) was confirmed by genetic studies. Discrimination of CSN3 alleles A and B was also obtained by DNA SSCP analysis. Sequencing of CSN3(B) revealed four transitions at position 247, 309, 471, and 591 compared with CSN3(A). From these transitions, the following amino acid substitutions are deduced: 44 Gln --> Arg, 65 Val --> Ile, 119 Val --> Ile, and 159 Ser --> Pro. Among the four mutations, only the 44 Gln --> Arg can be revealed by milk protein IEF analysis while at DNA level three further genetic variants should exist in addition to CSN3(A) and CSN3(B).

Single nucleotide polymorphisms (SNPs) within Bov-A2 SINE in the second intron of bovine and buffalo k-casein (CSN3) gene

The genetic polymorphism of an entire Bov-A2 element located in the second intron of the buffalo and bovine k-casein (CSN3) gene was investigated by amplification and sequencing of PCR products. Single nucleotide polymorphisms were detected. A PCR-RFLP method was developed to detect an A or G mutation at position 605 of bovine Bov-A2 element which creates a BfaI polymorphic site. The frequencies of the B allele, with the BfaI site, were for 0.275, 0.775, 0.750, 0.975, respectively, for Italian Holstein Friesian, Grey Alpine, Friuli Red Pied and Reggio bovine breeds. The mutation rate (substitutions and deletions/insertions per nucleotide site per year) was 2.5 x 10(-9) for Bov-A2 sequences in the second intron of CSN3. The comparison with other Bov-A2 elements suggests that this retroelement might be an important source of single nucleotide polymorphism for analysis of Bovidae genomes.

A case of familial nesidioblastosis: prenatal diagnosis of foetal hyperinsulinism

Persistent neonatal hyperinsulinaemic hypoglycaemia due to nesidioblastosis is a rare condition probably transmitted by an autosomal recessive inheritance. Recurrent hypoglycaemic episodes become evident after birth and cause severe neurological damage without intensive treatment. The intrauterine detection of hypoglycaemia and hyperinsulinism in newborns subsequently diagnosed as affected by nesidioblastosis has not yet been reported. We describe a case of familial nesidioblastosis in which an intrauterine diagnosis could be suggested by high levels of insulin and C-peptide and low values of glucose in the amniotic fluid.

[Screening for obesity in a schoolchildren population of the 20th zone of Milan and a nutritional education intervention]

Our study was performed in 1986-'87 and 1987-'88 school years on 12.354 three to eighteen years old students (the whole scholastic population of zone 20 of Milan) in order to apply dietary education on obese subjects. Mean prevalence of obesity was 13.4% with elevated percentages in 11 to 13 years old students (17.9%), with respect to primary (14.1%), high school (12.4%) and nursery school (4.7%). The 36% of obese subjects (more than 50% of adolescents) had already tempted to reduce body weight. Intervention reduced % weight excess (from 33.6 +/- 0.5% to, 28.8 +/- 0.5% after 12 months, p less than 0.001); 67% of obese subjects lost weight and body weight returned within normal limits in 31% of subjects. An educational dietetic strategy may be successful in childhood obesity.

Variability of reduced glutathione levels in Massese ewes and its effect on daily milk production

The variability of the erythrocyte concentration of the tripeptide glutathione was studied in four flocks of Massese sheep. A relationship was found between glutathione level and stage of lactation in which the second month showed the lowest content. Genotype at transferrin and haemoglobin loci was associated with glutathione levels. Homozygotes at the transferrin locus yielded higher levels, while the D allele at the same locus was associated with lower concentrations. Animals with haemoglobin AA showed higher contents of glutathione. Also, a negative correlation was found between daily milk production and glutathione level.