The sequence of porcine αs2-casein cDNA

Molecular Characterization of the Llamas (Lama glama) Casein Cluster Genes Transcripts (CSN1S1, CSN2, CSN1S2, CSN3) and Regulatory Regions

In the present paper, we report for the first time the characterization of llama (Lama glama) caseins at transcriptomic and genetic level. A total of 288 casein clones transcripts were analysed from two lactating llamas. The most represented mRNA populations were those correctly assembled (85.07%) and they encoded for mature proteins of 215, 217, 187 and 162 amino acids respectively for the CSN1S1, CSN2, CSN1S2 and CSN3 genes. The exonic subdivision evidenced a structure made of 21, 9, 17 and 6 exons for the αs1-, β-, αs2- and κ-casein genes respectively. Exon skipping and duplication events were evidenced. Two variants A and B were identified in the αs1-casein gene as result of the alternative out-splicing of the exon 18. An additional exon coding for a novel esapeptide was found to be cryptic in the κ-casein gene, whereas one extra exon was found in the αs2-casein gene by the comparison with the Camelus dromedaries sequence. A total of 28 putative phosphorylated motifs highlighted a complex heterogeneity and a potential variable degree of post-translational modifications. Ninety-six polymorphic sites were found through the comparison of the lama casein cDNAs with the homologous camel sequences, whereas the first description and characterization of the 5'- and 3'-regulatory regions allowed to identify the main putative consensus sequences involved in the casein genes expression, thus opening the way to new investigations -so far- never achieved in this species.

Biochemical and chemical supports for a transnatal olfactory continuity through sow maternal fluids

Recognition of the mother is of major importance for the survival of mammalian neonates. This recognition is based, immediately after birth, on the detection of odours that have been learned by the fetus in utero. If the ethological basis of a transnatal olfactory continuity is well established, little is known on the nature of its olfactory cues, and nothing about the presence of potential carrier proteins in the maternal fluids such as amniotic fluid, colostrum and milk. We have identified the components of the pig putative maternal pheromone in these fluids of the sow. We also used a ligand-oriented approach to functionally characterize carrier proteins for these compounds in the maternal fluids. Six proteins were identified, using binding assay, immunodetection and peptide mapping by mass spectrometry. These proteins are known to transport hydrophobic ligands in biological fluids. Among them, alpha-1 acid glycoprotein (AGP) and odorant-binding protein (OBP) have been described in the oral sphere of piglets as being involved in the detection of pig putative maternal pheromone components. These are the first chemical and biochemical data supporting a transnatal olfactory continuity between the fetal and the postnatal environments.

Comparative analysis of gene sequence of goat CSN1S1 F and N alleles and characterization of CSN1S1 transcript variants in mammary gland

In this paper, we report the full characterization, at DNA and RNA level, of the defective goat CSN1S1 F and N alleles and an extensive comparison with the A allele counterpart. By utilizing genomic DNA as template, we amplified the whole CSN1S1 gene plus 1972/3 nucleotides of the 5' region plus 610 nucleotides of the 3' region of the goat CSN1S1 N and CSN1S1 F alleles. Comparison of sequences of the N, F and A CSN1S1 alleles showed a total of 118 polymorphic sites. In particular, both the N and the F alleles are characterized by a deletion of the cytosine at the 23rd nucleotide of the 9th exon. The resulting one-nucleotide frameshift determines a premature stop codon (TGA, nucleotides 17-19 of the 12th exon). On the basis of the information so far available, it seems reasonable to hypothesize that the CSN1S1 N allele might be originated by interallelic recombination events. Comparison of transcripts produced by the N and F alleles shows a remarkable variability in alternative splicing events which concern, even though with different percentage ratios, mainly the lack of the 9th exon, the deletion of the last 5 nucleotides of the 9th exon and the contemporary deletion of exons 10 and 11.

Comparative aspects of milk caseins

The caseins comprise the major protein component of milk of most mammals and are secreted as micelles that also carry high concentrations of calcium. They are phosphoproteins that represent the products of four genes, equivalent to those that encode the bovine alpha s1, alpha s2, beta, and kappa-caseins. There is considerable variation in the relative proportions of the particular caseins across species. The primary sequences of the alpha s1, alpha s2, and beta-caseins also show considerable species variation consistent with rapidly evolving genes that are proposed to have a common precursor. In contrast, the kappa-caseins exhibit features that demonstrate a separate origin and function where they are proposed to stabilise the micelle structure. This review focuses on comparative aspects of the caseins across a number of species for which information is now available.

Zn(2+)-selective purification of recombinant proteins from the milk of transgenic animals

The milk of transgenic livestock is becoming a viable, large-scale source of post-translationally complex, recombinant therapeutic proteins. Recombinant vitamin K-dependent proteins such as human protein C (rhPC) and Factor IX can be produced in milk. However, rate limitations in post-translational modification such as intrachain proteolytic cleavage and gamma-carboxylation occur in the mammary gland. Thus, most desirable recombinant products often exist as sub-populations in milk because the mammary gland tends to secrete incompletely processed polypeptides. In general, a nonaffinity purification strategy by which to purify mature recombinant proteins from milk is desirable. Zn2+ is used to selectively modify ion-exchange adsorption behavior of endogenous and recombinant milk proteins through conformational changes which cause aggregation and or precipitation. Zn(2+)-selective precipitation of milk and recombinant proteins results in the purification of active rhPC at high yield from the milk of transgenic pigs using expanded bed chromatography. This method selects for rhPC which is both heterodimeric and properly gamma-carboxylated. Due to the homology of milk proteins among different species, this same Zn(2+)-selective precipitation strategy is useful for developing purification methods for other recombinant proteins from the milk of transgenic livestock.

Structure and expression of the mouse casein gene locus

The analysis of yeast artificial chromosomes (YACs) containing the complete mouse casein gene locus revealed the presence of five casein genes, alpha-, beta-, gamma-, delta-, and kappa-casein, in this order, in the locus. The alpha- and beta-casein genes are only 10 kb apart and have convergent transcriptional orientations. The distance between the beta-casein gene and the alpha s2-like gamma-casein gene is about 70 kb, and these genes have divergent transcriptional orientations. The gamma- and delta-casein genes, both encoding a alpha s2-like casein, are linked within 60 kb and convergently transcribed. The kappa-casein gene is located about 100 kb from the delta-gene. Except for the presence of the delta-casein gene, the organization of the mouse casein locus resembles that of the bovine locus, including the transcriptional orientation of the genes. In contrast to the other casein genes, which are strongly induced at mid-lactation, expression of the delta-casein gene is abruptly induced upon parturition. Comparative analysis of alpha s2-like sequences from various species suggests that the ancestral alpha s2-like gene duplicated around the time of radiation of the rodent and artiodactylid ancestors.

Separation of recombinant human protein C from transgenic animal milk using immobilized metal affinity chromatography

Protein C is an important serine protease due to its ability to proteolytically cleave activated Factors V and VIII. Excess coagulation and blood agglutination can lead to plugged capillaries, thereby reducing oxygen transport to interstitial tissues. To treat patients with hereditary and acquired protein C deficiency would require a greater amount of Protein C than that available from human plasma. However, the potential demand for this protein could be met by the production of human protein C from transgenic animal mammary glands. Thus, research into inexpensive, efficient methods to purify proteins from transgenic animal milk will be a critical area of study for the large scale production of protein C. Immobilized metal affinity chromatography (IMAC) is a novel method for the purification of protein C. A proposed method of purification is to take advantage of protein C's strong metal ion binding characteristics with IMAC to assist in the separation from transgenic animal milk. The separation procedure is benchmarked against current systems in use by the American Red Cross for purification of Protein C from transgenic porcine milk. Common problems in developing separation schemes for new therapeutics are the initial availability of the product (protein), and time-to-market concerns. Extensive experimental tests for scaleable purification schemes are often cost and time prohibitive. In order to optimize an IMAC protocol with minimal waste of time and resources, total quality management tools have been adopted. Initial experiments were designed to choose buffer conditions, eluents, immobilized valence metals, and flow rates using Taguchi experimental design, which is a total quality management (TQM) tool. One of the values of Taguchi methods lies in the use of Latin orthogonal sets. Through the use of the orthogonal sets, the total number of experiments may be reduced, shortening the focus time on optimal conditions.

Structures and functionalities of milk proteins

During the last decade, marked progress has been made in the study of the fine details of the structures of milk proteins such as caseins, beta-lactoglobulin, alpha-lactalbumin, and lactotransferrin. Many of the functional properties of the individual milk proteins, as well as the milk protein products, may be described at the molecular level. This article is an attempt to thoroughly review the three-dimensional structures of major milk proteins, and to correlate them with the functional aspects of these proteins as food ingredients.

RFLP and linkage analysis of the porcine casein loci--CASAS1, CASAS2, CASB and CASK

Restriction fragment length polymorphisms (RFLPs) were revealed at the porcine casein loci with the following combinations of restriction endonucleases and porcine cDNA clones: alpha s1-casein (TaqI); alpha s2-casein (BamHI); and beta-casein (SacI). These RFLPs were shown to be under simple monogenic control by segregation analysis of two- and three-generation families. The CASAS1, CASAS2 and CASB casein loci were also shown to be linked with no recombinant haplotypes observed amongst 77 meioses in Large White and Meishan F1 and F2 crosses. No recombinants were observed in a further 106 meioses that were informative for linkage between CASAS1 and CASAS2.

Structure and function of milk protein genes

Interspecies comparisons of cDNA and mosaic milk protein genes have confirmed their high rate of evolution, but the overall gene organization has been conserved. The three Ca-sensitive casein genes, which share common motifs in the promoter region and contain similar sequences that encode signal peptide and multiple phosphorylation sites, probably derived from a common ancestor. alpha s1- and alpha s2-casein genes, divided into many small exons, undergo complex splicing, and the deleted caseins arise from exon skipping. The four bovine casein genes are clustered on 200 kb of chromosome 6. alpha-Lactalbumin and beta-lactoglobulin pseudogenes occur in ruminants. Study of the expression of native and modified milk protein genes in mammary cell lines and transgenic animals and DNA footprinting have shown the occurrence of important regulatory motifs in the proximal 5' flanking region, including one recognized by a specific mammary nuclear factor. Good stage- and tissue-specific expression has been obtained in transgenic animals with milk protein genes having less than a 3-kb 5' flanking region. Better knowledge of both the structure and function of milk protein genes, which has already allowed the use of powerful techniques for the rapid identification of alleles, offers the potential for the genetic modification of milk composition.

Bovine alpha s2-casein D is generated by exon VIII skipping

Bovine alpha s2-casein D (CasD) differs from the common type A by the deletion of a stretch of 9 amino acids (aa) starting at a position not precisely known, either at aa 50, 51, or 52. The sequence of cloned PCR-amplified genomic DNA from three homozygous cows, two unrelated females carrying the CasD allele and one carrying the CasA allele, did not reveal any deletion and showed two identical nucleotide (nt) substitutions in the 1.7-kb region of both CasD alleles encompassing codons 43-75 in the cDNA encoding alpha s2-CasA. This strongly suggests that the deleted bovine alpha s2-CasD arises from skipping the 27-nt exon, now identified as exon VIII, which encodes aa 51-59 of alpha s2-CasA. The G-->T transversion (allele A-->D) affecting the last nt of exon VIII, i.e., the 5' consensus splicing site, might be responsible for the altered splicing of the primary transcript of alpha s2-CasD.

Characterization of 24 porcine (dA-dC)n-(dT-dG)n microsatellites: genotyping of unrelated animals from four breeds and linkage studies

Twenty-four PCR primer pairs were designed for the detection of porcine microsatellites. Polymorphism was investigated in 76 unrelated animals from four different breeds: Duroc, Landrace, Hampshire, and Yorkshire. Compared with human microsatellites, a general lower heterozygosity was detected; however, for each microsatellite a significant variation between breeds in number of alleles and heterozygosity was seen. Mean heterozygosity was found to be significantly higher (P < 0.01%) in the Yorkshire breed than in the other three breeds. Linkage analyses with the CEPH linkage packet were performed in a backcross family comprising 45 animals, of which 43 had informative meioses. Ten of the microsatellites could be assigned to six different linkage groups, demonstrating that linkage mapping with microsatellites can be carried out with great efficiency in a relatively small number of animals. Four of the linkage groups represent Chromosomes (Chrs) 4, 6, 7, and 8 respectively, while two linkage groups are unassigned.