Molecular characterization and in-vitro hormonal requirements for expression of two casein genes from a marsupial

Abstract

Two marsupial casein genes have been isolated from a tammar wallaby (Macropus eugenii) mammary gland cDNA library. Comparisons of the tammar alpha- and beta-casein genes with their eutherian homologous reveal extensive divergence at the levels of nucleotide and amino acid sequences. Regions of similarity between the tammar and eutherian Ca(2+)-sensitive caseins are restricted to the major phosphorylation sites and the signal peptides. Quantification of casein mRNA levels in hormone-stimulated mammary gland explants from tammars in late pregnancy suggests that maximal induction of the beta-casein gene is dependent upon prolactin and insulin, while maximal induction of the alpha-casein gene is dependent upon prolactin, insulin and cortisol. These results are in contrast to earlier studies which show that the maximal induction of a putative 19 kDa casein, alpha-lactalbumin and beta-lactoglobulin in the tammar mammary gland is dependent upon prolactin alone. The expression of the latter three genes is not modulated by other hormones known to play a role in the in-vitro initiation of lactation in eutherians.

Lactation transcriptomics in the Australian marsupial, Macropus eugenii: transcript sequencing and quantification

“…During this analysis 2 putative splice variants were identified in alpha-casein resulting in the in frame deletion of 8 (aa 82–89) and 14 (aa 125–138) amino acid fragments corresponding to short exons in other species. In addition the alpha-casein C terminal sequence has been improved and found to be much more similar to the possum ( Trichosurus vulpecula ) sequence than previously reported [ 25 ]. Automatic contig sequence annotation using BLAST searches (E-values < e-10) resulted in similar hit rate of about 60% against a number of databases; the non redundant protein database, the set of GenScan protein predictions from the opossum genome, the complete opossum genome sequence and 49% with the Ensembl cDNA predictions from the human genome.…”

Investigating the genetic polymorphism of sheep milk proteins: a useful tool for dairy production

“…They are important in determining the surface properties of casein micelles and essential for rennet curd formation . The β ‐casein family includes several eutherian and two marsupial proteins for which the amino acid and nucleotide sequence is known . Eutherian β ‐caseins sequences (encoded by the CSN2 gene) are characterised by a highly conserved 15 residue signal sequence although the mature proteins show a degree of divergence across species in terms of amino acid identity similarly to that observed for the α s1‐caseins .…”