Molecular characterization and in-vitro hormonal requirements for expression of two casein genes from a marsupial.
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.
Collet
C
C
CSIRO Division of Wildlife and Ecology, Lyneham, Australian Capital Territory.
Joseph
R
R
Nicholas
K
K
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002364:Caseins / Q000096:biosynthesis / Q000235:genetics*; D004247:DNA / Q000235:genetics; D005260:Female; D015870:Gene Expression; D008321:Mammary Glands, Animal / Q000378:metabolism; D008394:Marsupialia / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D002364:Caseins; D012333:RNA, Messenger; D004247:DNA