Cloning and expression of the transferrin and ferritin genes in a marsupial, the brushtail possum (Trichosurus vulpecula)

Transferrin and ferritin cDNAs have been isolated and characterised from th e common brushtail possum (Trichosurus vulpecula), the first marsupial exam ples of these genes. The transferrin cDNA encodes a 711 amino acid pre-prot ein which shows high levels of amino acid identity with eutherian transferr ins (58-60%) and lactoferrins (54-56%). Phylogenetic analysis suggests that the possum transferrin has evolved independently along a pathway distinct from that of the eutherian transferrins and lactoferrins. Possum H-ferritin is a 182 residue protein which shares 86-94% amino acid identity with mamm alian, avian and amphibian sequences. Ferritin mRNA was detected in all tis sues tested, whereas transferrin was highly expressed in possum liver and m ammary gland, and at lower levels in heart, testis and lung. In the possum mammary gland, ferritin mRNA was expressed throughout lactation with higher levels during the first 30 days which coincides with the high iron concent ration of milk at this time. The transferrin gene was differentially expres sed during lactation with peak mRNA levels detected during the first 6 days of lactation and after day 106 throughout late lactation. The pattern of t ransferrin mRNA expression in the mammary gland was identical to that of an other whey protein, the late lactation protein, suggesting that the transcr iption of these genes may be regulated by a similar mechanism in this tissu e. (C) 1999 Elsevier Science B.V. All rights reserved.