Acute involution in the tammar wallaby : identification of genes and putative novel milk proteins implicated in mammary gland function

AbstractMarsupials provide a suitable alternative model to studying mammary gland involution. They have evolved a different reproductive strategy from eutherians, giving birth to an altricial young and secreting milk that changes in composition during lactation. In this study, we used a marsupial-specific EST microarray to identify 47 up-regulated genes during mammary gland involution in the tammar wallaby (Macropus eugenii). These include the pro-apoptotic tumour necrosis factor receptor superfamily 21 (TNFRSF21) gene, whose expression in the mammary gland has not previously been reported. Genes encoding putative novel milk proteins which may protect the mammary gland from infection were also found to be up-regulated, such as amiloride binding protein 1 (ABP1), complement component 1QB (C1QB), complement component 4A (C4A) and colony stimulating factor 2 receptor β (CSF2Rβ). Our results show that the marsupial reproductive strategy was successfully exploited to identify genes and putative novel milk proteins implicated in mammary gland involution

Marsupial milk : identifying signals for regulating mammary function and development of the young

The role of milk in providing nutrition for the young is well established. However, it is becoming apparent that milk has a more comprehensive role in programming and regulating growth and development of the suckled young, and an autocrine impact on the mammary gland so that it functions appropriately during the lactation cycle. This central role of milk is best studied in animal models, such as marsupials that have evolved a different lactation strategy to eutherians and allow researchers to more easily identify regulatory mechanisms that are not as readily apparent in eutherian species. For example, the tammar wallaby (Macropus eugenii) has evolved with a unique reproductive strategy of a short gestation, birth of an altricial young and a relatively long lactation during which the mother progressively changes the composition of the major, and many of the minor components of milk. Thus, in contrast to eutherians, there is a far greater investment in development of the young during lactation and it is likely that many of the signals that regulate development of eutherian embryos in utero are delivered by the milk. This requires the co-ordinated development and function of the mammary gland. Inappropriate timing of these signalling events in mammals may result in either limited or abnormal development of the young, and potentially a higher incidence of mature onset disease. The tammar is emerging as an attractive model to better understand the role of milk factors in these processes