REGULATION OF MSX-1, MSX-2, BMP-2 AND BMP-4 DURING FETAL AND POSTNATAL MAMMARY-GLAND DEVELOPMENT

Expression of the Msx-1 and Msx-2 homeobox genes have been shown to be co-ordinately regulated with the Bmp-2 and Bmp-4 ligands in a variety of developing tissues. Here we report that transcripts from all four genes are developmentally regulated during both foetal and postnatal m ammary gland development. The location and timecourse of the Bmp and M sx expression point to a role for Msx and Bmp gene products in the con trol of epithelial-mesenchymal interactions. Expression of Msx-2, but not Msx-1, Bmp-2 or Bmp-4 was decreased following ovariectomy, while e xpression of the human Msx-2 homologue was regulated by 17 beta-oestra diol in the MCF-7 breast cancer cell line. The regulation of Msx-2 exp ression by oestrogen raises the possibility that hormonal regulation o f mammary development is mediated through the control of epithelial-me senchymal interactions.