Regulated expression of homeobox genes Msx-1 and Msx-2 in mouse mammary gland development suggests a role in hormone action and epithelial-stromal interactions.
The murine homeobox genes Msx-1 and Msx-2 are related to the Drosophila msh gene and are expressed in a variety of tissues during mouse embryogenesis. We now report the developmentally regulated expression of Msx-1 and Msx-2 in the mouse mammary gland and show that their expression patterns point toward significant functional roles. Msx-1 and Msx-2 transcripts were present in glands of virgin mice and in glands of mice in early pregnancy, but transcripts decreased dramatically during late pregnancy. Low levels of Msx-1 transcripts were detected in glands from lactating animals and during the first days of involution, whereas Msx-2 expression was not detected during lactation or early involution. Expression of both genes increased gradually as involution progressed. Msx-2 but not Msx-1 expression was decreased following ovariectomy or following exposure to anti-estrogen implanted directly into the gland. Hormonal regulation of Msx-2 expression was confirmed when transcripts returned to normal levels after estrogen was administered to ovariectomized animals. In situ molecular hybridization for Msx-1 showed transcripts localized to the mammary epithelium, whereas Msx-2 expression was confined to the periductal stroma. Mammary stroma from which mammary epithelium had been removed did not transcribe detectable amounts of Msx-2, showing that expression is regulated by contiguous mammary epithelium, and indicating a role for these homeobox genes in mesenchymal-epithelial interactions during mammary development.
Friedmann
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Y
Department of Biology, University of California, Santa Cruz, Santa Cruz, California, 95064, USA.
Daniel
C W
CW
D000818:Animals; D015152:Blotting, Northern; D004268:DNA-Binding Proteins / Q000235:genetics; D004847:Epithelial Cells; D004848:Epithelium / Q000502:physiology; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics; D006728:Hormones / Q000502:physiology*; D051957:MSX1 Transcription Factor; D008321:Mammary Glands, Animal / Q000737:chemistry / Q000196:embryology*; D051379:Mice; D008810:Mice, Inbred C57BL; D011247:Pregnancy; D012313:RNA / Q000302:isolation & purification; D017154:Stromal Cells / Q000502:physiology*; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000235:genetics
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D006728:Hormones; D051957:MSX1 Transcription Factor; C084119:MSX2 protein; D014157:Transcription Factors; D012313:RNA