Spatial and temporal pattern of cellular myc oncogene expression in developing human placenta: implications for embryonic cell proliferation.
We have analyzed staged human placentas by Northern, dot blot, and in situ hybridization to human c-myc probes. Placental RNA exhibits a stage-specific appearance of a 2.4 kb transcript of the c-myc gene. The frequency of this transcript varies 20 to 30 fold over the course of placental development, showing a peak at 4-5 weeks after conception, where the myc transcripts comprise about 0.05% by weight of the total placental mRNA. A clear decline in placental c-myc transcription is seen before the end of the first trimester of pregnancy. In situ hybridization to 125I-labeled myc probes demonstrates an unequal spatial distribution of myc transcripts in placental with particularly high expression in the cytotrophoblastic shell of early placenta. Labeling of placental explants with 3H-thymidine, the localization of myc transcripts to cytotrophoblasts, and the temporal pattern of myc expression all support a strong correlation between myc transcript abundance and cytotrophoblast proliferation. We argue for a role for the c-myc gene in the proliferation of normal cells in this tissue.
D002455:Cell Division; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D009693:Nucleic Acid Hybridization; D009857:Oncogenes; D010920:Placenta / Q000502:physiology*; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics; D014018:Tissue Distribution; D014158:Transcription, Genetic; D014327:Trophoblasts / Q000502:physiology
D012333:RNA, Messenger