title: A multicopy c-Myc transgene as a nuclear label: overgrowth of Myctg50 cells in allophenic mice.
abstract: To trace cell lineages and the origin and fate of cells in transplantation and embryo chimeras, a DNA/DNA in situ hybridization cell labelling system was developed, based on a 50-copy murine c-myc transgene on mouse chromosome 8. Elevated levels of cMyc mRNA were found in Myc*tg50 (Myctg50/0 and Myctg50/Myctg50) transgenic tissues, but adult transgenic NMRI mice were anatomically and histologically indistinguishable from control NMRI mice and did not develop tumours on a wild-type or nude (nu/nu) background. The hybridization label detected transgenic nuclei with an efficiency of approximately 80%. In muscle grafts, this transgene label was successfully applied to trace donor cells in a labelled host and to study the invasion of a graft by host cells. When the cMyc hybridization was used in allophenic mice of the control<-->NMRI-Myctg50/? (nu/+ or +/+) type, an up to a three-fold excess of MYC*tg50 positive over control nuclei was found in all organs examined (ventricle, skeletal muscle, liver, small intestine). This overgrowth of MYC*tg50 cells is probably due to transgene expression. Four out of seven (C57BL/6xBALB/c) or (C57BL/6xNMRI)<-->MYC*tg50 allophenic mice displayed anatomical abnormalities, e.g. an enlarged thymus and a tumour in the groin region. As these abnormalities were only observed in allophenic mice, they might be due to the imbalance of growth potential between MYC*tg50 transgenic and normal cells in the same individual.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000502:physiology; D002678:Chimera; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D005260:Female; D016259:Genes, myc; D017403:In Situ Hybridization; D007421:Intestine, Small / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D009374:Neoplasms, Experimental / Q000235:genetics* / Q000473:pathology; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic