Unexpected thymic hyperplasia in transgenic mice harboring a neuronal promoter fused with simian virus 40 large T antigen.
The hypothalamic peptide growth hormone-releasing factor (GRF) regulates the secretion and production of growth hormone from the anterior pituitary (M. C. Gelato and G. R. Merriam, Annu. Rev. Physiol. 48:569-591). To study GRF gene regulation, transgenic mice were generated that harbor the human GRF promoter fused to the coding sequences from the simian virus 40 early region. These mice had normal hypothalamic functions but unexpectedly suffered from severe thymic hyperplasia. Immunohistochemical analysis revealed that large T antigen was expressed in the thymic epithelial cells.  These cells have endocrine properties and are known to produce thymic hormones [corrected]. The thymic hyperplasia was the apparent consequence of inappropriate production of T-cell maturation factors by epithelial cells and could involve increased self renewal of apparently normal T stem cells in the thymus.
D000818:Animals; D000957:Antigens, Viral, Tumor / Q000235:genetics*; D005786:Gene Expression Regulation; D011905:Genes, ras; D013007:Growth Hormone-Releasing Hormone / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic / Q000502:physiology*; D009414:Nerve Growth Factors / Q000235:genetics; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D013952:Thymus Hyperplasia / Q000235:genetics*; D014018:Tissue Distribution
D000957:Antigens, Viral, Tumor; D009414:Nerve Growth Factors; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D013007:Growth Hormone-Releasing Hormone