CHARACTERIZATION OF THE IMPRINTED IPW GENE - ALLELIC EXPRESSION IN NORMAL AND TUMORIGENIC HUMAN TISSUES

IPW (Imprinted gene in the Prader-Willi syndrome region) is a recently identified paternally expressed gene, Previous work has demonstrated IPW expression in the human fetus and adult, with monoallelic expressi on in adult lymphoblasts and fibroblasts, and in fetal tissues. To fur ther examine the expression of IPW, a series of experiments were carri ed out using RT-PCR to measure IPW expression in placentae and various fetal and tumor tissues, Biallelic expression of IPW was found in tes ticular germ cell tumor and bladder cancer cells, suggesting loss of i mprinting in the latter case. Both H19 and Insulin-like growth Factor 2 (IGF2), two additional imprinted genes, also showed biallelic expres sion in those same tumors that demonstrated IPW biallelic expression. Of note, the naturally occurring parthenogenetic-derived mature terato ma unexpectedly expressed large amounts of IPW, Lastly, the pluripoten t embryonal cancer cell line Tera-2 expressed IPW at the same level be fore and after differentiation induced by retinoic acid, suggesting th at this gene functions in a 'housekeeping' capacity throughout cell gr owth. This was in contradistinction to H19 and IGF2, both of which sho wed significant transcriptional upregulation after Tera-2 cell differe ntiation.