Expression analysis of endogenous menin, the product of the multiple endocrine neoplasia type 1 gene, in cell lines and human tissues

We have investigated the endogenous expression of menin, a protein encoded by the gene mutated in multiple endocrine neoplasia type I (MEN1), Western blot analysis showed strong expression of menin as a 68 kDa protein in all of 7 human and primate cell lines tested. In a panel of 12 fetal human tiss ue extracts, 68 kDa menin was readily detected in brain cortex, kidney, pit uitary, testis and thymus and weakly detected in thyroid. Reproducible band s other than 68 kDa were observed in adrenal and heart. whereas menin was u ndetectable in river, lung, pancreas and skin. Analysis of synchronized HeL a cells revealed no variation in the amount or size of menin throughout the cell cycle. Protein expression was compared between lymphoblastoid cell li nes from healthy controls and MEN1 patients carrying nonsense mutations on 1 allele. No truncated protein was detected in either cytoplasmic or nuclea r fractions in mutation-carrying cells. The expression level and cellular l ocation of full-length menin did not differ between cell lines derived from MEN1 patients and healthy donors. This suggests that the wild-type allele has been up-regulated in mutation-carrying cells to compensate for the loss of 1 functional allele. (C) 2000 Wiley-Liss, Inc.