The human homologue of the Aspergillus nuclear migration gene nudC is preferentially expressed in dividing cells and ciliated epithelia

We recently identified a novel human gene, HnudC, homologous to an Aspergillus nidulans gene coding for a protein crucial to nuclear migration, cell wall morphogenesis, and cell growth. While mRNA for this gene is expressed in most tissues, HNUDC protein expression is highly regulated. To provide insight into the function of this protein, we performed immunohistochemical analysis of the distribution of HNUDC in 19 different human tissues. Intense immunolabeling was observed in proliferating cells, including spermatocytes at all stages, early hematopoietic cells, cortical thymocytes, immunoblasts, and basal colonic and esophageal mucosa. Within a given tissue, cells with different proliferative capacities demonstrated different levels of HNUDC expression. HNUDC was also highly expressed in ciliated epithelia including those found in ependyma, bronchial mucosa, and fallopian tubes. Immunolabeling was moderate in several non-proliferating tissues, but little or no labeling was observed in most other tissues examined. We also demonstrated by western blotting that most cell lines express extremely high levels of HNUDC compared to their normal counterparts. While this supports a role for HnudC in cell proliferation, these data indicate that cell lines are not a reliable measure of HNUDC protein expression in normal tissues. We conclude that HNUDC is highly expressed in cell lines and the proliferating cells of normal tissues, consistent with our hypothesis that HNUDC is conserved throughout evolution for a crucial function in cell division. In addition, the high level in ciliated cells suggests an important role in ciliary motility or assembly, analogous to its role in A. nidulans nuclear movement.