Nestin overexpression promotes the embryonic development of heart and brain through the regulation of cell proliferation.

Nestin, an intermediate filament protein, is a key regulator of various extracellular proteins that play important roles in cell growth and differentiation. In recent years, nestin has been widely accepted as a molecular marker for neural stem/progenitor cells. However, its function during embryogenesis remains largely unknown since its depletion is lethal after stage embryonic day 8.5 (E8.5). In order to understand the role of this protein in vivo, we compared the heart and brain tissues of control mice with those of mice overexpressing a human nestin cDNA transgene under the control of a ROSA26 promoter. In these tissues we examined the general histology and cell size, the presence of apoptotic cells by TUNEL assay, and the presence of progenitor cell markers like SOX2. Compared to controls, mouse embryos overexpressing the human nestin transgene have a larger size and display characteristic morphological changes including a larger heart and forebrain. In these tissues we found corresponding increases in the size of cardiomyocytes and brain cells, as well as indications of augmented cell proliferation. In contrast, apoptosis was not significantly altered. Co-staining brain sections with SOX2 and Ki67 showed that most of the proliferating cells in the forebrain were neural stem cells. Moreover, nestin overexpression was responsible for a marked activation of the PI3K/Akt signaling pathway. Taken together, the results of this study indicate that nestin plays an important role in the embryonic development of at least two mouse organs (heart and brain) through the regulation of cell proliferation.