Interkinetic nuclear migration during early development of midgut and ureteric epithelia

Interkinetic nuclear migration (INM) is a well-known phenomenon that accompanies progenitor expansion in the vertebrate neural tube and non-neural ectoderm-derived epithelial tissues. In INM, progenitor cell nuclei migrate along the apicobasal axis of the epithelial layer in synchrony with cell cycle progression, resulting in 'pseudostratification'. Although INM has long been considered a general feature of epithelial development, detailed characteristics of INM in the gut and ureteric epithelia are little known. In this study, we observe pseudostratification in the developing midgut and ureteric epithelial progenitors by scanning electron microscopy and assess their cell cycle duration by 5-bromo-2'-deoxyuridine labeling. By applying multi-dimensional scaling, we demonstrate the roundtrip migration of nuclei between the basement membrane and the apical side in the developing midgut. Partial INM has been also shown for the ureteric epithelial nuclei. Our findings reveal INM in gut and ureteric progenitors that is similar to that in ventricular neurogenesis, and suggest that INM is a general strategy for the expansion of epithelial progenitors.