Quantitative analyses of neuroepithelial cell shapes during bending of the mouse neural plate.

Despite a wealth of information about cell behaviors contributing to neurulation in chick embryos, similar behaviors in mouse embryos have yet to be well characterized. This study examines cell behaviors occurring during bending of the mouse neural plate, in particular, qualitative and quantitative changes in neuroepithelial cell shape. Our current results demonstrate that in mouse embryos 1) the median hinge point (MHP), a localized region of neural plate that becomes anchored to the underlying prechordal plate mesoderm or notochord/notochordal plate and forms a midline longitudinal furrow around which folding of the remaining neural plate (i.e., the part of the neural plate not involved in MHP formation) occurs, develops during stages of neural fold elevation; 2) the MHP is enriched with wedge-shaped neuroepithelial cells but has significantly fewer spindle-shaped, inverted wedge-shaped, and globular neuroepithelial cells than do the adjacent paired lateral areas of the neuroepithelium (L); and 3) each L is enriched with spindle-shaped, inverted wedge-shaped, and globular neuroepithelial cells but has significantly fewer wedge-shaped neuroepithelial cells than does the MHP. Thus wedging of neuroepithelial cells occurs during bending of the mouse neural plate and is localized to the MHP during neural fold elevation. Similarly, previous studies in the chick have shown that neuroepithelial cells become wedge shaped during bending of the neural plate and that such cell wedging is localized to the MHP during neural fold elevation. Such studies also have shed light on the roles of MHP formation and localized wedging of neuroepithelial cells within the MHP in the chick; however, such roles have yet to be elucidated in the mouse.(ABSTRACT TRUNCATED AT 250 WORDS)