During corticogenesis, radial glia-derived neural progenitors divide and migrate along radial fibers to their designated positions
within the cortical plate. The microtubule-associated proteins doublecortin (DCX) and doublecortin-like (DCL) are critically
involved in neuronal migration and division, and may function in a partially redundant pathway. Since little is known about
the important early stages of corticogenesis, when neurogenesis is extensive, we addressed a possible differential role by
examining spatiotemporal expression patterns of DCX, DCL, and the radial glia marker vimentin during murine development. We
found expression patterns of DCL and DCX to differ remarkably prior to embryonic day (E)13. DCL was already expressed at E9
and largely overlapped with vimentin, whereas DCX expression started modestly from E10/E11 onward. DCL was mainly found in
the ventricular zone, often in mitotic cells and in pial-oriented radial fibers. In contrast, DCX was expressed in tangential
fibers in the outer cortical regions. After E13, DCX and DCL expression largely overlapped but DCL expression had disappeared
from the ventricular zone. Also, DCL levels were attenuated, whereas DCX remained high beyond E17. In conclusion, DCX and
DCL are differentially expressed, particularly during early corticogenesis, consistent with their different functional roles.
Given its involvement in mitosis, DCL appears to have a unique role in the early neuroepithelium that is different from later
developmental stages when DCX is coexpressed.