Drives expression in cells of the ventral midline of the embryonic CNS.
Midline expression is present in all midline cells from segments S1 to A8/9.
Expression assayed at stages 9, 11, 13, and 17. Expression may be continuous between assayed stages in some tissues.
In embryos, expression specific to CNS midline precursor cells (CMP); not expressed in ventral ectodermal cells.