STAGE-SPECIFIC EXPRESSION OF ALKALINE-PHOSPHATASE DURING NEURAL DEVELOPMENT IN THE MOUSE

The expression pattern of tissue nonspecific alkaline phosphatase (TNA P) in the developing neural tube of mouse is reported. Homogeneous AP activity in the neuroepithelium becomes prominent at E8.5. At E9.5, di stinctly AP-positive cells appear in the brain and spinal cord area. A t stages E10.5 to E12.5, AP positivity is observed between the mesence phalon and the rhombencephalon, along the entire spinal cord and crani al nerves emerging from the myelencephalon. At E13.5, strongly AP posi tive fibers become prominent in the pons. At E14.5, AP expression in b rain tissue is considerably reduced and there is a complete absence of AP activity in the nerve cells and glial cells of adult brain. The ch oroid plexus remains distinctly positive for AP expression until the a dult stage. Northern blot analysis and reverse-transcriptase polymeras e chain reaction amplification of RNA indicate that this AP activity r esults from the expression of the Akp-2 locus. This AP expression patt ern is distinct from those reported for the expression of GD3, nestin, Hox 2.3, and Wnt-1 during brain development. We conclude that AP is a useful marker of a subpopulation of neuroectodermal cells present in the neural tube as early as E8.5, at which stages there are no other A P positive intraembryonic cells except PGCs. (C) 1994 Wiley-Liss, Inc.