THE SPATIAL AND TEMPORAL EXPRESSION OF HNK-1 BY MYOGENIC AND SKELETOGENIC CELLS IN THE EMBRYONIC RAT

The existence of phenotypic differences within a population of cells p rovides evidence for discrete stages in cellular differentiation and/o r identifies subsets of cells with unique functional properties. The m onoclonal antibody HNK-1 has been widely shown to identify subpopulati ons of cells in the developing nervous system. In this paper we focus on the developmental expression of HNK-1 immunoreactivity by derivativ es of semitic (paraxial) mesoderm. We show that between embryonic day 12 and 14 (E12-E14) the HNK-1 epitope is transiently expressed by post mitotic myotomal cells. In E14-E17 developing vertebral columns (which are derived from semitic sclerotomal cells), HNK-1 immunolabeling was expressed by subpopulations of skeletogenic cells, including perinoto chordal cells associated with the forming annulus fibrosus and cells w ithin or adjacent to the perichondrium. Chondrocytes within forming ce ntra and vertebral arches did not exhibit HNK-1 immunoreactivity. Thes e results, taken together, show that the expression of the HNK-1 epito pe can be used to identify subsets of myogenic and skeletogenic cells both spatially and temporally in the developing rat.