Fetal Development of Neuroectodermal Structures

Abstract

The earliest cytokeratins — of the simple epithelium type only — are expressed in oocytes, eggs, blastula, gastrula, and postgastrulation epithelia as has been shown for mouse and frog (Xenopus) (Jackson et al. 1980; Franz et al. 1983; Godsave et al. 1984, 1986; Lehtonen 1985; Franz and Franke 1986; Fouquet et al. 1988). Cytokeratins and vimentin are coexpressed during most of the differentiation stages of the female germ line. In the Xenopus oocyte, vimentin was reported first as a perinuclear ring and cytokeratins are detectable later in the cell cortex (Godsave et al. 1984). Klymkowsky et al. (1987) discovered a polar assymmetry in cytokeratin organization until early blastula. In stage 14 and 17 embryos of Xenopus, cells of the neural plate and neural groove with significant cytokeratin immunostaining (monoclonal antibody Iu-5) were seen (Herrmann et al. 1989). A detailed discussion of the expression of intermediate filament proteins in early embryonic development of vertebrates and invertebrates is given by Biessmann and Walter (1989).