FYN EXPRESSION DURING EARLY NEUROGENESIS IN MOUSE EMBRYOS

Fyn is a member of the Src family of tyrosine kinases which are though t to play important roles in cell to cell interactions during morphoge nesis. The developmental profile of Fyn expression was examined using mutant mice in which lacZ gene was introduced into this locus. The exp ression was characteristic in the neural system, Though at low levels, it was detected in the headfold at embryonic day (E) 7.5 and in the l uminal surface of neuroectoderm along the entire neural groove at E8.5 . The expression appeared regional in rhombomeres at E8.5 and E9.5. Co nsistent expression was also found at a low level in the notochord. Th e expression was high in later stages of the neural tube which consist s of three layers; it was in the marginal layer but not in the germina l layer. High expression was also found in developing dorsal root fila ments of neural crest origin; Non-expression in dividing neuroepitheli al cells and expression in developing neural fibers appeared ubiquitou s features of Fyn expression throughout the entire brain.