Monoclonal antibody 3CB2 recognizes an antigen expressed in discrete c
ell types derived from ectoderm and mesoderm. Biochemical and immunohi
stochemical studies indicate that the antigen recognized by the antibo
dy is a 55 kDa cytoplasmic protein that may be an intermediate filamen
t associated protein (IFAP). Developmental studies show that 3CB2 anti
gen is intensely expressed very early in the chick embryo, in the neur
al tube, myotomes, and in mesenchymal cells of visceral arches and the
presumptive facial area. As development proceeds, antigen expression
becomes restricted to astrocytes and radial glia cells throughout the
brain. A detailed immunohistochemical study of the developing chick re
tina shows that the expression of 3CB2 antigen at embryonic day 8 (E8)
is restricted to Muller cells, with the pattern of expression closely
related to their degree of differentiation. We show, by immunocytoche
mistry labeling of entire Muller cells dissociated from retinas of E16
-E20, that 3CB2 monoclonal is labeling the whole cell. 3CB2 selectivel
y labels Muller cells in the rat and chameleon, but not their retinal
horizontal cell axons. 3CB2 monoclonal is a very sensitive marker for
early differentiating Muller cells. Our results provide evidence that
3CB2 antigen is a cytoskeletal component which may be involved in the
morphogenesis of these cells, and also perhaps in the outgrowth of som
e axons. (C) 1995 Wiley-Liss, Inc.