Fig. 1. WEC faithfully reproduces neurogenesis in vivo. Double immunofluorescence for TIS21 (a-f) and MAP2 (a'-f') on sagittal cryosections through the ventral mesencephalon (a-c') and rostral telencephalon (d-f') of embryos developed in utero up to E9.5 (E9.5) or E10.5 (E10.5) or in utero to E9.5 followed by WEC for 24 hours (E9.5+24h WEC). Note the caudal (ca) to rostral (ro) gradient of neurogenesis in the ventral mesencephalon. Filled arrowheads, apical (ventricular) side of the neuroepithelium; arrows, neuronal layer; open arrowheads, auto-fluorescent blood cells (absent in embryos developed in WEC because of the loss of blood cells after opening of the yolk sac); open arrow, reaction of the anti-mouse secondary antibody with the skin, presumably with adsorbed mouse immunoglobulins present in the mouse serum used for WEC. Dotted lines delineate the boundaries of the neuroepithelium. Scale bar: 100 µm.