FIG. 3.

Earliest detection and expansion of the Chrna7:Cre cell lineage as defined by Chrna7:Cre × ROSA26-loxP(lacZ) alleles and X-gal staining. The expression of Chrna7:Cre is not detected in E8.0 embryos (the anterior (a) to posterior (p) direction is noted), but X-gal is detected at E9.0 where it is restricted to rhombomeres 3 (r3) and 5 (r5) of the developing hindbrain of the recently “turned” embryos. The otic vesicle (o), eye (e), and heart (h) are identified. This expression extends rapidly to other parts of the embryo from E9.25 through E9.5 until X-gal expression is present in cells within most tissues and organs. Scale bars are 1 mm.