Pax2;8 affects invagination but not early marker expression. Shortly after the otocyst is detached from the ectoderm, Pax2 expression is throughout the ventral and medial aspect of the developing ear (as revealed by a LacZ-reporter for Pax2). In contrast, the reporter for Pax2 shows in the Pax2;8 double null mouse a much wider expression including areas outside the partially invaginated otic placode. Expression profile of four genes known to be important for overall ear development (Eya1, Dll) and for neurosensory development (Jag1, Notch) show no expression changes in simple Pax2 or compound Pax2;8 double mutants, suggesting that Pax2 and Pax8 have little effect on these early markers. However, there is a reduction in otocyst size and a delayed detachment from the ectoderm in Pax2;8 double null mice. Bar indicates 100 um.