Fig. 7. Analysis of Bax^-/- mice confirms that spinal interneuron apoptosis in Pcdh- mutant mice represents an exacerbation of an underlying normal developmental pattern. (A-C) P0 hemicords from control and Bax^-/- mice immunostained as indicated. (D) Quantification demonstrates that the sizes of these and other ventral interneuron populations (but not dorsal populations) are increased in the Bax^-/- spinal cord at P0, indicating that they undergo a normal period of developmental apoptosis. (E) Quantification of dorsal horn interneurons in P5 Bax^-/- spinal cords confirms that they do undergo a normal period of developmental apoptosis, but only after birth. (F) The increased apoptosis observed in Pcdh- null mutants represents an exacerbation of an underlying developmental pattern, as the percentage decrease in each interneuron population correlates strongly with its percentage increase in Bax^-/- neonates. Scale bar: 100 µm.