Fig. 1. Dorsal-ventral disparity in spinal interneuron apoptosis in Pcdh- null mutant mice. (A-D) TUNEL (A), IB4 staining (C), and immunostaining with antibodies against cleaved caspase 3 (B) or Gfap (D) all demonstrate increased signs of apoptosis and neurodegeneration primarily in the ventral horn of Pcdh- ^del/del spinal cords, as compared with littermate controls, at P0. Arrowheads in C mark blood vessels that, in addition to microglia, are stained by IB4. (E,F) In E12 (E) and P0 (F) Pcdh- ^fus spinal cords, anti-GFP immunostaining demonstrates uniform expression of -Pcdh-GFP fusion proteins. (G) In situ hybridization using a riboprobe against the Pcdh- constant exons also yields uniform labeling of dorsal and ventral horns. (H) RT-PCR analysis of E16 spinal cord RNA demonstrates that all 22 variable exon-constant exon spliced transcripts can be detected. RT, reverse transcriptase. (I) Schematic of the mouse Pcdh- genomic locus, indicating the 22 variable exons (A, B and C subfamilies, blue) and three constant exons (ce, red). Scale bar: 100 µm.