Fig. 3. chn is necessary for proper development of the embryonic PNS. Embryos were stained with 22c10 antibody (gray) and anti-ß-galactosidase (brown, a marker for the balancer chromosome) antibodies. Lateral views of segments T1 (at left) to A4 are shown. Insets show higher magnification views of the lateral A2 group of chordotonal organs (arrowed). (A) chn^ECJ1/+ embryo. Its nervous system appears wild type. d, l, v' and v indicate the dorsal, lateral, ventral' and ventral neuronal clusters. Black and white arrowheads point to the dbp and the v'chn1 neurons. (B) chn^ECJ1 homozygous embryo. Note the disorganized pattern, the reduced number of neurons compared with (A), the absence of dbp and v'chn1 neurons, and the altered morphology of the lateral group. (C) chn^ECJ1 embryo in which UAS-chn is expressed with the 69B-Gal4 driver. Note the substantial recovery of the wild-type phenotype.