The lateral chordotonal 5 (Lch5) neurons of scrak08255/scra8 embryos are shifted dorsally, disorganised and enlarged compared to wild type. There is an increase in the amount of DNA within the enlarged Lch5 neurons, indicative of multinucleate cells. There is a loss of Lch5 ligament cells in the mutant embryos, with the mutant embryos having an average of two ligament cells per Lch5 cluster (compared to five in wild-type embryos). The cap cells are present in normal number and orientation in the mutant Lch5 clusters.
scrak08255/scra8 embryos show a drastic decrease in the number of scolopale/sheath cells throughout the peripheral nervous system. The lack of scolopale cells is particularly evident in the Ch lineages, with the five neurons of the Lch5 clusters often having no associated scolopale. No sheath cells are detectable in the ventral' abdominal compartment of the mutant embryos (three sheath cells are seen in this region in wild-type embryos). The number of external sensory (ES) neurons in the ventral' region is reduced compared to wild type. ES organs of the lateral region tend not to lose sheath cells.
The ventral multidendritic neurons are unchanged in number in scrak08255/scra8 embryos, but they are increased in size. There is no reduction in the number of ventral ES structural cells.
scrak08255/scra8 embryos show no difference in the levels of apoptosis compared to controls from stage 10 until the end of embryogenesis.
scrak08255/scra8 embryos have relatively higher numbers of mitotic cells than wild-type embryos by the end of stage 12. This phenotype becomes more striking during the latter stages of embryonic development. Mitotic bodies are seen within differentiated peripheral nervous system neurons.
Homozygous embryos exhibit an increase in neuronal body size and a concomitant reduction in the total number of neurons due to cell fusion.