Fig. 7. A model explaining the loss-of-function and gain-of-function phenotypes of hb with respect to the NB7-3 lineage. (A) The development of the wild-type NB7-3 showing the relevant markers in the postmitotic neurons. (B) Lack of Hb leads to a complete loss of EW1 and only a transient presence of GW. By stage 15, the missing cells might have died by apoptosis (PCD). Although EW3 is detectable by markers, it does not express the neuropeptide Crz. (C) Overexpression of hb might transform the second GMC completely into a GMC7-3a fate, while the third GMC might often generate only EW1 type cells.
