A. Prokop et al., HOMEOTIC REGULATION OF SEGMENT-SPECIFIC DIFFERENCES IN NEUROBLAST NUMBERS AND PROLIFERATION IN THE DROSOPHILA CENTRAL-NERVOUS-SYSTEM, Mechanisms of development, 74(1-2), 1998, pp. 99-110
The number and pattern of neuroblasts that initially segregate from th
e neuroectoderm in the early Drosophila embryo is identical in thoraci
c and abdominal segments. However, during late embryogenesis differenc
es in the numbers of neuroblasts and in the extent of neuroblast proli
feration arise between these regions. We show that the homeotic genes
Ultrabithorax and abdominal-A regulate these late differences, and tha
t misexpression of either gene in thoracic neuroblasts after segregati
on is sufficient to induce abdominal behaviour. However, in wild type
embryos we only detect abdominal-A and Ultrabithorax proteins in early
neuroblasts. Furthermore, transplantation experiments reveal that seg
ment-specific behaviour is determined prior to neuroblast segregation
Thus, the segment-specific differences in neuroblast behaviour seem to
be determined in the early embryo, mediated through the expression of
homeotic genes in early neuroblasts, and executed in later programmes
controlling neuroblast numbers and proliferation. (C) 1998 Elsevier S
cience Ireland Ltd. All rights reserved.