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Published on: January 12, 2015
The role of morphogenetic cell death during Drosophila embryonic head development
C Nassif1, A Daniel, J A Lengyel
1Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles 90095-1606, USA.
Abstract:
This article addresses the role of programmed cell death (apoptosis) during embryonic head development of Drosophila. Previous studies showed that reaper (rpr) is expressed in and required by cells undergoing apoptosis. We have analyzed the correlation between the pattern of expression of rpr and morphogenetic movements affecting head development. Furthermore, we have investigated the defects in head development resulting from the absence of apoptosis in embryos deficient for rpr. Our results show that, in the head, domains of high incidence of cell death as marked by expression of rpr correlate with regions where most morphogenetic movements occur; these regions are involved in formation of mouth structures, the internalization of neural progenitors, and head involution. Cellular events driving these movements are delamination, invagination, and intercalation as well as disruption and reformation of contacts among epithelial cells. The analysis of rpr-deficient embryos demonstrates that, despite of the widespread occurrence of apoptosis during normal head morphogenesis, many aspects of this process proceed in an apparently unperturbed manner even when cell death is blocked. In particular, movements that happen early during embryonic development and that are evolutionarily more ancient (e.g., formation of the dorsal ridge and the pharynx) take place almost normally in rpr-deficient embryos. Later events which are mostly associated with head involution (e.g., retraction of the clypeolabrum, formation of the dorsal pouch, fusion of lateral gnathal lobes) are evolutionarily more recent and fail to occur normally in rpr-deficient embryos.
Insights
Programmed cell death (apoptosis) is crucial for Drosophila head development, particularly for evolutionarily recent morphogenetic movements like head involution. Blocking apoptosis impacts later developmental stages more than earlier ones.
Area of Science:
- Developmental Biology
- Cell Biology
- Genetics
Background:
- Programmed cell death, or apoptosis, plays a role in embryonic development.
- The gene reaper (rpr) is expressed in apoptotic cells and is required for apoptosis.
- Head development in Drosophila involves complex morphogenetic movements.
Purpose of the Study:
- To investigate the role of apoptosis, specifically the rpr gene, in Drosophila embryonic head development.
- To correlate the expression pattern of rpr with morphogenetic movements during head formation.
- To analyze head development defects in embryos lacking apoptosis due to rpr deficiency.
Main Methods:
- Analysis of rpr gene expression patterns in relation to morphogenetic movements.
- Examination of head development in Drosophila embryos deficient for the rpr gene.
- Observation of cellular events such as delamination, invagination, and cell contact dynamics.
Main Results:
- High incidence of rpr expression, indicating cell death, correlates with key morphogenetic regions in the head, including mouth structure formation, neural progenitor internalization, and head involution.
- Apoptosis is widespread during normal head morphogenesis, involving epithelial cell delamination, invagination, and intercalation.
- rpr-deficient embryos show largely normal development in early, evolutionarily ancient processes (dorsal ridge, pharynx formation) but exhibit defects in later, evolutionarily recent events (head involution, clypeolabrum retraction, dorsal pouch formation, gnathal lobe fusion).
Conclusions:
- Apoptosis, regulated by rpr, is essential for specific morphogenetic movements during Drosophila head development.
- Evolutionarily recent morphogenetic events in head development are more sensitive to the absence of apoptosis than ancient ones.
- The study highlights the differential requirement of apoptosis for various stages and types of morphogenetic processes.
