Mechanisms of steroid-triggered programmed cell death in Drosophila

Dpp signaling and the induction of neoplastic tumors by caspase-inhibited apoptotic cells in Drosophila

“…Apoptosis plays a significant role in a number of processes during Drosophila development, such as salivary gland histolysis (15), sculpting the larval head (9), and the removal of excess ommatidial cells (16). However, apoptosis plays little if any role during the normal development of other tissues, such as the wing imaginal disk (17,18).…”

20-Hydroxyecdysone (20E) Primary Response Gene E75 Isoforms Mediate Steroidogenesis Autoregulation and Regulate Developmental Timing in Bombyx

“…2 In insects, 20-hydroxyecdysone (20E; ecdysone is the immediate precursor of 20E; 20E and ecdysone are the main ecdysteroids) is the actual steroid hormone. The ecdysone receptor (EcR) and its partner molecule, Ultraspiracle (USP), form the functional NR complex of 20E.…”

“…In conjunction with EcR-USP, 20E activates a small set of early response genes encoding several transcription factors that further activate a large set of downstream late response genes. Pulses of 20E signals initiate major developmental transitions in insects, including egg hatching, larval-larval molting, and larval-pupal-adult metamorphosis (1,2). NRs form a large and conserved superfamily of ligand-activated transcription factors that are essential for growth, development, reproduction, homeostasis, and metabolism.…”

Steroid Hormones in Drosophila: How Ecdysone Coordinates Developmental Signalling with Cell Growth and Division

“…For example, the histolysis of the larval salivary gland and midgut at the end of metamorphosis is stage-specific, ecdysone triggered, programmed cell death, which results in the removal of the component of these larval structures no longer required in the adult fly. In line with an apoptotic mechanism, previous studies have shown that cell death activators are upregulated in the third instar larval tissues, including the salivary glands and midgut in response to ecdysone (reviewed in (Jiang, Baehrecke, and Thummel 1997;Baehrecke 2000;Yin and Thummel 2005)). The ecdysone pulse is also essential for differentiation and patterning of the larval imaginal tissues required for development of adult structures (Hall and Thummel 1998;Thummel 2000, 1998;Zheng et al 2003).…”

“…As cell division and patterning are tightly linked in Drosophila imaginal tissues, the process of metamorphosis controlled by ecdysone involves coordination of the developmental signals that regulate proliferation and differentiation. Although much work has focused on the downstream targets linking the ecdysone pathway to programmed cell death and cell differentiation (Baehrecke 2000;Jiang, Baehrecke, and Thummel 1997;Yin and Thummel 2005), the relationship between ecdysone and cell cycle is a relatively unexplored field. Here we review the evidence that the ecdysone pulse is critical for controlling cell growth and division in Drosophila.…”