Two Independent Functions of Collier/Early B Cell Factor in the Control of Drosophila Blood Cell Homeostasis

Abstract

Blood cell production in the Drosophila hematopoietic organ, the lymph gland, is controlled by intrinsic factors and extrinsic signals. Initial analysis of Collier/Early B Cell Factor function in the lymph gland revealed the role of the Posterior Signaling Center (PSC) in mounting a dedicated cellular immune response to wasp parasitism. Further, premature blood cell differentiation when PSC specification or signaling was impaired, led to assigning the PSC a role equivalent to the vertebrate hematopoietic niche. We report here that Collier is expressed in a core population of lymph gland progenitors and cell autonomously maintains this population. The PSC contributes to lymph gland homeostasis by regulating blood cell differentiation, rather than by maintaining core progenitors. In addition to PSC signaling, switching off Collier expression in progenitors is required for efficient immune response to parasitism. Our data show that two independent sites of Collier/Early B Cell Factor expression, hematopoietic progenitors and the PSC, achieve control of hematopoiesis.

Novel Organelles with Elements of Bacterial and Eukaryotic Secretion Systems Weaponize Parasites of Drosophila

“…Genetically stable stocks with the desired, uniform genotypes were used for infections and crosses were not necessary. The y w strain of D. melanogaster (used as wild type) and Dome-MESO-GFP (gift from M. Crozatier [41]) (see Key Resource Table (KRT)) were used. Dome-MESO -GFP is a synthetic construct that replaces lacZ with GFP expression in P{dome-lacZ.MESO} (Fly Base FBtp0022619) and produces GFP marked regions of domeless (the fly JAK/STAT receptor) expression [41].…”

“…The y w strain of D. melanogaster (used as wild type) and Dome-MESO-GFP (gift from M. Crozatier [41]) (see Key Resource Table (KRT)) were used. Dome-MESO -GFP is a synthetic construct that replaces lacZ with GFP expression in P{dome-lacZ.MESO} (Fly Base FBtp0022619) and produces GFP marked regions of domeless (the fly JAK/STAT receptor) expression [41]. Flies were raised on standard fly food [cornmeal (65 g/L), sucrose (140 g/L), agar (10 g/L), and yeast (35 g/L) with tegosept made in 95% ethanol (22.6 ml/L) and propionic acid (5 ml/L)] (see KRT) medium and maintained long term at 18°C with inspection and flipping to new vials every three to four weeks.…”

Drosophilahematopoiesis under normal conditions and in response to immune stress

“…In particular, ablation of PSC cells by targeted expression of the proapoptotic gene reaper in these cells had no effect on the maintenance of MZ progenitors and resulted in a decrease in crystal cell differentiation . Along the same line, reduction of PSC cell numbers or alteration of PSC signaling properties deregulated hemocyte differentiation without affecting the pool of core progenitors . Furthemore, Antp mutant larvae, which are devoid of a PSC , still harbor a normal proportion of blood cell progenitors .…”

The matrix protein Tiggrin regulates plasmatocyte maturation inDrosophilalarva

“…9). In pluripotent stem cells, cells in G 1 phase are more likely to undergo differentiation Calder et al, 2013;Coronado et al, 2013;Sela et al, 2012), possibly owing to cell cycle stagedependent expression of key developmental regulators (Pauklin and Vallier, 2013;Singh et al, 2015). Perhaps our data showing that Wee1 and Stg regulate Tig expression is an example of G 2 phasedependent developmental regulation.…”

“…A centrally located medullary zone (MZ) contains prohemocytes with stem cell-like properties, whereas differentiating hemocytes are located in the peripheral cortical zone (CZ) (Evans et al, 2009;Jung et al, 2005). In addition, a small group of cells termed the posterior signaling center (PSC) controls differentiation and specification of hemocytes in the CZ (Benmimoun et al, 2015;Oyallon et al, 2016). Although much remains to be understood, the fly LG has developed into a powerful model for hematopoiesis and stem cell/progenitor regulation (Crozatier and Meister, 2007;Crozatier and Vincent, 2011;Letourneau et al, 2016;Martinez-Agosto et al, 2007;MorinPoulard et al, 2013;Shim et al, 2013).…”