The EBF transcription factor Collier directly promotes Drosophila blood cell progenitor maintenance independently of the niche

Abstract

The maintenance of stem or progenitor cell fate relies on intrinsic factors as well as local cues from the cellular microenvironment and systemic signaling. In the lymph gland, an hematopoietic organ in Drosophila larva, a group of cells called the Posterior Signaling Centre (PSC), whose specification depends on the EBF transcription factor Collier (Col) and the HOX factor Antennapedia (Antp), has been proposed to form a niche required to maintain the pool of hematopoietic progenitors (prohemocytes). In contrast with this model, we show here that genetic ablation of the PSC does not cause an increase in blood cell differentiation or a loss of blood cell progenitors. Furthermore, although both col and Antp mutant larvae are devoid of PSC, the massive prohemocyte differentiation observed in col mutant is not phenocopied in Antp mutant. Interestingly, beside its expression in the PSC, Col is also expressed at low levels in prohemocytes and we show that this expression persists in PSC-ablated and Antp mutant larvae. Moreover, targeted knockdown and rescue experiments indicate that Col expression is required in the prohemocytes to prevent their differentiation. Together, our findings show that the PSC is dispensable for blood cell progenitor maintenance and reveal the key role of the conserved transcription factor Col as an intrinsic regulator of hematopoietic progenitor fate.hematopoiesis | Drosophila | stem cell niche | EBF

Drosophila Condensin II subunit Chromosome-associated Protein-D3 regulates cell fate determination through non-cell-autonomous signaling

“…It regulates head development (Crozatier et al, 1996, is important for embryonic muscle cell fate specification Dubois et al, 2007) and regulates hematopoietic progenitor cell fate (Pennetier et al, 2012;Benmimoun et al, 2015). KNOT is expressed in postmitotic neurons and controls class IV-specific dendritic arbor morphology in the Drosophila peripheral nervous system (Crozatier and Vincent, 2008;Hattori et al, 2013;Jinushi-Nakao et al, 2007).…”

Macrophages and cellular immunity in Drosophila melanogaster

“…It has been reported that PSC cells send out several molecular cues to regulate the differentiation state of the Lymph Gland, including Serrate (Ser), Hedgehog (Hh), Wingless (Wg, Wnt), Decapentaplegic (Dpp, BMP) and Pvf1 (PDGF/VEGF-related factor) [59, 66, 68, 74, 75]. A recent study has challenged the roles of the PSC and Hedgehog signaling in maintaining progenitor maintenance, although it did confirm PSC function in inducing lamellocyte differentiation upon parasitization [76]. Serrate expression and the consequent activation of Notch signaling are required for crystal cell production [59] and maintaining the expression of Collier, a transcription factor which is highly expressed in PSC cells and has roles in the Lymph Gland response to wasp infestation [67, 76].…”

“…A recent study has challenged the roles of the PSC and Hedgehog signaling in maintaining progenitor maintenance, although it did confirm PSC function in inducing lamellocyte differentiation upon parasitization [76]. Serrate expression and the consequent activation of Notch signaling are required for crystal cell production [59] and maintaining the expression of Collier, a transcription factor which is highly expressed in PSC cells and has roles in the Lymph Gland response to wasp infestation [67, 76]. Wingless signaling has a dual role in the Lymph Gland.…”

The matrix protein Tiggrin regulates plasmatocyte maturation inDrosophilalarva

“…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).…”