Biology subjects

Waltzer, L.

Publications and source records attributed to Waltzer, L..

4 recordsLinked to original sources

bioRxiv2023

Adenine methylation is very scarce in the drosophila genome and not erased by the Ten Eleven Translocation dioxygenase.

N6-methyladenine (6mA) DNA modification has recently been described in metazoans, including in drosophila, for which the erasure of this epigenetic mark has been ascribed to the Ten Eleven Translocation (TET) enzyme. Here, we re-evaluated 6mA presence and TET impact on drosophila genome. Using axenic or conventional breeding conditions, we found traces of 6mA by LC-MS/MS and no significant increase in 6mA levels in the absence of TET, suggesting that this modification is present at very low levels in the drosophila genome but not regulated by TET. Consistent with this latter hypothesis, further molecular and genetic analyses showed that TET does not demethylate 6mA but acts essentially in an enzymatic-independent manner. Our results call for further caution concerning the role and regulation of 6mA DNA modification in metazoans and underline the importance of TET non-enzymatic activity for fly development.

molecular biology↗

bioRxiv2021

Characterization of the Drosophila adult hematopoietic system reveals a rare cell population with differentiation and proliferation potential.

While many studies have described Drosophila embryonic and larval blood cells, the hematopoietic system of the imago remains poorly characterized and conflicting data have been published concerning adult hematopoiesis. Using a combination of blood cell markers, we show that the adult hematopoietic system is essentially composed of a few distinct mature blood cell types. In addition, our transcriptomics results indicate that adult and larval blood cells have both common and specific features and it appears that adult hemocytes reactivate many gene expressed in embryonic blood cells. Interestingly, we identify a small set of blood cells that do not express differentiation markers but maintain the progenitor marker domeMeso. Yet, we show that these cells are derived from the posterior signaling center, a specialized population of cells present in the larval lymph gland, rather than from larval blood cell progenitors, and that their maintenance depends on the EBF transcription factor Collier. Furthermore, while these cells are normally quiescent, we find that some of them can differentiate and proliferate in response to bacterial infection. In sum, our results indicate that adult flies harbor a small population of specialized cells with limited hematopoietic potential and further support the idea that no substantial hematopoiesis takes place during adulthood.

developmental biology↗

bioRxiv2020

The Drosophila MOZ homolog Enok controls Notch-dependent induction of the RUNX gene lozenge independently of its histone-acetyl transferase activity.

The human KAT6 lysine acetyltransferase MOZ has been shown to be an essential player in the field of normal and malignant hematopoiesis. It belongs to a highly conserved family of epigenetic factors and remodels chromatin by acetylating histone tails in association with its partners of the ING5 complex. Here, we report that its Drosophila counterpart Enok is required during larval hematopoiesis to control the Notch-dependent induction of circulating crystal cells. In particular enok is essential to allow expression of the RUNX factor Lozenge (Lz) that controls the crystal cell specific transcriptional program. We demonstrate that this function involves neither the Eaf6 and Ing5 subunits of the Drosophila ING5 complex, nor Enok own acetyltransferase activity. We identify in lz third intron a hematopoietic enhancer, which is both required to promote expression in Notch-activated crystal cell precursors in an enok-dependent manner and bound by Enok. The non-catalytic mode of action of Enok is likely conserved in MOZ/KAT6 proteins and might be of high relevance in mammalian hematopoiesis, whether normal or malignant.

developmental biology↗

bioRxiv2020

Differential activation of JAK-STAT signaling in blood cell progenitors reveals functional compartmentalization of the Drosophila lymph gland.

Blood cells arise from diverse pools of stem and progenitor cells. Understanding progenitor heterogeneity is a major challenge. The Drosophila larval lymph gland is a well-studied model to understand blood progenitor maintenance and recapitulates several aspects of vertebrate hematopoiesis. However in-depth analysis has focused on progenitors located in lymph gland anterior lobes (AP), ignoring the progenitors from the posterior lobes (PP). Using in situ expression mapping and transcriptome analysis we reveal PP heterogeneity and identify molecular-genetic tools to study this abundant progenitor population. Functional analysis shows that PP resist differentiation upon immune challenge, in a JAK-STAT-dependent manner. Upon wasp parasitism, AP downregulate JAK-STAT signaling and form lamellocytes. In contrast, we show that PP activate STAT92E and remain undifferentiated. Stat92E knockdown in PP or genetically reducing JAK-STAT signaling permits PP lamellocyte differentiation. We discuss how heterogeneity and compartmentalization allow functional segregation in response to systemic cues and could be widely applicable. HighlightsWe provide an in situ and transcriptome map of larval blood progenitors Posterior lymph gland progenitors are refractory to immune challenge STAT activation after wasp parasitism maintains posterior progenitors

developmental biology↗