Overexpression of jumu induces melanotic nodules by activating Toll signaling in Drosophila

Drosophila jumu modulates apoptosis via a JNK-dependent pathway and is required for other processes in wing development

Previous studies in several model organisms have revealed that members of the Forkhead (Fkh) transcription factor family have multiple functions. Drosophila Jumeau (Jumu), a member of this family, participates in cardiogenesis, hematopoiesis and immune system homeostasis. Here, we show that loss of jumu function positively regulates or triggers apoptosis via a JNK-dependent pathway in wing development. jumu mutants showed reduced wing size and increased apoptosis. Moreover, we observed a loss of the anterior cross vein (ACV) phenotype that was similar to that observed in wings in which JNK signaling has been ectopically activated. The JNK signaling markers puckered (puc) and p-JNK were also significantly increased in the wing discs of jumu mutants. In addition, apoptosis induced by the loss of jumu was rescued by knocking down JNK, indicating a role for JNK in reducing jumu-induced apoptosis. Jumu could also control wing margin development via the positive regulation of cut expression, and the observed wing margin defect did not result from a loss of jumu-induced apoptosis. Further, jumu deficiency in the pupal wing could induce multiple wing hairs via a Rho1-mediated planar cell polarity pathway, but abnormal Rho1 expression was not why jumu loss induced apoptosis via a JNK-dependent pathway in wing discs.

Drosophila as a Genetic Model for Hematopoiesis

In this FlyBook chapter, we present a survey of the current literature on the development of the hematopoietic system in Drosophila The Drosophila blood system consists entirely of cells that function in innate immunity, tissue integrity, wound healing, and various forms of stress response, and are therefore functionally similar to myeloid cells in mammals. The primary cell types are specialized for phagocytic, melanization, and encapsulation functions. As in mammalian systems, multiple sites of hematopoiesis are evident in Drosophila and the mechanisms involved in this process employ many of the same molecular strategies that exemplify blood development in humans. Drosophila blood progenitors respond to internal and external stress by coopting developmental pathways that involve both local and systemic signals. An important goal of these Drosophila studies is to develop the tools and mechanisms critical to further our understanding of human hematopoiesis during homeostasis and dysfunction.

Jumu is required for circulating hemocyte differentiation and phagocytosis in Drosophila

Background

The regulatory mechanisms of hematopoiesis and cellular immunity show a high degree of similarity between insects and mammals, and Drosophila has become a good model for investigating cellular immune responses. Jumeau (Jumu) is a member of the winged-helix/forkhead (FKH) transcription factor family and is required for Drosophila development. Adult jumu mutant flies show defective hemocyte phagocytosis and a weaker defense capability against pathogen infection. Here, we further investigated the role of jumu in the regulation of larval hemocyte development and phagocytosis.

Methods

In vivo phagocytosis assays, immunohistochemistry, Real-time quantitative PCR and immunoblotting were performed to investigate the effect of Jumu on hemocyte phagocytosis. 5-Bromo-2-deoxyUridine (BrdU) labeling, phospho-histone H3 (PH3) and TdT-mediated dUTP Nick-End Labeling (TUNEL) staining were performed to analyze the proliferation and apoptosis of hemocyte; immunohistochemistry and Mosaic analysis with a repressible cell marker (MARCM) clone analysis were performed to investigate the role of Jumu in the activation of Toll pathway.

Results

Jumu indirectly controls hemocyte phagocytosis by regulating the expression of NimC1 and cytoskeleton reorganization. The loss of jumu also causes abnormal proliferation and differentiation in circulating hemocytes. Our results suggest that a severe deficiency of jumu leads to the generation of enlarged multinucleate hemocytes by affecting the normal cell mitosis process and induces numerous lamellocytes by activating the Toll pathway.

Conclusions

Jumu regulates circulating hemocyte differentiation and phagocytosis in Drosophila. Our findings provide new insight into the mechanistic roles of cytoskeleton regulatory proteins in phagocytosis and establish a basis for further analyses of the regulatory mechanism of the mammalian ortholog of Jumu in mammalian innate immunity.

Electronic supplementary material

The online version of this article (10.1186/s12964-018-0305-3) contains supplementary material, which is available to authorized users.

Flos Chrysanthemi Indici extract improves a high-sucrose diet-induced metabolic disorder in Drosophila

Flos Chrysanthemi Indici (CI) is a traditional medicinal plant used in the treatment of inflammatory diseases. However, the pharmacological role of CI in metabolic diseases, especially in diseases induced by insulin metabolism disorders, remains poorly understood. In the present study, Drosophila melanogaster (Drosophila) were fed with high-sugar diet (HSD) to induce a model similar to Type 2 diabetes (T2D) in order to determine whether CI extracts improve the metabolic disorder. It was demonstrated that the CI extracts could improve growth rate, body size, lifespan, reproductive capacity and fat storage, and CI especially improved the fat metabolism and cell size in S6k and Akt1 mutant flies. In conclusion, the present study provides novel evidence that CI may be an effective drug for the treatment of T2D.

The Drosophila lymph gland is an ideal model for studying hematopoiesis

Hematopoiesis in Drosophila melanogaster occurs throughout the entire life cycle, from the embryo to adulthood. The healthy lymph gland, as a hematopoietic organ during the larval stage, can give rise to two mature types of hemocytes, plasmatocytes and crystal cells, which persist into the pupal and adult stages. Homeostasis of the lymph gland is tightly controlled by a series of conserved factors and signaling pathways, which also play key roles in mammalian hematopoiesis. Thus, revealing the hematopoietic mechanisms in Drosophila will advance our understanding of hematopoietic stem cells and their niche as well as leukemia in mammals. In addition, the lymph gland employs a battery of strategies to produce lamellocytes, another type of mature hemocyte, to fight against parasitic wasp eggs, making the lymph gland an important immunological organ. In this review, the developmental process of the lymph gland and the regulatory networks of hematopoiesis are summarized. Moreover, we outline the current knowledge and novel insight into homeostasis of the lymph gland.

Dual role for Jumu in the control of hematopoietic progenitors in the Drosophila lymph gland

The Drosophila lymph gland is a hematopoietic organ in which the maintenance of hematopoietic progenitor cell fate relies on intrinsic factors and extensive interaction with cells within a microenvironment. The posterior signaling center (PSC) is required for maintaining the balance between progenitors and their differentiation into mature hemocytes. Moreover, some factors from the progenitors cell-autonomously control blood cell differentiation. Here, we show that Jumeau (Jumu), a member of the forkhead (Fkh) transcription factor family, controls hemocyte differentiation of lymph gland through multiple regulatory mechanisms. Jumu maintains the proper differentiation of prohemocytes by cell-autonomously regulating the expression of Col in medullary zone and by non-cell-autonomously preventing the generation of expanded PSC cells. Jumu can also cell-autonomously control the proliferation of PSC cells through positive regulation of dMyc expression. We also show that a deficiency of jumu throughout the lymph gland can induce the differentiation of lamellocytes via activating Toll signaling.