An anti-inflammatory transcriptional cascade conserved from flies to humans.

Innate immunity is an ancestral process that can induce pro- and anti-inflammatory states. A major challenge is to characterize transcriptional cascades that modulate the response to inflammation. Since the Drosophila glial cells missing (Gcm) transcription factor has an anti-inflammatory role, we explored its regulation and evolutionary conservation. Here, we show that the murine Gcm2 (mGcm2) gene is expressed in a subpopulation of aged microglia (chronic inflammation) and upon lysophosphatidylcholine (LPC)-induced central nervous system (CNS) demyelination (acute inflammation). Moreover, mGcm2 conditional knockout mice show an increased inflammatory phenotype upon aging or LPC injection, and hGCM2 is expressed in active demyelinating lesions of patients with multiple sclerosis. Finally, Drosophila Gcm expression is induced upon aging and acute challenge, and its overexpression decreases the inflammatory phenotype. Altogether, these data indicate that the inducible Gcm cascade is conserved from flies to humans and represents a potential therapeutic target in the control of the inflammatory response.

Toward a Consensus in the Repertoire of Hemocytes Identified in Drosophila.

The catalog of the Drosophila immune cells was until recently limited to three major cell types, based on morphology, function and few molecular markers. Three recent single cell studies highlight the presence of several subgroups, revealing a large diversity in the molecular signature of the larval immune cells. Since these studies rely on somewhat different experimental and analytical approaches, we here compare the datasets and identify eight common, robust subgroups associated to distinct functions such as proliferation, immune response, phagocytosis or secretion. Similar comparative analyses with datasets from different stages and tissues disclose the presence of larval immune cells resembling embryonic hemocyte progenitors and the expression of specific properties in larval immune cells associated with peripheral tissues.

Temporal specificity and heterogeneity of Drosophila immune cells.

Immune cells provide defense against non-self and have recently been shown to also play key roles in diverse processes such as development, metabolism, and tumor progression. The heterogeneity of Drosophila immune cells (hemocytes) remains an open question. Using bulk RNA sequencing, we find that the hemocytes display distinct features in the embryo, a closed and rapidly developing system, compared to the larva, which is exposed to environmental and metabolic challenges. Through single-cell RNA sequencing, we identify fourteen hemocyte clusters present in unchallenged larvae and associated with distinct processes, e.g., proliferation, phagocytosis, metabolic homeostasis, and humoral response. Finally, we characterize the changes occurring in the hemocyte clusters upon wasp infestation, which triggers the differentiation of a novel hemocyte type, the lamellocyte. This first molecular atlas of hemocytes provides insights and paves the way to study the biology of the Drosophila immune cells in physiological and pathological conditions.

Whole transcriptome analysis of human erythropoietic cells during ontogenesis suggests a role of VEGFA gene as modulator of fetal hemoglobin and pharmacogenomic biomarker of treatment response to hydroxyurea in ß-type hemoglobinopathy patients.

BACKGROUND: Human erythropoiesis is characterized by distinct gene expression profiles at various developmental stages. Previous studies suggest that fetal-to-adult hemoglobin switch is regulated by a complex mechanism, in which many key players still remain unknown. Here, we report our findings from whole transcriptome analysis of erythroid cells, isolated from erythroid tissues at various developmental stages in an effort to identify distinct molecular signatures of each erythroid tissue. RESULTS: From our in-depth data analysis, pathway analysis, and text mining, we opted to focus on the VEGFA gene, given its gene expression characteristics. Selected VEGFA genomic variants, identified through linkage disequilibrium analysis, were explored further for their association with elevated fetal hemoglobin levels in ß-type hemoglobinopathy patients. Our downstream analysis of non-transfusion-dependent ß-thalassemia patients, ß-thalassemia major patients, compound heterozygous sickle cell disease/ß-thalassemia patients receiving hydroxyurea as fetal hemoglobin augmentation treatment, and non-thalassemic individuals indicated that VEGFA genomic variants were associated with disease severity in ß-thalassemia patients and hydroxyurea treatment efficacy in SCD/ß-thalassemia compound heterozygous patients. CONCLUSIONS: Our findings suggest that VEGFA may act as a modifier gene of human globin gene expression and, at the same time, serve as a genomic biomarker in ß-type hemoglobinopathy disease severity and hydroxyurea treatment efficacy.