The Repo Homeodomain Transcription Factor Suppresses Hematopoiesis in Drosophila and Preserves the Glial Fate.

Despite their different origins, Drosophila glia and hemocytes are related cell populations that provide an immune function. Drosophila hemocytes patrol the body cavity and act as macrophages outside the nervous system, whereas glia originate from the neuroepithelium and provide the scavenger population of the nervous system. Drosophila glia are hence the functional orthologs of vertebrate microglia, even though the latter are cells of immune origin that subsequently move into the brain during development. Interestingly, the Drosophila immune cells within (glia) and outside (hemocytes) the nervous system require the same transcription factor glial cells deficient/glial cells missing (Glide/Gcm) for their development. This raises the issue of how do glia specifically differentiate in the nervous system, and hemocytes in the procephalic mesoderm. The Repo homeodomain transcription factor and panglial direct target of Glide/Gcm is known to ensure glial terminal differentiation. Here we show that Repo also takes center stage in the process that discriminates between glia and hemocytes. First, Repo expression is repressed in the hemocyte anlagen by mesoderm-specific factors. Second, Repo ectopic activation in the procephalic mesoderm is sufficient to repress the expression of hemocyte-specific genes. Third, the lack of Repo triggers the expression of hemocyte markers in glia. Thus, a complex network of tissue-specific cues biases the potential of Glide/Gcm. These data allow us to revise the concept of fate determinants and help us to understand the bases of cell specification. Both sexes were analyzed.SIGNIFICANCE STATEMENT Distinct cell types often require the same pioneer transcription factor, raising the issue of how one factor triggers different fates. In Drosophila, glia and hemocytes provide a scavenger activity within and outside the nervous system, respectively. While they both require the glial cells deficient/glial cells missing (Glide/Gcm) transcription factor, glia originate from the ectoderm, and hemocytes from the mesoderm. Here we show that tissue-specific factors inhibit the gliogenic potential of Glide/Gcm in the mesoderm by repressing the expression of the homeodomain protein Repo, a major glial-specific target of Glide/Gcm. Repo expression in turn inhibits the expression of hemocyte-specific genes in the nervous system. These cell-specific networks secure the establishment of the glial fate only in the nervous system and allow cell diversification.

Intraoperative confocal laser endomicroscopy for real-time in vivo tissue characterization during surgical procedures.

INTRODUCTION: Probe-based confocal laser endomicroscopy (pCLE) is an innovative technique providing real-time, in vivo optical biopsies. A previous ex vivo phase of the study (PERSEE) allowed identifying accurate pCLE criteria for the diagnosis of hepatic and peritoneal surgical specimens. This study aimed at evaluating the pCLE role for in vivo intra-abdominal tissue characterization during digestive cancer surgical procedures. METHODS: Between October 2014 and July 2015, consecutive patients diagnosed with digestive cancers and scheduled for a surgical resection or an exploratory laparoscopy were prospectively enrolled. Endomicroscopic images were acquired using a motorized Confocal Miniprobe™ with a bending distal tip providing easy access to abdominal organs. It was connected to an endomicroscopy system that allowed near-infrared illumination (at a wavelength of 785 nm) in conjunction with indocyanine green for contrast agent. A live audiovisual transmission was established between the surgeon and the pathologist for real-time interpretation of optical biopsies. Intraoperative pCLE performance for the diagnosis of suspicious nodules was assessed using corresponding surgical histopathology as reference standard. RESULTS: 21 consecutive patients were successfully enrolled. Live audiovisual transmission between the surgeon and the pathologist was successfully established in all cases. 62 pCLE sequences were acquired from different tissues [peritoneum (n = 27), liver (n = 21), lymph node (n = 4), diaphragm (n = 3), colon (n = 3), stomach (n = 2), and adrenal gland (n = 2)]. Malignant tissues were identified by fluorescently enhanced irregular cancerous tubes contrasting with dark glandular lumen and extracellular matrix. pCLE sensitivities and specificities were 67% and 100%, and 38% and 100% for peritoneal and hepatic carcinogenesis, respectively. One benign incident was reported during the trial with no patient consequence. CONCLUSIONS: Real-time intraoperative pCLE with near-infrared illumination is feasible and safe, provides additional information in terms of tissue characterization, and, in combination with telepathology, allows interactive collaboration between the surgeon and the pathologist during surgical procedures. Trial registration clinicaltrials.gov Identifier: NCT02312167.

The Gcm/Glide molecular and cellular pathway: new actors and new lineages.

In Drosophila, the transcription factor Gcm/Glide plays a key role in cell fate determination and cellular differentiation. In light of its crucial biological impact, major efforts have been put for analyzing its properties as master regulator, from both structural and functional points of view. However, the lack of efficient antibodies specific to the Gcm/Glide protein precluded thorough analyses of its regulation and activity in vivo. In order to relieve such restraints, we designed an epitope-tagging approach to "FLAG"-recognize and analyze the functional protein both in vitro (exogenous Gcm/Glide) and in vivo (endogenous protein). We here (i) reveal a tight interconnection between the small RNA and the Gcm/Glide pathways. AGO1 and miR-1 are Gcm/Glide targets whereas miR-279 negatively controls Gcm/Glide expression (ii) identify a novel cell population, peritracheal cells, expressing and requiring Gcm/Glide. Peritracheal cells are non-neuronal neurosecretory cells that are essential in ecdysis. In addition to emphasizing the importance of following the distribution and the activity of endogenous proteins in vivo, this study provides new insights and a novel frame to understand the Gcm/Glide biology.

Industrialized GMP Production of CD34+ Cells (ProtheraCytes®) at Clinical Scale for Treatment of Ischemic Cardiac Diseases Is Feasible and Safe.

Regenerative medicine now needs to pass a crucial turning point, from academic research to the market. Several sources/types of cells have been experimented with, more or less successfully. CD34+ cells have demonstrated multipotent or even pluripotent capacities, making them good candidates for regenerative medicine, particularly for treating heart diseases. Strongly encouraged by the results we achieved in a pilot study using CD34+ stem cells in patients with poor-prognosis acute myocardial infarcts (AMIs), we soon began the development of an industrialized platform making use of a closed automated device (StemXpand®) and a disposable kit (StemPack®) for the large-scale expansion of CD34+ cells with reproducible good manufacturing practice (GMP). This scalable platform can produce expanded CD34+ cells (ProtheraCytes®) of sufficient quality that, interestingly, express early markers of the cardiac and endothelial pathways and early cardiac-mesoderm markers. They also contain CD34+ pluripotent cells characterized as very small embryonic-like stem cells (VSELs), capable of differentiating under appropriate stimuli into different tissue lineages, including endothelial and cardiomyocytic ones.