Stephanie Vargas Aguilar

Mature differentiated macrophages can self-maintain by local proliferation in tissues and can be extensively expanded in culture under specific conditions, but the mechanisms of this phenomenon remain only partially defined. Here, we show that SIRT1, an evolutionary conserved regulator of life span, positively affects macrophage self-renewal ability in vitro and in vivo Overexpression of SIRT1 during bone marrow-derived macrophage differentiation increased their proliferative capacity. Conversely, decrease of SIRT1 expression by shRNA inactivation, CRISPR/Cas9 mediated deletion and pharmacological inhibition restricted macrophage self-renewal in culture. Furthermore, pharmacological SIRT1 inhibition in vivo reduced steady state and cytokine-induced proliferation of alveolar and peritoneal macrophages. Mechanistically, SIRT1 inhibition negatively regulated G1/S transition, cell cycle progression and a network of self-renewal genes. This included inhibition of E2F1 and Myc and concomi...

Some of the phenotypes of mice deficient for the lysosomal cysteine endopeptidase cathepsin L (Ctsl) are characterized by large dysmorphic vesicles in the cytoplasm. Specifically, the heart (dilative cardiomyopathy), the thyroid (impaired thyroglobulin processing) and keratinocytes (periodic hair loss and epidermal hyperproliferation) are affected. We hypothesized that the formation of aberrant vesicles is owing to defects in macroautophagy. Therefore, primary mouse embryonic fibroblasts (MEF), which were derived fromCtsl-/-animals crossed with mice transgenic for the autophagy marker GFP-LC3, were investigated.Ctsl-/-MEF show increased number and size of vesicular structures belonging to the ‘acidic’ cellular compartment and are also characterized by GFP-LC3. Induction of autophagy by nutrient starvation or rapamycin treatment showed no significant impairment of the initiation of autophagy, the formation of autophagosomes or autophagosome-lysosome fusion inCtsl-/-MEF, but co-localization of GFP-LC3 and Lamp1 revealed unusually large autophagolysosomes filled with Lamp1. Furthermore, the soluble lysosomal enzyme cathepsin D was elevated inCtsl-/-MEF. Thus, degradation of autophagolysosomal content is impaired in the absence of Ctsl. This could slow the turnover of autophagolysosomes and result in accumulation of the dysmorphic and ‘acidic’ vesicles that were previously described in the context of the pathological phenotypes ofCtsl-/-mice.

As you can see below, while the referees find the analysis potentially interesting they also find it too preliminary at this stage for consideration here. The referees raise different issues with the analysis that are clearly outlined below. Among some of the points raised are that as NAM can inhibit other enzymes like PARP that further data supporting the key role of SIRT1 in this process is needed. Referee #3 also finds that more in vivo data is needed to support the main conclusions. Given the comments raised I am afraid that I can't offer to consider publication here.

Microglia development follows a stepwise program Microglia are cells that defend the central nervous system. However, because they migrate into the brain during development, the changes that they undergo, including those that affect gene expression, have been difficult to document. Matcovitch-Natan et al. transcriptionally profiled gene expression and analyzed epigenetic signatures of microglia at the single-cell level in the early postnatal life of mice. They identified three stages of microglia development, which are characterized by gene expression and linked with chromatin changes, occurring in sync with the developing brain. Furthermore, they showed that the proper development of microglia is affected by the microbiome. Science , this issue p. 789

Alveolar macrophages (AM) are tissue resident macrophages of the lung that can be expanded in culture, but it is unknown to what extent culture affects their in vivo identity. Here we show that long-term ex vivo expanded mouse AM (exAM) maintain core AM gene expression but show culture adaptations related to adhesion, metabolism and proliferation. Strikingly, even after several months in culture exAM reacquired full transcriptional and epigenetic identity upon transplantation into the lung and could self-maintain in the natural niche long-term. Changes in open chromatin regions (OCR) observed in culture were fully reversible in transplanted exAM (texAM) and resulted in a gene expression profile indistinguishable from resident AM. Our results demonstrate that long-term proliferation of AM in culture does not compromise cellular identity in vivo. The demonstrated robustness of exAM identity provides new opportunities for mechanistic analysis and highlights the therapeutic potential of...