Transcription factor recruitment to genomic sites of action is primarily due to direct protein:DNA interactions. The subsequent recruitment of coregulatory complexes leads to either transcriptional ...activation or repression. In contrast to this canonical scheme, some transcription factors, such as the glucocorticoid receptor (GR), behave as transcriptional repressors when recruited to target genes through protein tethering. We have investigated the genome-wide prevalence of tethering between GR and Stat3 and found nonreciprocal interactions, namely that GR tethering to DNA-bound Stat3 results in transcriptional repression, whereas Stat3 tethering to GR results in synergism. Further, other schemes of GR and Stat3 corecruitment to regulatory modules result in transcriptional synergism, including neighboring and composite binding sites. The results indicate extensive transcriptional interactions between Stat3 and GR; further, they provide a genome-wide assessment of transcriptional regulation by tethering and a molecular basis for integration of signals mediated by GR and Stats in health and disease.
► Extensive cooperative genomic recruitment of GR and Stat3 ► Binding of GR and Stat3 to neighboring DNA sites results in transcriptional synergism ► Stat3 tethering to GR is associated with transcriptional synergism ► GR tethering to Stat3 is linked to trans-repression by GR
Genome technologies have defined a complex genetic architecture in major infectious, inflammatory, and autoimmune disorders. High density marker arrays and Immunochips have powered genome-wide ...association studies (GWAS) that have mapped nearly 450 genetic risk loci in 22 major inflammatory diseases, including a core of common genes that play a central role in pathological inflammation. Whole-exome and whole-genome sequencing have identified more than 265 genes in which mutations cause primary immunodeficiencies and rare forms of severe inflammatory bowel disease. Combined analysis of inflammatory disease GWAS and primary immunodeficiencies point to shared proteins and pathways that are required for immune cell development and protection against infections and are also associated with pathological inflammation. Finally, sequencing of chromatin immunoprecipitates containing specific transcription factors, with parallel RNA sequencing, has charted epigenetic regulation of gene expression by proinflammatory transcription factors in immune cells, providing complementary information to characterize morbid genes at infectious and inflammatory disease loci.
HoxA genes exhibit central roles during development and causal mutations have been found in several human syndromes including limb malformation. Despite their importance, information on how these ...genes are regulated is lacking. Here, we report on the first identification of bona fide transcriptional enhancers controlling HoxA genes in developing limbs and show that these enhancers are grouped into distinct topological domains at the sub-megabase scale (sub-TADs). We provide evidence that target genes and regulatory elements physically interact with each other through contacts between sub-TADs rather than by the formation of discreet "DNA loops". Interestingly, there is no obvious relationship between the functional domains of the enhancers within the limb and how they are partitioned among the topological domains, suggesting that sub-TAD formation does not rely on enhancer activity. Moreover, we show that suppressing the transcriptional activity of enhancers does not abrogate their contacts with HoxA genes. Based on these data, we propose a model whereby chromatin architecture defines the functional landscapes of enhancers. From an evolutionary standpoint, our data points to the convergent evolution of HoxA and HoxD regulation in the fin-to-limb transition, one of the major morphological innovations in vertebrates.
Leishmaniasis is a disease caused by the protozoan parasite Leishmania and is known to affect millions of individuals worldwide. In recent years, we have established the critical role played by ...Leishmania zinc-metalloprotease GP63 in the modulation of host macrophage signalling and functions, favouring its survival and progression within its host. Leishmania major lacking GP63 was reported to cause limited infection in mice, however, it is still unclear how GP63 may influence the innate inflammatory response and parasite survival in an in vivo context. Therefore, we were interested in analyzing the early innate inflammatory events upon Leishmania inoculation within mice and establish whether Leishmania GP63 influences this initial inflammatory response. Experimentally, L. major WT (L. majorWT), L. major GP63 knockout (L. majorKO), or L. major GP63 rescue (L. majorR) were intraperitoneally inoculated in mice and the inflammatory cells recruited were characterized microscopically and by flow cytometry (number and cell type), and their infection determined. Pro-inflammatory markers such as cytokines, chemokines, and extracellular vesicles (EVs, e.g. exosomes) were monitored and proteomic analysis was performed on exosome contents. Data obtained from this study suggest that Leishmania GP63 does not significantly influence the pathogen-induced inflammatory cell recruitment, but rather their activation status and effector function. Concordantly, internalization of promastigotes during early infection could be influenced by GP63 as fewer L. majorKO amastigotes were found within host cells and appear to maintain in host cells over time. Collectively this study provides a clear analysis of innate inflammatory events occurring during L. major infection and further establish the prominent role of the virulence factor GP63 to provide favourable conditions for host cell infection.
The identification of a stable pool of progenitor/stem cells in the adult pituitary has renewed the interest of identifying mechanisms for maintenance of pituitary cells throughout life. Whereas ...developmental studies have shown that progenitor expansion is the major source of new differentiated cells during pituitary organogenesis, the contribution of these progenitors for maintenance of the adult tissue is not clear although progenitors were clearly involved in cell expansion following end-organ ablation, notably after adrenalectomy and/or gonadectomy. We have used a genetic trick that eliminates dividing cells by apoptosis in order to assess the contribution of differentiated corticotropes and melanotropes for maintenance of their population in the adult pituitary. The system relies on chromosome instability created by the action of the Cre recombinase on inverted loxP sites. Expression of Cre recombinase in corticotropes and melanotropes led to progressive loss of corticotropes whereas melanotropes were unaffected. Because the Cre transgene is not expressed in progenitors, the data indicate that maintenance of the adult corticotrope pool is primarily due to self-duplication of differentiated cells. In contrast, melanotropes do not divide. Maintenance of corticotropes by self-duplication contrasts with the reported proliferative response of undifferentiated cells observed after adrenalectomy. If corticotrope reentry into cell cycle constitutes a normal mechanism to maintain the adult corticotrope pool, this same mechanism may also be perturbed during corticotrope adenoma development in Cushing's disease.
Abstract
The efficacy of the B cell-targeting drug rituximab (RTX) in childhood idiopathic nephrotic syndrome (INS) suggests that B cells may be implicated in disease pathogenesis. However, B ...cell characterization in children with INS remains limited. Here, using single-cell RNA sequencing, we demonstrate that a B cell transcriptional program poised for effector functions represents the major immune perturbation in blood samples from children with active INS. This transcriptional profile was associated with an extrafollicular B cell response marked by the expansion of atypical B cells (atBCs), marginal zone-like B cells, and antibody-secreting cells (ASCs). Flow cytometry of blood from 13 children with active INS and 24 healthy donors confirmed the presence of an extrafollicular B cell response denoted by the expansion of proliferating RTX-sensitive extrafollicular (CXCR5
–
) CD21
low
T-bet
+
CD11c
+
atBCs and short-lived T-bet
+
ASCs in INS. Together, our study provides evidence for an extrafollicular origin for humoral immunity in active INS.
MYSM1 has emerged as an important regulator of hematopoietic stem cell function, blood cell production, immune response, and other aspects of mammalian physiology. It is a metalloprotease family ...protein with deubiquitinase catalytic activity, as well as SANT and SWIRM domains. MYSM1 normally localizes to the nucleus, where it can interact with chromatin and regulate gene expression, through deubiquitination of histone H2A and non-catalytic contacts with other transcriptional regulators. A cytosolic form of MYSM1 protein was also recently described and demonstrated to regulate signal transduction pathways of innate immunity, by promoting the deubiquitination of TRAF3, TRAF6, and RIP2. In this work we review the current knowledge on the molecular mechanisms of action of MYSM1 protein in transcriptional regulation, signal transduction, and potentially other cellular processes. The functions of MYSM1 in different cell types and aspects of mammalian physiology are also reviewed, highlighting the key checkpoints in hematopoiesis, immunity, and beyond regulated by MYSM1. Importantly, mutations in MYSM1 in human were recently linked to a rare hereditary disorder characterized by leukopenia, anemia, and other hematopoietic and developmental abnormalities. Our growing knowledge of MYSM1 functions and mechanisms of actions sheds important insights into its role in mammalian physiology and the etiology of the MYSM1-deficiency disorder in human.
Explosives used in construction have been implicated as sources of NO3 – contamination in groundwater, but direct forensic evidence is limited. Identification of blasting-related NO3 – can be ...complicated by other NO3 – sources, including agriculture and wastewater disposal, and by hydrogeologic factors affecting NO3 – transport and stability. Here we describe a study that used hydrogeology, chemistry, stable isotopes, and mass balance calculations to evaluate groundwater NO3 – sources and transport in areas surrounding a highway construction site with documented blasting in New Hampshire. Results indicate various groundwater responses to contamination: (1) rapid breakthrough and flushing of synthetic NO3 – (low δ15N, high δ18O) from dissolution of unexploded NH4NO3 blasting agents in oxic groundwater; (2) delayed and reduced breakthrough of synthetic NO3 – subjected to partial denitrification (high δ15N, high δ18O); (3) relatively persistent concentrations of blasting-related biogenic NO3 – derived from nitrification of NH4 + (low δ15N, low δ18O); and (4) stable but spatially variable biogenic NO3 – concentrations, consistent with recharge from septic systems (high δ15N, low δ18O), variably affected by denitrification. Source characteristics of denitrified samples were reconstructed from dissolved-gas data (Ar, N2) and isotopic fractionation trends associated with denitrification (Δδ15N/Δδ18O ≈ 1.31). Methods and data from this study are expected to be applicable in studies of other aquifers affected by explosives used in construction.
The combinatorial expression of Hox genes along the body axes is a major determinant of cell fate and plays a pivotal role in generating the animal body plan. Loss of HOXA13 and HOXD13 transcription ...factors (HOX13) leads to digit agenesis in mice, but how HOX13 proteins regulate transcriptional outcomes and confer identity to the distal-most limb cells has remained elusive. Here, we report on the genome-wide profiling of HOXA13 and HOXD13 in vivo binding and changes of the transcriptome and chromatin state in the transition from the early to the late-distal limb developmental program, as well as in Hoxa13−/−; Hoxd13−/− limbs. Our results show that proper termination of the early limb transcriptional program and activation of the late-distal limb program are coordinated by the dual action of HOX13 on cis-regulatory modules.
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•The early transcription program persists in late-distal limb cells lacking HOX13•Expression of late-distal-specific genes largely relies on HOX13 function•HOX13 regulates H3K27 modification at regulatory elements•HOX13 coordinates the early to the late-distal program transition in the limb bud
HOX13 homeobox transcription factors determine digit cell fate during limb bud development. Sheth et al. identify HOX13-dependent regulation of gene expression and chromatin state that suggests HOX13 activity at cis regulatory modules allows for a coordinated transition from the early to the late-distal program in the developing limb bud.
Stem and progenitor cells are the main mediators of tissue renewal and repair, both under homeostatic conditions and in response to physiological stress and injury. Hematopoietic system is ...responsible for the regeneration of blood and immune cells and is maintained by bone marrow-resident hematopoietic stem and progenitor cells (HSPCs). Hematopoietic system is particularly susceptible to injury in response to genotoxic stress, resulting in the risk of bone marrow failure and secondary malignancies in cancer patients undergoing radiotherapy. Here we analyze the in vivo transcriptional response of HSPCs to genotoxic stress in a mouse whole-body irradiation model and, together with p53 ChIP-Seq and studies in p53-knockout (p53KO) mice, characterize the p53-dependent and p53-independent branches of this transcriptional response. Our work demonstrates the p53-independent induction of inflammatory transcriptional signatures in HSPCs in response to genotoxic stress and identifies multiple novel p53-target genes induced in HSPCs in response to whole-body irradiation. In particular, we establish the direct p53-mediated induction of P2X7 expression on HSCs and HSPCs in response to genotoxic stress. We further demonstrate the role of P2X7 in hematopoietic response to acute genotoxic stress, with P2X7 deficiency significantly extending mouse survival in irradiation-induced hematopoietic failure. We also demonstrate the role of P2X7 in the context of long-term HSC regenerative fitness following sublethal irradiation. Overall our studies provide important insights into the mechanisms of HSC response to genotoxic stress and further suggest P2X7 as a target for pharmacological modulation of HSC fitness and hematopoietic response to genotoxic injury.
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