The rockefeller university

The 14 authors of the first review article on hidradenitis suppurativa (HS) pathogenesis published 2008 in EXPERIMENTAL DERMATOLOGY cumulating from the 1st International Hidradenitis Suppurativa Research Symposium held March 30-April 2, 2006 in Dessau, Germany with 33 participants were prophetic when they wrote "Hopefully, this heralds a welcome new tradition: to get to the molecular heart of HS pathogenesis, which can only be achieved by a renaissance of solid basic HS research, as the key to developing more effective HS therapy." (Kurzen et al. What causes hidradenitis suppurativa? Exp Dermatol 2008;17:455). Fifteen years later, there is no doubt that the desired renaissance of solid basic HS research is progressing with rapid steps and that HS has developed deep roots among inflammatory diseases in Dermatology and beyond, recognized as "the only inflammatory skin disease than can be healed". This anniversary article of 43 research-performing authors from all around the globe in the official journal of the European Hidradenitis Suppurativa Foundation e.V. (EHSF e.V.) and the Hidradenitis Suppurativa Foundation, Inc (HSF USA) summarizes the evidence of the intense HS clinical and experimental research during the last 15 years in all aspects of the disease and provides information of the developments to come in the near future.

Limitations to successful gene therapy with adeno-associated virus (AAV) can comprise pre-existing neutralizing antibodies to the vector capsid that can block cellular entry, or inefficient transduction of target cells that can lead to sub-optimal expression of the therapeutic transgene. Recombinant serotype 3 AAV (AAV3) is an emerging candidate for liver-directed gene therapy. In this study, we integrated rational design by using a combinatorial library derived from AAV3B capsids with directed evolution by in vitro selection for liver-targeted AAV variants. The AAV3B-DE5 variant described herein was undetectable in the original viral library but gained a selective advantage upon in vitro passaging in human hepatocarcinoma spheroid cultures. AAV3B-DE5 contains 24 capsid amino acid substitutions compared with AAV3B, distributed among all five variable regions, with strong selective pressure on VR-IV, VR-V, and VR-VII. In vivo, AAV3B-DE5 demonstrated improved human hepatocyte tropism in a liver chimeric mouse model. Importantly, this variant exhibited reduced seroreactivity to human intravenous immunoglobulin (i.v. Ig), as well as individual serum samples from 100 healthy human donors. Therefore, molecular evolution using a combinatorial library platform generated a viral capsid with high hepatocyte tropism and enhanced evasion of pre-existing AAV neutralizing antibodies.

Cancer cells rewire their metabolism and rely on endogenous antioxidants to mitigate lethal oxidative damage to lipids. However, the metabolic processes that modulate the response to lipid peroxidation are poorly defined. Using genetic screens, we compared metabolic genes essential for proliferation upon inhibition of cystine uptake or glutathione peroxidase-4 (GPX4). Interestingly, very few genes were commonly required under both conditions, suggesting that cystine limitation and GPX4 inhibition may impair proliferation via distinct mechanisms. Our screens also identify tetrahydrobiopterin (BH4) biosynthesis as an essential metabolic pathway upon GPX4 inhibition. Mechanistically, BH4 is a potent radical-trapping antioxidant that protects lipid membranes from autoxidation, alone and in synergy with vitamin E. Dihydrofolate reductase catalyzes the regeneration of BH4, and its inhibition by methotrexate synergizes with GPX4 inhibition. Altogether, our work identifies the mechanism by which BH4 acts as an endogenous antioxidant and provides a compendium of metabolic modifiers of lipid peroxidation. Genetic screens reveal a compendium of metabolic modifiers of lipid peroxidation. Tetrahydrobiopterin is essential under GPX4 inhibition, acting as a radical-trapping antioxidant that inhibits lipid peroxidation and is regenerated by DHFR.

Through recurrent bouts synchronous with the hair cycle, quiescent melanocyte stem cells (McSCs) become activated to generate proliferative progeny that differentiate into pigment-producing melanocytes. The signaling factors orchestrating these events remain incompletely understood. Here, we use single-cell RNA sequencing with comparative gene expression analysis to elucidate the transcriptional dynamics of McSCs through quiescence, activation, and melanocyte maturation. Unearthing converging signs of increased WNT and BMP signaling along this progression, we endeavored to understand how these pathways are integrated. Employing conditional lineage-specific genetic ablation studies in mice, we found that loss of BMP signaling in the lineage leads to hair graying due to a block in melanocyte maturation. We show that interestingly, BMP signaling functions downstream from activated McSCs and maintains WNT effector, transcription factor LEF1. Employing pseudotime analysis, genetics, and chromatin landscaping, we show that following WNT-mediated activation of McSCs, BMP and WNT pathways collaborate to trigger the commitment of proliferative progeny by fueling LEF1and MITF-dependent differentiation. Our findings shed light upon the signaling interplay and timing of cues that orchestrate melanocyte lineage progression in the hair follicle and underscore a key role for BMP signaling in driving complete differentiation.

Bacterial genomes are being sequenced at an exponentially increasing rate, but our inability to decipher their transcriptional wiring limits our ability to derive new biology from these sequences. De novo determination of regulatory interactions requires accurate prediction of regulators' DNA binding and precise determination of biologically significant binding sites. Here we address these challenges by solving the DNA-specificity code of extracytoplasmic function sigma factors (ECF sigma s), a major family of bacterial regulators, and determining their putative regulons. We generated an aligned collection of ECF sigma s and their promoters by leveraging the autoregulatory nature of ECF sigma s as a means of promoter discovery and analyzed it to identify and characterize the conserved amino acid-nucleotide interactions that determine promoter specificity. This enabled de novo prediction of ECF sigma specificity, which we combined with a statistically rigorous phylogenetic footprinting pipeline based on precomputed orthologs to predict the direct targets of similar to 67% of ECF sigma s. This global survey indicated that some ECF sigma s are conserved global regulators controlling many genes throughout the genome, which are important under many conditions, while others are local regulators, controlling a few closely linked genes in response to specific stimuli in select species. This analysis reveals important organizing principles of bacterial gene regulation and presents a conceptual and computational framework for deciphering gene regulatory networks.

Liver is the central organ responsible for whole-body metabolism, and its constituent hepatocytes are the major players that carry out liver functions. Although they are highly differentiated and rarely divide, hepatocytes re-enter the cell cycle following hepatic loss due to liver damage or injury. However, the exact molecular mechanisms underlying cell cycle re-entry remain undefined. Gdown1 is an RNA polymerase II (Pol II)-associated protein that has been linked to the function of the Mediator transcriptional coactivator complex. We recently found that Gdown1 ablation in mouse liver leads to down-regulation of highly expressed liver-specific genes and a concomitant cell cycle re-entry associated with the induction of cell cycle-related genes. Unexpectedly, in view of a previously documented inhibitory effect on transcription initiation by Pol II in vitro, we found that Gdown1 is associated with elongating Pol II on the highly expressed genes and that its ablation leads to a reduced Pol II occupancy that correlates with the reduced expression of these genes. Based on these observations, we discuss the in vitro and in vivo functions of Gdown1 and consider mechanisms by which the dysregulated Pol II recruitment associated with Gdown1 loss might induce quiescent cell re-entry into the cell cycle.

Locus control region (LCR) functions define cellular identity and have critical roles in diseases such as cancer, although the hierarchy of structural components and associated factors that drive functionality are incompletely understood. Here we show that OCA-B, a B cell-specific coactivator essential for germinal center (GC) formation, forms a ternary complex with the lymphoid-enriched OCT2 and GC-specific MEF2B transcription factors and that this complex occupies and activates an LCR that regulates the BCL6 proto-oncogene and is uniquely required by normal and malignant GC B cells. Mechanistically, through OCA-B-MED1 interactions, this complex is required for Mediator association with the BCL6 promoter. Densely tiled CRISPRi screening indicates that only LCR segments heavily bound by this ternary complex are essential for its function. Our results demonstrate how an intimately linked complex of lineage- and stage-specific factors converges on specific and highly essential enhancer elements to drive the function of a cell-type-defining LCR.

Inborn errors of human interferon gamma (IFN-gamma) immunity underlie mycobacterial disease. We report a patient with mycobacterial disease due to inherited deficiency of the transcription factor T-bet. The patient has extremely low counts of circulating Mycobacterium-reactive natural killer (NK), invariant NKT (iNKT), mucosal-associated invariant T (MATT), and V delta 2(+) gamma delta T lymphocytes, and of Mycobacterium-non reactive classic T(H)1 lymphocytes, with the residual populations of these cells also producing abnormally small amounts of IFN-gamma. Other lymphocyte subsets develop normally but produce low levels of IFN-gamma, with the exception of CD8(+) alpha beta T and non-classic CD4(+) cep T(H)1* lymphocytes, which produce IFN-gamma normally in response to mycobacterial antigens. Human T-bet deficiency thus underlies mycobacterial disease by preventing the development of innate (NK) and innate-like adaptive lymphocytes (iNKT, MATT, and V delta 2(+) gamma delta T cells) and IFN-gamma production by them, with mycobacterium-specific, IFN-gamma-producing, purely adaptive CD8(+) alpha beta T and CD4(+) alpha beta T(H)1* cells unable to compensate for this deficit.

The replication of DNA in chromosomes is initiated at sequences called origins at which two replisome machines are assembled at replication forks that move in opposite directions. Interestingly, in vivo studies observe that the two replication forks remain fastened together, often referred to as a replication factory. Replication factories containing two replisomes are well documented in cellular studies of bacteria (Escherichia coli and Bacillus subtilis) and the eukaryote, Saccharomyces cerevisiae. This basic twin replisome factory architecture may also be preserved in higher eukaryotes. Despite many years of documenting the existence of replication factories, the molecular details of how the two replisome machines are tethered together has been completely unknown in any organism. Recent structural studies shed new light on the architecture of a eukaryote replisome factory, which brings with it a new twist on how a replication factory may function.

Hearing and balance rely on the capacity of mechanically sensitive hair bundles to transduce vibrations into electrical signals that are forwarded to the brain. Hair bundles possess tip links that interconnect the mechanosensitive stereocilia and convey force to the transduction channels. A dimer of dimers, each of these links comprises two molecules of protocadherin 15 (PCDH15) joined to two of cadherin 23 (CDH23). The "handshake" that conjoins the four molecules can be disrupted in vivo by intense stimulation and in vitro by exposure to Ca2+ chelators. Using hair bundles from the rat's cochlea and the bullfrog's sacculus, we observed that extensive recovery of mechanoelectrical transduction, hair bundle stiffness, and spontaneous bundle oscillation can occur within seconds after Ca2+ chelation, especially if hair bundles are deflected toward their short edges. Investigating the phenomenon in a two-compartment ionic environment that mimics natural conditions, we combined iontophoretic application of a Ca2+ chelator to selectively disrupt the tip links of individual frog hair bundles with displacement clamping to control hair bundle motion and measure forces. Our observations suggest that, after the normal Ca2+ concentration has been restored, mechanical stimulation facilitates the reconstitution of functional tip links.