Single Amino Acid Change Underlies Distinct Roles of H2A.Z Subtypes in Human Syndrome.

The developmental disorder Floating-Harbor syndrome (FHS) is caused by heterozygous truncating mutations in SRCAP, a gene encoding a chromatin remodeler mediating incorporation of histone variant H2A.Z. Here, we demonstrate that FHS-associated mutations result in loss of SRCAP nuclear localization, alter neural crest gene programs in human in vitro models and Xenopus embryos, and cause craniofacial defects. These defects are mediated by one of two H2A.Z subtypes, H2A.Z.2, whose knockdown mimics and whose overexpression rescues the FHS phenotype. Selective rescue by H2A.Z.2 is conferred by one of the three amino acid differences between the H2A.Z subtypes, S38/T38. We further show that H2A.Z.1 and H2A.Z.2 genomic occupancy patterns are qualitatively similar, but quantitatively distinct, and H2A.Z.2 incorporation at AT-rich enhancers and expression of their associated genes are both sensitized to SRCAP truncations. Altogether, our results illuminate the mechanism underlying a human syndrome and uncover selective functions of H2A.Z subtypes during development.

Krause corpuscles are genital vibrotactile sensors for sexual behaviours.

Krause corpuscles, which were discovered in the 1850s, are specialized sensory structures found within the genitalia and other mucocutaneous tissues1-4. The physiological properties and functions of Krause corpuscles have remained unclear since their discovery. Here we report the anatomical and physiological properties of Krause corpuscles of the mouse clitoris and penis and their roles in sexual behaviour. We observed a high density of Krause corpuscles in the clitoris compared with the penis. Using mouse genetic tools, we identified two distinct somatosensory neuron subtypes that innervate Krause corpuscles of both the clitoris and penis and project to a unique sensory terminal region of the spinal cord. In vivo electrophysiology and calcium imaging experiments showed that both Krause corpuscle afferent types are A-fibre rapid-adapting low-threshold mechanoreceptors, optimally tuned to dynamic, light-touch and mechanical vibrations (40-80 Hz) applied to the clitoris or penis. Functionally, selective optogenetic activation of Krause corpuscle afferent terminals evoked penile erection in male mice and vaginal contraction in female mice, while genetic ablation of Krause corpuscles impaired intromission and ejaculation of males and reduced sexual receptivity of females. Thus, Krause corpuscles of the clitoris and penis are highly sensitive mechanical vibration detectors that mediate sexually dimorphic mating behaviours.

A vagal reflex evoked by airway closure.

Airway integrity must be continuously maintained throughout life. Sensory neurons guard against airway obstruction and, on a moment-by-moment basis, enact vital reflexes to maintain respiratory function1,2. Decreased lung capacity is common and life-threatening across many respiratory diseases, and lung collapse can be acutely evoked by chest wall trauma, pneumothorax or airway compression. Here we characterize a neuronal reflex of the vagus nerve evoked by airway closure that leads to gasping. In vivo vagal ganglion imaging revealed dedicated sensory neurons that detect airway compression but not airway stretch. Vagal neurons expressing PVALB mediate airway closure responses and innervate clusters of lung epithelial cells called neuroepithelial bodies (NEBs). Stimulating NEBs or vagal PVALB neurons evoked gasping in the absence of airway threats, whereas ablating NEBs or vagal PVALB neurons eliminated gasping in response to airway closure. Single-cell RNA sequencing revealed that NEBs uniformly express the mechanoreceptor PIEZO2, and targeted knockout of Piezo2 in NEBs eliminated responses to airway closure. NEBs were dispensable for the Hering-Breuer inspiratory reflex, which indicated that discrete terminal structures detect airway closure and inflation. Similar to the involvement of Merkel cells in touch sensation3,4, NEBs are PIEZO2-expressing epithelial cells and, moreover, are crucial for an aspect of lung mechanosensation. These findings expand our understanding of neuronal diversity in the airways and reveal a dedicated vagal pathway that detects airway closure to help preserve respiratory function.

Prox2 and Runx3 vagal sensory neurons regulate esophageal motility.

Vagal sensory neurons monitor mechanical and chemical stimuli in the gastrointestinal tract. Major efforts are underway to assign physiological functions to the many distinct subtypes of vagal sensory neurons. Here, we use genetically guided anatomical tracing, optogenetics, and electrophysiology to identify and characterize vagal sensory neuron subtypes expressing Prox2 and Runx3 in mice. We show that three of these neuronal subtypes innervate the esophagus and stomach in regionalized patterns, where they form intraganglionic laminar endings. Electrophysiological analysis revealed that they are low-threshold mechanoreceptors but possess different adaptation properties. Lastly, genetic ablation of Prox2 and Runx3 neurons demonstrated their essential roles for esophageal peristalsis in freely behaving mice. Our work defines the identity and function of the vagal neurons that provide mechanosensory feedback from the esophagus to the brain and could lead to better understanding and treatment of esophageal motility disorders.

Febrile-range hyperthermia accelerates caspase-dependent apoptosis in human neutrophils.

Human neutrophilic polymorphonuclear leukocytes (PMNs) are central to innate immunity and are responsible for clearance of pathogens. PMNs undergo a tightly regulated apoptosis program that allows for timely clearance of PMNs without extravasation of toxic intracellular contents. We investigated the rate of spontaneous apoptosis of human peripheral blood PMNs cultured at basal (37 degrees C) and febrile-range (39.5 degrees C) temperatures (FRT). We found that PMN apoptosis is accelerated at FRT, reaching approximately 90% completion by 8 h at 39.5 degrees C vs 18 h at 37 degrees C based on morphologic criteria. Caspase-8 activation peaked within 15 min of PMN exposure to FRT, and subsequent activation of caspase-3 and -9, cleavage of the BH3 (Bcl-2 homology domain 3) only protein Bid, and mitochondrial release of cytochrome c were also greater in FRT-exposed PMNs. Inhibition of caspase-3, -8, and -9 conferred comparable protection from apoptosis in FRT-exposed PMNs. These results demonstrate that exposure to FRT enhances caspase-8 activation and subsequent mitochondrial-dependent and mitochondrial-independent apoptosis pathways. The PMN survival factors G-CSF, GM-CSF, and IL-8 each prolonged PMN survival at 37 degrees C and 39.5 degrees C, but did not reduce the difference in survival at the two temperatures. In a mouse model of intratracheal endotoxin-induced alveolitis, coexposure to FRT (core temperature approximately 39.5 degrees C) doubled the proportion of bronchoalveolar PMNs undergoing apoptosis compared with euthermic mice. This process may play an important role in limiting inflammation and tissue injury during febrile illnesses.

Zika Virus Infection Induces Cranial Neural Crest Cells to Produce Cytokines at Levels Detrimental for Neurogenesis.

Zika virus (ZIKV) infection during pregnancy is linked to microcephaly, which is attributed to infection of developing brain structures. ZIKV infects neural progenitor cells in vitro, though its effects on other developmentally relevant stem cell populations, including cranial neural crest cells (CNCCs), have not been assessed. CNCCs give rise to most cranial bones and exert paracrine effects on the developing brain. Here, we report that CNCCs are productively infected by ZIKV, but not by the related dengue virus. ZIKV-infected CNCCs undergo limited apoptosis but secrete cytokines that promote death and drive aberrant differentiation of neural progenitor cultures. Addition of two such cytokines, LIF or VEGF, at levels comparable to those secreted by ZIKV-infected CNCCs is sufficient to recapitulate premature neuronal differentiation and apoptotic death of neural progenitors. Thus, our results suggest that CNCC infection by ZIKV may contribute to associated embryopathies through signaling crosstalk between developing face and brain structures.

Genome-wide activity-dependent MeCP2 phosphorylation regulates nervous system development and function.

Autism spectrum disorders such as Rett syndrome (RTT) have been hypothesized to arise from defects in experience-dependent synapse maturation. RTT is caused by mutations in MECP2, a nuclear protein that becomes phosphorylated at S421 in response to neuronal activation. We show here that disruption of MeCP2 S421 phosphorylation in vivo results in defects in synapse development and behavior, implicating activity-dependent regulation of MeCP2 in brain development and RTT. We investigated the mechanism by which S421 phosphorylation regulates MeCP2 function and show by chromatin immunoprecipitation-sequencing that this modification occurs on MeCP2 bound across the genome. The phosphorylation of MeCP2 S421 appears not to regulate the expression of specific genes; rather, MeCP2 functions as a histone-like factor whose phosphorylation may facilitate a genome-wide response of chromatin to neuronal activity during nervous system development. We propose that RTT results in part from a loss of this experience-dependent chromatin remodeling.

Acetaminophen has limited antipyretic activity in critically ill patients.

PURPOSE: Fever occurs commonly in the critically ill patients and may adversely affect outcome. Acetaminophen is one of the most commonly used antipyretic agents in the intensive care unit; however, there is little evidence that it is effective in this population. The objective of this study was to analyze the antipyretic activity of acetaminophen in critically ill patients. MATERIALS AND METHODS: We performed a retrospective study of medical intensive care unit and surgical intensive care unit patients with systemic inflammatory response syndrome and compared the resolution of fever in the presence and absence of acetaminophen treatment by comparing the absolute reduction in body temperature and the rate of cooling over comparable time frames in fevers that were untreated and those treated with acetaminophen. RESULTS: We analyzed 166 febrile episodes (body temperature, >38 degrees C) in 59 patients with systemic inflammatory response syndrome without cancer, neurologic disease, or liver disease. Acetaminophen was administered for 88 of 166 fevers. Febrile episodes in which other antipyretic drugs or external cooling were administered were excluded. The response to acetaminophen was variable, but the absolute temperature reduction was slightly higher (mean, 0.86 versus 0.56 degrees C; P = .0362), and the cooling rate was slightly more rapid (mean, 0.20 versus 0.13 degrees C per hour; P = .0152) in acetaminophen-treated versus untreated fevers. There were no obvious differences between the most and least responsive patients. CONCLUSIONS: We conclude that acetaminophen has significant albeit modest antipyretic activity in critically ill patients.