Postmitotic accumulation of histone variant H3.3 in new cortical neurons establishes neuronal chromatin, transcriptome, and identity.

Histone variants, which can be expressed outside of S-phase and deposited DNA synthesis-independently, provide long-term histone replacement in postmitotic cells, including neurons. Beyond replenishment, histone variants also play active roles in gene regulation by modulating chromatin states or enabling nucleosome turnover. Here, we uncover crucial roles for the histone H3 variant H3.3 in neuronal development. We find that newborn cortical excitatory neurons, which have only just completed replication-coupled deposition of canonical H3.1 and H3.2, substantially accumulate H3.3 immediately postmitosis. Codeletion of H3.3-encoding genes H3f3a and H3f3b from newly postmitotic neurons abrogates H3.3 accumulation, markedly alters the histone posttranslational modification landscape, and causes widespread disruptions to the establishment of the neuronal transcriptome. These changes coincide with developmental phenotypes in neuronal identities and axon projections. Thus, preexisting, replication-dependent histones are insufficient for establishing neuronal chromatin and transcriptome; de novo H3.3 is required. Stage-dependent deletion of H3f3a and H3f3b from 1) cycling neural progenitor cells, 2) neurons immediately postmitosis, or 3) several days later, reveals the first postmitotic days to be a critical window for de novo H3.3. After H3.3 accumulation within this developmental window, codeletion of H3f3a and H3f3b does not lead to immediate H3.3 loss, but causes progressive H3.3 depletion over several months without widespread transcriptional disruptions or cellular phenotypes. Our study thus uncovers key developmental roles for de novo H3.3 in establishing neuronal chromatin, transcriptome, identity, and connectivity immediately postmitosis that are distinct from its role in maintaining total histone H3 levels over the neuronal lifespan.

Impact of a mobile decision support tool on antimicrobial stewardship indicators in St. John's, Canada.

OBJECTIVES: Inappropriate antibiotic use contributes to antimicrobial resistance. The SpectrumTM app provides antibiotic decision support, based on local antimicrobial resistance rates. We determined the impact of regional implementation of the app on inpatient antimicrobial appropriateness, inpatient antimicrobial usage (AMU), population-based Clostridioides difficile infection (CDI) rates and cost, using a retrospective, before and after quasi-experimental design, including a one-year study period. METHODS: The SpectrumTM app was released to prescribers in February, 2019. We performed two one-day inpatient point prevalence surveys using the National Antimicrobial Prescribing Survey tool, six months before (June 25, 2018) and six months after (June 25, 2019) app dissemination. Inpatient AMU in Defined Daily Dose/1000 patient days and CDI incidence were compared, before and after app dissemination. RESULTS: The pre-survey included 184 prescriptions, and the post-survey included 197 prescriptions. Appropriateness was 97/176 (55.1%) pre, and 126/192 (65.6%) post (+10.5%, p = 0.051). Inpatient AMU declined by 6.6 DDD/1000 patient days per month, and CDI declined by 0.3 cases per month. Cost savings associated with reduced AMU were $403.98/bed/year and associated with reduced CDI were $82,078/year. CONCLUSION: We observed improvement in antimicrobial stewardship indicators following SpectrumTM implementation. We cannot determine the cause of these improvements.

Chromatin remodeler Arid1a regulates subplate neuron identity and wiring of cortical connectivity.

Loss-of-function mutations in chromatin remodeler gene ARID1A are a cause of Coffin-Siris syndrome, a developmental disorder characterized by dysgenesis of corpus callosum. Here, we characterize Arid1a function during cortical development and find unexpectedly selective roles for Arid1a in subplate neurons (SPNs). SPNs, strategically positioned at the interface of cortical gray and white matter, orchestrate multiple developmental processes indispensable for neural circuit wiring. We find that pancortical deletion of Arid1a leads to extensive mistargeting of intracortical axons and agenesis of corpus callosum. Sparse Arid1a deletion, however, does not autonomously misroute callosal axons, implicating noncell-autonomous Arid1a functions in axon guidance. Supporting this possibility, the ascending axons of thalamocortical neurons, which are not autonomously affected by cortical Arid1a deletion, are also disrupted in their pathfinding into cortex and innervation of whisker barrels. Coincident with these miswiring phenotypes, which are reminiscent of subplate ablation, we unbiasedly find a selective loss of SPN gene expression following Arid1a deletion. In addition, multiple characteristics of SPNs crucial to their wiring functions, including subplate organization, subplate axon-thalamocortical axon cofasciculation ("handshake"), and extracellular matrix, are severely disrupted. To empirically test Arid1a sufficiency in subplate, we generate a cortical plate deletion of Arid1a that spares SPNs. In this model, subplate Arid1a expression is sufficient for subplate organization, subplate axon-thalamocortical axon cofasciculation, and subplate extracellular matrix. Consistent with these wiring functions, subplate Arid1a sufficiently enables normal callosum formation, thalamocortical axon targeting, and whisker barrel development. Thus, Arid1a is a multifunctional regulator of subplate-dependent guidance mechanisms essential to cortical circuit wiring.

Atypical presentation of right-sided native valve infective endocarditis.

A previously healthy 55-year-old man presented to hospital with 10 days of progressive dyspnea with fever, night sweats, and a productive cough and no history of recreational drug use or occupational or animal exposures. His wife had developed similar symptoms 2 weeks earlier but had since recovered. Physical exam revealed a new systolic murmur best heard at the left lower sternal border. Transesophageal echocardiogram demonstrated severe tricuspid regurgitation with a small vegetation. Blood cultures were positive for non-typeable Haemophilus influenzae. This case illustrates the necessity of both timely and proficient diagnosis of H. influenzae infection and the unique challenges associated with detecting H. influenzae-related pathology. Clinicians should be aware of the variable presentations of Haemophilus infection, including respiratory infection, neurological infection, and infective endocarditis. Given the fastidious nature of H. influenzae and variability between subtype pathogenicity, microbiology laboratories require tools to culture and differentiate Haemophilus species.

Un homme de 55 ans auparavant en santé s'est présenté à l'hôpital parce que depuis dix jours, il ressentait une dyspnée progressive accompagnée de fièvre, de sueurs nocturnes, de toux productive et aucuns antécédents de consommation de drogues récréatives ou d'expositions en milieu de travail ou à des animaux. Sa femme avait souffert de symptômes semblables deux semaines auparavant, mais s'était rétablie. L'examen physique a révélé un nouveau murmure systolique mieux perçu au niveau du bord inférieur gauche du sternum. L'échocardiographie transoesophagienne a révélé une régurgitation tricuspidienne marquée et de petites végétations. Les hémocultures ont donné des résultats positifs à l'Haemophilus influenzae non typable. Ce cas démontre la nécessité de poser un diagnostic rapide et compétent de l'infection à H. influenzae et les difficultés propres au dépistage des pathologies liées à l'H. influenzae. Les cliniciens devraient connaître les diverses manifestations de l'infection à Haemophilus, y compris l'infection respiratoire, l'infection neurologique et l'endocardite infectieuse. Étant donné le caractère exigeant de l'H. influenzae et la variabilité de la pathogénicité de ses sous-types, les laboratoires de microbiologie ont besoin d'outils pour mettre en culture et différencier les espèces d'Haemophilus.

Telehealth in the time of Corona: 'doctor in the house'.

The COVID-19 pandemic has led to many physicians working from home whenever possible. Although the concept of 'remote' patient care has been around for decades, present circumstances have provided a grand impetus in that direction with a view to protecting both patient and caregiver. In this article, we discuss some of the various challenges to moving forward with telemedicine, drawing in part on our own experiences in dealing with the COVID-19 pandemic. Clinical, technical, financial and cultural barriers to telemedicine are identified, along with a discussion concerning anticipated benefits. We conclude that the COVID-19 pandemic will likely forever change how healthcare is conducted as telemedicine figures increasingly prominently in the clinical landscape.

Symmetric neural progenitor divisions require chromatin-mediated homologous recombination DNA repair by Ino80.

Chromatin regulates spatiotemporal gene expression during neurodevelopment, but it also mediates DNA damage repair essential to proliferating neural progenitor cells (NPCs). Here, we uncover molecularly dissociable roles for nucleosome remodeler Ino80 in chromatin-mediated transcriptional regulation and genome maintenance in corticogenesis. We find that conditional Ino80 deletion from cortical NPCs impairs DNA double-strand break (DSB) repair, triggering p53-dependent apoptosis and microcephaly. Using an in vivo DSB repair pathway assay, we find that Ino80 is selectively required for homologous recombination (HR) DNA repair, which is mechanistically distinct from Ino80 function in YY1-associated transcription. Unexpectedly, sensitivity to loss of Ino80-mediated HR is dependent on NPC division mode: Ino80 deletion leads to unrepaired DNA breaks and apoptosis in symmetric NPC-NPC divisions, but not in asymmetric neurogenic divisions. This division mode dependence is phenocopied following conditional deletion of HR gene Brca2. Thus, distinct modes of NPC division have divergent requirements for Ino80-dependent HR DNA repair.

Digenic Heterozygous Mutations in SLC34A3 and SLC34A1 Cause Dominant Hypophosphatemic Rickets with Hypercalciuria.

CONTEXT: Hypophosphatemia and metabolic bone disease are associated with hereditary hypophosphatemic rickets with hypercalciuria (HHRH) due to biallelic mutations of SLC34A3 encoding the NPT2C sodium-phosphate cotransporter and nephrolithiasis/osteoporosis, hypophosphatemic 1 (NPHLOP1) due to monoallelic mutations in SLC34A1 encoding the NPT2A sodium-phosphate cotransporter. OBJECTIVE: To identify a genetic cause of apparent dominant transmission of HHRH. DESIGN AND SETTING: Retrospective and prospective analysis of clinical and molecular characteristics of patients studied in 2 academic medical centers. METHODS: We recruited 4 affected and 3 unaffected members of a 4-generation family in which the proband presented with apparent HHRH. We performed clinical examinations, biochemical and radiological analyses, and molecular studies of genomic DNA. RESULTS: The proband and her affected sister and mother carried pathogenic heterozygous mutations in 2 related genes, SLC34A1 (exon 13, c.1535G>A; p.R512H) and SLC34A3 (exon 13, c.1561dupC; L521Pfs*72). The proband and her affected sister inherited both gene mutations from their mother, while their clinically less affected brother, father, and paternal grandmother carried only the SLC34A3 mutation. Renal phosphate-wasting exhibited both a gene dosage-effect and an age-dependent attenuation of severity. CONCLUSIONS: We describe a kindred with autosomal dominant hypophosphatemic rickets in which whole exome analysis identified digenic heterozygous mutations in SLC34A1 and SLC34A3. Subjects with both mutations were more severely affected than subjects carrying only one mutation. These findings highlight the challenges of assigning causality to plausible genetic variants in the next generation sequencing era.

Valve Hemodynamics Following Transcatheter or Surgical Aortic Valve Replacement in Patients With Small Aortic Annulus.

This study aimed to compare the hemodynamic performance of transcatheter and surgical aortic valves in patients with severe symptomatic aortic stenosis and small aortic annulus (SAA) and to determine the valve hemodynamics according to transcatheter valve type. Consecutive surgical aortic valve replacement (SAVR) and transcatheter aortic valve replacement (TAVR) patients with SAA were case-matched (1:1) on the basis of sex, body surface area, aortic annulus diameter, and left ventricular ejection fraction. A total of 357 patients in each group constituted the final study population. A second match on the basis of aortic annulus diameter and valve/annulus calcium burden was performed within the TAVR group to compare the valve performance between balloon- (n = 52) and self-expanding (n = 52) transcatheter valve systems (BEV, SEV). The echocardiograms performed at hospital discharge were used for evaluating valve hemodynamics. The mean annulus diameter of the study population was 19.2 ± 0.3 mm. The TAVR group (vs SAVR) exhibited lower mean gradient (12 ± 7 mm Hg vs 15 ± 6 mm Hg, p <0.001), larger effective orifice area (1.46 ± 0.39 cm2 vs 1.25 ± 0.37 cm2, p <0.001) and a lower rate of severe prosthesis-patient mismatch (PPM) (14% vs 24%, p = 0.001). Moderate-severe AR was present in 2.5% of the TAVR recipients versus none patient in the SAVR group. There were no differences in valve hemodynamics between balloon-expanding transcatheter valve system and self-expanding transcatheter valve system, and similar rates of severe PPM were observed in both groups (p = 0.488). In conclusion, TAVR presented superior valve hemodynamics and lower incidence of severe PPM compared with SAVR in SAA patients. Similar valve performance results were observed between transcatheter valve types.

Medically actionable comorbidities in adults with Costello syndrome.

Costello syndrome (CS) is an autosomal-dominant condition caused by activating missense mutations in HRAS. There is little literature describing health concerns specific to adults with CS. Parents of individuals with CS need to know what to anticipate as their children age. We surveyed a group of 20 adults and older adolescents with CS regarding their medical concerns and lifestyle characteristics. We identified several previously undescribed actionable medical concerns in adults with CS. First, the high prevalence of anxiety in this cohort indicates that screening for anxiety is warranted since this is a treatable condition that can have a significant impact on quality of life. Second, adults with CS should be monitored for progressive contractures or other problems that could decrease mobility. This is especially important in a population that seems to have increased risk for osteopenia. Finally, the lack of cancer diagnoses in adulthood is of interest, although the cohort is too small to draw definitive conclusions about cancer risk in adults with CS. Ongoing follow-up of the current cohort of adults with CS is necessary to delineate progressive medical and physical problems, which is essential for providing targeted management recommendations and anticipatory guidance to families.

Anesthetic Management of the Narrowed Airway.

Airway narrowing can be idiopathic or can occur as a result of airway tumors, hematomas, infections, and other pathologic conditions. Endoscopic management variously involves balloon dilatation, stent placement, laser vaporization of pathologic tissue, microdebridement, and other interventions, using either a rigid or a flexible bronchoscope. Jet ventilation is frequently used in such settings, especially when the presence of an endotracheal tube would interfere with the procedure. In desperate cases, extracorporeal membrane oxygenation may be used in managing the critical airway.

Costello syndrome: Clinical phenotype, genotype, and management guidelines.

Costello syndrome (CS) is a RASopathy caused by activating germline mutations in HRAS. Due to ubiquitous HRAS gene expression, CS affects multiple organ systems and individuals are predisposed to cancer. Individuals with CS may have distinctive craniofacial features, cardiac anomalies, growth and developmental delays, as well as dermatological, orthopedic, ocular, and neurological issues; however, considerable overlap with other RASopathies exists. Medical evaluation requires an understanding of the multifaceted phenotype. Subspecialists may have limited experience in caring for these individuals because of the rarity of CS. Furthermore, the phenotypic presentation may vary with the underlying genotype. These guidelines were developed by an interdisciplinary team of experts in order to encourage timely health care practices and provide medical management guidelines for the primary and specialty care provider, as well as for the families and affected individuals across their lifespan. These guidelines are based on expert opinion and do not represent evidence-based guidelines due to the lack of data for this rare condition.

Significant mitral regurgitation in patients undergoing TAVR: Mechanisms and imaging variables associated with improvement.

BACKGROUND: Significant mitral regurgitation (MR) is associated with poorer outcomes in patients undergoing transcatheter aortic valve replacement (TAVR). Factors associated with MR improvement have not been studied thoroughly. METHODS: Retrospective analysis of consecutive patients treated with TAVR with more than mild MR at baseline. MR evolution was assessed at 1-3 and 6-12 months after intervention. MR severity and mechanisms were assessed by echocardiography. Mitral annulus calcification (MAC) was quantified using preoperative cardiac CT. RESULTS: From 674 consecutive TAVR recipients, 78 with more than mild MR had a 6-12 months follow-up. Following TAVR, MR improved in 34 patients (43%), remained stable in 38 (49%) and worsened in 6 (8%). Patients with MR improvement had greater tenting area (141 ± 56 vs. 99 ± 40 mm2 , P < 0.01), tenting height (7.2 ± 1.9 vs. 5.6 ± 1.9 mm, P < 0.01) and lower ejection fraction (43 ± 16 vs. 52 ± 14%, P = 0.01). MAC was frequent (87.7% of patients) and a trend in greater MAC was observed in patients without MR improvement (3560 ± 5587 vs. 2053 ± 2800, P = 0.16). In multivariable analysis, tenting area (OR per 10 mm2 increase: 1.012, 95% CI, 1.001-1.024 P = 0.039) and annulus calcifications associated with leaflet restriction (OR = 0.108, 95% CI, 0.012-0.956, P = 0.045) were independently associated with MR outcome after TAVR. CONCLUSION: Larger mitral valve tenting area was associated with more improvement of MR after TAVR whereas extensive MAC associated with leaflet restriction was associated with less improvement. This may help in the clinical decision-making process of TAVR candidates with concomitant MR.

Transcarotid Compared With Other Alternative Access Routes for Transcatheter Aortic Valve Replacement.

Background The optimal access for patients undergoing transcatheter aortic valve replacement (TAVR) who are not candidates for a transfemoral approach has not been elucidated. The purpose of this study was to compare the safety, feasibility, and early clinical outcomes of transcarotid TAVR compared with thoracic approaches. Methods and Results From a multicenter consecutive cohort of 329 alternative-access TAVR patients (2012-2017), we identified 101 patients who underwent transcarotid TAVR and 228 patients who underwent a transapical or transaortic TAVR. Preprocedural success and 30-day clinical outcomes were compared using multivariable propensity score analysis to account for between-group differences in baseline characteristics. All transcarotid cases were performed under general anesthesia, mainly using the left common carotid artery (97%). Propensity-matched groups had similar rates of 30-day all-cause mortality (2.1% versus 4.6%; P=0.37), stroke (2.1% versus 3.5%; P=0.67; transcarotid versus transapical/transaortic, respectively), new pacemaker implantation, and major vascular complications. Transcarotid TAVR was associated with significantly less new-onset atrial fibrillation (3.2% versus 19.0%; P=0.002), major or life-threatening bleeding (4.3% versus 19.9%; P=0.002), acute kidney injury (none versus 12.1%; P=0.002), and shorter median length of hospital stay (6 versus 8 days; P<0.001). Conclusions Transcarotid vascular access for TAVR is safe and feasible and is associated with encouraging short-term clinical outcomes. Our data suggest a clinical benefit of transcarotid TAVR with respect to atrial fibrillation, major bleeding, acute kidney injury, and length of stay compared with the more invasive transapical or transaortic strategies. Randomized studies are required to ascertain whether transcarotid TAVR yields equivalent results to other alternative vascular access routes.

Haemodynamic outcomes following aortic valve-in-valve procedure.

Background and objectives: Transcatheter aortic valve-in-valve implantation (ViV) has emerged as a valuable technique to treat failed surgical bioprostheses (BPs) in patients with high risk for redo surgical aortic valve replacement (SAVR). Small BP size (≤21 mm), stenotic pattern of degeneration and pre-existing prosthesis-patient mismatch (PPM) have been associated with worse clinical outcomes after ViV. However, no study has evaluated the actual haemodynamic benefit associated with ViV. This study aims to compare haemodynamic status observed at post-ViV, pre-ViV and early after initial SAVR and to determine the factors associated with worse haemodynamic outcomes following ViV, including the rates of high residual gradient and 'haemodynamic futility'. Methods: Early post-SAVR, pre-ViV and post-ViV echocardiographic data of 79 consecutive patients who underwent aortic ViV at our institution were retrospectively analysed. The primary study endpoint was suboptimal valve haemodynamics (SVH) following ViV defined by the Valve Academic Research Consortium 2 as the presence of high residual aortic mean gradient (≥20 mm Hg) and/or at least moderate aortic regurgitation (AR). Haemodynamic futility of ViV was defined as <10 mm Hg decrease in mean aortic gradient and no improvement in AR compared with pre-ViV. Results: SVH was found in 61% of patients (57% high residual gradient, 4% moderate AR) after ViV versus 24% early after SAVR. Pre-existing PPM and BP mode of failure by stenosis were independently associated with the primary endpoint (OR: 2.87; 95% CI 1.08 to 7.65; p=0.035 and OR: 3.02; 95% CI 1.08 to 8.42; p=0.035, respectively) and with the presence of high residual gradient (OR: 4.38; 95% CI 1.55 to 12.37; p=0.005 and OR: 5.37; 95% CI 1.77 to 16.30; p=0.003, respectively) following ViV. Criteria of ViV haemodynamic futility were met in 7.6% overall and more frequently in patients with pre-existing PPM and stenotic BP (18.5%) compared with other patients (2.0%). ViV restored haemodynamic function to early post-SAVR level in only 34% of patients. Conclusion: Although ViV was associated with significant haemodynamic improvement compared with pre-ViV in >90% of patients, more than half harboured SVH outcome. Furthermore, only one-third of patients had a restoration of valve haemodynamic function to the early post-SAVR level. Pre-existing PPM and stenosis pattern of BP degeneration were the main factors associated with SVH and haemodynamic futility following ViV. These findings provide strong support for the prevention of PPM at the time of initial SAVR and careful preprocedural patient screening.