B. subtilis MutS2 splits stalled ribosomes into subunits without mRNA cleavage.

Stalled ribosomes are rescued by pathways that recycle the ribosome and target the nascent polypeptide for degradation. In E. coli, these pathways are triggered by ribosome collisions through the recruitment of SmrB, a nuclease that cleaves the mRNA. In B. subtilis, the related protein MutS2 was recently implicated in ribosome rescue. Here we show that MutS2 is recruited to collisions by its SMR and KOW domains, and we reveal the interaction of these domains with collided ribosomes by cryo-EM. Using a combination of in vivo and in vitro approaches, we show that MutS2 uses its ABC ATPase activity to split ribosomes, targeting the nascent peptide for degradation through the ribosome quality control pathway. However, unlike SmrB, which cleaves mRNA in E. coli, we see no evidence that MutS2 mediates mRNA cleavage or promotes ribosome rescue by tmRNA. These findings clarify the biochemical and cellular roles of MutS2 in ribosome rescue in B. subtilis and raise questions about how these pathways function differently in diverse bacteria.

A role for the S4-domain containing protein YlmH in ribosome-associated quality control in Bacillus subtilis.

Ribosomes trapped on mRNAs during protein synthesis need to be rescued for the cell to survive. The most ubiquitous bacterial ribosome rescue pathway is trans-translation mediated by tmRNA and SmpB. Genetic inactivation of trans-translation can be lethal, unless ribosomes are rescued by ArfA or ArfB alternative rescue factors or the ribosome-associated quality control (RQC) system, which in Bacillus subtilis involves MutS2, RqcH, RqcP and Pth. Using transposon sequencing in a trans-translation-incompetent B. subtilis strain we identify a poorly characterized S4-domain-containing protein YlmH as a novel potential RQC factor. Cryo-EM structures reveal that YlmH binds peptidyl-tRNA-50S complexes in a position analogous to that of S4-domain-containing protein RqcP, and that, similarly to RqcP, YlmH can co-habit with RqcH. Consistently, we show that YlmH can assume the role of RqcP in RQC by facilitating the addition of poly-alanine tails to truncated nascent polypeptides. While in B. subtilis the function of YlmH is redundant with RqcP, our taxonomic analysis reveals that in multiple bacterial phyla RqcP is absent, while YlmH and RqcH are present, suggesting that in these species YlmH plays a central role in the RQC.

Intestinal endothelial cells increase HIV infection and latency in resting and activated CD4 + T cells, particularly affecting CCR6 + CD4 + T cells.

BACKGROUND: With suppressive antiretroviral therapy, HIV infection is well-managed in most patients. However, eradication and cure are still beyond reach due to latent viral reservoirs in CD4 + T cells, particularly in lymphoid tissue environments including the gut associated lymphatic tissues. In HIV patients, there is extensive depletion of T helper cells, particularly T helper 17 cells from the intestinal mucosal area, and the gut is one of the largest viral reservoir sites. Endothelial cells line lymphatic and blood vessels and were found to promote HIV infection and latency in previous studies. In this study, we examined endothelial cells specific to the gut mucosal area-intestinal endothelial cells-for their impact on HIV infection and latency in T helper cells. RESULTS: We found that intestinal endothelial cells dramatically increased productive and latent HIV infection in resting CD4 + T helper cells. In activated CD4 + T cells, endothelial cells enabled the formation of latent infection in addition to the increase of productive infection. Endothelial-cell-mediated HIV infection was more prominent in memory T cells than naïve T cells, and it involved the cytokine IL-6 but did not involve the co-stimulatory molecule CD2. The CCR6 + T helper 17 subpopulation was particularly susceptible to such endothelial-cell-promoted infection. CONCLUSION: Endothelial cells, which are widely present in lymphoid tissues including the intestinal mucosal area and interact regularly with T cells physiologically, significantly increase HIV infection and latent reservoir formation in CD4 + T cells, particularly in CCR6 + T helper 17 cells. Our study highlighted the importance of endothelial cells and the lymphoid tissue environment in HIV pathology and persistence.

The impact of pediatric intensivists on the management of pediatric diabetic ketoacidosis in pediatric intensive care units.

INTRODUCTION: The impact of pediatric intensivists on managing pediatric patients with diabetic ketoacidosis (DKA) remains unknown. This study aimed to evaluate the impact of pediatric intensivists on outcomes in pediatric intensive care units (PICUs). METHODS: This was a two-institution retrospective study of patients with DKA admitted to the PICU between 2012 and 2023. Pediatric patients (< 19 years of age) were included if they met the moderate to severe DKA criteria on PICU admission. The patients were subsequently divided into two groups based on the presence or absence of a pediatric intensivist. The primary outcome was the PICU length of stay (LOS). Secondary outcomes were adverse events during DKA treatment, hospital LOS, and mortality. RESULTS: Fifty-two patients admitted to the PICU with a median age of 13.00 years (range, 0-18 years) were included; 32 (61.54%) were female. Patients managed by pediatric intensivists had significantly shorter PICU LOS (2.52 vs. 3.69 days, p < 0.05). Also, adverse events during DKA treatment were significantly decreased in the high-intensity group compared to the low-intensity group (12.50% vs. 50.00%, p < 0.05). CONCLUSIONS: High-intensity ICU staffing was associated with shorter PICU LOS and lower adverse events in pediatric patients with DKA. Our results suggest that dedicated pediatric intensivists can improve outcomes of critically ill pediatric patients with DKA.

Incidence and Mortality Trends in Critically Ill Children: A Korean Population-Based Study.

BACKGROUND: Monitoring mortality trends can help design ways to improve survival, but observation of national mortality trends in critically ill children is lacking for the Korean population. METHODS: We analyzed the incidence and mortality trends of children younger than 18 years admitted to an intensive care unit (ICU) from 2012 to 2018 using the Korean National Health Insurance database. Neonates and neonatal ICU admissions were excluded. Multivariable logistic regression analyses were performed to estimate the odds ratio of in-hospital mortality according to admission year. Trends in incidence and in-hospital mortality of subgroups according to admission department, age, presence of intensivists, admissions to pediatric ICU, mechanical ventilation, and use of vasopressors were evaluated. RESULTS: The overall mortality of critically ill children was 4.4%. There was a significant decrease in mortality from 5.5% in 2012 to 4.1% in 2018 (P for trend < 0.001). The incidence of ICU admission in children remained around 8.5/10,000 population years (P for trend = 0.069). In-hospital mortality decreased by 9.2% yearly in adjusted analysis (P < 0.001). The presence of dedicated intensivists (P for trend < 0.001, mortality decrease from 5.7% to 4.0%) and admission to pediatric ICU (P for trend < 0.001, mortality decrease from 5.0% to 3.2%) were associated with significant decreasing trends in mortality. CONCLUSION: Mortality among critically ill children improved during the study period, and the improving trend was prominent in children with high treatment requirements. Varying mortality trends, according to ICU organizations, highlight that advances in medical knowledge should be supported structurally.

Complications of the Central Nervous System in Pediatric Patients With Common Cold Coronavirus Infection During 2014-2019.

BACKGROUND: In pediatric patients, the common cold coronavirus (ccCoV) usually causes mild respiratory illness. There are reports of coronavirus causing central nervous system (CNS) infection in experimental animal models. Some immunocompromised patients have also been reported to have fatal CNS infections with ccCoV. The aim of this study was to investigate the clinical characteristics of CNS complications related to ccCoV infection. METHODS: From January 2014 to December 2019, a retrospective analysis was performed of medical records from hospitalized patients under 19 years of age whose ccCoV was detected through polymerase chain reaction in respiratory specimens. The CNS complications were defined as clinically diagnosed seizure, meningitis, encephalopathy, and encephalitis. RESULTS: A total of 436 samples from 420 patients were detected as ccCoV. Among the 420 patients, 269 patients were immunocompetent and 151 patients were immunocompromised. The most common type of ccCoV was OC43 (52% in immunocompetent, 37% in immunocompromised). CNS complications were observed in 9.4% (41/436). The most common type of CNS complication was the fever-provoked seizure under pre-existing neurologic disease (42% in immunocompetent and 60% in immunocompromised patients). Among patients with CNS complications, two immunocompetent patients required intensive care unit admission due to encephalitis. Three patients without underlying neurological disease started anti-seizure medications for the first time at this admission. There was no death related to ccCoV infection. CONCLUSION: ccCoV infection may cause severe clinical manifestations such as CNS complications or neurologic sequelae, even in previously healthy children.

Lung-RADS Category 3 and 4 Nodules on Lung Cancer Screening in Clinical Practice.

BACKGROUND. Lung-RADS category 3 and 4 nodules account for most screening-detected lung cancers and are considered actionable nodules with management implications. The cancer frequency among such nodules is estimated in the Lung-RADS recommendations and has been investigated primarily by means of retrospectively assigned Lung-RADS classifications. OBJECTIVE. The purpose of this study was to assess the frequency of cancer among lung nodules assigned Lung-RADS category 3 or 4 at lung cancer screening (LCS) in clinical practice and to evaluate factors that affect the cancer frequency within each category. METHODS. This retrospective study was based on review of clinical radiology reports of 9148 consecutive low-dose CT LCS examinations performed for 4798 patients between June 2014 and January 2021 as part of an established LCS program. Unique nodules assigned Lung-RADS category 3 or 4 (4A, 4B, or 4X) that were clinically categorized as benign or malignant in a multidisciplinary conference that considered histologic analysis and follow-up imaging were selected for further analysis. Benign diagnoses based on stability required at least 12 months of follow-up imaging. Indeterminate nodules were excluded. Cancer frequencies were evaluated. RESULTS. Of the 9148 LCS examinations, 857 (9.4%) were assigned Lung-RADS category 3, and 721 (7.9%) were assigned category 4. The final analysis included 1297 unique nodules in 1139 patients (598 men, 541 women; mean age, 66.0 ± 6.3 years). A total of 1108 of 1297 (85.4%) nodules were deemed benign, and 189 of 1297 (14.6%) were deemed malignant. The frequencies of malignancy of category 3, 4A, 4B, and 4X nodules were 3.9%, 15.5%, 36.3%, and 76.8%. A total of 45 of 46 (97.8%) endobronchial nodules (all category 4A) were deemed benign on the basis of resolution. Cancer frequency was 13.1% for solid, 24.4% for part-solid, and 13.5% for ground-glass nodules. CONCLUSION. In the application of Lung-RADS to LCS clinical practice, the frequency of Lung-RADS category 3 and 4 nodules and the cancer frequency in these categories were higher than the prevalence and cancer risk estimated for category 3 and 4 nodules in the Lung-RADS recommendations and those reported in earlier studies in which category assignments were retrospective. Nearly all endobronchial category 4A nodules were benign. CLINICAL IMPACT. Future Lung-RADS iterations should consider the findings of this study from real-world practice to improve the clinical utility of the system.

Multiple endocrine neoplasia type 2 and autoimmune polyendocrine syndromes (type 1 diabetes mellitus and Graves' disease) in a 16-year-old male with Kabuki syndrome.

Multiple endocrine neoplasia type 2A (MEN2A) is caused by germline pathogenic variants in the RET proto-oncogene and is characterized by medullary thyroid cancer (MTC), pheochromocytoma, and hyperparathyroidism. Autoimmune polyendocrine syndromes (APS) are defined as multiple endocrine gland insufficiency associated with loss of immune tolerance. APS type 2 (APS-2) consists of at least two of the following diseases: type 1 diabetes mellitus (T1DM), autoimmune thyroid disease, and Addison's disease. We describe the clinical, molecular, and biochemical findings of MEN2A, APS-2, and Kabuki syndrome (KS) in a 16-year-old male. Whole exome sequencing was performed to identify the genetic cause of the pheochromocytoma and syndromic features including facial dysmorphism, developmental delay, and epilepsy. RET pathogenic variant and KMT2D pathogenic variant were identified, and he was diagnosed with MEN2A and KS. This is the first case of association between MEN2 and APS in adolescence and the second proven case in humans. In addition, this is the first report of MEN2 and APS in KS.

Human OAS1 activation is highly dependent on both RNA sequence and context of activating RNA motifs.

2'-5'-Oligoadenylate synthetases (OAS) are innate immune sensors of cytosolic double-stranded RNA (dsRNA) and play a critical role in limiting viral infection. dsRNA binding induces allosteric structural changes in OAS1 that reorganize its catalytic center to promote synthesis of 2'-5'-oligoadenylate and thus activation of endoribonuclease L. Specific RNA sequences and structural motifs can also enhance activation of OAS1 through currently undefined mechanisms. To better understand these drivers of OAS activation, we tested the impact of defined sequence changes within a short dsRNA that strongly activates OAS1. Both in vitro and in human A549 cells, appending a 3'-end single-stranded pyrimidine (3'-ssPy) can strongly enhance OAS1 activation or have no effect depending on its location, suggesting that other dsRNA features are necessary for correct presentation of the motif to OAS1. Consistent with this idea, we also find that the dsRNA binding position is dictated by an established consensus sequence (WWN9WG). Unexpectedly, however, not all sequences fitting this consensus activate OAS1 equivalently, with strong dependence on the identity of both partially conserved (W) and non-conserved (N9) residues. A picture thus emerges in which both specific RNA features and the context in which they are presented dictate the ability of short dsRNAs to activate OAS1.

A Case Report for Using Methylprednisolone for Severe ARDS Caused by SARS-CoV-2 Delta Variant in a Pediatric Patient With Lennox-Gastaut Syndrome.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resulted in the coronavirus disease 2019 (COVID-19) pandemic. COVID-19 can result in fatal comorbidities, including acute respiratory distress syndrome (ARDS). Several reports suggest that children have milder illness, though severe cases have still been reported. We report a 9-year-old boy with ARDS caused by the SARS-CoV-2 delta (B.1.617.2) variant. He was admitted to our hospital and carefully observed due to underlying Lennox-Gastaut syndrome. He developed intractable seizures with a high fever. Although the seizures were controlled, his respiratory condition deteriorated to severe ARDS. High-dose methylprednisolone was administered with high positive end-expiratory pressure and low tidal volume. After ARDS treatment, oxygenation improved sufficiently to permit extubation. This case suggests that close observation is required in pediatric patients with neurologic comorbidities because of an increased risk for severe COVID-19.

Two Case Reports of Life-Threatening Croup Caused by the SARS-CoV-2 Omicron BA.2 Variant in Pediatric Patients.

Croup is a common upper airway infection characterized by a barking cough, stridor, and hoarseness. It is usually caused by viral infection. A small number of croup caused by coronavirus disease 2019 (COVID-19) has been reported in children before the omicron variant surge. Previously reported cases indicated that croup caused by COVID-19 can be treated in the same manner as those with other viral causes. We describe two cases (9-month-old girl and 11-month-old boy) of previously healthy infants who presented with a barking cough and chest retraction and required endotracheal intubation and cardiopulmonary resuscitation. Despite receiving dexamethasone and nebulized racemic epinephrine (NRE) treatment for croup in the emergency department, these patients still developed acute respiratory failure. Reverse transcription polymerase chain reaction (RT-PCR) of nasopharyngeal samples revealed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) omicron BA.2 variant (Stealth omicron) and no other common respiratory viral pathogens. Both patients were treated with mechanical ventilation, dexamethasone, and NRE in the pediatric intensive care unit. The duration of intubation was 112 hours and 80 hours, respectively. Both patients were discharged without complications. To the best of our knowledge, this is the first report of life-threatening croup produced by the omicron BA.2 variant and confirmed by RT-PCR. We suggest that this SARS-CoV-2 variant may cause severe croup that may not improve with conventional treatment, even in children without underlying diseases.

Correlation between vancomycin clearance and cystatin C-based glomerular filtration rate in paediatric patients.

AIMS: Because of limitations with the serum creatinine-based glomerular filtration rate (GFRcr), estimates of the serum cystatin C-based glomerular filtration rate (GFRcys) are getting attention to predict vancomycin clearance (CLvan). We evaluated the correlations between (i) CLvan and GFRcr, and (ii) CLvan and GFRcys in paediatric patients. METHODS: We evaluated a retrospective cohort of patients between 1 and 19 years old admitted to a tertiary hospital between 2017 and 2019. CLvan was estimated using measured vancomycin trough concentrations. We conducted Spearman's correlation analyses between CLvan and 1/creatinine, GFRcr, 1/cystatin C and GFRcys. Subgroup analyses were conducted for the young child, child, adolescent subgroups, intensive care unit patients and low body weight (<10th percentile) patients. RESULTS: We analysed 40 patients. GFRcys correlated with CLvan better than GFRcr did (ρ = 0.731, P < 0.001 vs ρ = 0.504, P = 0.001). In the subgroup analyses, the correlation between GFRcys and CLvan was stronger than that between GFRcr and CLvan (child subgroup ρ = 0.712, P = 0.002 vs ρ = 0.282, P = 0.289; intensive care unit patients ρ = 0.772, P < 0.001 vs ρ = 0.540, P = 0.004; low body weight patients ρ = 0.671, P < 0.001 vs ρ = 0.464, P = 0.022). CONCLUSIONS: Serum cystatin C-based GFR strongly correlates with vancomycin clearance, suggesting the possibility of better prediction models than creatinine-based GFR. Further prospective studies are required for the validation of the prediction model in a large paediatric population.

Safe threshold of capillary blood glucose for predicting early future neonatal hypoglycaemia in babies born to mothers with gestational diabetes mellitus, an observational, retrospective cohort study.

BACKGROUND: There is increasing pressure to get women and babies home rapidly after birth. Babies born to mothers with gestational diabetes mellitus (GDM) currently get 24-h inpatient monitoring. We investigated whether a low-risk group of babies born to mothers with GDM could be defined for shorter inpatient hypoglycaemia monitoring. METHODS: Observational, retrospective cohort study conducted in a tertiary maternity hospital in 2018. Singleton, term babies born to women with GDM and no other risk factors for hypoglycaemia, were included. Capillary blood glucose (BG) testing and clinical observations for signs of hypoglycaemia during the first 24-h after birth. BG was checked in all babies before the second feed. Subsequent testing occurred if the first result was < 2.0 mmol/L, or clinical suspicion developed for hypoglycaemia. Neonatal hypoglycaemia, defined as either capillary or venous glucose ≤ 2.0 mmol/L and/or clinical signs of neonatal hypoglycaemia requiring oral or intravenous dextrose (lethargy, abnormal feeding behaviour or seizures). RESULTS: Fifteen of 106 babies developed hypoglycaemia within the first 24-h. Maternal and neonatal characteristics were not predictive. All babies with hypoglycaemia had an initial capillary BG ≤ 2.6 mmol/L (Area under the ROC curve (AUC) 0.96, 95% Confidence Interval (CI) 0.91-1.0). This result was validated on a further 65 babies, of whom 10 developed hypoglycaemia, in the first 24-h of life. CONCLUSION: Using the 2.6 mmol/L threshold, extended monitoring as an inpatient could have been avoided for 60% of babies in this study. Whilst prospective validation is needed, this approach could help tailor postnatal care plans for babies born to mothers with GDM.

Health disparities of critically ill children according to poverty: the Korean population-based retrospective cohort study.

BACKGROUND: There is a lack of nationwide studies on critically ill patients' health disparity under the National Health Insurance (NHI) system. We evaluated health disparities in intensive care unit (ICU) admission, outcomes, and readmission in impoverished children. METHODS: We conducted a retrospective cohort study using a national database from the Korean NHI and Medical Aid Program (MAP). MAP supports the population whose household income is lower than 40% of the median Korean household income. We defined poverty as being a MAP beneficiary and compared the poverty and non-poverty groups. Patients between 28 days and 18 years old who were admitted to the ICU were included. Hospital mortality and readmission were analyzed with adjustment for patient characteristics, hospital type, and management procedures. RESULTS: Out of 17,893 patients, 1153 (6.4%) patients were in poverty. The age-standardized ICU admission rate was higher in the poverty group (126.9 vs. 80.2 per 100,000 person-years). There was more age-standardized mortality in the poverty group (11.8 vs. 4.3 per 100,000 person-years). Patients in the poverty group did not have a statistically different risk of adjusted in-hospital mortality to those in the non-poverty group (odds ratio: 1.15, confidence interval [CI]: 0.84-1.55) but had a higher readmission rate (hazard ratio 1.25, CI 1.09-1.42). CONCLUSION: Under the NHI system, the disparity in pediatric critical care outcomes according to poverty is not definite, but the healthcare disparity in pre- and post-hospital care is a concern. Further studies are required to improve pre- and post-hospital healthcare quality of impoverished children.

FMRP Interacts with RARα in Synaptic Retinoic Acid Signaling and Homeostatic Synaptic Plasticity.

The fragile X syndrome (FXS) is an X-chromosome-linked neurodevelopmental disorder with severe intellectual disability caused by inactivation of the fragile X mental retardation 1 (FMR1) gene and subsequent loss of the fragile X mental retardation protein (FMRP). Among the various types of abnormal synaptic function and synaptic plasticity phenotypes reported in FXS animal models, defective synaptic retinoic acid (RA) signaling and subsequent defective homeostatic plasticity have emerged as a major synaptic dysfunction. However, the mechanism underlying the defective synaptic RA signaling in the absence of FMRP is unknown. Here, we show that RARα, the RA receptor critically involved in synaptic RA signaling, directly interacts with FMRP. This interaction is enhanced in the presence of RA. Blocking the interaction between FMRP and RARα with a small peptide corresponding to the critical binding site in RARα abolishes RA-induced increases in excitatory synaptic transmission, recapitulating the phenotype seen in the Fmr1 knockout mouse. Taken together, these data suggest that not only are functional FMRP and RARα necessary for RA-dependent homeostatic synaptic plasticity, but that the interaction between these two proteins is essential for proper transcription-independent RA signaling. Our results may provide further mechanistic understanding into FXS synaptic pathophysiology.

Effect of Removing Chocolate Milk on Milk and Nutrient Intake Among Urban Secondary School Students.

INTRODUCTION: Schools across the United States have removed sweetened, flavored milk from cafeterias to reduce students' sugar consumption and improve their health. However, evidence on the impact of the removal is limited. We examined the effect of a policy that removed chocolate milk from secondary schools on students' milk consumption and estimated milk-related nutrient intake. METHODS: We collected data on milk selection and consumption during 1 lunch period in 24 California public secondary schools pre-policy (N = 3,158 students in 2016) and post-policy (N = 2,966 students in 2018). Schools had a student population that was 38% Asian and 29% Latino, with 63% qualifying for free or reduced-price meals. We used linear mixed effects models to assess changes in milk selection and waste, and we estimated related changes in added sugars, calcium, protein, and vitamin D consumed from milk. RESULTS: The proportion of students selecting milk declined 13.6%, from 89.5% pre-policy to 75.9% post-policy (95% CI for difference, 10.8% tο 16.4%), but the proportion of milk wasted remained stable (37.1% vs 39.3%; 95% CI for difference, -0.2% to 4.6%). Although average per-student milk consumption declined by less than 1 ounce per student (from 4.8 oz to 3.8 oz; 95% CI for difference, -1.1 oz to -0.7 oz), we observed no significant reductions in average per-student intake of calcium, protein, or vitamin D from milk. Estimated added sugars from milk declined significantly, by 3.1 grams per student (95% CI, -3.2 g to -2.9 g). CONCLUSION: Removing chocolate milk modestly reduced student milk consumption without compromising average intake of key milk-related nutrients, and consumption of added sugars from milk declined significantly. Secondary schools should consider removing chocolate milk to support healthy beverage consumption.

Retinoic Acid Receptor RARα-Dependent Synaptic Signaling Mediates Homeostatic Synaptic Plasticity at the Inhibitory Synapses of Mouse Visual Cortex.

Homeostatic synaptic plasticity is a synaptic mechanism through which the nervous system adjusts synaptic excitation and inhibition to maintain network stability. Retinoic acid (RA) and its receptor RARα have been established as critical mediators of homeostatic synaptic plasticity. In vitro studies reveal that RA signaling enhances excitatory synaptic strength and decreases inhibitory synaptic strength. However, it is unclear whether RA-mediated homeostatic synaptic plasticity occurs in vivo, and if so, whether it operates at specific types of synapses. Here, we examine the impact of RA/RARα signaling in the monocular zone of primary visual cortex (V1m) in mice of either sex. Exogenous RA treatment in acute cortical slices resulted in a reduction in mIPSCs of layer 2/3 pyramidal neurons, an effect mimicked by visual deprivation induced by binocular enucleation in postcritical period animals. Postnatal deletion of RARα blocked RA's effect on mIPSCs. Cell type-specific deletion of RARα revealed that RA acted specifically on parvalbumin (PV)-expressing interneurons. RARα deletion in PV+ interneurons blocked visual deprivation-induced changes in mIPSCs, demonstrating the critical involvement of RA signaling in PV+ interneurons in vivo Moreover, visual deprivation- or RA-induced downregulation of synaptic inhibition was absent in the visual cortical circuit of constitutive and PV-specific Fmr1 KO mice, strongly suggesting a functional interaction between fragile X mental retardation protein and RA signaling pathways. Together, our results demonstrate that RA/RARα signaling acts as a key component for homeostatic regulation of synaptic transmission at the inhibitory synapses of the visual cortex.SIGNIFICANCE STATEMENTIn vitro studies established that retinoic acid (RA) and its receptor RARα play key roles in homeostatic synaptic plasticity, a mechanism by which synaptic excitation/inhibition balance and network stability are maintained. However, whether synaptic RA signaling operates in vivo remains undetermined. Here, using a conditional RARα KO mouse and cell type-specific Cre-driver lines, we showed that RARα signaling in parvalbumin-expressing interneurons is crucial for visual deprivation-induced homeostatic synaptic plasticity at inhibitory synapses in visual cortical circuits. Importantly, this form of synaptic plasticity is absent when fragile X mental retardation protein is selectively deleted in parvalbumin-expressing interneurons, suggesting a functional connection between RARα and fragile X mental retardation protein signaling pathways in vivo Thus, dysfunction of RA-dependent homeostatic plasticity may contribute to cortical circuit abnormalities in fragile X syndrome.

Postnatal Ablation of Synaptic Retinoic Acid Signaling Impairs Cortical Information Processing and Sensory Discrimination in Mice.

Retinoic acid (RA) and its receptors (RARs) are well established essential transcriptional regulators during embryonic development. Recent findings in cultured neurons identified an independent and critical post-transcriptional role of RA and RARα in the homeostatic regulation of excitatory and inhibitory synaptic transmission in mature neurons. However, the functional relevance of synaptic RA signaling in vivo has not been established. Here, using somatosensory cortex as a model system and the RARα conditional knock-out mouse as a tool, we applied multiple genetic manipulations to delete RARα postnatally in specific populations of cortical neurons, and asked whether synaptic RA signaling observed in cultured neurons is involved in cortical information processing in vivo Indeed, conditional ablation of RARα in mice via a CaMKIIα-Cre or a layer 5-Cre driver line or via somatosensory cortex-specific viral expression of Cre-recombinase impaired whisker-dependent texture discrimination, suggesting a critical requirement of RARα expression in L5 pyramidal neurons of somatosensory cortex for normal tactile sensory processing. Transcranial two-photon imaging revealed a significant increase in dendritic spine elimination on apical dendrites of somatosensory cortical layer 5 pyramidal neurons in these mice. Interestingly, the enhancement of spine elimination is whisker experience-dependent as whisker trimming rescued the spine elimination phenotype. Additionally, experiencing an enriched environment improved texture discrimination in RARα-deficient mice and reduced excessive spine pruning. Thus, RA signaling is essential for normal experience-dependent cortical circuit remodeling and sensory processing.SIGNIFICANCE STATEMENT The importance of synaptic RA signaling has been demonstrated in in vitro studies. However, whether RA signaling mediated by RARα contributes to neural circuit functions in vivo remains largely unknown. In this study, using a RARα conditional knock-out mouse, we performed multiple regional/cell-type-specific manipulation of RARα expression in the postnatal brain, and show that RARα signaling contributes to normal whisker-dependent texture discrimination as well as regulating spine dynamics of apical dendrites from layer (L5) pyramidal neurons in S1. Deletion of RARα in excitatory neurons in the forebrain induces elevated spine elimination and impaired sensory discrimination. Our study provides novel insights into the role of RARα signaling in cortical processing and experience-dependent spine maturation.

Examining the cost-effectiveness of baseline left ventricular function assessment among breast cancer patients undergoing anthracycline-based therapy.

BACKGROUND: There is a lack of consensus to guide which breast cancer patients require left ventricular function assessment (LVEF) prior to anthracycline therapy; the cost-effectiveness of screening this patient population has not been previously evaluated. METHODS: We performed a retrospective analysis of the Yale Nuclear Cardiology Database, including 702 patients with baseline equilibrium radionuclide angiography (ERNA) scan prior to anthracycline and/or trastuzumab therapy. We sought to examine associations between abnormal baseline LVEF and potential cardiac risk factors. Additionally, we designed a Markov model to determine the incremental cost-effectiveness ratio (ICER) of ERNA screening for women aged 55 with stage I-III breast cancer from a payer perspective over a lifetime horizon. RESULTS: An abnormal LVEF was observed in 2% (n = 14) of patients. There were no significant associations on multivariate analysis performed on self-reported risk factors. Our analysis showed LVEF screening is cost-effective with ICER of $45,473 per QALY gained. For a willingness-to-pay threshold of $100,000/ QALY, LVEF screening had an 81.9% probability of being cost-effective. Under the same threshold, screening was cost-effective for non-anthracycline cardiotoxicity risk of RR ≤ 0.58, as compared to anthracycline regimens. CONCLUSIONS: Age, preexisting cardiac risk factors and coronary artery disease did not predict a baseline abnormal LVEF. While the prevalence of an abnormal baseline LVEF is low in patients with breast cancer, our results suggest that cardiac screening prior to anthracycline is cost-effective.