Unusual X chromosome inactivation maintenance in female alveolar type 2 cells is correlated with increased numbers of X-linked escape genes and sex-biased gene expression

X-linked transient antenatal Bartter syndrome related to MAGED2 gene: Enriching the phenotypic description and pathophysiologic investigation

PURPOSE

Transient Bartter syndrome related to pathogenic variants of MAGED2 is the most recently described antenatal Bartter syndrome. Despite its transient nature, it is the most severe form of Bartter syndrome in the perinatal period. Our aim was to describe 14 new cases and to try to explain the incomplete penetrance in women.

METHODS

We report on 14 new cases, including 3 females, and review the 40 cases described to date. We tested the hypothesis that MAGED2 is transcriptionally regulated by differential methylation of its CpG-rich promotor by pyrosequencing of DNA samples extracted from fetal and adult leukocytes and kidney samples.

RESULTS

Analysis of the data from 54 symptomatic patients showed spontaneous resolution of symptoms in 27% of cases, persistent complications in 41% of cases, and fatality in 32% of cases. Clinical anomalies were reported in 76% of patients, mostly renal anomalies (52%), cardiovascular anomalies (29%), and dysmorphic features (13%). A developmental delay was reported in 24% of patients. Variants were found in all regions of the gene. Methylation analysis of the MAGED2 CpG-rich promotor showed a correlation with gender, independent of age, tissue or presence of symptoms, excluding a role for this mechanism in the incomplete penetrance in women.

CONCLUSION

This work enriches the phenotypic and genetic description of this recently described disease and deepens our understanding of the pathophysiological role and regulation of MAGED2. Finally, by describing the wide range of outcomes in patients, this work opens the discussion on genetic counseling offered to families.

[X chromosome regulation and female functional specificities: Are two Xs better than one?]

What if the presence of two X chromosomes confers functional specificities on female cells and contributes to the different susceptibilites of men and women to certain diseases? One of the X chromosomes is randomly silenced in each female cell from the embryonic stage, theoretically making the sexes equal. This silencing of the X chromosome is a unique epigenetic process, affecting an entire chromosome and resulting in mosaic expression of X-linked genes throughout the body. However, some genes escape this process and X-inactivation appears to be somewhat labile in certain cell types. What are the physiological implications of these observations? This question is beginning to be explored, particularly in the immune and nervous systems, where several pathologies have sexual bias.

Maternal exposure to polystyrene nanoplastics induces sex-specific cardiotoxicity in offspring mice

Globally, plastic pollution threatens human health, particularly affecting the hearts of offspring exposed to maternal environmental factors early in development. Few studies have specifically addressed sex-specific cardiac injury in offspring resulting from maternal exposure to polystyrene nanoplastics (PS-NPs). This study investigates the potential cardiac injury in offspring following maternal exposure to 1 mg/L PS-NPs. Pregnant C57BL/6J mice were exposed to PS-NPs until 3 weeks postpartum to establish a maternal exposure model. Heart tissues were collected and weighed, and the transcriptomes of the offspring hearts were sequenced and analyzed using high-throughput RNA sequencing. Immunohistochemical staining was performed to assess the effects of PS-NPs on cardiac immune infiltration, fibrosis, and apoptosis in the offspring. PS-NPs caused a significant reduction in heart and body weight in female offspring compared to males. Additionally, PS-NPs induced sex-specific transcriptional reprogramming and metabolic disruptions in the offspring. PS-NPs also induced significant fibrosis, apoptosis, and increased CD68+ macrophage infiltration in offspring hearts. Notably, PS-NPs induced distinct cardiovascular diseases in the offspring. Fluid shear stress and atherosclerosis were significantly enriched in PS-NP-treated male offspring, while viral myocarditis was predominantly enriched in PS-NP-treated females. Our findings suggest that PS-NPs induce cardiotoxicity in offspring by disrupting metabolism, impairing immunity, and triggering fibrosis and apoptosis, with sex-specific differences. This study provides novel insights and a foundation for understanding sex-specific pharmacological differences and interventions in PS-NP-induced cardiovascular disease in offspring.

Cross-species comparison of airway epithelium transcriptomics

Studies of lung transcriptomics across species are essential for understanding the complex biology and disease mechanisms of this vital organ. Single-cell RNA sequencing (scRNA-seq) has emerged as a key tool for understanding cell dynamics across various species. However, comprehensive cross-species comparisons are limited. Therefore, the aims of this study was to investigate the transcriptomic similarities and differences in lung cells across four species-humans, monkeys, mice, and rats-in healthy and asthma conditions using scRNA-seq. The results revealed significant transcriptomic similarities between monkeys and humans and significant cross-species conservation of cell-specific marker genes, transcription factors (TFs), and biological pathways. Additionally, we explored sex differences, identifying distinct sex-specific expression patterns that may influence disease susceptibility. These insights refine our understanding of the mechanism underlying airway cell biology across species and have important implications for studying lung diseases, particularly the mechanisms of mucus clearance in asthma.

Sex as a biological variable in ageing: insights and perspectives on the molecular and cellular hallmarks

Sex-specific differences in lifespan and ageing are observed in various species. In humans, women generally live longer but are frailer and suffer from different age-related diseases compared to men. The hallmarks of ageing, such as genomic instability, telomere attrition or loss of proteostasis, exhibit sex-specific patterns. Sex chromosomes and sex hormones, as well as the epigenetic regulation of the inactive X chromosome, have been shown to affect lifespan and age-related diseases. Here we review the current knowledge on the biological basis of sex-biased ageing. While our review is focused on humans, we also discuss examples of model organisms such as the mouse, fruit fly or the killifish. Understanding these molecular differences is crucial as the elderly population is expected to double worldwide by 2050, making sex-specific approaches in the diagnosis, treatment, therapeutic development and prevention of age-related diseases a pressing need.

The conneXion between sex and immune responses

There are notable sex-based differences in immune responses to pathogens and self-antigens, with female individuals exhibiting increased susceptibility to various autoimmune diseases, and male individuals displaying preferential susceptibility to some viral, bacterial, parasitic and fungal infections. Although sex hormones clearly contribute to sex differences in immune cell composition and function, the presence of two X chromosomes in female individuals suggests that differential gene expression of numerous X chromosome-linked immune-related genes may also influence sex-biased innate and adaptive immune cell function in health and disease. Here, we review the sex differences in immune system composition and function, examining how hormones and genetics influence the immune system. We focus on the genetic and epigenetic contributions responsible for altered X chromosome-linked gene expression, and how this impacts sex-biased immune responses in the context of pathogen infection and systemic autoimmunity.

Etiologic distribution of dizziness/vertigo in a neurological outpatient clinic according to the criteria of the international classification of vestibular disorders: a single-center study

OBJECTIVE

The study aimed to determine the etiological characteristics of patients with dizziness/vertigo attending a neurological clinic according to the criteria of the International Classification of Vestibular Disorders (ICVD), hoping to provide a valuable reference for clinicians to diagnose and treat dizziness/vertigo.

METHOD

A total of 638 consecutive patients with a chief complaint of dizziness/vertigo who attended the vertigo clinic of our neurology department from January 2019 to January 2020 were included. Clinical data of patients, including baseline data, medical history, neurological, neuro-otological, and auxiliary examination results were collected. The etiologic distribution of dizziness/vertigo was determined by analyzing the diagnoses of patients.

RESULTS

Of the 638 patients with dizziness/vertigo, 38.8% were males, 61.2% were females, with a male: female ratio of 1:1.58 and a mean age of 52.9 ± 16.9 years. Benign paroxysmal positional vertigo (BPPV) was the most common cause of dizziness/vertigo in both female (38.9%) and male patients (25.5%). Subgroup analysis based on sex showed that vestibular migraine (VM) and probable autoimmune inner ear disease (p-AIED) were more prevalent in female patients (10.7% and 3.8%, respectively), while vascular vertigo/dizziness was more common in male patients (10.1%). Subgroup analysis based on age showed that the most common diseases were VM in patients aged 0-30 years (27.4%), BPPV in patients aged 31-60 years (27.1%) and 61-100 years (46.0%). Episodic vestibular syndrome (EVS) was the most commonly observed, accounting for up to 60.6% (389/638) of all patients, and the most common diagnoses were BPPV (55.3%, 215/389), VM (15.2%, 59/389), primary unilateral peripheral vestibular dysfunction (p-UPVD) of unknown etiology (11.8%, 46/389), p-AIED (4.4%, 17/389), and vascular vertigo/dizziness (2.8%, 11/389) in these patients. Chronic vestibular syndrome (CVS) was found in 14.0% (90/638) of the patients, and the most common diagnoses were persistent postural-perceptual dizziness (PPPD, 35.6%, 32/90), psychogenic dizziness (18.9%, 17/90), p-UPVD of unknown etiology (15.6%, 14/90), vascular vertigo/dizziness (15.6%, 14/90), and bilateral vestibulopathy (7.8%, 7/90). Acute vestibular syndrome (AVS) was observed in 8.4% (54/638) of the patients, and the most common diagnoses were p-UPVD of unknown etiology (31.5%, 17/54), vestibular neuritis (24.1%, 13/54), probable labyrinthine apoplexy (16.7%, 9/54), stroke (13.0%, 7/54), and psychogenic dizziness (11.1%, 6/54). 16.4% (105/638) of the patients were found to have other disorders, including 15.2% (16/105) of patients with internal diseases, and 84.8% (89/105) of patients with unknown causes. In terms of localization diagnosis, 56.1%, 17.0%, 10.0%, and 16.4% of the patients were diagnosed with peripheral vestibular disorder, central vestibular disorder, psychiatric and functional vestibular disorders, and other disorders, respectively.

CONCLUSION

(1) Dizziness/vertigo was more common in females, which was frequently caused by damage to the vestibular system. Non-vestibular or unknown etiologies were also seen in some patients; (2) VM was more prevalent in women than in men, vascular vertigo/dizziness was more commonly observed in men; (3) EVS was more common in patients with dizziness/vertigo. The most common causes of dizziness/vertigo were peripheral vestibular disorders in patients with AVS and EVS, PPPD and psychogenic dizziness in patients with CVS. The most common causes were BPPV and p-UPVD of unknown etiology in patients with a peripheral vestibular disorder, VM and vascular vertigo/dizziness in patients with central vestibular disorder, PPPD and psychogenic dizziness in patients with psychiatric and functional vestibular disorders.

XIST directly regulates X-linked and autosomal genes in naive human pluripotent cells

X chromosome inactivation (XCI) serves as a paradigm for RNA-mediated regulation of gene expression, wherein the long non-coding RNA XIST spreads across the X chromosome in cis to mediate gene silencing chromosome-wide. In female naive human pluripotent stem cells (hPSCs), XIST is in a dispersed configuration, and XCI does not occur, raising questions about XIST's function. We found that XIST spreads across the X chromosome and induces dampening of X-linked gene expression in naive hPSCs. Surprisingly, XIST also targets specific autosomal regions, where it induces repressive chromatin changes and gene expression dampening. Thereby, XIST equalizes X-linked gene dosage between male and female cells while inducing differences in autosomes. The dispersed Xist configuration and autosomal localization also occur transiently during XCI initiation in mouse PSCs. Together, our study identifies XIST as the regulator of X chromosome dampening, uncovers an evolutionarily conserved trans-acting role of XIST/Xist, and reveals a correlation between XIST/Xist dispersal and autosomal targeting.

Mechanics of Lung Development

We summarize how skeletal muscle and lung developmental biology fields have been bridged to benefit from mouse genetic engineering technologies and to explore the role of fetal breathing-like movements (FBMs) in lung development, by using skeletal muscle-specific mutant mice. It has been known for a long time that FBMs are essential for the lung to develop properly. However, the cellular and molecular mechanisms transducing the mechanical forces of muscular activity into specific genetic programs that propel lung morphogenesis (development of the shape, form and size of the lung, its airways, and gas exchange surface) as well as its differentiation (acquisition of specialized cell structural and functional features from their progenitor cells) are only starting to be revealed. This chapter is a brief synopsis of the cumulative findings from that ongoing quest. An update on and the rationale for our recent International Mouse Phenotyping Consortium (IMPC) search is also provided.