Neurodevelopmental disorders associated variants in ADAT3 disrupt the activity of the ADAT2/ADAT3 tRNA deaminase complex and impair neuronal migration

The ADAT2/ADAT3 complex catalyzes the adenosine to inosine modification at the wobble position of eukaryotic tRNAs. Mutations in ADAT3 , the catalytically inactive subunit of the ADAT2/ADAT3 complex, have been identified in patients presenting with severe neurodevelopmental disorders (NDDs). Yet, the physiological function of ADAT2/ADAT3 complex during brain development remains totally unknown. Here we showed that maintaining a proper level of ADAT2/ADAT3 catalytic activity is required for correct radial migration of projection neurons in the developing mouse cortex. In addition, we not only reported 7 new NDD patients carrying biallelic variants in ADAT3 but also deeply characterize the impact of those variants on ADAT2/ADAT3 structure, biochemical properties, enzymatic activity and tRNAs editing and abundance. We demonstrated that all the identified variants alter both the expression and the activity of the complex leading to a significant decrease of I 34 with direct consequence on their steady-state. Using in vivo complementation assays, we correlated the severity of the migration phenotype with the degree of the loss of function caused by the variants. Altogether, our results indicate a critical role of ADAT2/ADAT3 during cortical development and provide cellular and molecular insights into the pathogenicity of ADAT3-related neurodevelopmental disorder.

Early life adversity shapes social subordination and cell type-specific transcriptomic patterning in the ventral hippocampus

Adverse events in early life can modulate the response to additional stressors later in life and increase the risk of developing psychiatric disorders. The underlying molecular mechanisms responsible for these effects remain unclear. Here, we uncover that early life adversity (ELA) in mice leads to social subordination. Using single-cell RNA sequencing (scRNA-seq), we identified cell type-specific changes in the transcriptional state of glutamatergic and GABAergic neurons in the ventral hippocampus of ELA mice after exposure to acute social stress in adulthood. These findings were reflected by an alteration in excitatory and inhibitory synaptic transmission induced by ELA in response to acute social stress. Finally, enhancing the inhibitory network function through transient diazepam treatment during an early developmental sensitive period reversed the ELA-induced social subordination. Collectively, this study significantly advances our understanding of the molecular, physiological, and behavioral alterations induced by ELA, uncovering a previously unknown cell type-specific vulnerability to ELA.

Sex shapes cell-type-specific transcriptional signatures of stress exposure in the mouse hypothalamus

Stress-related psychiatric disorders and the stress system show prominent differences between males and females, as well as strongly divergent transcriptional changes. Despite several proposed mechanisms, we still lack the understanding of the molecular processes at play. Here, we explore the contribution of cell types to transcriptional sex dimorphism using single-cell RNA sequencing. We identify cell-type-specific signatures of acute restraint stress in the paraventricular nucleus of the hypothalamus, a central hub of the stress response, in male and female mice. Further, we show that a history of chronic mild stress alters these signatures in a sex-specific way, and we identify oligodendrocytes as a major target for these sex-specific effects. This dataset, which we provide as an online interactive app, offers the transcriptomes of thousands of individual cells as a molecular resource for an in-depth dissection of the interplay between cell types and sex on the mechanisms of the stress response.

The co-chaperone Fkbp5 shapes the acute stress response in the paraventricular nucleus of the hypothalamus of male mice

Disturbed activation or regulation of the stress response through the hypothalamic-pituitary-adrenal (HPA) axis is a fundamental component of multiple stress-related diseases, including psychiatric, metabolic, and immune disorders. The FK506 binding protein 51 (FKBP5) is a negative regulator of the glucocorticoid receptor (GR), the main driver of HPA axis regulation, and FKBP5 polymorphisms have been repeatedly linked to stress-related disorders in humans. However, the specific role of Fkbp5 in the paraventricular nucleus of the hypothalamus (PVN) in shaping HPA axis (re)activity remains to be elucidated. We here demonstrate that the deletion of Fkbp5 in Sim1+ neurons dampens the acute stress response and increases GR sensitivity. In contrast, Fkbp5 overexpression in the PVN results in a chronic HPA axis over-activation, and a PVN-specific rescue of Fkbp5 expression in full Fkbp5 KO mice normalizes the HPA axis phenotype. Single-cell RNA sequencing revealed the cell-type-specific expression pattern of Fkbp5 in the PVN and showed that Fkbp5 expression is specifically upregulated in Crh+ neurons after stress. Finally, Crh-specific Fkbp5 overexpression alters Crh neuron activity, but only partially recapitulates the PVN-specific Fkbp5 overexpression phenotype. Together, the data establish the central and cell-type-specific importance of Fkbp5 in the PVN in shaping HPA axis regulation and the acute stress response.

Single-cell molecular profiling of all three components of the HPA axis reveals adrenal ABCB1 as a regulator of stress adaptation

Chronic activation and dysregulation of the neuroendocrine stress response have severe physiological and psychological consequences, including the development of metabolic and stress-related psychiatric disorders. We provide the first unbiased, cell type-specific, molecular characterization of all three components of the hypothalamic-pituitary-adrenal axis, under baseline and chronic stress conditions. Among others, we identified a previously unreported subpopulation of Abcb1b+ cells involved in stress adaptation in the adrenal gland. We validated our findings in a mouse stress model, adrenal tissues from patients with Cushing's syndrome, adrenocortical cell lines, and peripheral cortisol and genotyping data from depressed patients. This extensive dataset provides a valuable resource for researchers and clinicians interested in the organism's nervous and endocrine responses to stress and the interplay between these tissues. Our findings raise the possibility that modulating ABCB1 function may be important in the development of treatment strategies for patients suffering from metabolic and stress-related psychiatric disorders.

Social dominance mediates behavioral adaptation to chronic stress in a sex-specific manner

Sex differences and social context independently contribute to the development of stress-related disorders. However, less is known about how their interplay might influence behavior and physiology. Here we focused on social hierarchy status, a major component of the social environment in mice, and whether it influences behavioral adaptation to chronic stress in a sex-specific manner. We used a high-throughput automated behavioral monitoring system to assess social dominance in same-sex, group-living mice. We found that position in the social hierarchy at baseline was a significant predictor of multiple behavioral outcomes following exposure to chronic stress. Crucially, this association carried opposite consequences for the two sexes. This work demonstrates the importance of recognizing the interplay between sex and social factors and enhances our understating of how individual differences shape the stress response.

Most people experience chronic stress at some point in their life, which may increase their chances of developing depression or anxiety. There is evidence that chronic stress may more negatively impact the well-being of women, placing them as higher risk of developing these mental health conditions. The biological factors that underlie these differences are not well understood, which leaves clinicians and scientists struggling to develop and provide effective treatments.

The social environment has a powerful influence on how people experience and cope with stress. For example, a person’s social and socioeconomic status can change their perception of and reaction to everyday stress. Researchers have found differences in how men and women relate to their social standing. One way for scientists to learn more about the biological processes involved is to study the effect of social standing and chronic stress in male and female mice.

Now, Karamihalev, Brivio et al. show that social status influences the behavior of stressed mice in a sex-specific way. In the experiments, an automated observation system documented the behavior of mice living in all female or male groups. Karamihalev, Brivio et al. determined where each animal fit into the social structure of their group. Then, they exposed some groups of mice to mild chronic stress and compared their behaviors to groups of mice housed in normal conditions. They found that both the sex and social status of each played a role in how they responded to stress. For example, subordinate males displayed more anxious behavior under stressful circumstances, while dominant females acted bolder and less anxious.

More studies in mice are needed to understand the biological basis of these social- and sex-based differences in stress response. Learning more may help scientists understand why some individuals are more susceptible to the effects of stress and lead to the development of personalized prevention or treatment strategies for anxiety and depression.

Sex differences: Transcriptional signatures of stress exposure in male and female brains

More than two-thirds of patients suffering from stress-related disorders are women but over two-thirds of suicide completers are men. These are just some examples of the many sex differences in the prevalence and manifestations of stress-related disorders, such as major depressive disorder, post-traumatic stress disorder, and anxiety disorders, which have been extensively documented in clinical research. Nonetheless, the molecular origins of this sex dimorphism are still quite obscure. In response to this lack of knowledge, the NIH recently advocated implementing sex as biological variable in the design of preclinical studies across disciplines. As a result, a newly emerging field within psychiatry is trying to elucidate the molecular causes underlying the clinically described sex dimorphism. Several studies in rodents and humans have already identified many stress-related genes that are regulated by acute and chronic stress in a sex-specific fashion. Furthermore, current transcriptomic studies have shown that pathways and networks in male and female individuals are not equally affected by stress exposure. In this review, we give an overview of transcriptional studies designed to understand how sex influences stress-specific transcriptomic changes in rodent models, as well as human psychiatric patients, highlighting the use of different methodological techniques. Understanding which mechanisms are more affected in males, and which in females, may lead to the identification of sex-specific mechanisms, their selective contribution to stress susceptibility, and their role in the development of stress-related psychiatric disorders.

Tyr120Asp mutation alters domain flexibility and dynamics of MeCP2 DNA binding domain leading to impaired DNA interaction: Atomistic characterization of a Rett syndrome causing mutation

Mutations in the X-linked MECP2 gene represent the main origin of Rett syndrome, causing a profound intellectual disability in females. MeCP2 is an epigenetic transcriptional regulator containing two main functional domains: a methyl-CpG binding domain (MBD) and a transcription repression domain (TRD). Over 600 pathogenic mutations were reported to affect the whole protein; almost half of missense mutations affect the MBD. Understanding the impact of these mutations on the MBD structure and interaction with DNA will foster the comprehension of their pathogenicity and possibly genotype/phenotype correlation studies. Herein, we use molecular dynamics simulations to obtain a detailed view of the dynamics of WT and mutated MBD in the presence and absence of DNA. The pathogenic mutation Y120D is used as paradigm for our studies. Further, since the Y120 residue was previously found to be a phosphorylation site, we characterize the dynamic profile of the MBD also in the presence of Y120 phosphorylation (pY120). We found that addition of a phosphate group to Y120 or mutation in aspartic acid affect domain mobility that samples an alternative conformational space with respect to the WT, leading to impaired ability to interact with DNA. Experimental assays showing a significant reduction in the binding affinity between the mutated MBD and the DNA confirmed our predictions.

Treatment of childhood acute lymphoblastic leukemia in central America: a lower-middle income countries experience

BACKGROUND

Five Asociación de Hemato-Oncología de Centroamérica (AHOPCA) countries have used an adapted BFM-based protocol for childhood acute lymphoblastic leukemia (ALL).

PROCEDURE

In the AHOPCA-ALL 2008 protocol, patients were stratified by age, white blood cell count, immunophenotype, central nervous system involvement, day 8 prednisone response, and morphologic bone marrow response to induction therapy. Patients at Standard Risk (SR) received a three-drug induction regimen, a reinduction phase, and maintenance with protracted intrathecal therapy. Those at Intermediate (IR) and High Risk (HR) received, in addition, daunorubicin during induction therapy, a consolidation phase and two or three reinduction phases respectively.

RESULTS

From August 2008 through July 2012, 1,313 patients were enrolled: 353 in SR, 548 in IR, 412 in HR. During induction therapy, 3.0% of patients died, 2.7% abandoned treatment, 1.1% had resistant ALL, and 93.2% achieved morphological complete remission (CR). Deaths and abandonment in first CR occurred in 2.7% and in 7.0% of patients, respectively. The relapse rate at a median observation time of 2.1 years was 15.0%. At 3 years, the event-free survival (EFS) and overall survival (OS), with abandonment considered as an event, were 59.4% (SE 1.7) and 68.2% (SE 1.6). Three-year EFS was 68.5% (SE 3.0), 62.1% (SE 2.6), and 47.8% (SE 3.2) for SR, IR, and HR groups. Adolescents had a significantly higher relapse rate (P = 0.001).

CONCLUSIONS

This experience shows that common international studies are feasible in lower-middle income countries. Toxic deaths, abandonment of treatment, and relapses remain major obstacles to the successful treatment. Alternative treatment strategies may be beneficial.

[Efficacy and difficulty in a program of home care for patients with cancer in an advanced stage]

The difficulties experienced by nurses working in a service for domiciliary assistance have been studied through a series of three observations performed at the occasion of the weekly team meetings, at the first visit, the second week of treatment, the week preceding interruption of therapy. Pain problems pose far less difficulties than those linked to the overall physical and psychological management of the patients, which worsen as the time goes on. Specific attention is given to the familiar setting and to the motives which lead to the interruption of the nursing relationships.