Rack1 is essential for corticogenesis by preventing p21-dependent senescence in neural stem cells

EFTUD2 Regulates Cortical Morphogenesis via Modulation of Caspase-3 and Aifm1 Splicing Pathways

Elongation Factor Tu GTP-Binding Domain Containing 2 (EFTUD2), a core spliceosomal GTPase associated with Mandibulofacial Dysostosis with Microcephaly (MFDM), plays a mechanistically undefined role in cerebral development. To investigate its pathophysiological contributions, murine models are generated through conditional Eftud2 ablation and in utero electroporation of human pathogenic EFTUD2 variants into cortical neural stem cells (NSCs). Embryonic NSC-specific Eftud2 knockout resulted in cortical disorganization and microcephaly, while pathogenic variants led to significant neuronal loss. Integrative transcriptomic and immunofluorescence analyses revealed that Eftud2 deficiency triggers apoptotic pathways, contributing to cortical malformations. Mechanistic studies using RNA co-immunoprecipitation and full-length transcriptome sequencing demonstrated that Eftud2 directly interacts with Caspase3 and Aifm1 transcripts, regulating their alternative splicing to generate pro-apoptotic isoforms. Splicing assays functionally validated this regulatory mechanism, showing its role in activating cell death pathways and disrupting neurodevelopmental homeostasis. These findings elucidate EFTUD2's critical role in maintaining apoptotic balance during corticogenesis and identify defective splicing regulation as the molecular basis of MFDM. This study provides insights for advancing diagnostic frameworks and therapeutic strategies for neurodevelopmental disorders.

D-galactose Induces Senescence in Adult Mouse Neural Stem Cells by Imbalanced Oxidant and Antioxidant Activity and Differential Expression of Specific Hub Genes

Cellular senescence is a permanent state of cell cycle arrest that occurs in proliferating cells under various stresses causing age-related disorders. This study investigated the role of D-galactose in inducing premature senescence of neural stem cells (NSCs) and the genes involved in this process. After NSC isolation and proliferation, senescence was induced with 10, 20, or 30 µM concentrations of D-galactose for 24 h. Cell viability was tested using the MTT assay, and senescent cells were identified based on increased lysosomal β-galactosidase activity. In addition, levels of NO and malondialdehyde (MDA) oxidative biomarkers but also total thiols (T-SH) and total antioxidant FRAP, as well as inflammatory cytokines, were investigated. Besides, RNA-Seq was performed on the various groups, the gene network was mapped, and genes with the most significant changes were examined. Treatment of NSCs with 20 or 30 µM concentrations of D-galactose caused a significant decrease in cell survival, a number of neurospheres, and a number of neurosphere-derived cells, compared to the control group. In addition, the number of BrdU + cells significantly decreased after induction of NSC senescence with 10 or 20 μM D-galactose, whereas aging-related β-galactosidase (SA-β-gal) increased significantly. Moreover, treatment with 10 or 20 μM D-galactose showed a significant increase in NO production, but not malondialdehyde (MDA). However, the levels of total thiol (T-SH) and antioxidant FRAP levels decreased significantly. Furthermore, TNF-α and IL-6 cytokines significantly increased in NSCs treated with 20 μM, but not 10 μM, D-galactose. Finally, a gene network consisting of 860 gene orthologs was mapped using RNA-Seq. Protein interactions were obtained in 11 hub genes which were classified using gene ontology based on molecular function, biological processes, or cellular processes. Genes with the most significant changes in aging included Fn1, Itga2, Itga3, Itga6, Itga8, Ptk2b, Grin2b, Cacna2d3, Pde4d, Shisa6, and Stac3. This study showed that D-galactose reduces NSC proliferation and antioxidant activity while increasing oxidative stress and inflammatory cytokines. A survey of the genes involved in premature aging may be used as therapeutic candidates for aging-related disorders.

Rack1 promotes breast cancer stemness properties and tumorigenesis through the E2F1-SOX2 axis

BACKGROUND

Breast cancer remains the most prevalent malignancy and the leading cause of cancer-related mortality among women worldwide. The primary factors contributing to the deterioration and death of patients with breast cancer are metastasis, recurrence, and drug resistance. These phenomena are closely related to the presence of breast cancer stem cells; however, the exact mechanisms regulating stemness remain to be elucidated. Rack1 (Receptor for Activated C Kinase 1), a well-known versatile scaffold protein, has been implicated in tumorigenesis and progression in numerous cancer types; however, its specific role in breast cancer stemness remains to be elucidated.

METHODS

Using bioinformatic and immunohistochemical approaches, we validated that the expression level of Rack1 is associated with cancer stemness and affects the prognosis of patients. Through a series of experimental methods including mammosphere formation assay, flow cytometry, qPCR, Western blotting, and CHX assays, we validated at the molecular and cellular levels the mechanism by which Rack1 influences cancer stemness via the E2F1/SOX2 axis. Furthermore, by designing and utilizing lentiviral constructs to establish xenograft tumor models in mice, we further confirmed in vivo the impact of the Rack1/E2F1/SOX2 axis on the tumorigenic capacity of breast cancer cells.

RESULTS

Our findings indicate that Rack1 plays a critical role in preserving the stemness characteristics of breast cancer cells. Mechanistically, the observed effects of Rack1 are achieved through the modulation of SOX2 expression, a master transcription factor that regulates cancer cell stemness and maintenance. We further demonstrate that Rack1 increases the stability of the E2F1 protein by inhibiting its ubiquitination and subsequent proteasome-mediated degradation, which in turn transcriptionally upregulates SOX2, thereby maintaining breast cancer cell stemness and tumorigenesis.

CONCLUSION

This study thus unveils a novel mechanism through which Rack1 executes its oncogenic function. This study also demonstrates that targeting the Rack1-E2F-SOX2 axis may be a potential strategy to inhibit breast cancer development and progression.

Hyperoxia shows duration-dependent effects on the lengths of cell cycle phases in fetal cortical neural stem cells

Fetal neural stem cells (NSCs) physiologically reside under low-oxygen conditions (1%-5% of tissue pO2), but are often transferred and maintained under atmospheric oxygen levels of 21% pO2 (hyperoxia) for in vitro investigations. These altered oxygen conditions lead to adaptive changes in NSCs which complicate the interpretation of in vitro data. However, the underlying adaption dynamics remain largely enigmatic. Here we investigated short-term hyperoxia effects (5 days in 3% pO2 followed by 2 days in 21% pO2) in comparison to continuous hyperoxia effects (7 days in 21% pO2) and physioxic control (7 days in 3% pO2). We utilized cortical NSCs to analyze the cell cycle phases by flow cytometry and cumulative BrdU incorporation assay. NSCs showed a severe reduction of cell proliferation when cultivated under continuous hyperoxia, but no changes after short-term hyperoxia. Subsequent cell cycle analysis as assessed by flow cytometry revealed a clear shift of NSCs from G0/G1-phase towards S- or G2/M-phase after both continuous and short-term hyperoxia. However, while cell cycle length was dramatically reduced by short-term hyperoxia, it was increased during continuous hyperoxia. Taken together, our results demonstrate the beneficial effect of physioxia for expanding NSCs in vitro and reveal differential effects of short-term hyperoxia compared to continuous hyperoxia.

PiRNA CFAPIR inhibits cardiac fibrosis by regulating the muscleblind-like protein MBNL2

Myocardial fibroblasts transform into myofibroblasts during the progression of cardiac fibrosis, together with excessive cardiac fibroblast proliferation. Hence, the prevention and treatment of cardiac fibrosis are significant factors for inhibiting the development of heart failure. P-element Induced WImpy testis-interacting RNAs (PiRNA) are widely expressed in the heart, but their involvement in cardiac fibrosis has not yet been confirmed. We identified differentially expressed PiRNAs using Arraystar PiRNA expression profiling in Angiotensin II models of cardiac fibrosis in vivo and in vitro. We then explored cardiac-fibrosis-associated PiRNA-related proteins, RNA-protein interactomes, immunoprecipitation, and pulldown. We detected fibrosis markers and pathway-related proteins using immunofluorescence, qRT-PCR, and Western blot. We uncovered cardiac fibrosis associated PiRNA (CFAPIR) that was obviously dysregulated during cardiac fibrosis, whereas its overexpression reversed fibrosis in vivo and in vitro. Mechanistically, CFAPIR competitively bound muscleblind like protein 2 (MBNL2) and the cyclin-dependent kinase inhibitor P21 to regulate the TGF-β1/SMAD3 signaling pathway.

Rack1 regulates B-cell development and function by binding to and stabilizing the transcription factor Pax5

The transcription factor Pax5 activates genes essential for B-cell development and function. However, the regulation of Pax5 expression remains elusive. The adaptor Rack1 can interact with multiple transcription factors and modulate their activation and/or stability. However, its role in the transcriptional control of B-cell fates is largely unknown. Here, we show that CD19-driven Rack1 deficiency leads to pro-B accumulation and a simultaneous reduction in B cells at later developmental stages. The generation of bone marrow chimeras indicates a cell-intrinsic role of Rack1 in B-cell homeostasis. Moreover, Rack1 augments BCR and TLR signaling in mature B cells. On the basis of the aberrant expression of Pax5-regulated genes, including CD19, upon Rack1 deficiency, further exploration revealed that Rack1 maintains the protein level of Pax5 through direct interaction and consequently prevents Pax5 ubiquitination. Accordingly, Mb1-driven Rack1 deficiency almost completely blocks B-cell development at the pro-B-cell stage. Ectopic expression of Pax5 in Rack1-deficient pro-B cells partially rescues B-cell development. Thus, Rack1 regulates B-cell development and function through, at least partially, binding to and stabilizing Pax5.

Spliceosomal GTPase Eftud2 deficiency-triggered ferroptosis leads to Purkinje cell degeneration

Spliceosomal GTPase elongation factor Tu GTP binding domain containing 2 (EFTUD2) is a causative gene for mandibulofacial dysostosis with microcephaly (MFDM) syndrome comprising cerebellar hypoplasia and motor dysfunction. How EFTUD2 deficiency contributes to these symptoms remains elusive. Here, we demonstrate that specific ablation of Eftud2 in cerebellar Purkinje cells (PCs) in mice results in severe ferroptosis, PC degeneration, dyskinesia, and cerebellar atrophy, which recapitulates phenotypes observed in patients with MFDM. Mechanistically, Eftud2 promotes Scd1 and Gch1 expression, upregulates monounsaturated fatty acid phospholipids, and enhances antioxidant activity, thereby suppressing PC ferroptosis. Importantly, we identified transcription factor Atf4 as a downstream target to regulate anti-ferroptosis effects in PCs in a p53-independent manner. Inhibiting ferroptosis efficiently rescued cerebellar deficits in Eftud2 cKO mice. Our data reveal an important role of Eftud2 in maintaining PC survival, showing that pharmacologically or genetically inhibiting ferroptosis may be a promising therapeutic strategy for EFTUD2 deficiency-induced disorders.

Mitogen signaling strength and duration can control cell cycle decisions

Decades ago, mitogen-promoted signaling duration and strength were observed to be sensed by the cell and to be critical for its decisions: to proliferate or differentiate. Landmark publications established the importance of mitogen signaling not only in the G1 cell cycle phase but also through the S and the G2/M transition. Despite these early milestones, how mitogen signal duration and strength, short and strong or weaker and sustained, control cell fate has been largely unheeded. Here, we center on cardinal signaling-related questions, including (i) how fluctuating mitogenic signals are converted into cell proliferation-differentiation decisions and (ii) why extended duration of weak signaling is associated with differentiation, while bursts of strong and short induce proliferation but, if too strong and long, induce irreversible senescence. Our innovative broad outlook harnesses cell biology and protein conformational ensembles, helping us to define signaling strength, clarify cell cycle decisions, and thus cell fate.

Alzheimer's Amyloid-β Accelerates Cell Senescence and Suppresses SIRT1 in Human Neural Stem Cells

As a lifelong source of neurons, neural stem cells (NSCs) serve multiple crucial functions in the brain. The senescence of NSCs may be associated with the onset and progression of Alzheimer's disease (AD). Our study reveals a noteworthy finding, indicating that the AD-associated pathogenic protein amyloid-β (Aβ) substantially enhances senescence-related characteristics of human NSCs. These characteristics encompass the enhanced expression of p16 and p21, the upregulation of genes associated with the senescence-associated secretory phenotype (SASP), increased SA-β-gal activity, and the activation of the DNA damage response. Further studies revealed that Aβ treatment significantly downregulates the SIRT1 protein which plays a crucial role in regulating the aging process and decreases downstream PGC-1α and FOXO3. Subsequently, we found that SIRT1 overexpression significantly alleviates a range of Aβ-induced senescent markers in human NSCs. Taken together, our results uncover that Aβ accelerates cellular senescence in human NSCs, making SIRT1 a highly promising therapeutic target for senescent NSCs which may contribute to age-related neurodegenerative diseases, including AD.

Substrate-dependent interaction of SPOP and RACK1 aggravates cardiac fibrosis following myocardial infarction

Speckle-type pox virus and zinc finger (POZ) protein (SPOP), a substrate recognition adaptor of cullin-3 (CUL3)/RING-type E3 ligase complex, is investigated for its role in cardiac fibrosis in our study. Cardiac fibroblasts (CFs) activation was achieved with TGF-β1 (20 ng/mL) and MI mouse model was established by ligation of the left anterior descending coronary, and lentivirus was employed to mediate interference of SPOP expression. SPOP was increased both in fibrotic post-MI mouse hearts and TGF-β1-treated CFs. The gain-of-function of SPOP promoted myofibroblast transformation in CFs, and exacerbated cardiac fibrosis and cardiac dysfunction in MI mice, while the loss-of-function of SPOP exhibited the opposite effects. Mechanistically, SPOP bound to the receptor of activated protein C kinase 1 (RACK1) and induced its ubiquitination and degradation by recognizing Ser/Thr-rich motifs on RACK1, leading to Smad3-mediated activation of CFs. Forced RACK1 expression canceled the effects of SPOP on cardiac fibrosis. The study reveals therapeutic targets for fibrosis-related cardiac diseases.

Neuroligin 2 governs synaptic morphology and function through RACK1-cofilin signaling in Drosophila

Neuroligins are transmembrane cell adhesion proteins well-known for their genetic links to autism spectrum disorders. Neuroligins can function by regulating the actin cytoskeleton, however the factors and mechanisms involved are still largely unknown. Here, using the Drosophila neuromuscular junction as a model, we reveal that F-Actin assembly at the Drosophila NMJ is controlled through Cofilin signaling mediated by an interaction between DNlg2 and RACK1, factors not previously known to work together. The deletion of DNlg2 displays disrupted RACK1-Cofilin signaling pathway with diminished actin cytoskeleton proteo-stasis at the terminal of the NMJ, aberrant NMJ structure, reduced synaptic transmission, and abnormal locomotion at the third-instar larval stage. Overexpression of wildtype and activated Cofilin in muscles are sufficient to rescue the morphological and physiological defects in dnlg2 mutants, while inactivated Cofilin is not. Since the DNlg2 paralog DNlg1 is known to regulate F-actin assembly mainly via a specific interaction with WAVE complex, our present work suggests that the orchestration of F-actin by Neuroligins is a diverse and complex process critical for neural connectivity.

RACK1 facilitates breast cancer progression by competitively inhibiting the binding of β-catenin to PSMD2 and enhancing the stability of β-catenin

The receptor for activated C kinase 1 (RACK1) is a key scaffolding protein with multifunctional and multifaceted properties. By mediating protein-protein interactions, RACK1 integrates multiple intracellular signals involved in the regulation of various physiological and pathological processes. Dysregulation of RACK1 has been implicated in the initiation and progression of many tumors. However, the exact function of RACK1 in cancer cellular processes, especially in proliferation, remains controversial. Here, we show that RACK1 is required for breast cancer cell proliferation in vitro and tumor growth in vivo. This effect of RACK1 is associated with its ability to enhance β-catenin stability and activate the canonical WNT signaling pathway in breast cancer cells. We identified PSMD2, a key component of the proteasome, as a novel binding partner for RACK1 and β-catenin. Interestingly, although there is no interaction between RACK1 and β-catenin, RACK1 binds PSMD2 competitively with β-catenin. Moreover, RACK1 prevents ubiquitinated β-catenin from binding to PSMD2, thereby protecting β-catenin from proteasomal degradation. Collectively, our findings uncover a novel mechanism by which RACK1 increases β-catenin stability and promotes breast cancer proliferation.

A defined roadmap of radial glia and astrocyte differentiation from human pluripotent stem cells

Human gliogenesis remains poorly understood, and derivation of astrocytes from human pluripotent stem cells (hPSCs) is inefficient and cumbersome. Here, we report controlled glial differentiation from hPSCs that bypasses neurogenesis, which otherwise precedes astrogliogenesis during brain development and in vitro differentiation. hPSCs were first differentiated into radial glial cells (RGCs) resembling resident RGCs of the fetal telencephalon, and modulation of specific cell signaling pathways resulted in direct and stepwise induction of key astroglial markers (NFIA, NFIB, SOX9, CD44, S100B, glial fibrillary acidic protein [GFAP]). Transcriptomic and genome-wide epigenetic mapping and single-cell analysis confirmed RGC-to-astrocyte differentiation, obviating neurogenesis and the gliogenic switch. Detailed molecular and cellular characterization experiments uncovered new mechanisms and markers for human RGCs and astrocytes. In summary, establishment of a glia-exclusive neural lineage progression model serves as a unique serum-free platform of manufacturing large numbers of RGCs and astrocytes for neuroscience, disease modeling (e.g., Alexander disease), and regenerative medicine.

Role of hypoxia in cellular senescence

Senescent cells persist and continuously secrete proinflammatory and tissue-remodeling molecules that poison surrounding cells, leading to various age-related diseases, including diabetes, atherosclerosis, and Alzheimer's disease. The underlying mechanism of cellular senescence has not yet been fully explored. Emerging evidence indicates that hypoxia is involved in the regulation of cellular senescence. Hypoxia-inducible factor (HIF)- 1α accumulates under hypoxic conditions and regulates cellular senescence by modulating the levels of the senescence markers p16, p53, lamin B1, and cyclin D1. Hypoxia is a critical condition for maintaining tumor immune evasion, which is promoted by driving the expression of genetic factors (such as p53 and CD47) while triggering immunosenescence. Under hypoxic conditions, autophagy is activated by targeting BCL-2/adenovirus E1B 19-kDa interacting protein 3, which subsequently induces p21WAF1/CIP1 as well as p16Ink4a and increases β-galactosidase (β-gal) activity, thereby inducing cellular senescence. Deletion of the p21 gene increases the activity of the hypoxia response regulator poly (ADP-ribose) polymerase-1 (PARP-1) and the level of nonhomologous end joining (NHEJ) proteins, repairs DNA double-strand breaks, and alleviates cellular senescence. Moreover, cellular senescence is associated with intestinal dysbiosis and an accumulation of D-galactose derived from the gut microbiota. Chronic hypoxia leads to a striking reduction in the amount of Lactobacillus and D-galactose-degrading enzymes in the gut, producing excess reactive oxygen species (ROS) and inducing senescence in bone marrow mesenchymal stem cells. Exosomal microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) play important roles in cellular senescence. miR-424-5p levels are decreased under hypoxia, whereas lncRNA-MALAT1 levels are increased, both of which induce cellular senescence. The present review focuses on recent advances in understanding the role of hypoxia in cellular senescence. The effects of HIFs, immune evasion, PARP-1, gut microbiota, and exosomal mRNA in hypoxia-mediated cell senescence are specifically discussed. This review increases our understanding of the mechanism of hypoxia-mediated cellular senescence and provides new clues for anti-aging processes and the treatment of aging-related diseases.

Dysregulation of the chromatin environment leads to differential alternative splicing as a mechanism of disease in a human model of autism spectrum disorder

Autism spectrum disorder (ASD) affects 1 in 44 children. Chromatin regulatory proteins are overrepresented among genes that contain high risk variants in ASD. Disruption of the chromatin environment leads to widespread dysregulation of gene expression, which is traditionally thought of as a mechanism of disease pathogenesis associated with ASD. Alternatively, alterations in chromatin dynamics could also lead to dysregulation of alternative splicing, which is understudied as a mechanism of ASD pathogenesis. The anticonvulsant valproic acid (VPA) is a well-known environmental risk factor for ASD that acts as a class I histone deacetylase inhibitor. However, the precise molecular mechanisms underlying defects in human neuronal development associated with exposure to VPA are understudied. To dissect how VPA exposure and subsequent chromatin hyperacetylation influence molecular signatures involved in ASD pathogenesis, we conducted RNA sequencing (RNA-seq) in human cortical neurons that were treated with VPA. We observed that differentially expressed genes (DEGs) were enriched for mRNA splicing, mRNA processing, histone modification and metabolism related gene sets. Furthermore, we observed widespread increases in the number and the type of alternative splicing events. Analysis of differential transcript usage (DTU) showed that exposure to VPA induces extensive alterations in transcript isoform usage across neurodevelopmentally important genes. Finally, we find that DEGs and genes that display DTU overlap with known ASD-risk genes. Altogether, these findings suggest that, in addition to differential gene expression, changes in alternative splicing correlated with alterations in the chromatin environment could act as an additional mechanism of disease in ASD.

The Labyrinthine Landscape of APP Processing: State of the Art and Possible Novel Soluble APP-Related Molecular Players in Traumatic Brain Injury and Neurodegeneration

Amyloid Precursor Protein (APP) and its cleavage processes have been widely investigated in the past, in particular in the context of Alzheimer’s Disease (AD). Evidence of an increased expression of APP and its amyloidogenic-related cleavage enzymes, β-secretase 1 (BACE1) and γ-secretase, at the hit axon terminals following Traumatic Brain Injury (TBI), firstly suggested a correlation between TBI and AD. Indeed, mild and severe TBI have been recognised as influential risk factors for different neurodegenerative diseases, including AD. In the present work, we describe the state of the art of APP proteolytic processing, underlining the different roles of its cleavage fragments in both physiological and pathological contexts. Considering the neuroprotective role of the soluble APP alpha (sAPPα) fragment, we hypothesised that sAPPα could modulate the expression of genes of interest for AD and TBI. Hence, we present preliminary experiments addressing sAPPα-mediated regulation of BACE1, Isthmin 2 (ISM2), Tetraspanin-3 (TSPAN3) and the Vascular Endothelial Growth Factor (VEGFA), each discussed from a biological and pharmacological point of view in AD and TBI. We finally propose a neuroprotective interaction network, in which the Receptor for Activated C Kinase 1 (RACK1) and the signalling cascade of PKCβII/nELAV/VEGF play hub roles, suggesting that vasculogenic-targeting therapies could be a feasible approach for vascular-related brain injuries typical of AD and TBI.

RNA sequencing of blood from sex- and age-matched discordant siblings supports immune and transcriptional dysregulation in autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental condition with onset in early childhood, still diagnosed only through clinical observation due to the lack of laboratory biomarkers. Early detection strategies would be especially useful in screening high-risk newborn siblings of children already diagnosed with ASD. We performed RNA sequencing on peripheral blood, comparing 27 pairs of ASD children vs their sex- and age-matched unaffected siblings. Differential gene expression profiling, performed applying an unpaired model found two immune genes, EGR1 and IGKV3D-15, significantly upregulated in ASD patients (both p adj = 0.037). Weighted gene correlation network analysis identified 18 co-expressed modules. One of these modules was downregulated among autistic individuals (p = 0.035) and a ROC curve using its eigengene values yielded an AUC of 0.62. Genes in this module are primarily involved in transcriptional control and its hub gene, RACK1, encodes for a signaling protein critical for neurodevelopment and innate immunity, whose expression is influenced by various hormones and known "endocrine disruptors". These results indicate that transcriptomic biomarkers can contribute to the sensitivity of an intra-familial multimarker panel for ASD and provide further evidence that neurodevelopment, innate immunity and transcriptional regulation are key to ASD pathogenesis.

RACK1 is evolutionary conserved in satellite stem cell activation and adult skeletal muscle regeneration

Skeletal muscle growth and regeneration involves the activity of resident adult stem cells, namely satellite cells (SC). Despite numerous mechanisms have been described, different signals are emerging as relevant in SC homeostasis. Here we demonstrated that the Receptor for Activated C-Kinase 1 (RACK1) is important in SC function. RACK1 was expressed transiently in the skeletal muscle of post-natal mice, being abundant in the early phase of muscle growth and almost disappearing in adult mature fibers. The presence of RACK1 in interstitial SC was also detected. After acute injury in muscle of both mouse and the fruit fly Drosophila melanogaster (used as alternative in vivo model) we found that RACK1 accumulated in regenerating fibers while it declined with the progression of repair process. To note, RACK1 also localized in the active SC that populate recovering tissue. The dynamics of RACK1 levels in isolated adult SC of mice, i.e., progressively high during differentiation and low compared to proliferating conditions, and RACK1 silencing indicated that RACK1 promotes both the formation of myotubes and the accretion of nascent myotubes. In Drosophila with depleted RACK1 in all muscle cells or, specifically, in SC lineage we observed a delayed recovery of skeletal muscle after physical damage as well as the low presence of active SC in the wound area. Our results also suggest the coupling of RACK1 to muscle unfolded protein response during SC activation. Collectively, we provided the first evidence that transient levels of the evolutionarily conserved factor RACK1 are critical for adult SC activation and proper skeletal muscle regeneration, favoring the efficient progression of SC from a committed to a fully differentiated state.

Protocol for analysis of senescent neuronal stem cells in genetic-modified embryonic mice using in utero electroporation technique

Here, we present a detailed protocol for identification and analysis of senescent neuronal stem cells (NSCs) in the developing mouse embryonic neocortex using in utero electroporation. We describe the procedures of in utero electroporation and brain slide preparation. We then detail the procedures of senescence-associated β-galactosidase (SA-β-Gal) staining and immunofluorescence staining, followed by microscope imaging analysis. This combined approach can be used to study the in situ senescence of in utero electroporated embryonic brains.

For complete details on the use and execution of this protocol, please refer to Zhu et al. (2021).

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Identification of senescent cells in the developing brain by SA-β-Gal staining

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In utero electroporation of pCAG-Cre-GFP plasmid into NSCs in loxP embryonic brains

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SA-β-Gal and anti-GFP co-staining to identify the senescent NSCs in embryonic brain

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A modified protocol for imaging and quantification of in situ labeled senescent NSCs

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

How can same-gene mutations promote both cancer and developmental disorders?

The question of how same-gene mutations can drive both cancer and neurodevelopmental disorders has been puzzling. It has also been puzzling why those with neurodevelopmental disorders have a high risk of cancer. Ras, MEK, PI3K, PTEN, and SHP2 are among the oncogenic proteins that can harbor mutations that encode diseases other than cancer. Understanding why some of their mutations can promote cancer, whereas others promote neurodevelopmental diseases, and why even the same mutations may promote both phenotypes, has important clinical ramifications. Here, we review the literature and address these tantalizing questions. We propose that cell type–specific expression of the mutant protein, and of other proteins in the respective pathway, timing of activation (during embryonic development or sporadic emergence), and the absolute number of molecules that the mutations activate, alone or in combination, are pivotal in determining the pathological phenotypes—cancer and (or) developmental disorders.