How Does p73 Cause Neuronal Defects?

Decoding the ubiquitin language: Orchestrating transcription initiation and gene expression through chromatin remodelers and histones

Eukaryotic transcription is a finely orchestrated process and it is controlled by transcription factors as well as epigenetic regulators. Transcription factors and epigenetic regulators undergo different types of posttranslational modifications including ubiquitination to control transcription process. Ubiquitination, traditionally associated with protein degradation, has emerged as a crucial contributor to the regulation of chromatin structure through ubiquitination of histone and chromatin remodelers. Ubiquitination introduces new layers of intricacy to the regulation of transcription initiation through controlling the equilibrium between euchromatin and heterochromatin states. Nucleosome, the fundamental units of chromatin, spacing in euchromatin and heterochromatin states are regulated by histone modification and chromatin remodeling complexes. Chromatin remodeling complexes actively sculpt the chromatin architecture and thereby influence the transcriptional states of genes. Therefore, understanding the dynamic behavior of nucleosome spacing is critical as it impacts various cellular functions through controlling gene expression profiles. In this comprehensive review, we discussed the intricate interplay between ubiquitination and transcription initiation, and illuminated the underlying molecular mechanisms that occur in a variety of biological contexts. This exploration sheds light on the complex regulatory networks that govern eukaryotic transcription, providing important insights into the fine orchestration of gene expression and chromatin dynamics.

The c-Abl/p73 pathway induces neurodegeneration in a Parkinson's disease model

Parkinson's disease is the second most common neurodegenerative disorder. Although it is clear that dopaminergic neurons degenerate, the underlying molecular mechanisms are still unknown, and thus, successful treatment is still elusive. One pro-apoptotic pathway associated with several neurodegenerative diseases is the tyrosine kinase c-Abl and its target p73. Here, we evaluated the contribution of c-Abl and p73 in the degeneration of dopaminergic neurons induced by the neurotoxin 6-hydroxydopamine as a model for Parkinson's disease. First, we found that in SH-SY5Y cells treated with 6-hydroxydopamine, c-Abl and p73 phosphorylation levels were up-regulated. Also, we found that the pro-apoptotic p73 isoform TAp73 was up-regulated. Then, to evaluate whether c-Abl tyrosine kinase activity is necessary for 6-hydroxydopamine-induced apoptosis, we co-treated SH-SY5Y cells with 6-hydroxydopamine and Imatinib, a c-Abl specific inhibitor, observing that Imatinib prevented p73 phosphorylation, TAp73 up-regulation, and protected SH-SY5Y cells treated with 6-hydroxydopamine from apoptosis. Interestingly, this observation was confirmed in the c-Abl conditional null mice, where 6-hydroxydopamine stereotaxic injections induced a lesser reduction of dopaminergic neurons than in the wild-type mice significantly. Finally, we found that the intraperitoneal administration of Imatinib prevented the death of dopaminergic neurons induced by injecting 6-hydroxydopamine stereotaxically in the mice striatum. Thus, our findings support the idea that the c-Abl/p73 pathway is involved in 6-hydroxydopamine degeneration and suggest that inhibition of its kinase activity might be used as a therapeutical drug in Parkinson's disease.

TAp63 regulates bone remodeling by modulating the expression of TNFRSF11B/Osteoprotegerin

ABBREVIATIONS

MSC, mesenchymal stem cells; OPG, osteoprotegerin; RUNX2, Run-trelated transcription factor 2.

Mutations in TP73 cause impaired mucociliary clearance and lissencephaly

TP73 belongs to the TP53 family of transcription factors and has therefore been well studied in cancer research. Studies in mice, however, have revealed non-oncogenic activities related to multiciliogenesis. Utilizing whole-exome sequencing analysis in a cohort of individuals with a mucociliary clearance disorder and cortical malformation, we identified homozygous loss-of-function variants in TP73 in seven individuals from five unrelated families. All affected individuals exhibit a chronic airway disease as well as a brain malformation consistent with lissencephaly. We performed high-speed video microscopy, immunofluorescence analyses, and transmission electron microscopy in respiratory epithelial cells after spheroid or air liquid interface culture to analyze ciliary function, ciliary length, and number of multiciliated cells (MCCs). The respiratory epithelial cells studied display reduced ciliary length and basal bodies mislocalized within the cytoplasm. The number of MCCs is severely reduced, consistent with a reduced number of cells expressing the transcription factors crucial for multiciliogenesis (FOXJ1, RFX2). Our data demonstrate that autosomal-recessive deleterious variants in the TP53 family member TP73 cause a mucociliary clearance disorder due to a defect in MCC differentiation.

Deciphering the Nature of Trp73 Isoforms in Mouse Embryonic Stem Cell Models: Generation of Isoform-Specific Deficient Cell Lines Using the CRISPR/Cas9 Gene Editing System

Simple Summary

The Trp73 gene is involved in the regulation of multiple biological processes such as response to stress, differentiation and tissue architecture. This gene gives rise to structurally different N and C-terminal isoforms which lead to differences in its biological activity in a cell type dependent manner. However, there is a current lack of physiological models to study these isoforms. The aim of this study was to generate specific p73-isoform-deficient mouse embryonic stem cell lines using the CRISPR/Cas9 system. Their special features, self-renewal and pluripotency, make embryonic stem cells a useful research tool that allows the generation of cells from any of the three germ layers carrying specific inactivation of p73-isoforms. Characterization of the generated cell lines indicates that while the individual elimination of TA- or DN-p73 isoform is compatible with pluripotency, it results in alterations of the transcriptional profiles and the pluripotent state of the embryonic stem cells in an isoform-specific manner.

Abstract

The p53 family has been widely studied for its role in various physiological and pathological processes. Imbalance of p53 family proteins may contribute to developmental abnormalities and pathologies in humans. This family exerts its functions through a profusion of isoforms that are generated by different promoter usage and alternative splicing in a cell type dependent manner. In particular, the Trp73 gene gives rise to TA and DN-p73 isoforms that confer p73 a dual nature. The biological relevance of p73 does not only rely on its tumor suppression effects, but on its pivotal role in several developmental processes. Therefore, the generation of cellular models that allow the study of the individual isoforms in a physiological context is of great biomedical relevance. We generated specific TA and DN-p73-deficient mouse embryonic stem cell lines using the CRISPR/Cas9 gene editing system and validated them as physiological bona fide p73-isoform knockout models. Global gene expression analysis revealed isoform-specific alterations of distinctive transcriptional networks. Elimination of TA or DN-p73 is compatible with pluripotency but prompts naïve pluripotent stem cell transition into the primed state, compromising adequate lineage differentiation, thus suggesting that differential expression of p73 isoforms acts as a rheostat during early cell fate determination.

Pseudogene ACTBP2 increases blood-brain barrier permeability by promoting KHDRBS2 transcription through recruitment of KMT2D/WDR5 in Aβ1-42 microenvironment

The blood–brain barrier (BBB) has a vital role in maintaining the homeostasis of the central nervous system (CNS). Changes in the structure and function of BBB can accelerate Alzheimer’s disease (AD) development. β-Amyloid (Aβ) deposition is the major pathological event of AD. We elucidated the function and possible molecular mechanisms of the effect of pseudogene ACTBP2 on the permeability of BBB in Aβ_1–42 microenvironment. BBB model treated with Aβ_1–42 for 48 h were used to simulate Aβ-mediated BBB dysfunction in AD. We proved that pseudogene ACTBP2, RNA-binding protein KHDRBS2, and transcription factor HEY2 are highly expressed in ECs that were obtained in a BBB model in vitro in Aβ_1–42 microenvironment. In Aβ_1–42-incubated ECs, ACTBP2 recruits methyltransferases KMT2D and WDR5, binds to KHDRBS2 promoter, and promotes KHDRBS2 transcription. The interaction of KHDRBS2 with the 3′UTR of HEY2 mRNA increases the stability of HEY2 and promotes its expression. HEY2 increases BBB permeability in Aβ_1–42 microenvironment by transcriptionally inhibiting the expression of ZO-1, occludin, and claudin-5. We confirmed that knocking down of Khdrbs2 or Hey2 increased the expression levels of ZO-1, occludin, and claudin-5 in APP/PS1 mice brain microvessels. ACTBP2/KHDRBS2/HEY2 axis has a crucial role in the regulation of BBB permeability in Aβ_1–42 microenvironment, which may provide a novel target for the therapy of AD.

Molecular Mechanisms and Function of the p53 Protein Family Member - p73

Over 20 years after identification of p53 and its crucial function in cancer progression, two members of the same protein family were identified, namely p63 and p73. Since then, a body of information has been accumulated on each of these genes and their interrelations. Biological role of p73 has been elucidated thanks to four distinct knockout mice models: (i) with deletion of the entire TP73 gene, (ii) with deletion of exons encoding the full length TAp73 isoforms, (iii) with deletions of exons encoding the shorter DNp73 isoform, and (iv) with deletion of exons encoding C-terminal of the alpha isoform. This work, as well as expression studies in cancer and overwhelming body of molecular studies, allowed establishing major role of TP73 both in cancer and in neuro-development, as well as ciliogenesis, and metabolism. Here, we recapitulate the major milestones of this endeavor.

Tantalizing role of p53 molecular pathways and its coherent medications in neurodegenerative diseases

Neurodegenerative diseases are incongruous, commonly age-related disorders characterized by progressive neuronal loss, comprising the most prevalent being Alzheimer's disease, Parkinson's disease, and Huntington's disease. Perilous health states are anticipated following the neurodegeneration. Their etiology remains largely ambiguous, while various mechanisms are ascribed to their pathogenesis. A recommended conception is regarding the role of p53, as a transcription factor regulating numerous cellular pathways comprising apoptosis. Neuronal fates are a feasible occurrence that contributes to all neurodegenerative diseases. In this work, we review the research investigated the potential role of p53 in the pathogenesis of these diseases. We put special emphasis on intricate We not only describe aberrant changes in p53 level/activity observed in CNS regions affected by particular diseases but, most importantly, put special attention to the complicated reciprocal tuning connections prevailing between p53 and molecules considered in pathological hallmarks of these disorders. Natural and synthetic medications regulating p53 expression are regarded as well.

Regulation of Adult Neurogenesis in Mammalian Brain

Adult neurogenesis is a multistage process by which neurons are generated and integrated into existing neuronal circuits. In the adult brain, neurogenesis is mainly localized in two specialized niches, the subgranular zone (SGZ) of the dentate gyrus and the subventricular zone (SVZ) adjacent to the lateral ventricles. Neurogenesis plays a fundamental role in postnatal brain, where it is required for neuronal plasticity. Moreover, perturbation of adult neurogenesis contributes to several human diseases, including cognitive impairment and neurodegenerative diseases. The interplay between extrinsic and intrinsic factors is fundamental in regulating neurogenesis. Over the past decades, several studies on intrinsic pathways, including transcription factors, have highlighted their fundamental role in regulating every stage of neurogenesis. However, it is likely that transcriptional regulation is part of a more sophisticated regulatory network, which includes epigenetic modifications, non-coding RNAs and metabolic pathways. Here, we review recent findings that advance our knowledge in epigenetic, transcriptional and metabolic regulation of adult neurogenesis in the SGZ of the hippocampus, with a special attention to the p53-family of transcription factors.

TAp73 regulates ATP7A: possible implications for ageing-related diseases

The p53 family member p73 controls a wide range of cellular function. Deletion of p73 in mice results in increased tumorigenesis, infertility, neurological defects and altered immune system. Despite the extensive effort directed to define the molecular underlying mechanism of p73 function a clear definition of its transcriptional signature and the extent of overlap with the other p53 family members is still missing. Here we describe a novel TAp73 target, ATP7A a member of a large family of P-type ATPases implicated in human neurogenerative conditions and cancer chemoresistance. Modulation of TAp73 expression influences basal expression level of ATP7A in different cellular models and chromatin immunoprecipitation confirmed a physical direct binding of TAp73 on ATP7A genomic regions. Bioinformatic analysis of expression profile datasets of human lung cancer patients suggests a possible implication of TAp73/ATP7A axis in human cancer. These data provide a novel TAp73-dependent target which might have implications in ageing-related diseases such as cancer and neurodegeneration.

The long noncoding RNA TP73-AS1 promotes tumorigenicity of medulloblastoma cells

Medulloblastoma is the most common malignant brain cancer in children. Since previous studies have mainly focused on alterations in the coding genome, our understanding of the contribution of long noncoding RNAs (lncRNAs) to medulloblastoma biology is just emerging. Using patient-derived data, we show that the promoter of lncRNA TP73-AS1 is hypomethylated and that the transcript is highly expressed in the SHH subgroup. Furthermore, high expression of TP73-AS1 is correlated with poor outcome in patients with TP53 wild-type SHH tumors. Silencing TP73-AS1 in medulloblastoma tumor cells induced apoptosis, while proliferation and migration were inhibited in culture. In vivo, silencing TP73-AS1 in medulloblastoma tumor cells resulted in reduced tumor growth, reduced proliferation of tumor cells, increased apoptosis and led to prolonged survival of tumor-bearing mice. Together, our study suggests that the lncRNA TP73-AS1 is a prognostic marker and therapeutic target in medulloblastoma tumors and serves as a proof of concept that lncRNAs are important factors in the disease.

Zika virus infection induces MiR34c expression in glioblastoma stem cells: new perspectives for brain tumor treatments

Zika virus (ZIKV) is a flavivirus with a marked effect on fetal nervous system development. ZIKV treatment has recently been found to also have a benefit against glioblastoma, a highly aggressive brain tumor with a poor prognosis. The reported data do not completely explain the mechanism beyond this effect. Nevertheless, in the majority of the cases no adverse effect has been found in healthy adult humans. In this study, we characterized the ZIKV infection mechanism on glioblastoma stem cells, which are considered responsible for the tumor progression and resistance to conventional therapies. Moreover, we explain why the action of this virus is directed to the stem cells in the nervous system counterpart. Our results confirm the effectiveness of ZIKV treatment against glioblastoma, indicating novel molecular targets that can be introduced for more powerful therapies.

Cajal-Retzius neurons are required for the development of the human hippocampal fissure

Cajal-Retzius neurons (CRN) are the main source of Reelin in the marginal zone of the developing neocortex and hippocampus (HC). They also express the transcription factor p73 and are complemented by later-appearing GABAergic Reelin⁺ interneurons. The human dorsal HC forms at gestational week 10 (GW10), when it develops a rudimentary Ammonic plate and incipient dentate migration, although the dorsal hippocampal fissure (HF) remains shallow and contains few CRN. The dorsal HC transforms into the indusium griseum (IG), concurrently with the rostro-caudal appearance of the corpus callosum, by GW14-17. Dorsal and ventral HC merge at the site of the former caudal hem, which is located at the level of the future atrium of the lateral ventricle and closely connected with the choroid plexus. The ventral HC forms at GW11 in the temporal lobe. The ventral HF is wide open at GW14-16 and densely populated by large numbers of CRNs. These are in intimate contact with the meninges and meningeal blood vessels, suggesting signalling through diverse pathways. At GW17, the fissure deepens and begins to fuse, although it is still marked by p73/Reelin⁺ CRNs. The p73KO mouse illustrates the importance of p73 in CRN for HF formation. In the mutant, Tbr1/Reelin⁺ CRNs are born in the hem but do not leave it and subsequently disappear, so that the mutant cortex and HC lack CRN from the onset of corticogenesis. The HF is absent, which leads to profound architectonic alterations of the HC. To determine which p73 isoform is important for HF formation, isoform-specific TAp73- and DeltaNp73-deficient embryonic and early postnatal mice were examined. In both mutants, the number of CRNs was reduced, but each of their phenotypes was much milder than in the global p73KO mutant missing both isoforms. In the TAp73KO mice, the HF of the dorsal HC failed to form, but was present in the ventral HC. In the DeltaNp73KO mice, the HC had a mild patterning defect along with a shorter HF. Complex interactions between both isoforms in CRNs may contribute to their crucial activity in the developing brain.

Topoisomerase IIβ-binding protein 1 activates expression of E2F1 and p73 in HPV-positive cells for genome amplification upon epithelial differentiation

High-risk human papillomaviruses (HPVs) constitutively activate the ataxia telangiectasia mutated (ATM) and the ataxia telangiectasia and Rad3-related (ATR) DNA damage repair pathways for viral genome amplification. HPVs activate these pathways through the immune regulator STAT-5. For the ATR pathway, STAT-5 increases expression of the topoisomerase IIβ-binding protein 1 (TopBP1), a scaffold protein that binds ATR and recruits it to sites of DNA damage. TopBP1 also acts as a transcriptional regulator and we investigated how this activity influenced the HPV life cycle. We determined that TopBP1 levels are increased in cervical intraepithelial neoplasias as well as cervical carcinomas, consistent with studies in HPV-positive cell lines. Suppression of TopBP1 by shRNAs impairs HPV genome amplification and activation of the ATR pathway but does not affect the total levels of ATR and CHK1. In contrast, knockdown reduces the expression of other DNA damage factors such as RAD51 and Mre11 but not BRCA2 or NBS1. Interestingly, TopBP1 positively regulates the expression of E2F1, a TopBP1 binding partner, and p73, in HPV positive cells in contrast to effects in other cell types. TopBP1 transcriptional activity is regulated by AKT and treatment with AKT inhibitors suppresses expression of E2F1 and p73 without interfering with ATR signaling. Importantly, the levels of p73 are elevated in HPV-positive cells and knockdown impairs HPV genome amplification. This demonstrates that p73, like p63 and p53, is an important regulator of the HPV life cycle that is controlled by the transcriptional activating properties of the multifunctional TopBP1 protein.

Sustained protein synthesis and reduced eEF2K levels in TAp73-\- mice brain: a possible compensatory mechanism

The transcription factor p73 is a member of the p53 family, of which the transactivation domain containing isoform (TAp73) plays key roles in brain development and neuronal stem cells. TAp73 also facilitates homoeostasis and prevents oxidative damage in vivo by inducing the expression of its target genes. Recently, we found that in addition to its role in regulation of transcription, TAp73 also affects mRNA translation. In cultured cells, acute TAp73 depletion activates eEF2K, which phosphorylates eEF2 reducing mRNA translation elongation. As a consequence, there is a reduction in global proteins synthesis rates and reprogramming of the translatome, leading to a selective decrease in the translation of rRNA processing factors. Given the dramatic effects of Tap73 depletion in vitro it was important to determine whether similar effects were observed in vivo. Here, we report the surprising finding that in brains of TAp73 KO mice there is a reduced level of eEF2K, which allows protein synthesis rates to be maintained suggesting a compensation model. These data provide new insights to the role of TAp73 in translation regulation and the eEF2K pathway in the brain.

The p53 Family in Brain Disease

SIGNIFICANCE

The p53 family of transcription factors, including p53, p63, and p73, plays key roles in both biological and pathological processes, including cancer and neural development. Recent Advances: In recent years, a growing body of evidence has indicated that the entire p53 family is involved in the regulation of the central nervous system (CNS) functions as well as in the pathogenesis of several neurological disorders. Mechanistically, the p53 proteins control neuronal cell fate, terminal differentiation, and survival, via a complex interplay among the family members.

CRITICAL ISSUES

In this article, we discuss the involvement of the p53 family in neurobiology and in pathological conditions affecting the CNS, including neuroinflammation.

FUTURE DIRECTIONS

Understanding the molecular mechanism(s) underlying the function of the p53 family could improve our general knowledge of the pathogenesis of brain disorders and potentially pave the road for new therapeutic intervention. Antioxid. Redox Signal. 29, 1-14.

Integrin-β4 is a novel transcriptional target of TAp73

As a member of p53 family, p73 has attracted intense investigations due to its structural and functional similarities to p53. Among more than ten p73 variants, the transactivation (TA) domain-containing isoform TAp73 is the one that imitates the p53's behavior most. TAp73 induces apoptosis and cell cycle arrest, which endows it the capacity of tumour suppression. Also, it can exert diverse biological influences on cells through activating a complex and context dependent transcriptional programme. The transcriptional activities further broaden its roles in more intricate biological processes. In this article, we report that p73 is a positive regulator of a cell adhesion related gene named integrin β4 (ITGB4). This finding may have implications for the dissection of the biological mechanisms underlining p73 functions.

The hypoxic tumour microenvironment

Cancer progression often benefits from the selective conditions present in the tumour microenvironment, such as the presence of cancer-associated fibroblasts (CAFs), deregulated ECM deposition, expanded vascularisation and repression of the immune response. Generation of a hypoxic environment and activation of its main effector, hypoxia-inducible factor-1 (HIF-1), are common features of advanced cancers. In addition to the impact on tumour cell biology, the influence that hypoxia exerts on the surrounding cells represents a critical step in the tumorigenic process. Hypoxia indeed enables a number of events in the tumour microenvironment that lead to the expansion of aggressive clones from heterogeneous tumour cells and promote a lethal phenotype. In this article, we review the most relevant findings describing the influence of hypoxia and the contribution of HIF activation on the major components of the tumour microenvironment, and we summarise their role in cancer development and progression.

Metabolic pathways regulated by TAp73 in response to oxidative stress

Reactive oxygen species are involved in both physiological and pathological processes including neurodegeneration and cancer. Therefore, cells have developed scavenging mechanisms to maintain redox homeostasis under control. Tumor suppressor genes play a critical role in the regulation of antioxidant genes. Here, we investigated whether the tumor suppressor gene TAp73 is involved in the regulation of metabolic adaptations triggered in response to oxidative stress. H₂O₂ treatment resulted in numerous biochemical changes in both control and TAp73 knockout (TAp73−/−) mouse embryonic fibroblasts, however the extent of these changes was more pronounced in TAp73−/− cells when compared to control cells. In particular, loss of TAp73 led to alterations in glucose, nucleotide and amino acid metabolism. In addition, H₂O₂ treatment resulted in increased pentose phosphate pathway (PPP) activity in null mouse embryonic fibroblasts. Overall, our results suggest that in the absence of TAp73, H₂O₂ treatment results in an enhanced oxidative environment, and at the same time in an increased pro-anabolic phenotype. In conclusion, the metabolic profile observed reinforces the role of TAp73 as tumor suppressor and indicates that TAp73 exerts this function, at least partially, by regulation of cellular metabolism.

Fifty-Hertz Magnetic Field Affects the Epigenetic Modulation of the miR-34b/c in Neuronal Cells

The exposure to extremely low-frequency magnetic fields (ELF-MFs) has been associated to increased risk of neurodegenerative diseases, although the underlying molecular mechanisms are still undefined. Since epigenetic modulation has been recently encountered among the key events leading to neuronal degeneration, we here aimed at assessing if the control of gene expression mediated by miRNAs, namely miRs-34, has any roles in driving neuronal cell response to 50-Hz (1 mT) magnetic field in vitro. We demonstrate that ELF-MFs drive an early reduction of the expression level of miR-34b and miR-34c in SH-SY5Y human neuroblastoma cells, as well as in mouse primary cortical neurons, by affecting the transcription of the common pri-miR-34. This modulation is not p53 dependent, but attributable to the hyper-methylation of the CpG island mapping within the miR-34b/c promoter. Incubation with N-acetyl-l-cysteine or glutathione ethyl-ester fails to restore miR-34b/c expression, suggesting that miRs-34 are not responsive to ELF-MF-induced oxidative stress. By contrast, we show that miRs-34 control reactive oxygen species production and affect mitochondrial oxidative stress triggered by ELF-MFs, likely by modulating mitochondria-related miR-34 targets identified by in silico analysis. We finally demonstrate that ELF-MFs alter the expression of the α-synuclein, which is specifically stimulated upon ELF-MFs exposure via both direct miR-34 targeting and oxidative stress. Altogether, our data highlight the potential of the ELF-MFs to tune redox homeostasis and epigenetic control of gene expression in vitro and shed light on the possible mechanism(s) producing detrimental effects and predisposing neurons to degeneration.

p73 Regulates Primary Cortical Neuron Metabolism: a Global Metabolic Profile

The transcription factor p73 has been demonstrated to play a significant role in survival and differentiation of neuronal stem cells. In this report, by employing comprehensive metabolic profile and mitochondrial bioenergetics analysis, we have explored the metabolic alterations in cortical neurons isolated from p73 N-terminal isoform specific knockout animals. We found that loss of the TAp73 or ΔNp73 triggers selective biochemical changes. In particular, p73 isoforms regulate sphingolipid and phospholipid biochemical pathway signaling. Indeed, sphinganine and sphingosine levels were reduced in p73-depleted cortical neurons, and decreased levels of several membrane phospholipids were also observed. Moreover, in line with the complexity associated with p73 functions, loss of the TAp73 seems to increase glycolysis, whereas on the contrary, loss of ΔNp73 isoform reduces glucose metabolism, indicating an isoform-specific differential effect on glycolysis. These changes in glycolytic flux were not reflected by parallel alterations of mitochondrial respiration, as only a slight increase of mitochondrial maximal respiration was observed in p73-depleted cortical neurons. Overall, our findings reinforce the key role of p73 in regulating cellular metabolism and point out that p73 exerts its functions in neuronal biology at least partially through the regulation of metabolic pathways.

De novo missense variants in HECW2 are associated with neurodevelopmental delay and hypotonia

BACKGROUND

The causes of intellectual disability (ID) are diverse and de novo mutations are increasingly recognised to account for a significant proportion of ID.

METHODS AND RESULTS

In this study, we performed whole exome sequencing on a large cohort of patients with ID or neurodevelopmental delay and identified four novel de novo predicted deleterious missense variants in HECW2 in six probands with ID/developmental delay and hypotonia. Other common features include seizures, strabismus, nystagmus, cortical visual impairment and dysmorphic facial features. HECW2 is an ubiquitin ligase that stabilises p73, a crucial mediator of neurodevelopment and neurogenesis.

CONCLUSION

This study implicates pathogenic genetic variants in HECW2 as potential causes of neurodevelopmental disorders in humans.

P53 functional abnormality in mesenchymal stem cells promotes osteosarcoma development

It has been shown that p53 has a critical role in the differentiation and functionality of various multipotent progenitor cells. P53 mutations can lead to genome instability and subsequent functional alterations and aberrant transformation of mesenchymal stem cells (MSCs). The significance of p53 in safeguarding our body from developing osteosarcoma (OS) is well recognized. During bone remodeling, p53 has a key role in negatively regulating key factors orchestrating the early stages of osteogenic differentiation of MSCs. Interestingly, changes in the p53 status can compromise bone homeostasis and affect the tumor microenvironment. This review aims to provide a unique opportunity to study the p53 function in MSCs and OS. In the context of loss of function of p53, we provide a model for two sources of OS: MSCs as progenitor cells of osteoblasts and bone tumor microenvironment components. Standing at the bone remodeling point of view, in this review we will first explain the determinant function of p53 in OS development. We will then summarize the role of p53 in monitoring MSC fidelity and in regulating MSC differentiation programs during osteogenesis. Finally, we will discuss the importance of loss of p53 function in tissue microenvironment. We expect that the information provided herein could lead to better understanding and treatment of OS.