Dyrk1A phosphorylates p53 and inhibits proliferation of embryonic neuronal cells

DYRK1A roles in human neural progenitors

Introduction

Mutations in dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) represent one of the most prevalent monogenic causes of neurodevelopmental disorders (NDDs), often associated with intellectual developmental disorder and autism spectrum disorder. DYRK1A encodes a dual-specificity kinase (tyrosine and serine/threonine) that plays a key role in various cellular processes and is a critical regulator of nervous system development.

Methods

For the first time, we have characterized the DYRK1A interactome and study the consequences of DYRK1A depletion in human neural stem cells (hNSCs).

Results

We identified 35 protein partners of DYRK1A involved in essential pathways such as cell cycle regulation and DNA repair. Notably, five of these interactors are components of the anaphase-promoting complex (APC), and one is an additional ubiquitin ligase, RNF114 (also known as ZNF313), which is known to target p21. Many of these identified partners are also linked to other human NDDs, and several others (e.g., DCAF7 and GSPT1) may represent novel candidate genes for NDDs. DYRK1A knockdown (KD) in hNSCs using siRNA revealed changes in the expression of genes encoding proteins involved in extracellular matrix composition and calcium binding (e.g., collagens, TGFβ2 and UNC13A). While the majority of genes were downregulated following DYRK1A depletion, we observed an upregulation of early growth factors (EGR1 and EGR3), as well as E2F2 and its downstream targets. In addition, DYRK1A-KD led to a reduction in p21 protein levels, despite an increase in the expression of a minor transcript variant for this gene, and a decrease in ERK pathway activation.

Discussion

Together, the DYRK1A interactome in hNSCs and the gene expression changes induced by its depletion highlight the significant role of DYRK1A in regulating hNSC proliferation. Although the effects on various growth signaling pathways may appear contradictory, the overall impact is a marked reduction in hNSC proliferation. This research underscores the pivotal role of DYRK1A in neurodevelopment and identifies, among DYRK1A's protein partners and differentially expressed genes, potential novel candidate genes for NDDs and promising therapeutic targets for DYRK1A syndrome.

MicroRNA-298 determines the radio-resistance of colorectal cancer cells by directly targeting human dual-specificity tyrosine(Y)-regulated kinase 1A

BACKGROUND

Radiotherapy stands as a promising therapeutic modality for colorectal cancer (CRC); yet, the formidable challenge posed by radio-resistance significantly undermines its efficacy in achieving CRC remission.

AIM

To elucidate the role played by microRNA-298 (miR-298) in CRC radio-resistance.

METHODS

To establish a radio-resistant CRC cell line, HT-29 cells underwent exposure to 5 gray ionizing radiation that was followed by a 7-d recovery period. The quantification of miR-298 levels within CRC cells was conducted through quantitative RT-PCR, and protein expression determination was realized through Western blotting. Cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and proliferation by clonogenic assay. Radio-induced apoptosis was discerned through flow cytometry analysis.

RESULTS

We observed a marked upregulation of miR-298 in radio-resistant CRC cells. MiR-298 emerged as a key determinant of cell survival following radiation exposure, as its overexpression led to a notable reduction in radiation-induced apoptosis. Intriguingly, miR-298 expression exhibited a strong correlation with CRC cell viability. Further investigation unveiled human dual-specificity tyrosine(Y)-regulated kinase 1A (DYRK1A) as miR-298's direct target.

CONCLUSION

Taken together, our findings underline the role played by miR-298 in bolstering radio-resistance in CRC cells by means of DYRK1A downregulation, thereby positioning miR-298 as a promising candidate for mitigating radio-resistance in CRC.

From Churchill to Elephants: The Role of Protective Genes against Cancer

Richard Peto's paradox, first described in 1975 from an epidemiological perspective, established an inverse correlation between the probability of developing cancer in multicellular organisms and the number of cells. Larger animals exhibit fewer tumors compared to smaller ones, though exceptions exist. Mice are more susceptible to cancer than humans, while elephants and whales demonstrate significantly lower cancer prevalence rates than humans. How nature and evolution have addressed the issue of cancer in the animal kingdom remains largely unexplored. In the field of medicine, much attention has been devoted to cancer-predisposing genes, as they offer avenues for intervention, including blocking, downregulating, early diagnosis, and targeted treatment. Predisposing genes also tend to manifest clinically earlier and more aggressively, making them easier to identify. However, despite significant strides in modern medicine, the role of protective genes lags behind. Identifying genes with a mild predisposing effect poses a significant challenge. Consequently, comprehending the protective function conferred by genes becomes even more elusive, and their very existence is subject to questioning. While the role of variable expressivity and penetrance defects of the same variant in a family is well-documented for many hereditary cancer syndromes, attempts to delineate the function of protective/modifier alleles have been restricted to a few instances. In this review, we endeavor to elucidate the role of protective genes observed in the animal kingdom, within certain genetic syndromes that appear to act as cancer-resistant/repressor alleles. Additionally, we explore the role of protective alleles in conditions predisposing to cancer. The ultimate goal is to discern why individuals, like Winston Churchill, managed to live up to 91 years of age, despite engaging in minimal physical activity, consuming large quantities of alcohol daily, and not abstaining from smoking.

Sex-specific developmental alterations in DYRK1A expression in the brain of a Down syndrome mouse model

Aberrant neurodevelopment in Down syndrome (DS)-caused by triplication of human chromosome 21-is commonly attributed to gene dosage imbalance, linking overexpression of trisomic genes with disrupted developmental processes, with DYRK1A particularly implicated. We hypothesized that regional brain DYRK1A protein overexpression in trisomic mice varies over development in sex-specific patterns that may be distinct from Dyrk1a transcription, and reduction of Dyrk1a copy number from 3 to 2 in otherwise trisomic mice reduces DYRK1A, independent of other trisomic genes. DYRK1A overexpression varied with age, sex, and brain region, with peak overexpression on postnatal day (P) 6 in both sexes. Sex-dependent differences were also evident from P15-P24. Reducing Dyrk1a copy number confirmed that these differences depended on Dyrk1a gene dosage and not other trisomic genes. Trisomic Dyrk1a mRNA and protein expression were not highly correlated. Sex-specific patterns of DYRK1A overexpression during trisomic neurodevelopment may provide mechanistic targets for therapeutic intervention in DS.

Effects of small molecules on neurogenesis: Neuronal proliferation and differentiation

Neurons are believed to be non-proliferating cells. However, neuronal stem cells are still present in certain areas of the adult brain, although their proliferation diminishes with age. Just as with other cells, their proliferation and differentiation are modulated by various mechanisms. These mechanisms are foundational to the strategies developed to induce neuronal proliferation and differentiation, with potential therapeutic applications for neurodegenerative diseases. The most common among these diseases are Parkinson's disease and Alzheimer's disease, associated with the formation of β -amyloid (Aβ ) aggregates which cause a reduction in the number of neurons. Compounds such as LiCl, 4-aminothiazoles, Pregnenolone, ACEA, harmine, D2AAK1, methyl 3,4-dihydroxybenzoate, and shikonin may induce neuronal proliferation/differentiation through the activation of pathways: MAPK ERK, PI3K/AKT, NFκ B, Wnt, BDNF, and NPAS3. Moreover, combinations of these compounds can potentially transform somatic cells into neurons. This transformation process involves the activation of neuron-specific transcription factors such as NEUROD1, NGN2, ASCL1, and SOX2, which subsequently leads to the transcription of downstream genes, culminating in the transformation of somatic cells into neurons. Neurodegenerative diseases are not the only conditions where inducing neuronal proliferation could be beneficial. Consequently, the impact of pro-proliferative compounds on neurons has also been researched in mouse models of Alzheimer's disease.

Regulation of CMGC kinases by hypoxia

Hypoxia, a widespread occurrence observed in various malignant tumors, results from rapid tumor growth that outpaces the oxygen supply. Tumor hypoxia precipitates several effects on tumor biology; these include activating angiogenesis, intensifying invasiveness, enhancing the survival of tumor cells, suppressing anti-tumor immunity, and fostering resistance to therapy. Aligned with the findings that correlate CMGC kinases with the regulation of Hypoxia-Inducible Factor (HIF), a pivotal modulator, reports also indicate that hypoxia governs the activity of CMGC kinases, including DYRK1 kinases. Prolyl hydroxylation of DYRK1 kinases by PHD1 constitutes a novel mechanism of kinase maturation and activation. This modification "primes" DYRK1 kinases for subsequent tyrosine autophosphorylation, a vital step in their activation cascade. This mechanism adds a layer of intricacy to comprehending the regulation of CMGC kinases, and underscores the complex interplay between distinct post-translational modifications in harmonizing precise kinase activity. Overall, hypoxia assumes a substantial role in cancer progression, influencing diverse aspects of tumor biology that include angiogenesis, invasiveness, cell survival, and resistance to treatment. CMGC kinases are deeply entwined in its regulation. To fathom the molecular mechanisms underpinning hypoxia's impact on cancer cells, comprehending how hypoxia and prolyl hydroxylation govern the activity of CMGC kinases, including DYRK1 kinases, becomes imperative. This insight may pave the way for pioneering therapeutic approaches that target the hypoxic tumor microenvironment and its associated challenges. [BMB Reports 2023; 56(11): 584-593].

Insights from the protein interaction Universe of the multifunctional "Goldilocks" kinase DYRK1A

Human Dual specificity tyrosine (Y)-Regulated Kinase 1A (DYRK1A) is encoded by a dosage-dependent gene located in the Down syndrome critical region of human chromosome 21. The known substrates of DYRK1A include proteins involved in transcription, cell cycle control, DNA repair and other processes. However, the function and regulation of this kinase is not fully understood, and the current knowledge does not fully explain the dosage-dependent function of this kinase. Several recent proteomic studies identified DYRK1A interacting proteins in several human cell lines. Interestingly, several of known protein substrates of DYRK1A were undetectable in these studies, likely due to a transient nature of the kinase-substrate interaction. It is possible that the stronger-binding DYRK1A interacting proteins, many of which are poorly characterized, are involved in regulatory functions by recruiting DYRK1A to the specific subcellular compartments or distinct signaling pathways. Better understanding of these DYRK1A-interacting proteins could help to decode the cellular processes regulated by this important protein kinase during embryonic development and in the adult organism. Here, we review the current knowledge of the biochemical and functional characterization of the DYRK1A protein-protein interaction network and discuss its involvement in human disease.

Functions of SRPK, CLK and DYRK kinases in stem cells, development, and human developmental disorders

Human developmental disorders encompass a wide range of debilitating physical conditions and intellectual disabilities. Perturbation of protein kinase signalling underlies the development of some of these disorders. For example, disrupted SRPK signalling is associated with intellectual disabilities, and the gene dosage of DYRKs can dictate the pathology of disorders including Down's syndrome. Here, we review the emerging roles of the CMGC kinase families SRPK, CLK, DYRK, and sub-family HIPK during embryonic development and in developmental disorders. In particular, SRPK, CLK, and DYRK kinase families have key roles in developmental signalling and stem cell regulation, and can co-ordinate neuronal development and function. Genetic studies in model organisms reveal critical phenotypes including embryonic lethality, sterility, musculoskeletal errors, and most notably, altered neurological behaviours arising from defects of the neuroectoderm and altered neuronal signalling. Further unpicking the mechanisms of specific kinases using human stem cell models of neuronal differentiation and function will improve our understanding of human developmental disorders and may provide avenues for therapeutic strategies.

Maintaining Genome Integrity: Protein Kinases and Phosphatases Orchestrate the Balancing Act of DNA Double-Strand Breaks Repair in Cancer

DNA double-strand breaks (DSBs) are the most lethal DNA damages which lead to severe genome instability. Phosphorylation is one of the most important protein post-translation modifications involved in DSBs repair regulation. Kinases and phosphatases play coordinating roles in DSB repair by phosphorylating and dephosphorylating various proteins. Recent research has shed light on the importance of maintaining a balance between kinase and phosphatase activities in DSB repair. The interplay between kinases and phosphatases plays an important role in regulating DNA-repair processes, and alterations in their activity can lead to genomic instability and disease. Therefore, study on the function of kinases and phosphatases in DSBs repair is essential for understanding their roles in cancer development and therapeutics. In this review, we summarize the current knowledge of kinases and phosphatases in DSBs repair regulation and highlight the advancements in the development of cancer therapies targeting kinases or phosphatases in DSBs repair pathways. In conclusion, understanding the balance of kinase and phosphatase activities in DSBs repair provides opportunities for the development of novel cancer therapeutics.

DYRK1A promotes viral entry of highly pathogenic human coronaviruses in a kinase-independent manner

Identifying host genes essential for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has the potential to reveal novel drug targets and further our understanding of Coronavirus Disease 2019 (COVID-19). We previously performed a genome-wide CRISPR/Cas9 screen to identify proviral host factors for highly pathogenic human coronaviruses. Few host factors were required by diverse coronaviruses across multiple cell types, but DYRK1A was one such exception. Although its role in coronavirus infection was previously undescribed, DYRK1A encodes Dual Specificity Tyrosine Phosphorylation Regulated Kinase 1A and is known to regulate cell proliferation and neuronal development. Here, we demonstrate that DYRK1A regulates ACE2 and DPP4 transcription independent of its catalytic kinase function to support SARS-CoV, SARS-CoV-2, and Middle East Respiratory Syndrome Coronavirus (MERS-CoV) entry. We show that DYRK1A promotes DNA accessibility at the ACE2 promoter and a putative distal enhancer, facilitating transcription and gene expression. Finally, we validate that the proviral activity of DYRK1A is conserved across species using cells of nonhuman primate and human origin. In summary, we report that DYRK1A is a novel regulator of ACE2 and DPP4 expression that may dictate susceptibility to multiple highly pathogenic human coronaviruses.

The Conserved Transcriptional Activation Activity Identified in Dual-Specificity Tyrosine-(Y)-Phosphorylation-Regulated Kinase 1

Dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1 (DYRK1) encodes a conserved protein kinase that is indispensable to neuron development. However, whether DYRK1 possesses additional functions apart from kinase function remains poorly understood. In this study, we firstly demonstrated that the C-terminal of ascidian Ciona robusta DYRK1 (CrDYRK1) showed transcriptional activation activity independent of its kinase function. The transcriptional activation activity of CrDYRK1 could be autoinhibited by a repression domain in the N-terminal. More excitingly, both activation and repression domains were retained in HsDYRK1A in humans. The genes, activated by the activation domain of HsDYRK1A, are mainly involved in ion transport and neuroactive ligand-receptor interaction. We further found that numerous mutation sites relevant to the DYRK1A-related intellectual disability syndrome locate in the C-terminal of HsDYRK1A. Then, we identified several specific DNA motifs in the transcriptional regulation region of those activated genes. Taken together, we identified a conserved transcription activation domain in DYRK1 in urochordates and vertebrates. The activation is independent of the kinase activity of DYRK1 and can be repressed by its own N-terminal. Transcriptome and mutation data indicate that the transcriptional activation ability of HsDYRK1A is potentially involved in synaptic transmission and neuronal function related to the intellectual disability syndrome.

A transcription factor atlas of directed differentiation

Transcription factors (TFs) regulate gene programs, thereby controlling diverse cellular processes and cell states. To comprehensively understand TFs and the programs they control, we created a barcoded library of all annotated human TF splice isoforms (>3,500) and applied it to build a TF Atlas charting expression profiles of human embryonic stem cells (hESCs) overexpressing each TF at single-cell resolution. We mapped TF-induced expression profiles to reference cell types and validated candidate TFs for generation of diverse cell types, spanning all three germ layers and trophoblasts. Targeted screens with subsets of the library allowed us to create a tailored cellular disease model and integrate mRNA expression and chromatin accessibility data to identify downstream regulators. Finally, we characterized the effects of combinatorial TF overexpression by developing and validating a strategy for predicting combinations of TFs that produce target expression profiles matching reference cell types to accelerate cellular engineering efforts.

The Omnipresence of DYRK1A in Human Diseases

The increasing population will challenge healthcare, particularly because the worldwide population has never been older. Therapeutic solutions to age-related disease will be increasingly critical. Kinases are key regulators of human health and represent promising therapeutic targets for novel drug candidates. The dual-specificity tyrosine-regulated kinase (DYRKs) family is of particular interest and, among them, DYRK1A has been implicated ubiquitously in varied human diseases. Herein, we focus on the characteristics of DYRK1A, its regulation and functional role in different human diseases, which leads us to an overview of future research on this protein of promising therapeutic potential.

Inhibition of Dyrk1A Attenuates LPS-Induced Neuroinflammation via the TLR4/NF-κB P65 Signaling Pathway

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (Dyrk1A) is a highly conserved protein kinase, playing a key role in the regulation of physiological brain functions and pathological processes. In Alzheimer's disease (AD), Dyrk1A promotes hyperphosphorylation of tau protein and abnormal aggregation of amyloid-β protein (Aβ). This study investigated the role of Dyrk1A in regulating neuroinflammation, another critical factor that contributes to AD. In the present study, we used an immortalized murine BV2 microglia cell line induced by lipopolysaccharide (LPS) to study neuroinflammation. The expression and activity of Dyrk1A kinase were both increased by inflammation. Dyrk1A inhibition using harmine or siRNA silencing significantly reduced the production of proinflammatory factors in LPS-stimulated BV2 cells. Reactive oxygen species (ROS), tumor necrosis factor-α (TNF-α), and nitric oxide (NO), as well as the expression of the inflammatory proteins, cyclooxygenase 2 (COX2), and inducible nitric synthase (iNOS), were attenuated. In vivo, in ICR mice injected with LPS into the left lateral cerebral ventricle, harmine (20 mg/kg) administration decreased the expression of inflammatory proteins in the cortex and hippocampus of mice brain. In addition, immunohistochemical detection of ionized calcium-binding adapter molecule 1 (Iba1) and Nissl staining showed that harmine significantly attenuated microglia activation and neuronal damage in the CA1 region of hippocampus. Further mechanistic studies indicated that Dyrk1A suppression may be related to inhibition of the TLR4/NF-κB signaling pathway in LPS-induced neuroinflammation. Taken together, our studies suggest that Dyrk1A may be a novel target for the treatment of neurodegenerative diseases with an inflammatory component.

The Challenging Pathway of Treatment for Neurogenesis Impairment in Down Syndrome: Achievements and Perspectives

Down syndrome (DS), also known as trisomy 21, is a genetic disorder caused by triplication of Chromosome 21. Gene triplication may compromise different body functions but invariably impairs intellectual abilities starting from infancy. Moreover, after the fourth decade of life people with DS are likely to develop Alzheimer’s disease. Neurogenesis impairment during fetal life stages and dendritic pathology emerging in early infancy are thought to be key determinants of alterations in brain functioning in DS. Although the progressive improvement in medical care has led to a notable increase in life expectancy for people with DS, there are currently no treatments for intellectual disability. Increasing evidence in mouse models of DS reveals that pharmacological interventions in the embryonic and neonatal periods may greatly benefit brain development and cognitive performance. The most striking results have been obtained with pharmacotherapies during embryonic life stages, indicating that it is possible to pharmacologically rescue the severe neurodevelopmental defects linked to the trisomic condition. These findings provide hope that similar benefits may be possible for people with DS. This review summarizes current knowledge regarding (i) the scope and timeline of neurogenesis (and dendritic) alterations in DS, in order to delineate suitable windows for treatment; (ii) the role of triplicated genes that are most likely to be the key determinants of these alterations, in order to highlight possible therapeutic targets; and (iii) prenatal and neonatal treatments that have proved to be effective in mouse models, in order to rationalize the choice of treatment for human application. Based on this body of evidence we will discuss prospects and challenges for fetal therapy in individuals with DS as a potential means of drastically counteracting the deleterious effects of gene triplication.

The chromosome 21 kinase DYRK1A: emerging roles in cancer biology and potential as a therapeutic target

Dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) is a serine/threonine kinase that belongs to the DYRK family of proteins, a subgroup of the evolutionarily conserved CMGC protein kinase superfamily. Due to its localization on chromosome 21, the biological significance of DYRK1A was initially characterized in the pathogenesis of Down syndrome (DS) and related neurodegenerative diseases. However, increasing evidence has demonstrated a prominent role in cancer through its ability to regulate biologic processes including cell cycle progression, DNA damage repair, transcription, ubiquitination, tyrosine kinase activity, and cancer stem cell maintenance. DYRK1A has been identified as both an oncogene and tumor suppressor in different models, underscoring the importance of cellular context in its function. Here, we review mechanistic contributions of DYRK1A to cancer biology and its role as a potential therapeutic target.

A reassessment of Jackson's checklist and identification of two Down syndrome sub-phenotypes

Down syndrome (DS) is characterised by several clinical features including intellectual disability (ID) and craniofacial dysmorphisms. In 1976, Jackson and coll. identified a checklist of signs for clinical diagnosis of DS; the utility of these checklists in improving the accuracy of clinical diagnosis has been recently reaffirmed, but they have rarely been revised. The purpose of this work is to reassess the characteristic phenotypic signs and their frequencies in 233 DS subjects, following Jackson's checklist. 63.77% of the subjects showed more than 12 signs while none showed less than 5, confirming the effectiveness of Jackson's checklist for the clinical diagnosis of DS. An association between three phenotypic signs emerged, allowing us to distinguish two sub-phenotypes: Brachycephaly, short and broad Hands, short Neck (BHN), which is more frequent, and "non-BHN". The strong association of these signs might be interpreted in the context of the growth defects observed in DS children suggesting decreased cell proliferation. Lastly, cognitive assessments were investigated for 114 subjects. The lack of association between the presence of a physical sign or the number of signs present in a subject and cognitive skills disproves the stereotype that physical characteristics are predictive of degree of ID.

Novel and Potential Small Molecule Scaffolds as DYRK1A Inhibitors by Integrated Molecular Docking-Based Virtual Screening and Dynamics Simulation Study

The dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a novel, promising and emerging biological target for therapeutic intervention in neurodegenerative diseases, especially in Alzheimer's disease (AD). The molMall database, comprising rare, diverse and unique compounds, was explored for molecular docking-based virtual screening against the DYRK1A protein, in order to find out potential inhibitors. Ligands exhibiting hydrogen bond interactions with key amino acid residues such as Ile165, Lys188 (catalytic), Glu239 (gk+1), Leu241 (gk+3), Ser242, Asn244, and Asp307, of the target protein, were considered potential ligands. Hydrogen bond interactions with Leu241 (gk+3) were considered key determinants for the selection. High scoring structures were also docked by Glide XP docking in the active sites of twelve DYRK1A related protein kinases, viz. DYRK1B, DYRK2, CDK5/p25, CK1, CLK1, CLK3, GSK3β, MAPK2, MAPK10, PIM1, PKA, and PKCα, in order to find selective DYRK1A inhibitors. MM/GBSA binding free energies of selected ligand-protein complexes were also calculated in order to remove false positive hits. Physicochemical and pharmacokinetic properties of the selected six hit ligands were also computed and related with the proposed limits for orally active CNS drugs. The computational toxicity webserver ProTox-II was used to predict the toxicity profile of selected six hits (molmall IDs 9539, 11352, 15938, 19037, 21830 and 21878). The selected six docked ligand-protein systems were exposed to 100 ns molecular dynamics (MD) simulations to validate their mechanism of interactions and stability in the ATP pocket of human DYRK1A kinase. All six ligands were found to be stable in the ATP binding pocket of DYRK1A kinase.

Discovery of novel 6-hydroxybenzothiazole urea derivatives as dual Dyrk1A/α-synuclein aggregation inhibitors with neuroprotective effects

A role of Dyrk1A in the progression of Down syndrome-related Alzheimer's disease (AD) is well supported. However, the involvement of Dyrk1A in the pathogenesis of Parkinson's disease (PD) was much less studied, and it is not clear whether it would be promising to test Dyrk1A inhibitors in relevant PD models. Herein, we modified our previously published 1-(6-hydroxybenzo[d]thiazol-2-yl)-3-phenylurea scaffold of Dyrk1A inhibitors to obtain a new series of analogues with higher selectivity for Dyrk1A on the one hand, but also with a novel, additional activity as inhibitors of α-synuclein (α-syn) aggregation, a major pathogenic hallmark of PD. The phenyl acetamide derivative b27 displayed the highest potency against Dyrk1A with an IC50 of 20 nM and high selectivity over closely related kinases. Furthermore, b27 was shown to successfully target intracellular Dyrk1A and to inhibit SF3B1 phosphorylation in HeLa cells with an IC50 of 690 nM. In addition, two compounds among the Dyrk1A inhibitors, b1 and b20, also suppressed the aggregation of α-synuclein (α-syn) oligomers (with IC50 values of 10.5 μM and 7.8 μM, respectively). Both compounds but not the Dyrk1A reference inhibitor harmine protected SH-SY5Y neuroblastoma cells against α-syn-induced cytotoxicity, with b20 exhibiting a higher neuroprotective effect. Compound b1 and harmine were more efficient in protecting SH-SY5Y cells against 6-hydroxydopamine-induced cell death, an effect that was previously correlated to Dyrk1A inactivation in cells but not yet verified using chemical inhibitors. The presented dual inhibitors exhibited a novel activity profile encouraging for further testing in neurodegenerative disease models.

Dyrk1a from Gene Function in Development and Physiology to Dosage Correction across Life Span in Down Syndrome

Down syndrome is the main cause of intellectual disabilities with a large set of comorbidities from developmental origins but also that appeared across life span. Investigation of the genetic overdosage found in Down syndrome, due to the trisomy of human chromosome 21, has pointed to one main driver gene, the Dual-specificity tyrosine-regulated kinase 1A (Dyrk1a). Dyrk1a is a murine homolog of the drosophila minibrain gene. It has been found to be involved in many biological processes during development and in adulthood. Further analysis showed its haploinsufficiency in mental retardation disease 7 and its involvement in Alzheimer's disease. DYRK1A plays a role in major developmental steps of brain development, controlling the proliferation of neural progenitors, the migration of neurons, their dendritogenesis and the function of the synapse. Several strategies targeting the overdosage of DYRK1A in DS with specific kinase inhibitors have showed promising evidence that DS cognitive conditions can be alleviated. Nevertheless, providing conditions for proper temporal treatment and to tackle the neurodevelopmental and the neurodegenerative aspects of DS across life span is still an open question.

Discovery of Hydroxybenzothiazole Urea Compounds as Multitargeted Agents Suppressing Major Cytotoxic Mechanisms in Neurodegenerative Diseases

Multiple factors are causally responsible and/or contribute to the progression of Alzheimer's and Parkinson's diseases. The protein kinase Dyrk1A was identified as a promising target as it phosphorylates tau protein, α-synuclein, and parkin. The first goal of our study was to optimize our previously identified Dyrk1A inhibitors of the 6-hydroxy benzothiazole urea chemotype in terms of potency and selectivity. Our efforts led to the development of the 3-fluorobenzyl amide derivative 16b, which displayed the highest potency against Dyrk1A (IC₅₀ = 9.4 nM). In general, the diversification of the benzylamide moiety led to an enhanced selectivity over the most homologous isoform, Dyrk1B, which was a meaningful indicator, as the high selectivity could be confirmed in an extended selectivity profiling of 3b and 16b. Eventually, we identified the novel phenethyl amide derivative 24b as a triple inhibitor of Dyrk1A kinase activity (IC₅₀ = 119 nM) and the aggregation of tau and α-syn oligomers. We provide evidence that the novel combination of selective Dyrk1A inhibition and suppression of tau and α-syn aggregations of our new lead compound confers efficacy in several established cellular models of neurotoxic mechanisms relevant to neurodegenerative diseases, including α-syn- and 6-hydroxydopamine-induced cytotoxicities.

Almost famous: Human adenoviruses (and what they have taught us about cancer)

Papillomaviruses, polyomaviruses and adenoviruses are collectively categorized as the small DNA tumour viruses. Notably, human adenoviruses were the first human viruses demonstrated to be able to cause cancer, albeit in non-human animal models. Despite their long history, no human adenovirus is a known causative agent of human cancers, unlike a subset of their more famous cousins, including human papillomaviruses and human Merkel cell polyomavirus. Nevertheless, seminal research using human adenoviruses has been highly informative in understanding the basics of cell cycle control, gene expression, apoptosis and cell differentiation. This review highlights the contributions of human adenovirus research in advancing our knowledge of the molecular basis of cancer.

Dyrk1a Mutations Cause Undergrowth of Cortical Pyramidal Neurons via Dysregulated Growth Factor Signaling

BACKGROUND

Mutations in DYRK1A are a cause of microcephaly, autism spectrum disorder, and intellectual disability; however, the underlying cellular and molecular mechanisms are not well understood.

METHODS

We generated a conditional mouse model using Emx1-cre, including conditional heterozygous and homozygous knockouts, to investigate the necessity of Dyrk1a in the cortex during development. We used unbiased, high-throughput phosphoproteomics to identify dysregulated signaling mechanisms in the developing Dyrk1a mutant cortex as well as classic genetic modifier approaches and pharmacological therapeutic intervention to rescue microcephaly and neuronal undergrowth caused by Dyrk1a mutations.

RESULTS

We found that cortical deletion of Dyrk1a in mice causes decreased brain mass and neuronal size, structural hypoconnectivity, and autism-relevant behaviors. Using phosphoproteomic screening, we identified growth-associated signaling cascades dysregulated upon Dyrk1a deletion, including TrkB-BDNF (tyrosine receptor kinase B-brain-derived neurotrophic factor), an important regulator of ERK/MAPK (extracellular signal-regulated kinase/mitogen-activated protein kinase) and mTOR (mammalian target of rapamycin) signaling. Genetic suppression of Pten or pharmacological treatment with IGF-1 (insulin-like growth factor-1), both of which impinge on these signaling cascades, rescued microcephaly and neuronal undergrowth in neonatal mutants.

CONCLUSIONS

Altogether, these findings identify a previously unknown mechanism through which Dyrk1a mutations disrupt growth factor signaling in the developing brain, thus influencing neuronal growth and connectivity. Our results place DYRK1A as a critical regulator of a biological pathway known to be dysregulated in humans with autism spectrum disorder and intellectual disability. In addition, these data position Dyrk1a within a larger group of autism spectrum disorder/intellectual disability risk genes that impinge on growth-associated signaling cascades to regulate brain size and connectivity, suggesting a point of convergence for multiple autism etiologies.

GSK-3β, FYN, and DYRK1A: Master Regulators in Neurodegenerative Pathways

Protein kinases (PKs) have been recognized as central nervous system (CNS)-disease-relevant targets due to their master regulatory role in different signal transduction cascades in the neuroscience space. Among them, GSK-3β, FYN, and DYRK1A play a crucial role in the neurodegeneration context, and the deregulation of all three PKs has been linked to different CNS disorders with unmet medical needs, including Alzheimer's disease (AD), Parkinson's disease (PD), frontotemporal lobar degeneration (FTLD), and several neuromuscular disorders. The multifactorial nature of these diseases, along with the failure of many advanced CNS clinical trials, and the lengthy approval process of a novel CNS drug have strongly limited the CNS drug discovery. However, in the near-decade from 2010 to 2020, several computer-assisted drug design strategies have been combined with synthetic efforts to develop potent and selective GSK-3β, FYN, and DYRK1A inhibitors as disease-modifying agents. In this review, we described both structural and functional aspects of GSK-3β, FYN, and DYRK1A and their involvement and crosstalk in different CNS pathological signaling pathways. Moreover, we outlined attractive medicinal chemistry approaches including multi-target drug design strategies applied to overcome some limitations of known PKs inhibitors and discover improved modulators with suitable blood-brain barrier (BBB) permeability and drug-like properties.

Human Beta Cell Regenerative Drug Therapy for Diabetes: Past Achievements and Future Challenges

A quantitative deficiency of normally functioning insulin-producing pancreatic beta cells is a major contributor to all common forms of diabetes. This is the underlying premise for attempts to replace beta cells in people with diabetes by pancreas transplantation, pancreatic islet transplantation, and transplantation of beta cells or pancreatic islets derived from human stem cells. While progress is rapid and impressive in the beta cell replacement field, these approaches are expensive, and for transplant approaches, limited by donor organ availability. For these reasons, beta cell replacement will not likely become available to the hundreds of millions of people around the world with diabetes. Since the large majority of people with diabetes have some residual beta cells in their pancreata, an alternate approach to reversing diabetes would be developing pharmacologic approaches to induce these residual beta cells to regenerate and expand in a way that also permits normal function. Unfortunately, despite the broad availability of multiple classes of diabetes drugs in the current diabetes armamentarium, none has the ability to induce regeneration or expansion of human beta cells. Development of such drugs would be transformative for diabetes care around the world. This picture has begun to change. Over the past half-decade, a novel class of beta cell regenerative small molecules has emerged: the DYRK1A inhibitors. Their emergence has tremendous potential, but many areas of uncertainty and challenge remain. In this review, we summarize the accomplishments in the world of beta cell regenerative drug development and summarize areas in which most experts would agree. We also outline and summarize areas of disagreement or lack of unanimity, of controversy in the field, of obstacles to beta cell regeneration, and of challenges that will need to be overcome in order to establish human beta cell regenerative drug therapeutics as a clinically viable class of diabetes drugs.

A human isogenic iPSC-derived cell line panel identifies major regulators of aberrant astrocyte proliferation in Down syndrome

Astrocytes exert adverse effects on the brains of individuals with Down syndrome (DS). Although a neurogenic-to-gliogenic shift in the fate-specification step has been reported, the mechanisms and key regulators underlying the accelerated proliferation of astrocyte precursor cells (APCs) in DS remain elusive. Here, we established a human isogenic cell line panel based on DS-specific induced pluripotent stem cells, the XIST-mediated transcriptional silencing system in trisomic chromosome 21, and genome/chromosome-editing technologies to eliminate phenotypic fluctuations caused by genetic variation. The transcriptional responses of genes observed upon XIST induction and/or downregulation are not uniform, and only a small subset of genes show a characteristic expression pattern, which is consistent with the proliferative phenotypes of DS APCs. Comparative analysis and experimental verification using gene modification reveal dose-dependent proliferation-promoting activity of DYRK1A and PIGP on DS APCs. Our collection of human isogenic cell lines provides a comprehensive set of cellular models for further DS investigations.

Keiji Kawatani et al. developed a panel of Down syndrome (DS) isogenic astrocytes derived from iPSCs to observe the consequence of DS on astrocyte precursor proliferation, differentiation, and gene expression. Their results suggest a dose-dependent effect of DYRK1A and PIGP on DS-derived astrocyte precursor proliferation, and represent a valuable resource and cellular model for future DS research.

Hippocampal miR-211-5p regulates neurogenesis and depression-like behaviors in the rat

Emerging evidence has shown that microRNAs (miRNAs) contribute to the pathogenesis of depression, a potentially life-threatening and disabling mental disorder caused by the interaction of genetic and environmental factors. However, the specific miRNAs and their underlying molecular mechanisms as involved in the pathogenesis and development of depression remain largely unknown. In the present study, we screened miRNA expression profiles and found that miR-211-5p was significantly down-regulated within the dentate gyrus (DG) hippocampus in the chronic unpredictable mild stress (CUMS) induced rat model of depression. Deficits in miR-211-5p were accompanied with reductions in neurogenesis and increased apoptosis in these CUMS rats. In contrast, an up-regulation of miR-211-5p within the DG area in CUMS rats promoted neuronal neurogenesis, reduced neuronal apoptosis via suppression of the Dyrk1A/STAT3 signaling pathway and relieved depression-like behaviors in these CUMS rats. In rats subjected to a knock-down of miR-211-5p in the DG there was an increase in neuronal apoptosis and a decrease in neuronal regeneration, effects which were accompanied with an induction of depression-like behaviors. Taken together, the results of our study reveal that altered levels of miR-211-5p in the hippocampal DG area exert a significant impact on neurogenesis, apoptosis and thus depression-like behaviors in rats. These findings suggest that the miR-211-5p/Dyrk1A pathway plays an important role in the pathogenesis of depression and may serve as a potential therapeutic target for the treatment of depression.

Epigallocatechin-3-gallate inhibits the growth of three-dimensional in vitro models of neuroblastoma cell SH-SY5Y

The aim of the study is to investigate the potential of using three-dimensional (3D) in vitro neuroblastoma models to mimic the neuroblastoma microenvironment by testing a potential therapeutic compound—the natural extract epigallocatechin-3-gallate (EGCG), and to further elucidate the roles of DYRK1A in the growth and differentiation of neuroblastoma tissue. In vitro models based on a classic neuroblastoma cell line SH-SY5Y were employed, including 3D models with extracellular matrix and co-cultured with vascular endothelial cells. Cell viability was tested using AlamarBlue and Resazurin assay. The growth and differentiation of in vitro models of SH-SY5Y were analysed based on microscopy images obtained from immunofluorescence or real-time imaging. Protein expression level was investigated using immunoblotting analysis. The two-dimensional (2D) in vitro model implies the cytotoxicity and DYRK1A inhibition effect of EGCG and shows the induction of neuronal differentiation marker TuJ1. 3D in vitro models suggest that EGCG treatment compromised the growth of SH-SY5Y multicellular 3D spheroids and the viability of SH-SY5Y cultured in 3D Matrigel matrix. In addition, co-culture of SH-SY5Y with human vascular umbilical vein endothelial cells implied the inhibitory effects by EGCG in a vascularised microenvironment. In this study, novel 3D in vitro models of neuroblastoma were established in the application of testing a potential anti-cancer candidate compound EGCG. In pursuit of the goals of the 3Rs (replacement, reduction and refinement), the usage of these 3D in vitro models has the potential to reduce and eventually replace current animal models used in neuroblastoma research. The DYRK1A inhibiting nature of EGCG, together with the facts that EGCG inhibits the growth and induces the differentiation of neuroblastoma in vitro models, suggests an oncogene role of DRYK1A.

Protein phosphatase PPM1B inhibits DYRK1A kinase through dephosphorylation of pS258 and reduces toxic tau aggregation

Down syndrome (DS) is mainly caused by an extra copy of chromosome 21 (trisomy 21), and patients display a variety of developmental symptoms, including characteristic facial features, physical growth delay, intellectual disability, and neurodegeneration (i.e., Alzheimer's disease; AD). One of the pathological hallmarks of AD is insoluble deposits of neurofibrillary tangles (NFTs) that consist of hyperphosphorylated tau. The human DYRK1A gene is mapped to chromosome 21, and the protein is associated with the formation of inclusion bodies in AD. For example, DYRK1A directly phosphorylates multiple serine and threonine residues of tau, including Thr212. However, the mechanism underpinning DYRK1A involvement in Trisomy 21-related pathological tau aggregation remains unknown. Here, we explored a novel regulatory mechanism of DYRK1A and subsequent tau pathology through a phosphatase. Using LC-MS/MS technology, we analyzed multiple DYRK1A-binding proteins, including PPM1B, a member of the PP2C family of Ser/Thr protein phosphatases, in HEK293 cells. We found that PPM1B dephosphorylates DYRK1A at Ser258, contributing to the inhibition of DYRK1A activity. Moreover, PPM1B-mediated dephosphorylation of DYRK1A reduced tau phosphorylation at Thr212, leading to inhibition of toxic tau oligomerization and aggregation. In conclusion, our study demonstrates that DYRK1A autophosphorylates Ser258, the dephosphorylation target of PPM1B, and PPM1B negatively regulates DYRK1A activity. This finding also suggests that PPM1B reduces the toxic formation of phospho-tau protein via DYRK1A modulation, possibly providing a novel cellular protective mechanism to regulate toxic tau-mediated neuropathology in AD of DS.

DYRK1A: a down syndrome-related dual protein kinase with a versatile role in tumorigenesis

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a dual kinase that can phosphorylate its own activation loop on tyrosine residue and phosphorylate its substrates on threonine and serine residues. It is the most studied member of DYRK kinases, because its gene maps to human chromosome 21 within the Down syndrome critical region (DSCR). DYRK1A overexpression was found to be responsible for the phenotypic features observed in Down syndrome such as mental retardation, early onset neurodegenerative, and developmental heart defects. Besides its dual activity in phosphorylation, DYRK1A carries the characteristic of duality in tumorigenesis. Many studies indicate its possible role as a tumor suppressor gene; however, others prove its pro-oncogenic activity. In this review, we will focus on its multifaceted role in tumorigenesis by explaining its participation in some cancer hallmarks pathways such as proliferative signaling, transcription, stress, DNA damage repair, apoptosis, and angiogenesis, and finally, we will discuss targeting DYRK1A as a potential strategy for management of cancer and neurodegenerative disorders.

ReN VM spheroids in matrix: A neural progenitor three-dimensional in vitro model reveals DYRK1A inhibitors as potential regulators of radio-sensitivity

INTRODUCTION

Pre-clinical testing of small molecules for therapeutic development across many pathologies relies on the use of in-vitro and in-vivo models. When designed and implemented well, these models serve to predict the clinical outcome as well as the toxicity of the evaluated therapies. The two-dimensional (2D) reductionist approach where cells are incubated in a mono-layer on hard plastic microtiter plates is relatively inexpensive but not physiologically relevant. In contrast, well developed and applied three dimensional (3D) in vitro models could be employed to bridge the gap between 2D in vitro primary screening and expensive in vivo rodent models by incorporating key features of the tissue microenvironment to explore differentiation, cortical development, cancers and various neuronal dysfunctions. These features include an extracellular matrix, co-culture, tension and perfusion and could replace several hundred rodents in the drug screening validation cascade.

METHODS

Human neural progenitor cells from middle brain (ReN VM, Merck Millipore, UK) were expanded as instructed by the supplier (Merck Millipore, UK), and then seeded in 96-well low-attachment plates (Corning, UK) to form multicellular spheroids followed by adding a Matrigel layer to mimic extracellular matrix around neural stem cell niche. ReN VM cells were then differentiated via EGF and bFGF deprivation for 7 days and were imaged at day 7. Radiotherapy was mimicked via gamma-radiation at 2Gy in the absence and presence of selected DYRK1A inhibitors Harmine, INDY and Leucettine 41 (L41). Cell viability was measured by AlamarBlue assay. Immunofluorescence staining was used to assess cell pluripotency marker SOX2 and differentiation marker GFAP.

RESULTS

After 7 days of differentiation, neuron early differentiation marker (GFAP, red) started to be expressed among the cells expressing neural stem cell marker SOX2 (green). Radiation treatment caused significant morphology change including the reduced viability of the spheroids. These spheroids also revealed sensitizing potential of DYRK1A inhibitors tested in this study, including Harmine, INDY and L41.

DISCUSSION & CONCLUSIONS

Combined with the benefit of greatly reducing the issues associated with in vivo rodent models, including reducing numbers of animals used in a drug screening cascade, cost, ethics, and potential animal welfare burden, we feel the well-developed and applied 3D neural spheroid model presented in this study will provide a crucial tool to evaluate combinatorial therapies, optimal drug concentrations and treatment dosages.

Proline Hydroxylation Primes Protein Kinases for Autophosphorylation and Activation

Activation of dual-specificity tyrosine-phosphorylation-regulated kinases 1A and 1B (DYRK1A and DYRK1B) requires prolyl hydroxylation by PHD1 prolyl hydroxylase. Prolyl hydroxylation of DYRK1 initiates a cascade of events leading to the release of molecular constraints on von Hippel-Lindau (VHL) ubiquitin ligase tumor suppressor function. However, the proline residue of DYRK1 targeted by hydroxylation and the role of prolyl hydroxylation in tyrosine autophosphorylation of DYRK1 are unknown. We found that a highly conserved proline in the CMGC insert of the DYRK1 kinase domain is hydroxylated by PHD1, and this event precedes tyrosine autophosphorylation. Mutation of the hydroxylation acceptor proline precludes tyrosine autophosphorylation and folding of DYRK1, resulting in a kinase unable to preserve VHL function and lacking glioma suppression activity. The consensus proline sequence is shared by most CMGC kinases, and prolyl hydroxylation is essential for catalytic activation. Thus, formation of prolyl-hydroxylated intermediates is a novel mechanism of kinase maturation and likely a general mechanism of regulation of CMGC kinases in eukaryotes.

The DYRK Family of Kinases in Cancer: Molecular Functions and Therapeutic Opportunities

DYRK (dual-specificity tyrosine-regulated kinases) are an evolutionary conserved family of protein kinases with members from yeast to humans. In humans, DYRKs are pleiotropic factors that phosphorylate a broad set of proteins involved in many different cellular processes. These include factors that have been associated with all the hallmarks of cancer, from genomic instability to increased proliferation and resistance, programmed cell death, or signaling pathways whose dysfunction is relevant to tumor onset and progression. In accordance with an involvement of DYRK kinases in the regulation of tumorigenic processes, an increasing number of research studies have been published in recent years showing either alterations of DYRK gene expression in tumor samples and/or providing evidence of DYRK-dependent mechanisms that contribute to tumor initiation and/or progression. In the present article, we will review the current understanding of the role of DYRK family members in cancer initiation and progression, providing an overview of the small molecules that act as DYRK inhibitors and discussing the clinical implications and therapeutic opportunities currently available.

A Phenotypic Screening Assay Identifies Modulators of Diamond Blackfan Anemia

Diamond-Blackfan anemia (DBA) is a bone marrow failure syndrome caused by mutations in ribosomal protein genes. Pathogenic mechanisms are poorly understood but involve severely reduced proliferation of erythroid precursors. Because current DBA therapies are ineffective and associated with severe side effects, disease-specific therapies are urgently needed. We hypothesized that druggable molecular pathways underlying the defect can be revealed through phenotypic small-molecule screens. Accordingly, a screening assay was developed using c-kit+ fetal liver erythroid progenitors from a doxycycline-inducible DBA mouse model. The addition of doxycycline to the culture medium induces the phenotype and reduces proliferation to <10% of normal, such that rescue of proliferation can be used as a simple readout for screening. Here, we describe the assay rationale and efforts toward validation of a microtiter plate-compatible assay and its application in a pilot screen of 3871 annotated compounds. Ten hits demonstrated concentration-dependent activity, and we report a brief follow-up of one of these compounds. In conclusion, we established a robust scalable assay for screening molecules that rescue erythropoiesis in DBA.

Modeling Down syndrome in cells: From stem cells to organoids

Down Syndrome (DS) is a complex chromosomal disorder, with neurological issues, featuring among the symptoms. Primary neuronal cells and tissues are extremely useful, but limited both in supply and experimental manipulability. To better understand the cellular, molecular and pathological mechanisms involved in DS neurodevelopment and neurodegeneration, a range of different cellular models have been developed over the years including human: mouse hybrid cells, transchromosomic mouse embryonic stem cells (ESCs) and human ESC and induced pluripotent stem cells derived from different sources. All of these model systems have provided useful information in the study of DS. Furthermore, different technologies to genetically modify or correct trisomy of either single genes or the whole chromosome have been developed using these cellular models. New techniques and protocols to allow better modeling of cellular mechanisms and disease processes are being developed and the use of cerebral organoids offers great promise for future research into the neural phenotypes seen in DS.

DYRK1A Overexpression Alters Cognition and Neural-Related Proteomic Pathways in the Hippocampus That Are Rescued by Green Tea Extract and/or Environmental Enrichment

Down syndrome (DS), caused by trisomy of chromosome 21, is the most common genetic cause of intellectual disability. We recently discovered that green tea extracts containing epigallocatechin-3-gallate (EGCG) improve cognition in mice transgenic for Dyrk1a (TgDyrk1A) and in a trisomic DS mouse model (Ts65Dn). Interestingly, paired with cognitive stimulation, green tea has beneficial pro-cognitive effects in DS individuals. Dual Specificity Tyrosine-Phosphorylation-Regulated Kinase 1A (DYRK1A) is a major candidate to explain the cognitive phenotypes of DS, and inhibiting its activity is a promising pro-cognitive therapy. DYRK1A kinase activity can be normalized in the hippocampus of transgenic DYRK1A mice administering green tea extracts, but also submitting the animals to environmental enrichment (EE). However, many other mechanisms could also explain the pro-cognitive effects of green tea extracts and EE. To underpin the overall alterations arising upon DYRK1A overexpression and the molecular processes underneath the pro-cognitive effects, we used quantitative proteomics. We investigated the hippocampal (phospho)proteome in basal conditions and after treatment with a green tea extract containing EGCG and/or EE in TgDyrk1A and control mice. We found that Dyrk1A overexpression alters protein and phosphoprotein levels of key postsynaptic and plasticity-related pathways and that these alterations were rescued upon the cognitive enhancer treatments.

Modeling Down syndrome in animals from the early stage to the 4.0 models and next

The genotype-phenotype relationship and the physiopathology of Down Syndrome (DS) have been explored in the last 20 years with more and more relevant mouse models. From the early age of transgenesis to the new CRISPR/CAS9-derived chromosomal engineering and the transchromosomic technologies, mouse models have been key to identify homologous genes or entire regions homologous to the human chromosome 21 that are necessary or sufficient to induce DS features, to investigate the complexity of the genetic interactions that are involved in DS and to explore therapeutic strategies. In this review we report the new developments made, how genomic data and new genetic tools have deeply changed our way of making models, extended our panel of animal models, and increased our understanding of the neurobiology of the disease. But even if we have made an incredible progress which promises to make DS a curable condition, we are facing new research challenges to nurture our knowledge of DS pathophysiology as a neurodevelopmental disorder with many comorbidities during ageing.

Cell Fate Regulation upon DNA Damage: p53 Serine 46 Kinases Pave the Cell Death Road

Mild and massive DNA damage are differentially integrated into the cellular signaling networks and, in consequence, provoke different cell fate decisions. After mild damage, the tumor suppressor p53 directs the cellular response to cell cycle arrest, DNA repair, and cell survival, whereas upon severe damage, p53 drives the cell death response. One posttranslational modification of p53, phosphorylation at Serine 46, selectively occurs after severe DNA damage and is envisioned as a marker of the cell death response. However, the molecular mechanism of action of the p53 Ser46 phospho-isomer, the molecular timing of this phosphorylation event, and its activating effects on apoptosis and ferroptosis still await exploration. In this essay, the current body of evidence on the molecular function of this deadly p53 mark, its evolutionary conservation, and the regulation of the key players of this response, the p53 Serine 46 kinases, are reviewed and dissected.

Association of MDM2 gene SNP 309 polymorphism and human non-small cell lung cancer susceptibility: A meta-analysis

This updated meta-analysis was performed to evaluate the relationship of a common polymorphism (T309 G, rs2279744 T > G) in the murine double minute 2 (MDM2) gene with susceptibility and prognosis of non-small cell lung cancer (NSCLC). The Cochrane Library, PubMed, Embase, CNKI, WanFang and CNKI databases were searched comprehensively for related study. Odds ratios (ORs) with their 95% confidence intervals (95% CI) were calculated. 11 articles with a total 6470 NSCLC patients and 8027 controls met the inclusion criteria were included. MDM2 T309 G polymorphism might be strongly correlated with an increased risk of NSCLC. The overall pooled analysis indicated that MDM2 309 T/G polymorphism was significantly associated with NSCLC susceptibility in the whole population under allelic (OR: 1.22, 95% CI: 1.08-1.38), recessive (OR: 1.37, 95% CI: 1.15-1.63), dominant (OR: 1.23, 95% CI: 1.04-1.45), and homozygous genetic models (OR: 1.49, 95% CI: 1.20-1.86). The subgroup analysis showed a significant association of MDM2 309 T/G polymorphism with NSCLC susceptibility in Asian population, but not in Caucasian population. Besides, a significant association was found again in the female population. The meta-analysis provides convincing evidence that the MDM2 T309 G polymorphism may contribute to NSCLC susceptibility, especially for Asians and women.

Inhibition of DYRK1A-EGFR axis by p53-MDM2 cascade mediates the induction of cellular senescence

Activation of p53 may induce apoptosis or cellular senescence in stressed cells. We here report that epidermal growth factor receptor (EGFR) is downregulated by p53 activation in a subset of cancer cell lines, and this EGFR downregulation mediates cellular senescence caused by p53 activation. EGFR confers resistance to senescence by sustaining the ERK signaling. DYRK1A (dual-specificity tyrosine-phosphorylated and tyrosine-regulated kinase 1A), an EGFR-stabilizing kinase, is downregulated by p53 and, when ectopically expressed, can attenuate p53 activation-induced EGFR reduction and cellular senescence. We further showed that the increased degradation of DYRK1A caused by p53 activation was mediated by MDM2. MDM2 was found to physically interact with and ubiquitinate DYRK1A, ultimately leading to its proteosomal degradation. Importantly, administration of Nutlin-3a, which disrupts the binding of MDM2 to p53, but not that of MDM2 to DYRK1A, reduced the levels of DYRK1A and EGFR, induced senescence, and inhibited growth of tumor xenografts formed by U87 glioblastoma cells. Ectopic expression of EGFR in tumor xenografts attenuated senescence and tumor reduction caused by Nultin-3a. Our findings thus established a novel link between p53 and EGFR and may have implications in p53 activation-based therapies.

Combined Inhibition of DYRK1A, SMAD, and Trithorax Pathways Synergizes to Induce Robust Replication in Adult Human Beta Cells

Small-molecule inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) induce human beta cells to proliferate, generating a labeling index of 1.5%-3%. Here, we demonstrate that combined pharmacologic inhibition of DYRK1A and transforming growth factor beta superfamily (TGFβSF)/SMAD signaling generates remarkable further synergistic increases in human beta cell proliferation (average labeling index, 5%-8%, and as high as 15%-18%), and increases in both mouse and human beta cell numbers. This synergy reflects activation of cyclins and cdks by DYRK1A inhibition, accompanied by simultaneous reductions in key cell-cycle inhibitors (CDKN1C and CDKN1A). The latter results from interference with the basal Trithorax- and SMAD-mediated transactivation of CDKN1C and CDKN1A. Notably, combined DYRK1A and TGFβ inhibition allows preservation of beta cell differentiated function. These beneficial effects extend from normal human beta cells and stem cell-derived human beta cells to those from people with type 2 diabetes, and occur both in vitro and in vivo.

DYRK1A and cognition: A lifelong relationship

The dosage of the serine threonine kinase DYRK1A is critical in the central nervous system (CNS) during development and aging. This review analyzes the functions of this kinase by considering its interacting partners and pathways. The role of DYRK1A in controlling the differentiation of prenatal newly formed neurons is presented separately from its role at the pre- and post-synaptic levels in the adult CNS; its effects on synaptic plasticity are also discussed. Because this kinase is positioned at the crossroads of many important processes, genetic dosage errors in this protein produce devastating effects arising from DYRK1A deficiency, such as in MRD7, an autism spectrum disorder, or from DYRK1A excess, such as in Down syndrome. Effects of these errors have been shown in various animal models including Drosophila, zebrafish, and mice. Dysregulation of DYRK1A levels also occurs in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Finally, this review describes inhibitors that have been assessed in vivo. Accurate targeting of DYRK1A levels in the brain, with either inhibitors or activators, is a future research challenge.

DYRK1A Protein, A Promising Therapeutic Target to Improve Cognitive Deficits in Down Syndrome

Down syndrome (DS) caused by a trisomy of chromosome 21 (HSA21), is the most common genetic developmental disorder, with an incidence of 1 in 800 live births. Its phenotypic characteristics include intellectual impairment, early onset of Alzheimer’s disease, congenital heart disease, hypotonia, muscle weakness and several other developmental abnormalities, for the majority of which the pathogenetic mechanisms remain unknown. Among the numerous protein coding genes of HSA21, dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1A (DYRK1A) encodes a proline-directed serine/threonine and tyrosine kinase that plays pleiotropic roles in neurodevelopment in both physiological and pathological conditions. Numerous studies point to a crucial role of DYRK1A protein for brain defects in patients with DS. Thus, DYRK1A inhibition has shown benefits in several mouse models of DS, including improvement of cognitive behaviour. Lastly, a recent clinical trial has shown that epigallocatechine gallate (EGCG), a DYRK1A inhibitor, given to young patients with DS improved visual recognition memory, working memory performance and adaptive behaviour.

A facile consensus ranking approach enhances virtual screening robustness and identifies a cell-active DYRK1α inhibitor

BACKGROUND

Virtual screening is vital for contemporary drug discovery but striking performance fluctuations are commonly encountered, thus hampering error-free use. Results and Methodology: A conceptual framework is suggested for combining screening algorithms characterized by orthogonality (docking-scoring calculations, 3D shape similarity, 2D fingerprint similarity) into a simple, efficient and expansible python-based consensus ranking scheme. An original experimental dataset is created for comparing individual screening methods versus the novel approach. Its utilization leads to identification and phosphoproteomic evaluation of a cell-active DYRK1α inhibitor.

CONCLUSION

Consensus ranking considerably stabilizes screening performance at reasonable computational cost, whereas individual screens are heavily dependent on calculation settings. Results indicate that the novel approach, currently available as a free online tool, is highly suitable for prospective screening by nonexperts.

Development of novel 2,4-bispyridyl thiophene-based compounds as highly potent and selective Dyrk1A inhibitors. Part I: Benzamide and benzylamide derivatives

The protein kinase Dyrk1A modulates several processes relevant to the development or progression of Alzheimer's disease (AD), e. g. through phosphorylation of tau protein, amyloid precursor protein (APP) as well as proteins involved in the regulation of alternative splicing of tau pre-mRNA. Therefore, Dyrk1A has been proposed as a potential target for the treatment of AD. However, the co-inhibition of other closely related kinases of the same family of protein kinases (e.g. Dyrk1B and Dyrk2) or kinases from other families such as Clk1 limits the use of Dyrk1A inhibitors, as this may cause unpredictable side effects especially over long treatment periods. Herein, we describe the design and synthesis of a series of amide functionalized 2,4-bispyridyl thiophene compounds, of which the 4-fluorobenzyl amide derivative (31b) displayed the highest potency against Dyrk1A and remarkable selectivity over closely related kinases (IC50: Dyrk1A = 14.3 nM; Dyrk1B = 383 nM, Clk1 > 2 μM). This degree of selectivity over the frequently hit off-targets has rarely been achieved to date. Additionally, 31b inhibited Dyrk1A in intact cells with high efficacy (IC50 = 79 nM). Furthermore, 31b displayed a high metabolic stability in vitro with a half-life of 2 h. Altogether, the benzamide and benzylamide extension at the 2,4-bispyridyl thiophene core improved several key properties, giving access to compound suitable for future in vivo studies.

Rodent models in Down syndrome research: impact and future opportunities

Down syndrome is caused by trisomy of chromosome 21. To date, a multiplicity of mouse models with Down-syndrome-related features has been developed to understand this complex human chromosomal disorder. These mouse models have been important for determining genotype-phenotype relationships and identification of dosage-sensitive genes involved in the pathophysiology of the condition, and in exploring the impact of the additional chromosome on the whole genome. Mouse models of Down syndrome have also been used to test therapeutic strategies. Here, we provide an overview of research in the last 15 years dedicated to the development and application of rodent models for Down syndrome. We also speculate on possible and probable future directions of research in this fast-moving field. As our understanding of the syndrome improves and genome engineering technologies evolve, it is necessary to coordinate efforts to make all Down syndrome models available to the community, to test therapeutics in models that replicate the whole trisomy and design new animal models to promote further discovery of potential therapeutic targets.

Summary: Mouse models have boosted therapeutic options for Down syndrome, and improved models are being developed to better understand the pathophysiology of this genetic condition.

Mnb/Dyrk1A orchestrates a transcriptional network at the transition from self-renewing neurogenic progenitors to postmitotic neuronal precursors

The Down syndrome and microcephaly related gene Mnb/Dyrk1A encodes an evolutionary conserved protein kinase subfamily that plays important roles in neurodevelopment. minibrain (mnb) mutants of Drosophila melanogaster (Dm) exhibit reduced adult brains due to neuronal deficits generated during larval development. These deficits are the consequence of the apoptotic cell death of numerous neuronal precursors that fail to properly exit the cell cycle and differentiate. We have recently found that in both the Dm larval brain and the embryonic vertebrate central nervous system (CNS), a transient expression of Mnb/Dyrk1A promotes the cell cycle exit of newborn neuronal precursors by upregulating the expression of the cyclin-dependent kinase inhibitor p27kip1 (called Dacapo in Dm). In the larval brain, Mnb performs this action by regulating the expression of three transcription factors, Asense (Ase), Deadpan (Dpn) and Prospero (Pros), which are key regulators of the self-renewal, proliferation, and terminal differentiation of neural progenitor cells. We have here studied in detail the cellular/temporal expression pattern of Ase, Dpn, Pros and Mnb, and have analyzed possible regulatory effects among them at the transitions from neurogenic progenitors to postmitotic neuronal precursors in the Dm larval brain. The emerging picture of this analysis reveals an intricate regulatory network in which Mnb appears to play a pivotal role helping to delineate the dynamics of the expression patterns of Ase, Dpn and Pros, as well as their specific functions in the aforementioned transitions. Our results also show that Ase, Dpn and Pros perform several cross-regulatory actions and contribute to shape the precise cellular/temporal expression pattern of Mnb. We propose that Mnb/Dyrk1A plays a central role in CNS neurogenesis by integrating molecular mechanisms that regulate progenitor self-renewal, cell cycle progression and neuronal differentiation.

Autism-associated Dyrk1a truncation mutants impair neuronal dendritic and spine growth and interfere with postnatal cortical development

Autism is a prevailing neurodevelopmental disorder with a large genetic/genomic component. Recently, the dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1 A (DYRK1A) gene was implicated as a risk factor for autism spectrum disorder (ASD). We identified five DYRK1A variants in ASD patients and found that the dose of DYRK1A protein has a crucial role in various aspects of postnatal neural development. Dyrk1a loss of function and gain of function led to defects in dendritic growth, dendritic spine development and radial migration during cortical development. Importantly, two autism-associated truncations, R205X and E239X, were shown to be Dyrk1a loss-of-function mutants. Studies of the truncated Dyrk1a mutants may provide new insights into the role of Dyrk1a in brain development, as well as the role of Dyrk1a loss of function in the pathophysiology of autism.