Auswahl der wissenschaftlichen Literatur zum Thema „CDKL deficiency disorder“

The disease caused by mutations in the CDKL5 gene (encoding cyclin-dependent kinase 5, CDK5) belongs to the group of early (infantile) epileptic encephalopathies caused by alterations in the genome. Currently, the disease is called “developmental encephalopathy and epileptic encephalopathy type 2”. This disorder is a complex combination of symptoms that develop due to deficiency or absence of the CDKL5 gene product, which is serine/threonine kinase. The CDKL5 gene is located on X chromosome; the disease has an X-linked dominant inheritance pattern. This literature review summarizes relevant studies analyzing the disease caused by CDKL5 gene mutations, including its genetic and epidemiological aspects, clinical manifestations, characteristics of epilepsy, principles of diagnosis, and therapeutic approaches. We present a case series of several patients with genetic disorders involving the CDKL5 gene.

Rett syndrome (RTT) and CDKL5 deficiency disorder (CDD) are two rare X-linked developmental brain disorders with overlapping but distinct phenotypic features. This review examines the impact of loss of methyl-CpG-binding protein 2 (MeCP2) and cyclin-dependent kinase-like 5 (CDKL5) on clinical phenotype, deficits in synaptic- and circuit-homeostatic mechanisms, seizures, and sleep. In particular, we compare the overlapping and contrasting features between RTT and CDD in clinic and in preclinical studies. Finally, we discuss lessons learned from recent clinical trials while reviewing the findings from pre-clinical studies.

CDKL5 deficiency disorder (CDD) is a complex of clinical symptoms resulting from the presence of non-functional CDKL5 protein, i.e., serine-threonine kinase (previously referred to as STK9), or its complete absence. The clinical picture is characterized by epileptic seizures (that start within the first three months of life and most often do not respond to pharmacological treatment), epileptic encephalopathy secondary to seizures, and retardation of psychomotor development, which are often observed already in the first months of life. Due to the fact that CDKL5 is located on the X chromosome, the prevalence of CDD among women is four times higher than in men. However, the course is usually more severe among male patients. Recently, many clinical centers have analyzed this condition and provided knowledge on the function of CDKL5 protein, the natural history of the disease, therapeutic options, and their effectiveness and prognosis. The International CDKL5 Disorder Database was established in 2012, which focuses its activity on expanding knowledge related to this condition and disseminating such knowledge to the families of patients.

Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder is a rare neurodevelopmental disorder characterized by infantile-onset refractory epilepsy, profound developmental delays, and cerebral visual impairment. Although there is evidence that the presence of cerebral visual impairment in CDKL5 deficiency disorder is common, the potential impact of cerebral visual impairment severity on developmental attainment has not been explored directly. Focusing on a cohort of 46 children with CDKL5 deficiency disorder, examination features indicative of cerebral visual impairment were quantified and compared to developmental achievement. The derived cerebral visual impairment severity score was inversely correlated with developmental attainment, bolstering the supposition that cerebral visual impairment severity may provide a useful early biomarker of disease severity and prognosis. This study demonstrates the utility of a cerebral visual impairment score to better capture the range of cerebral visual impairment severity in the CDKL5 deficiency disorder population and further elucidates the interaction between cerebral visual impairment and developmental outcomes.

Abstract Cyclin-dependent kinase-like 5 (CDKL5), a serine-threonine kinase encoded by an X-linked gene, is highly expressed in the mammalian forebrain. Mutations in this gene cause CDKL5 deficiency disorder, a neurodevelopmental encephalopathy characterized by early-onset seizures, motor dysfunction, and intellectual disability. We previously found that mice lacking CDKL5 exhibit hyperlocomotion and increased impulsivity, resembling the core symptoms in attention-deficit hyperactivity disorder (ADHD). Here, we report the potential neural mechanisms and treatment for hyperlocomotion induced by CDKL5 deficiency. Our results showed that loss of CDKL5 decreases the proportion of phosphorylated dopamine transporter (DAT) in the rostral striatum, leading to increased levels of extracellular dopamine and hyperlocomotion. Administration of methylphenidate (MPH), a DAT inhibitor clinically effective to improve symptoms in ADHD, significantly alleviated the hyperlocomotion phenotype in Cdkl5 null mice. In addition, the improved behavioral effects of MPH were accompanied by a region-specific restoration of phosphorylated dopamine- and cAMP-regulated phosphoprotein Mr 32 kDa, a key signaling protein for striatal motor output. Finally, mice carrying a Cdkl5 deletion selectively in DAT-expressing dopaminergic neurons, but not dopamine receptive neurons, recapitulated the hyperlocomotion phenotype found in Cdkl5 null mice. Our findings suggest that CDKL5 is essential to control locomotor behavior by regulating region-specific dopamine content and phosphorylation of dopamine signaling proteins in the striatum. The direct, as well as indirect, target proteins regulated by CDKL5 may play a key role in movement control and the therapeutic development for hyperactivity disorders.

CDKL5 deficiency disorder (CDD) is a severe neurodevelopmental encephalopathy caused by mutations in the X-linked CDKL5 gene that encodes a serine/threonine kinase. CDD is characterised by the early onset of seizures and impaired cognitive and motor skills. Loss of CDKL5 in vitro and in vivo affects neuronal morphology at early and late stages of maturation, suggesting a link between CDKL5 and the neuronal cytoskeleton. Recently, various microtubule (MT)-binding proteins have been identified as interactors of CDKL5, indicating that its roles converge on regulating MT functioning. MTs are dynamic structures that are important for neuronal morphology, migration and polarity. The delicate control of MT dynamics is fundamental for proper neuronal functions, as evidenced by the fact that aberrant MT dynamics are involved in various neurological disorders. In this review, we highlight the link between CDKL5 and MTs, discussing how CDKL5 deficiency may lead to deranged neuronal functions through aberrant MT dynamics. Finally, we discuss whether the regulation of MT dynamics through microtubule-targeting agents may represent a novel strategy for future pharmacological approaches in the CDD field.

Cyclin-dependent–like kinase 5 (CDKL5) gene mutations lead to an X-linked disorder that is characterized by infantile epileptic encephalopathy, developmental delay, and hypotonia. However, we found that a substantial percentage of these patients also report a previously unrecognized anamnestic deficiency in pain perception. Consistent with a role in nociception, we found that CDKL5 is expressed selectively in nociceptive dorsal root ganglia (DRG) neurons in mice and in induced pluripotent stem cell (iPS)–derived human nociceptors. CDKL5-deficient mice display defective epidermal innervation, and conditional deletion of CDKL5 in DRG sensory neurons impairs nociception, phenocopying CDKL5 deficiency disorder in patients. Mechanistically, CDKL5 interacts with calcium/calmodulin-dependent protein kinase II α (CaMKIIα) to control outgrowth and transient receptor potential cation channel subfamily V member 1 (TRPV1)–dependent signaling, which are disrupted in both CDKL5 mutant murine DRG and human iPS–derived nociceptors. Together, these findings unveil a previously unrecognized role for CDKL5 in nociception, proposing an original regulatory mechanism for pain perception with implications for future therapeutics in CDKL5 deficiency disorder.

Abstract The X-linked neurodevelopmental diseases CDKL5 deficiency disorder (CDD) and Rett syndrome (RTT) are associated with intellectual disability, infantile spasms and seizures. Although mitochondrial dysfunction has been suggested in RTT, less is understood about mitochondrial function in CDD. A comparison of bioenergetics and mitochondrial function between isogenic wild-type and mutant neural progenitor cell (NPC) lines revealed increased oxygen consumption in CDD mutant lines, which is associated with altered mitochondrial function and structure. Transcriptomic analysis revealed differential expression of genes related to mitochondrial and REDOX function in NPCs expressing the mutant CDKL5. Furthermore, a similar increase in oxygen consumption specific to RTT patient–derived isogenic mutant NPCs was observed, though the pattern of mitochondrial functional alterations was distinct from CDKL5 mutant–expressing NPCs. We propose that aberrant neural bioenergetics is a common feature between CDD and RTT disorders. The observed changes in oxidative stress and mitochondrial function may facilitate the development of therapeutic agents for CDD and related disorders.

Mutations in the X-linked cyclin-dependent kinase-like 5 (CDKL5) gene cause CDKL5 deficiency disorder (CDD), which is a rare neurodevelopmental disease characterized by severe epilepsy and global developmental delay. Most children affected suffer from seizures beginning in the first months of life and severe impairment of cognitive and motor skills, with great impact on their quality of life. Most cannot walk, talk, or feed themselves, and many are confined to using a wheelchair. Although rare, CDKL5 deficiency disorder is one of the most common forms of genetic epilepsy. Currently, there is no cure or effective treatment for CDD, hence the great urge to develop novel and effective therapeutic strategies. Here, we present a methodology for the correction of a pathogenic variant in CDKL5 (c.1090G>T (p.Glu364*)), using CRISPR/Cas9 genome editing technology in patient-derived cell models, in order to expedite the discovery of new therapies for CDD. CRISPR/Cas9 is a precise and versatile method of genetic manipulation, and it only requires three components to target and correct genetic mutations: guide RNAs, Cas9 endonuclease, and homology-directed repair (HDR) templates. We first tested plasmid-based delivery of CRISPR/Cas9 for correction in primary fibroblasts. This system proved to be up to 66% efficient but it was associated with extremely variable and unpredictable editing efficiency (33±31%) in three separate experiments. Hence, we decided to test additional guides and to replace the plasmid-based system with a protein-based ribonucleoprotein (RNP) delivery system for more rapid action and greater stability. We tested the system in induced pluripotent stem cells (iPSCs) obtained by reprogramming the patient’s fibroblasts. We reported the generation of genetically corrected iPSCs, where the mutated CDKL5 c.1090G>T (p.Glu364*) was corrected to the wild-type, using RNP-mediated delivery of CRISPR/Cas9. Based on PCR cloning results of gene-corrected clones, we can state that our system is able to selectively target the p.Glu364* variant while preserving the wild-type CDKL5 allele in vitro. We then differentiated in parallel mutant and isogenic sets of cells into neural cells to assess the functional consequences of the edit in the affected cell type. We demonstrated that CRISPR/Cas9 gene editing restores the expression of CDKL5 protein in iPSC-derived neurons by Western blot. We also showed by RT-qPCR that mutant neurons carrying the c.1090G>T (p.Glu364*) in CDKL5 pre-sent reduced expression of CDKL5 mRNA compared to isogenic control. Our findings demonstrate that we can achieve targeted and allele-specific correction of CDKL5 (c.1090G>T (p.Glu364*)) variant using CRISPR/Cas9-RNP system in a patient-specific cell model. Moreover, we proved that correction of the mutation at the DNA level rescues CDKL5 protein expression and increases CDKL5 mRNA expression in isogenic neurons. The results of this study might be decisive in proving CRISPR/Cas9 potential to carry out genome editing in human cells, and ultimately for developing advanced therapies for CDD.

CDKL5 deficiency disorder (CDD) is a rare encephalopathy characterized by early onset epilepsy and severe intellectual disability. CDD is caused by mutations in the X-linked cyclin-dependent kinase-like 5 (CDKL5) gene, a member of a highly conserved family of serine-threonine kinases. Since kinase function alterations are associated with several pathologies, cancers, and also neurological disorders, these proteins can be both valuable biomarkers and potential drug targets for disease prognosis and treatment. Unfortunately, only a few physiological substrates of CDKL5 are currently known, which hampers the discovery of therapeutic strategies for CDD. Here we took advantage of a phospho-specific-antibody-microarray technology to identify potential direct CDKL5 substrates in a mouse model of the disorder. Among the potential CDKL5 targets, we show that SMAD3, a primary mediator of TGF-β action, is a direct phosphorylation target of CDKL5 and that CDKL5-dependent phosphorylation promotes SMAD3 protein stability. Importantly, we found that restoration of the SMAD3 signaling through TGF-β1 treatment normalized defective neuronal survival and maturation in Cdkl5 knockout (KO) neurons. Moreover, we demonstrate that Cdkl5 KO neurons are more vulnerable to neurotoxic/excitotoxic stimuli. In vivo treatment with TGF-β1 prevents increased NMDA-induced cell death in hippocampal neurons from Cdkl5 KO mice, suggesting an involvement of the SMAD3 signaling deregulation in the neuronal susceptibility to excitotoxic injury of Cdkl5 KO mice. In conclusion, this study contributes to a better understanding of the molecular pathomechanism underlying the clinical phenotype of CDD. Our finding has revealed a new CDKL5 substrate while also providing a panel of potential CDKL5 substrates for future studies aimed at increasing the definition of the signaling networks in which the protein kinase participates. In addition, our results have shown the first evidence of a new crucial role of CDKL5 in maintaining neuronal survival that could have important implications for susceptibility to neurodegeneration in patients with CDD.

CDKL5 è una chinasi con funzioni importanti, che agisce come regolatore trascrizionale nel nucleo, modula il ciclo cellulare e l'apoptosi, e percepisce il danno al DNA. Questa chinasi, molto espressa nei neuroni, è coinvolta nel corretto sviluppo del network neuronale e ha un ruolo fondamentale nello sviluppo delle sinapsi. Dunque, non è sorprendente che una diminuzione nei suoi livelli porti ad una grave condizione del neurosviluppo conosciuta come CDKL5 Deficiency Disorder (CDD), una rara encefalopatia. Molte mutazioni causative della patologia sono riportate essere nella regione codificante di CDKL5, ma l'identificazione di una nuova SNP nel 5'UTR di CDKL5, descritta da Evans et al. nel 2005, ci ha portati a considerare che questo 5'UTR potrebbe giocare un ruolo nel mantenere i livelli fisiologici della proteina modulando l'efficienza traduzionale del trascritto. Altre proteine con funzioni analoghe nei neuroni sono regolate attraverso il controllo traduzionale mediato dal loro 5'UTR. Dunque, abbiamo trovato che il 5'UTR di CDKL5 rispecchia le caratteristiche tipiche dei 5'UTR funzionali altamente strutturati e mostra una conservazione interessante durante l'evoluzione della sua sequenza. In più, abbiamo osservato che silenziando l'espressione del fattore dell'inizio della traduzione eucariotico eIF4B (fattore coinvolto nel rilassamento dei 5'UTR strutturati), si osserva una forte diminuzione di CDKL5. Abbiamo analizzato il 5'UTR di CDKL5 attraverso analisi bioinformatiche per poi analizzare sperimentalmente la sua funzionalità attraverso il Dual Luciferases Reporter Assay, evidenziando il ruolo di questa sequenza nella modulazione traduzionale della proteina attraverso meccanismi cap-dipendenti ed IRES-mediati. Per di più, abbiamo ottenuto una prima evidenza sperimentale di un possibile ruolo patogenico della SNP trovata da Evans. Infine, abbiamo quantificato il TSS usage dei diversi trascritti di CDKL5 utilizzando librarie CAGE di tessuti umani. Il nostro lavoro è il primo studio incentrato sul 5'UTR di CDKL5, e non dimostra solamente l'importanza del 5'UTR nella modulazione della proteina prodotta, ma anche introduce anche la possibilità di poter sviluppare nuove strategie terapeutiche per trattare la CDD.
CDKL5 is a protein kinase with important functions, acting as transcriptional regulator in the nucleus, modulating the cell cycle and apoptosis, and sensing DNA damages. This kinase, enriched in neurons, is involved in the correct development of the neuronal networks, and has a fundamental role in shaping synapses. Therefore, it does not come as a surprise that a decrease in its expression leads to a severe neurodevelopmental condition known as CDKL5 Deficiency Disorder (CDD), a rare X-linked epileptic encephalopathy. Most of the causative mutations of the disorder were reported in the CDKL5 coding region, but the identification of a novel SNP within the CDKL5 transcript leader, described by Evans et al. in 2005, led us to consider that its 5’UTR could also play a role in maintaining the physiological protein level by modulating the translational efficiency of the transcript. Other proteins with analogous functions in neurons are regulated by a translational control through their 5’UTRs. Indeed, we found that the CDKL5 5’UTR respects the typical features of a functional, highly-structured 5’UTRs and shows an impressive conservation throughout evolution. In addition, we observed that the silencing of eIF4B, a translational eukaryotic initiation factor involved in the unwinding of structured 5’UTR, correlated with a strong decrease of CDKL5. We analyzed the CDKL5 5’UTR by bioinformatic tools and verified the functionality of the various 5’UTR variants through a Dual Luciferases Reporter Assay, supporting a role of CDKL5 5’UTR in the translational modulation of the protein expression through cap-dependent and IRES-mediated mechanisms. Moreover, we obtained the first experimental hint pointing to a possible pathogenic role of the SNP found by Evans. Finally, we quantified the TSS usage of different CDKL5 transcript variants based on CAGE libraries, to better understand the meaning of the numerous alternative first exons of CDKL5 and their usage in the human tissues. Our work is the first comprehensive study about the 5’UTR of CDKL5, and not only demonstrates the importance of 5’UTR in the modulation of CDKL5, but also potentially open new options for therapeutic strategies to treat CDD.

CDKL5 (cyclin-dependent kinase-like 5) deficiency disorder (CDD) is a severe X-linked neurodevelopmental disease caused by mutations in the CDKL5 gene, characterized by early-onset epileptic seizures, intellectual disability, motor and visual impairment and respiratory dysregulation. Although pharmacological treatments are used to control seizures, there is currently no cure to ameliorate symptoms for CDD. Albeit delivery of a wild-type copy of the mutated gene to cells represents the most curative approach for a monogenic disease, proof-of-concept studies highlight significant efficacy caveats for brain gene therapy. The major one regards the low efficiency of gene delivery to the CNS by viral vectors. We used a secretable Igk-TATk-CDKL5 protein to enhance the efficiency of a gene therapy for CDD. In view of the properties of the Igk-chain leader sequence, the TATk-CDKL5 protein produced by infected cells is secreted via constitutive secretory pathways. Importantly, due to the transduction property of the TATk peptide, the secreted CDKL5 protein is internalized by cells. We compared the effects of a CDKL5 gene therapy with an IgK-TATk-CDKL5 gene therapy in a Cdkl5 KO mouse model to validate whether the Igk-TATk-CDKL5 approach significantly improve the therapeutic efficacy. We found that, although AAVPHP.B_Igk-TATk-CDKL5 and AAVPHP.B_CDKL5 vectors had similar brain infection efficiency, the AAVPHP.B_Igk-TATk-CDKL5 vector led to a higher CDKL5 protein replacement and Cdkl5 KO mice treated with the AAVPHP.B_Igk-TATk-CDKL5 vector showed a behavioral and neuroanatomical improvement in comparison with Cdkl5 KO mice treated with the AAVPHP.B_CDKL5 vector.

CDKL5 (cyclin dependent kinase like 5) deficiency disorder ( is a severe neurodevelopmental encephalopathy characterized by early onset epilepsy and intellectual disability.Studies in mouse models have linked CDKL5 deficiency to defects in neuronal maturation and synaptic plasticity, and disruption of the excitatory/inhibitory balance. Interestingly, increased density of both GABAergic synaptic terminals and parvalbumin inhibitory interneurons was recently observed in the primary visual cortex of Cdkl5 knockout ( mice, suggesting that excessive GABAergic transmission might contribute to the visual deficits characteristic of CDD. However, the functional relevance of cortical GABAergic circuits abnormalities in these mutant mice has not been investigated so far. Here we examined GABAergic circuits in the perirhinal cortex ( of Cdkl5 KO mice, where we previously observed imp aired long term potentiation ( associated with deficits in novel object recognition ( memory. We found a higher number of GABAergic ( immunopositive terminals in the PRC of Cdkl5 KO compared to wild type mice, suggesting that increased inhibitory transmission might contribute to LTP impairment. Interestingly, while exposure of PRC slices to the GABAA receptor antagonist picrotoxin had no positive effects on LTP in Cdkl5 KO mice, the selective GABAB receptor antagonist CGP55845 restored LTP magn itude, suggesting that exaggerated GABAB receptor mediated inhibition contributes to LTP impairment in mutants. Moreover, acute in vivo treatment with CGP55845 increased the number of PSD95 positive puncta as well as density and maturation of dendritic spi nes in PRC, and restored NOR memory in Cdkl5 KO mice. The present data show the efficacy of limiting excessive GABAB receptor mediated signaling in improving synaptic plasticity and cognition in CDD mice.