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Base editing restores CDKL5 expression and rescues neuronal deficits in a patient-derived model of CDKL5 deficiency disorder

ABSTRACT: CDKL5 (Cyclin-dependent kinase like 5) deficiency disorder (CDD) is a rare monogenic neurodevelopmental disorder caused by pathogenic mutations in the CDKL5 gene, with approximately 50% of reported variants being point mutations. Base editing presents a promising therapeutic strategy to correct such mutations, restore endogenous CDKL5 expression, and pave the way for novel treatments for CDD. To assess the therapeutic potential of base editing for CDD, we applied adenine base editing (ABE) to correct a CDKL5-R550* (c.1648C>T) mutation in induced pluripotent stem cells (iPSCs) derived from a CDD patient. Isogenic control, CDKL5-R550* mutant, and ABE-corrected iPSCs were differentiated into neurons and the restoration of CDKL5-related and functional recovery were assessed. In this study, we demonstrated that ABE successfully restored CDKL5 protein levels and CDKL5-dependent signalling pathways in edited iPSC-differentiated neurons to levels comparable to the isogenic control. Morphological deficits, and genes expression were normalized in the ABE-corrected neurons. This study provides evidence that ABE can precisely correct pathogenic mutation and functionally rescue some CDD-associated neuronal phenotypes in patient-derived cells, supporting its potential as a valuable gene therapy for CDD. Moreover, these findings underscore the broader applicability of base editing for treating other monogenic neurodevelopmental disorders caused by point mutations.

ORGANISM(S): Homo sapiens

PROVIDER: GSE325168 | GEO | 2026/03/27

REPOSITORIES: GEO

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Project description:Zebrafish has been recognized as a robust model organism in biomedical research for the investigation of human genetic disorders. Recently, we proposed the homozygous cdkl5sa21938 mutant zebrafish as a model of CDKL5 deficiency disorder (CDD), a rare developmental epileptic encephalopathy associated with broad range of symptoms. Since neurological phenotypes are the primary focus of investigations, the understanding of CDKL5 function beyond the brain remains limited. Therefore, the aim of this study was to expand the knowledge about Cdkl5-associated molecular mechanisms using the proposed cdkl5 zebrafish model and to evaluate their similarity to findings in mammalian systems. For this purpose, we conducted RNA-sequencing of whole cdkl5-/- mutant zebrafish and compare it to their wild-type siblings at two different stages of development (5 and 35 dpf). Most significant DEGs were related to muscle, neuronal and visual systems which are affected in CDD. Gene Ontology (GO) analysis revealed that at both stages the downregulated DEGs were mainly enriched in muscle development, extracellular matrix and actin cytoskeleton functions while at 35 dpf the upregulated DEGs were mainly enriched in eye development functions. KEGG pathway analysis showed the enrichment of downregulated DEGs in focal adhesion and ECM-receptor interaction pathways at both stages. Additionally, we found that DEGs related to neuronal development were mainly downregulated at both stages while several upregulated DEGs were enriched in synaptic signaling at 35dpf. Moreover, we identified many downregulated key DEGs of cartilage development at both stages and bone development at 35 dpf, potential explaining the impaired cdkl5-/- mutant craniofacial cartilage and bone mineralization defects and the CDD skeletal phenotypes. In conclusion, this study shows that Cdkl5 loss in the cdkl5-/- mutant zebrafish lead to the dysregulation of several genes involved in functions known to be associated with CDKL5 in mammalian systems and provide novel insights into the less studied CDKL5 functions and phenotypes.

Project description:Background: Mutations in the X-linked gene cyclin-dependent kinase-like 5 (CDKL5) cause a severe neurological disorder characterised by early-onset epileptic seizures, autism and intellectual disability (ID). Impaired hippocampal function has been implicated in other models of monogenic forms of autism spectrum disorders and ID and is often linked to epilepsy and behavioural abnormalities. Many individuals with CDKL5 deficiency disorder (CDD) have null mutations and complete loss of CDKL5 protein, therefore in the current study we used a Cdkl5-/y rat model to elucidate the impact of CDKL5 loss on cellular excitability and synaptic function of CA1 pyramidal cells (PCs). We hypothesised abnormal pre and/or post synaptic function underlie the enhanced LTP we observe in the hippocampus of Cdkl5-/y rats. Methods: To allow cross-species comparisons of phenotypes associated with the loss of CDKL5, we generated a loss of function mutation in exon 5 of the rat Cdkl5 gene and assessed the impact of the loss of CDLK5 using a combination of extracellular and whole-cell electrophysiological recordings, biochemistry, and histology. Results: Our results indicate that CA1 hippocampal LTP is enhanced in slices prepared from juvenile, but not adult, Cdkl5-/y rats. Enhanced LTP does not result from changes in NMDA receptor function or subunit expression as these remain unaltered throughout development. Furthermore, Ca2+ permeable AMPA receptor mediated currents are unchanged in Cdkl5-/y rats. We observe reduced mEPSC frequency accompanied by increased spine density in basal dendrites of CA1 PCs, however we find no evidence supporting an increase in silent synapses when assessed using a minimal stimulation protocol in slices. Additionally, we found no change in paired-pulse ratio, consistent with normal release probability at Schaffer collateral to CA1 PC synapses. Conclusions: Our data indicate a role for CDKL5 in hippocampal synaptic function and raise the possibility that altered intracellular signalling rather than synaptic deficits contribute to the altered plasticity. Limitations: This study has focussed on the electrophysiological and anatomical properties of hippocampal CA1 PCs across early postnatal development. Studies involving other brains regions, older animals and behavioural phenotypes associated with the loss of CDKL5 are needed to understand the pathophysiology of CDD.

Project description:The gain-of-function mutation of c.G6055A (p.G2019S) in Leucine-rich repeat kinase 2 (LRRK2) gene is the most prevalent genetic cause of Parkinson’s disease (PD). Although clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-based genome editing has been used to generate isogenic control lines, there are risks of creating indels and genomic instability together with a lower efficiency in non-dividing cells. The recent advance of adenine base editors (ABEs) could convert targeted A•T base pairs to G•C base pairs without double-strand DNA breaks or donor DNA templates and function in post-mitotic cells. Here, we demonstrate a complete correction of an induced pluripotent stem cell (iPSC) line derived from a PD patient having LRRK2 p.G2019S mutation using variable genome editing methods, including CRISPR/Cas9-based homology-directed repair (HDR) and ABEs. The corrected isogenic iPSCs derived dopaminergic neurons showed a down-regulated LRRK2 kinase activity, decreased phospho-a-synuclein accumulations, reduced apoptosis and restored neurite shrinkage phenotypes. The mutation correction efficacy, off-target and indels rates between CRISPR/Cas9-HDR and ABE were compared. Among the 47 clones generated by HDR, 3 clones (6.4%) were on-targeted corrected, while ABE showed a much higher correction rate (13 of 53 clones, 24.5%). Whole genome sequencing analysis revealed that there are 27 clones of HDR (57.4%) having deletions but none in clones of ABE, albeit ABE created 14 clones (26.4%) having off-target missense mutations. RNA sequencing and proteomic analysis of the mutant line identified 2220 differentially expressed genes compared with its isogenic control. Enrichment analysis demonstrated an over-representation of PD relevant pathways, including calcium ion dependent exocytosis, synaptic transports well as potential novel targets relevant to PD pathophysiology. These results envision that ABE could directly correct the pathogenic PD mutation in iPSCs for exploring the earliest events in PD pathophysiology and providing dopaminergic neurons for future cell therapies.

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Base editing restores CDKL5 expression and rescues neuronal deficits in a patient-derived model of CDKL5 deficiency disorder

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