Neuronal DNA repair reveals strategies to influence CRISPR editing outcomes
Ontology highlight
ABSTRACT: Genome editing is poised to revolutionize treatment of genetic diseases, but poor understanding and control of DNA repair outcomes hinders its therapeutic potential. DNA repair is especially understudied in nondividing cells like neurons, which must withstand decades of DNA damage without replicating. This lack of knowledge limits the efficiency and precision of genome editing in clinically relevant cells. To address this, we used induced pluripotent stem cells (iPSCs) and iPSC-derived neurons to examine how postmitotic human neurons repair Cas9-induced DNA damage. We discovered that neurons can take weeks to fully resolve this damage, compared to just days in isogenic iPSCs. Furthermore, Cas9-treated neurons upregulated unexpected DNA repair genes, including factors canonically associated with replication. Manipulating this response with chemical or genetic perturbations allowed us to direct neuronal repair toward desired editing outcomes. By studying DNA repair in postmitotic human cells, we uncovered unforeseen challenges and opportunities for precise therapeutic editing.
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.
Project description:CRISPR-Cas9 delivery by AAV holds promise for gene therapy but faces critical barriers due to its potential immunogenicity and limited payload capacity. Here, we demonstrate genome engineering in postnatal mice using AAV-split-Cas9, a multi-functional platform customizable for genome-editing, transcriptional regulation, and other previously impracticable AAV-CRISPR-Cas9 applications. We identify crucial parameters that impact efficacy and clinical translation of our platform, including viral biodistribution, editing efficiencies in various organs, antigenicity, immunological reactions, and physiological outcomes. These results reveal that AAV-CRISPR-Cas9 evokes host responses with distinct cellular and molecular signatures, but unlike alternative delivery methods, does not induce detectable cellular damage in vivo. Our study provides a foundation for developing effective genome therapeutics mRNA-Seq from muscles (9 samples; 3 mice x 3 conditions) and lymph nodes (9 samples; 3 mice x 3 conditions).
Project description:DNA damage has been implicated in neurodegenerative disorders, including Alzheimer’s disease and other tauopathies, but the consequences of genotoxic stress to postmitotic neurons are poorly understood. Here we demonstrate that p53, a key mediator of the DNA damage response, plays a neuroprotective role in a Drosophila model of tauopathy. Further, through a whole-genome ChIP-chip analysis we identify genes controlled by p53 in postmitotic neurons. We genetically validate a specific pathway, synaptic function, in p53-mediated neuroprotection. We then demonstrate that the control of synaptic genes by p53 is conserved in mammals. Collectively, our results implicate synaptic function as a central target in p53-dependent protection from neurodegeneration. 4 samples: tau vs. control
Project description:Precise genome editing is crucial for establishing isogenic human disease models and ex vivo stem cell therapy from the patient-derived human pluripotent stem cells (hPSCs). Unlike Cas9-mediated knock-in, cytosine base editor (CBE) and prime editor (PE) achieve the desirable gene correction without inducing DNA double strand breaks. However, hPSCs possess highly active DNA repair pathways and are particularly susceptible to p53-dependent cell death. These unique characteristics impede the efficiency of gene editing in hPSCs. Here, we demonstrate that dual inhibition of p53-mediated cell death and distinct activation of the DNA damage repair system upon DNA damage by CBE or PE additively enhanced editing efficiency in hPSCs. The BE4stem system comprised of dominant negative p53 (p53DD) and three UNG inhibitor (UGI), engineered to specifically diminish base excision repair (BER), improved CBE efficiency in hPSCs. Addition of dominant negative MLH1 to inhibit mismatch repair activity and p53DD in the conventional PE system also significantly enhanced PE efficiency in hPSCs. Thus, combined inhibition of the unique cellular cascades engaged in hPSCs upon gene editing could significantly enhance precise genome editing in these cells.
Project description:Precise genome editing is crucial for establishing isogenic human disease models and ex vivo stem cell therapy from the patient-derived human pluripotent stem cells (hPSCs). Unlike Cas9-mediated knock-in, cytosine base editor (CBE) and prime editor (PE) achieve the desirable gene correction without inducing DNA double strand breaks. However, hPSCs possess highly active DNA repair pathways and are particularly susceptible to p53-dependent cell death. These unique characteristics impede the efficiency of gene editing in hPSCs. Here, we demonstrate that dual inhibition of p53-mediated cell death and distinct activation of the DNA damage repair system upon DNA damage by CBE or PE additively enhanced editing efficiency in hPSCs. The BE4stem system comprised of dominant negative p53 (p53DD) and three UNG inhibitor (UGI), engineered to specifically diminish base excision repair (BER), improved CBE efficiency in hPSCs. Addition of dominant negative MLH1 to inhibit mismatch repair activity and p53DD in the conventional PE system also significantly enhanced PE efficiency in hPSCs. Thus, combined inhibition of the unique cellular cascades engaged in hPSCs upon gene editing could significantly enhance precise genome editing in these cells.
Project description:DNA damage has been implicated in neurodegenerative disorders, including Alzheimer’s disease and other tauopathies, but the consequences of genotoxic stress to postmitotic neurons are poorly understood. Here we demonstrate that p53, a key mediator of the DNA damage response, plays a neuroprotective role in a Drosophila model of tauopathy. Further, through a whole-genome ChIP-chip analysis we identify genes controlled by p53 in postmitotic neurons. We genetically validate a specific pathway, synaptic function, in p53-mediated neuroprotection. We then demonstrate that the control of synaptic genes by p53 is conserved in mammals. Collectively, our results implicate synaptic function as a central target in p53-dependent protection from neurodegeneration.
2015-01-06 | GSE40418 | GEO
Project description:Investigating the DNA repair outcomes induced by CRISPR gene editing
Project description:The activation status of some DNA damage repair proteins is closely related to the efficacy of CDDP chemotherapy in MIBC. In this study, we used CRISPR/cas9 gene-editing technology to construct hMSH2-deficient bladder cancer cells and confirmed that loss of hMSH2 decreased the sensitivity of bladder cancer cells to cisplatin. Transcriptome analysis was performed to find the potential genes that could be regulated by hMSH2.