B5 - Neurologic Diseases (excluding Ophthalmic and Auditory Diseases)
619: Novel AAV Gene Therapy Candidates Show Promise In Vitro and In Vivo for Treatment of PGAP3-CDG Syndrome
Type: Poster Session
Poster Board Number: 619
Presentation Details
Session Title: Wednesday Posters: Neurologic Diseases
PGAP3-Congenital Disorder of Glycosylation (PGAP3-CDG) is a devastating, rare neurological condition that disrupts the synthesis of Glycosylphosphatidylinositol (GPI) anchors. PGAP3-CDG patients exhibit a diverse spectrum of symptoms that vary in age of onset and severity including developmental delay, intellectual disability, seizures, hypotonia, and characteristically high levels of serum alkaline phosphatase (hyperphosphatasia). Currently, there is no evidence of a close genotype-phenotype correlation. Current treatment strategies for PGAP3-CDG only focus on management of symptoms and do not impact disease progression. Furthermore, the intricate pathogenic mechanisms associated with PGAP3 mutations, particularly in neurons and astrocytes, remain poorly understood, impeding therapeutic advancements. This underscores the urgent need to unravel the pathophysiology and develop effective interventions for PGAP3-CDG. To achieve that, we have designed four different AAV9-mediated gene therapy constructs to restore PGAP3 function. To comprehensively evaluate these constructs across diverse mutations representative of the disease spectrum, we established an innovative PGAP3-CDG in vitro model. Primary fibroblasts from PGAP3-CDG patients were reprogrammed into induced neural progenitor cells and further differentiated into induced astrocytes (iAs) using a direct conversion protocol. PGAP3-CDG iAs displayed abnormal mitochondrial morphology in immunofluorescence studies, as well as significantly altered mitochondrial activity using the Seahorse XFe96 platform. In co-culture assays with healthy mouse GFP+ neurons, PGAP3-CDG iAs induced a high degree of neuronal death compared to healthy iAs. Moreover, we generated induced neurons (iNs) using the PGAP3-CDG patient fibroblasts via direct chemical conversion, finding reduced neurite length and neuron with neurite percentage compared to controls. We have optimized our in vitro AAV9 transduction protocol in both iAs and iNs, and we have successfully transduced our both of our in vitro models, showing a robust expression pattern. All constructs showed improvement on the cellular phenotype, with transduced iAs showing a remarkable improvement on neuronal support. The constructs are also being evaluated in vivo on a PGAP3 Knockout model, with some showing improvement of biochemical and clasping phenotypes, as well as in wild type mice for an initial safety assessment. Overall our candidates show efficacy on both in vitro and in vivo PGAP3-CDG Models. Collectively, the combined findings of this study will allow us to identify the optimal gene therapy vector for PGAP3-CDG treatment. These findings will support the development of upcoming IND-enabling studies.
Plain Language Summary
PGAP3-Congenital Disorder of Glycosylation (PGAP3-CDG) is a rare neurological disorder with no effective treatment. Our study explores a promising gene therapy for PGAP3-CDG using innovative techniques. We created a model representing patient cells to understand the disease better. These cells showed abnormalities, providing insights into PGAP3-CDG's underlying mechanisms. Our gene therapy candidates, delivered through AAV9, significantly improved cell health in the lab. In live models, some candidates showed positive effects on both biochemistry and behavior. These findings suggest potential breakthroughs for PGAP3-CDG treatment, offering hope for a better future. Our next steps involve refining the gene therapy and moving towards necessary regulatory studies.
Julieth A. Sierra Delgado1, Matthew Simon2, Riya Talekar1, Xiaojin Zhang1, Abuzar Kaleem1, Meysam Ganjibakhsh1, Shrestha Sinha Ray1, Shibi B. Likhite1, Cathleen Lutz2, Kathrin Meyer1
1Nationwide Childrens Hospital, Columbus, OH,2The Jackson Laboratory, Bar Harbor, ME"
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