Gene replacement therapy for Piga GPI-anchor deficiency in the developing nervous system

Glycosylphosphatidylinositol (GPI) anchors are a class of post-translational modifications observed on over 150 proteins. Pathogenic variants in the GPI biosynthesis enzyme, PIGA, in humans are associated with several brain anomalies such as hypomyelination, cerebellar hypoplasia, ataxic gait, and can lead to premature mortality. We previously genetically deleted Piga from the embryonic mouse brain which led to early postnatal death and significant structural brain malformations similar to those observed in humans with PIGA variants. The current treatment options for PIGA patients only manage symptoms and provides palliative care, demonstrating a need for new therapeutic options. We employed an AAV9-mediated PIGA gene-replacement (AAV9-hPIGA) strategy to assess the efficacy of gene therapy in the brain. We show that a single intracerebroventricular treatment on the first day of life successfully rescued survival rates, structural brain anomalies, and neurological impairments. Additionally, we used mass spectrometry to identify and quantify GPI-anchored proteins in untreated and treated mutant mice. We found that AAV9-hPIGA treatment restored GPI-anchored protein levels in mutant animals. These investigations enhance our understanding of GPI-anchored protein production during brain development and contribute to the development of a more effective intervention for PIGA-related symptoms.