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, <i>PIGA</i>, 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 <i>Piga</i> from the embryonic mouse brain which led to early postnatal death and significant structural brain malformations similar to those observed in humans with <i>PIGA</i> variants. The current treatment options for <i>PIGA</i> patients only manage symptoms and provides palliative care, demonstrating a need for new therapeutic options. We employed an AAV9-mediated <i>PIGA</i> gene-replacement (AAV9-<i>hPIGA</i>) 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-<i>hPIGA</i> 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 <i>PIGA</i>-related symptoms.