Development of a Gene Therapy for UBA5 Deficiency - Project summary/Abstract Variants in the ubiquitin like modifier activating enzyme 5 (UBA5) result in an ultra-rare autosomal recessive disease with neurological presentations. UBA5 patients present with infantile spasms, failure to thrive, hypotonia, developmental delay, microcephaly, intellectual deficit, loss of motor skills and seizures. Most of the patients die in childhood. Current standard of care for UBA5 deficiency is focused on managing the clinical signs with standard anti-seizure medications or surgical procedures and physical therapies, but there is no treatment. Compound heterozygous mutations in UBA5 causes impairment in a ubiquitin-like post-translational modification pathway called Ubiquitin-fold modifier 1 (UFM1). UBA5 is an E1 activating enzyme on UFM1 pathway. The role of the UBA5 and UFM1 system in the central nervous system (CNS) has not been studied. This stems from lack of a viable mammalian model for UBA5 deficiency. Our team has identified the first viable Uba5 mouse model that carries patient mutation, exhibits an overt phenotype, and recapitulates presentations of UBA5 deficiency in patients including smaller body size, motor, cognitive and gait abnormalities. Our team has postmortem tissues of UAB5 patients, their clinical course, MRI and EEG records. The first neuropathological characterization of postmortem UBA5 patient brain indicates the shared features with Uba5 mice. To determine the top adeno associated virus (AAV) vector candidate for efficacy studies in Uba5 mouse, we developed four UBA5 expressing constructs and showed their 1) efficacy in restoration of expression and function of UBA5 in UBA5 Knockout HEK293T cells and 2) durability, safety, and cell type tropism in a one-year study in wild type mouse. The top candidate, AAV9-JeT-UBA5, restored motor, cognitive and most aspect of gait abnormalities in Uba5 mouse model treated by neonatal intracerebroventricular (ICV) treatment. However, weight of treated Uba5 mice did not get normalized. We hypothesize that gradual loss of transduced cells in liver prevented long term weight gain normalization. Since the overarching goal of this project is to develop a transformational AAV gene therapy to treat our symptomatic UBA5 patient cohort at UMass Chan, we need to address the therapeutic imperfections and develop biomarkers. We will perform CNS and periphery wide gene therapy of JeT-UBA5 in pre and post symptomatic Uba5 mouse to determine the therapeutic window and feasibility of gene therapy to rescue or modify disease course. We will use 1) AAV9 capsid for combined CSF and periphery wide gene delivery in Uba5 mouse and 2) a new blood-brain barrier penetrant capsid (BI-hTFR1; interact with human Transferrin Receptor (TFRC)) for very efficient gene delivery to CNS and periphery by systemic injection. We will perform an in-depth characterization of the Uba5 mouse model and its humanized version, expressing TFRC, with clinically relevant outcomes measure (MRI and EEG) and compare them with patient findings (Aim 1). Four gene therapy approaches will be performed in Aim 2. In Aim 3 metabolomic based biomarker discovery will be performed and the best gene therapy approach to normalize transcriptomic profile of Uba5 mouse of will be determined.
