Therapeutic suppression ofTubb4arescues H-ABC leukodystrophy

Hypomyelination and atrophy of basal ganglia and cerebellum (H-ABC) is a rare leukodystrophy associated with causal variants in β-tubulin 4A ( TUBB4A ). The recurring variant p.Asp249Asn (D249N) presents in infancy with dystonia, communication deficits, and loss of ambulation during the first decade of life. In this study, we characterized a genetic murine series ( Tubb4a KO/KO , Tubb4a D249N/+ , Tubb4a D249N/KO, and Tubb4a D249N/D249N ) to demonstrate that disease severity correlates with the expression of mutant Tubb4a and relative preservation of WT tubulin. To further evaluate the translational potential of Tubb4a suppression as a therapy in H-ABC, we identified a well-tolerated Tubb4a -targeted antisense oligonucleotide (ASO) candidate that selectively reduces Tubb4a. Notably, single intracerebroventricular (i.c.v.) administration of ASO in postnatal Tubb4a D249N/KO mice drastically extends its lifespan, improves motor phenotypes, and reduces seizures. Neuropathologically, treating ASO Tubb4a D249N/KO mice prevents myelin and oligodendrocyte loss and recovers visual evoked potential latencies in vivo . Furthermore, the microtubule function of Mbp mRNA transport from oligodendrocyte (OL) soma to myelin sheath is retained. A major limitation we noted is that ASOs fail to target cerebellar granule neurons even with multiple routes of administration in the brain. This is the first preclinical proof-of-concept for Tubb4a suppression via ASO as a disease-modifying therapy for H-ABC.