A novel preclinical mouse model recapitulates progressive phenotypes of Bryant-Li-Bhoj Syndrome

Bryant-Li-Bhoj Syndrome (BLBS; OMIM: 619720, 619721) is a Mendelian neurogenetic condition, first described in 2020, with a mixed neurodevelopmental/neurodegenerative phenotype and variable systemic features. To date, 100 affected individuals with 74 unique causative variants have been published. Clinical data and prior functional work in multiple model systems have emphasized the utility of interrogating the pathogenesis of multiple causal variants to identify a convergent, therapeutically targetable mechanism. Additionally, the ability to evaluate the efficacy of future therapeutics relies on the availability of a robustly validated preclinical model. Here, we characterize the developmental and neurobehavioral phenotypes of a novel BLBS mouse model harboring one of the most recurrent causative variants (h3-3a p.T45I). H3.3T45I mice recapitulate the BLBS natural history: perinatal growth restriction, delayed developmental milestones, and progressive motor and gait impairments. Adult mice additionally display craniofacial differences, impaired nest building, hyperactivity in a social context, and male-specific elevated aggression. The non-invasive, clinically translatable endpoints established here provide a validated preclinical platform for evaluating therapeutics for a community whose current standard of care is symptom management. Summary StatementA new mouse model mirrors the developmental delays, motor decline, and behavioral changes seen in individuals with this rare, progressive genetic brain disorder, providing a foundation for testing future therapies.