The study investigates the delivery of adeno-associated virus-9 (AAV9) to the central nervous system (CNS) via intravenous injection in neonatal and adult mice. AAV9 is a promising gene delivery vector that can cross the blood-brain barrier (BBB) and target various cell types in the CNS. In neonatal mice, AAV9 efficiently transduced motor neurons in the spinal cord and astrocytes in the brain, while in adult mice, it primarily transduced astrocytes in the spinal cord and brain regions such as the hippocampus and dentate gyrus. The study highlights the unique capacity of AAV9 to target specific cell types in the CNS, which could be clinically relevant for treating neurodegenerative diseases like spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS). The findings suggest that AAV9 may offer a non-invasive method for gene delivery to the CNS, potentially allowing for rapid and cost-effective generation of chimeric animals for gene overexpression or knock-down studies.The study investigates the delivery of adeno-associated virus-9 (AAV9) to the central nervous system (CNS) via intravenous injection in neonatal and adult mice. AAV9 is a promising gene delivery vector that can cross the blood-brain barrier (BBB) and target various cell types in the CNS. In neonatal mice, AAV9 efficiently transduced motor neurons in the spinal cord and astrocytes in the brain, while in adult mice, it primarily transduced astrocytes in the spinal cord and brain regions such as the hippocampus and dentate gyrus. The study highlights the unique capacity of AAV9 to target specific cell types in the CNS, which could be clinically relevant for treating neurodegenerative diseases like spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS). The findings suggest that AAV9 may offer a non-invasive method for gene delivery to the CNS, potentially allowing for rapid and cost-effective generation of chimeric animals for gene overexpression or knock-down studies.