AAV-Mediated GALC Gene Therapy Rescues Alpha-Synucleinopathy in the Spinal Cord of a Leukodystrophic Lysosomal Storage Disease Mouse Model

Abstract

Krabbe's disease (KD) is primarily a demyelinating disorder, but recent studies have identified the presence of neuronal protein aggregates in the brain, at least partially composed by alpha-synuclein (α-syn). The role of this protein aggregation in the pathogenesis of KD is largely unknown, but it has added KD to a growing list of lysosomal storage diseases that can be also be considered as proteinopathies. While the presence of these protein aggregates within the KD brain is now appreciated, the remainder of the central nervous system (CNS) remains uncharacterized. This study is the first to report the presence of thioflavin-S reactive inclusions throughout the spinal cord of both murine and human spinal tissue. Stereological analysis revealed the temporal and spatial accumulation of these inclusions within the neurons of the ventral spinal cord vs. those located in the dorsal cord. This study also confirmed that these thio-S positive accumulations are present within neuronal populations and are made up at least in part by α-syn in both the twitcher mouse and cord autopsied material from affected human patients. Significantly, neonatal gene therapy for galactosylceramidase, a treatment that strongly improves the survival and health of KD mice, but not bone marrow transplantation prevents the formation of these inclusions in spinal neurons. These results expand the understanding of α-syn protein aggregation within the CNS of individuals afflicted with KD and underlines the tractability of this problem via early gene therapy, with potential impact to other synucleinopathies such as PD.

Chronic lithium administration in a mouse model for Krabbe disease

“…Currently, many therapeutic approaches for KD are currently under pre‐clinical studies, as GT (mainly based on adeno‐associated vector), 36,68 chaperone‐mediated therapies, 11 or nanovector‐mediated ERT 20 . Among them, GT demonstrated to be able to increase GALC levels in the TWI tissues up to the WT levels, to reduce the cytotoxic PSY‐accumulations, to improve the motor behaviour of TWI mice, and, very importantly, to extend the lifespan from ~45 days to ~500 to 700 days 36 . Unfortunately, however, in all GT studies KD mice at a certain point died with uncertain complications 36,68‐70 .…”

“… 20 Among them, GT demonstrated to be able to increase GALC levels in the TWI tissues up to the WT levels, to reduce the cytotoxic PSY‐accumulations, to improve the motor behaviour of TWI mice, and, very importantly, to extend the lifespan from ~45 days to ~500 to 700 days. 36 Unfortunately, however, in all GT studies KD mice at a certain point died with uncertain complications. 36 , 68 , 69 , 70 Two very recently published papers suggest that GT could not be able to efficiently act on a long time due to the exhaustion of therapeutic AAV episomal DNA in specific regions, 23 or to the onset of additional pathological events unrelated to KD, as hepatocellular carcinoma (HCC).…”

“… 34 It is noteworthy that alpha‐synuclein aggregates have just been recently found accumulated in KD human and mouse brains. 31 , 32 , 35 , 36 …”

Alpha-Synuclein and Lipids: The Elephant in the Room?

“…Mutations in the GALC gene are responsible for Krabbe disease, a demyelinating disorder characterised by the presence of neuronal aggregates, in part composed of α-syn [200].…”

“…Galactosylceramidase treatment improves the survival and health of KD mice, prevents the formation of α-syn in spinal neurons [200] galactosylsphingosine accelerates aggregation of α-syn in a dose-dependent manner [202].…”