Abstract
The neuronal ceroid lipofuscinoses (NCLs), colloquially referred to as Batten disease (BD), encompass a heterogenous group of neurodegenerative lysosomal storage disorders resulting from variants in 13 known genes. The NCLs share many clinical phenotypes that include a progressive intellectual and motility disability, myoclonic epilepsy, blindness, and cerebral atrophy before eventual patient death. While individually rare genetic disorders, the NCLs collectively represent the most common neurodegenerative disorders found in children. The NCLS are grouped together based on shared clinical phenotypes and the deposition of lysosomal autofluorescent storage material. Currently, approved treatments for most forms of the NCLs focuses primarily on palliative care, though enzyme replacement therapy, stem cell therapy, gene therapy vectors, and pharmacological drug treatments have undergone clinical trials for their safety and efficacy for some forms of NCL. Recently, a viral vector gene therapy for several forms of Batten disease has been approved by the FDA.
Variants in ATP13A2 lead to the development of two distinct neurological disorders, Kufor-Rakeb Syndrome, a juvenile-onset parkinsonism and CLN12 Batten disease, an NCL, indicating that Parkinson’s and Batten disease may have similar mechanisms of development. The underlying cause of Parkinson’s Disease (PD) is unknown, though the accumulation of misfolded proteins suggests improper disposal of aggregate-prone proteins plays an important role in its pathogenesis. PD and Batten variants have been modeled in animal and cell models, though none fully recapitulate the pathology seen in humans. Therefore, it is imperative to develop more comprehensive models for disease study. My aim in this study was to establish a novel model of CLN12 Batten disease in human neurons for the assessment of pathological hallmarks.
To investigate CLN12 Batten disease, I established a novel line of iPSC derived CLN12 deficient neuronal cultures to provide accurate modeling of human cell biology. CRISPRi was implemented to inhibit the endogenous CLN12 locus through lentiviral transduction of sgRNAs into neurons, achieving a 99% knockdown. CLN12 knockdown in neurons resulted in changes in cell morphology, and lysosomal as well as mitochondrial dysfunction. Some of the hallmarks shown here were shared with other neurodegenerative disorders, highlighting a possible shared mechanism of action. Knockdown of CLN12 coincided with increased of α-synuclein deposition, inhibited lysosomal trafficking, changes in total neurite length, increased lysosomal cathepsin activity, decreased mitochondrial membrane potential and health and loss of dendritic synapse density.
Given the findings made here and recent publications, CLN12 bears a crucial role in maintaining neuronal homeostasis, its absence quickly leading to dysfunction in multiple interconnected systems. Collectively, these findings establish a human iPSC model of CLN12 deficiency as a viable tool for further research.