Base editing corrects the common Salla disease SLC17A5 c.115C>T variant

Free sialic acid storage disorders (FSASDs) result from pathogenic variations in the SLC17A5 gene, which encodes the lysosomal transmembrane protein sialin. Loss or deficiency of sialin impairs FSA transport out of the lysosome, leading to cellular dysfunction and neurological impairment, with the most severe form of FSASD resulting in death during early childhood. There are currently no therapies for FSASDs. Here, we evaluated the efficacy of CRISPR-Cas9-mediated homology directed repair (HDR) and adenine base editing (ABE) targeting the founder variant, SLC17A5 c.115C>T (p.Arg39Cys) in human dermal fibroblasts. We observed minimal correction of the pathogenic variant in HDR samples with a high frequency of undesired insertions/deletions (indels) and significant levels of correction for ABE-treated samples with no detectable indels, supporting previous work showing that CRISPR-Cas9-mediated ABE outperforms HDR. Furthermore, ABE treatment of either homozygous or compound heterozygous SLC17A5 c.115C>T human dermal fibroblasts demonstrated significant FSA reduction, supporting amelioration of disease pathology. Translation of this ABE strategy to mouse embryonic fibroblasts harboring the Slc17a5 c.115C>T variant in homozygosity recapitulated these results. Our study demonstrates the feasibility of base editing as a therapeutic approach for the FSASD variant SLC17A5 c.115C>T and highlights the usefulness of base editing in monogenic diseases where transmembrane protein function is impaired.

GM1 Gangliosidosis: Mechanisms and Management

The lysosomal storage disorder, GM1 gangliosidosis (GM1), is a neurodegenerative condition resulting from deficiency of the enzyme β-galactosidase (β-gal). Mutation of the GLB1 gene, which codes for β-gal, prevents cleavage of the terminal β-1,4-linked galactose residue from GM1 ganglioside. Subsequent accumulation of GM1 ganglioside and other substrates in the lysosome impairs cell physiology and precipitates dysfunction of the nervous system. Beyond palliative and supportive care, no FDA-approved treatments exist for GM1 patients. Researchers are critically evaluating the efficacy of substrate reduction therapy, pharmacological chaperones, enzyme replacement therapy, stem cell transplantation, and gene therapy for GM1. A Phase I/II clinical trial for GM1 children is ongoing to evaluate the safety and efficacy of adeno-associated virus-mediated GLB1 delivery by intravenous injection, providing patients and families with hope for the future.

Electrostatic Complementarity Drives Amyloid/Nucleic Acid Co-Assembly

Proteinaceous plaques associated with neurodegenerative diseases contain many biopolymers including the polyanions glycosaminoglycans and nucleic acids. Polyanion-induced amyloid fibrillation has been implicated in disease etiology, but structural models for amyloid/nucleic acid co-assemblies remain limited. Here we constrain nucleic acid/peptide interactions with model peptides that exploit electrostatic complementarity and define a novel amyloid/nucleic acid co-assembly. The structure provides a model for nucleic acid/amyloid co-assembly as well as insight into the energetic determinants involved in templating amyloid assembly.