De novo variants in SLC12A6 cause sporadic early-onset progressive sensorimotor neuropathy

Background Charcot-Marie- Tooth disease(CMT) is a clinically and genetically heterogeneous disorderof the peripheral nervous system. Biallelic variants in SLC12A6 have been associated with autosomal-recessive hereditary motorand sensory neuropathywith agenesisof the corpus callosum(HMSN/ACC). We identified heterozygous de novo variants in SLC12A6 in three unrelated patients with intermediate CMT. Methods We evaluated the clinical reports and electrophysiological data of three patients carrying de novo variants in SLC12A6 identified by diagnostic trio exome sequencing. For functional characterisation of the identified variants, potassium influx of mutated KCC3 cotransporterswas measured in Xenopusoocytes. Results We identified two different de novo missense changes (p.Arg207His and p.Tyr679Cys) in SLC12A6 in three unrelated individuals with early-onset progressive CMT. All presented with axonal/demyelinating sensorimotor neuropathy accompanied by spasticity in one patient. Cognition and brain MRI were normal. Modellingof the mutant KCC3 cotransporterin Xenopusoocytes showed a significant reduction in potassium influx for both changes. Conclusion Our findings expand the genotypic and phenotypic spectrum associated with SLC12A6 variants from autosomal-recessive HMSN/ACC to dominant-acting de novo variants causing a milder clinical presentation with early-onset neuropathy.