Autosomal dominant Zellweger Spectrum Disorder caused by de novo variants in PEX14 gene

Zellweger spectrum disorders (ZSDs) are known as autosomal recessive disorders caused by defective peroxisome biogenesis due to bi-allelic pathogenic variants in any of at least 13 different PEX genes. Here we report two unrelated patients who present with an autosomal dominant ZSD. We performed biochemical and genetic studies in blood and skin fibroblasts of the patients and demonstrated the pathogenicity of the identified PEX14 variants by functional cell studies. We identified two different single heterozygous de novo variants in the PEX14 genes of two patients diagnosed with ZSD. Both variants cause mRNA mis-splicing leading to stable expression of similar C-terminally truncated PEX14 proteins. Functional studies indicated that the truncated PEX14 proteins lost their function in peroxisomal matrix protein import and cause increased degradation of peroxisomes, i.e. pexophagy, thus exerting a dominant-negative effect on peroxisome functioning. Inhibition of pexophagy by different autophagy inhibitors or genetic knock-down of the peroxisomal autophagy receptor NBR1 resulted in restoration of peroxisomal functions in the patients’ fibroblasts. Our finding of an autosomal dominant ZSD expands the genetic repertoire of ZSDs. Our study underscores that single heterozygous variants should not be ignored as possible genetic cause of diseases with an established autosomal recessive mode of inheritance.