Autosomal dominant Zellweger spectrum disorder caused by de novo variants in PEX14 gene

Purpose: 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 2 unrelated patients who present with an autosomal dominant ZSD. Methods: 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. Results: We identified 2 different single heterozygous de novo variants in the PEX14 genes of 2 patients diagnosed with ZSD. Both variants cause messenger RNA 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, ie, pexophagy, thus exerting a dominant-negative effect on peroxisome functioning. Inhibition of pexophagy by different autophagy inhibitors or genetic knockdown of the peroxisomal autophagy receptor NBR1 resulted in restoration of peroxisomal functions in the patients' fibroblasts. Conclusion: 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 ge-netic cause of diseases with an established autosomal recessive mode of inheritance. & COPY; 2023 The Authors. Published by Elsevier Inc. on behalf of American College of Medical Genetics and Genomics. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

We report two unrelated patients with autosomal dominant Zellweger spectrum disorders (ZSDs). Biochemical and genetic studies revealed single heterozygous de novo variants in the PEX14 genes of both patients, leading to mRNA mis-splicing and expression of truncated PEX14 proteins. Functional studies demonstrated the dominant-negative effect of these truncated proteins on peroxisome functioning, which was restored by inhibition of pexophagy.