Background 3C/Ritscher-Schinzel syndrome is characterised by congenital cranio-cerebello-cardiac dysplasia, where CCDC22 and WASHC5 are accepted as the causative genes. In combination with the retromer or retriever complex, these genes play a role in endosomal membrane protein recycling. We aimed to identify the gene abnormality responsible for the pathogenicity in siblings with a 3C/Ritscher-Schinzel-like syndrome, displaying cranio-cerebello-cardiac dysplasia, coloboma, microphthalmia, chondrodysplasia punctata and complicated skeletal malformation.
Methods Exome sequencing was performed to identify pathogenic variants. Cellular biological analyses and generation of knockout mice were carried out to elucidate the gene function and pathophysiological significance of the identified variants.
Results We identified compound heterozygous pathogenic variants (c.1097dup; p.Cys366Trpfs*28 and c.2755G>A; p.Ala919Thr) in the VPS35L gene, which encodes a core protein of the retriever complex. The identified missense variant lacked the ability to form the retriever complex, and the frameshift variant induced non-sense-mediated mRNA decay, thereby confirming biallelic loss of function of VPS35L. In addition, VPS35L knockout cells showed decreased autophagic function in nutrient-rich and starvation conditions, as well as following treatment with Torin 1. We also generated Vps35l−/− mice and demonstrated that they were embryonic lethal at an early stage, between E7.5 and E10.5.
Conclusions Our results suggest that biallelic loss-of-function variants in VPS35L underlies 3C/Ritscher-Schinzel-like syndrome. Furthermore, VPS35L is necessary for autophagic function and essential for early embryonic development. The data presented here provide a new insight into the critical role of the retriever complex in fetal development.
- retriever complex
- chondrodysplasia punctata
- knockout mouse
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Contributors KK, FFV and TaO performed functional analyses. KK and HO generated the mutant mice. YO, HM, YN, ToO and SS analysed and interpreted the data. KK, HK and YK contributed the clinical data. KK and SS drafted the manuscript. TaO, ToO and YT revised the manuscript.
Funding This study was partially supported by JSPS KAKENHI Grant Number JP16K15530 (to SS), JP17H05088 (to ToO) and by the Program for an Integrated Database of Clinical and Genomic Information from the Japanese Agency for Medical Research and Development (to SS).
Competing interests None declared.
Patient consent for publication Parental/guardian consent obtained.
Ethics approval This study was approved by the institutional review board of Nagoya City University Graduate School of Medical Sciences and Nagoya University Graduate School of Medicine.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.