Background Hydranencephaly is a congenital anomaly leading to replacement of the cerebral hemispheres with a fluid-filled cyst. The goals of this work are to describe a novel autosomal-recessive syndrome that includes hydranencephaly (multinucleated neurons, anhydramnios, renal dysplasia, cerebellar hypoplasia and hydranencephaly (MARCH)); to identify its genetic cause(s) and to provide functional insight into pathomechanism.
Methods We used homozygosity mapping and exome sequencing to identify recessive mutations in a single family with three affected fetuses. Immunohistochemistry, RT-PCR and imaging in cell lines, and zebrafish models, were used to explore the function of the gene and the effect of the mutation.
Results We identified a homozygous nonsense mutation in CEP55 segregating with MARCH. Testing the effect of this allele on patient-derived cells indicated both a reduction of the overall CEP55 message and the production of a message that likely gives rise to a truncated protein. Suppression or ablation of cep55l in zebrafish embryos recapitulated key features of MARCH, most notably renal dysplasia, cerebellar hypoplasia and craniofacial abnormalities. These phenotypes could be rescued by full-length but not truncated human CEP55 message. Finally, we expressed the truncated form of CEP55 in human cells, where we observed a failure of truncated protein to localise to the midbody, leading to abscission failure and multinucleated daughter cells.
Conclusions CEP55 loss of function mutations likely underlie MARCH, a novel multiple congenital anomaly syndrome. This association expands the involvement of centrosomal proteins in human genetic disorders by highlighting a role in midbody function.
- multinucleated neurons
- Potter sequence
- renal dysplasia
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Collaborators FORGE Canada Consortium (FORGE Steering Committee membership is listed in Supplement 1) Canadian Rare Diseases: Models & Mechanisms Network (Canadian Rare Diseases: Models & Mechanisms Network Committee memberships are listed in Supplement 1).
Contributors PF and HHA contributed equally. PF provided clinical care, designed the study, performed homozygosity mapping and wrote the initial manuscript. HHA and RH performed confocal microscopy, RT-PCR, aided in study design and contributed to manuscript preparation. JP, CSG, CR and YPL performed zebrafish experiments and contributed to manuscript preparation. ELB performed confocal microscopy, RT-PCR, and contributed to manuscript preparation. BC provided clinical care and contributed to manuscript preparation. LS performed variant validation and contributed to manuscript preparation. JM and SF provided bioinformatics support and contributed to the manuscript preparation. FORGE and RDMM are consortia that supported the study and members were involved in gene identification, connecting the collaborating authors and providing feedback on the manuscript. NK and EED designed the zebrafish experiments, aided in overall study design and contributed to manuscript preparation. CG and MRDB performed neuropathological analysis, immunohistochemistry, western blotting and contributed to manuscript preparation.
Funding This work was supported in part by the FORGE Canada consortium and a catalyst grant from the Canadian Rare Diseases: Models & Mechanisms Network (RDMM). Both of these initiatives are funded through grants from the Canadian Institutes of Health Research (CIHR) and Genome Canada with additional funding for FORGE being provided by the Ontario Genomics Institute, Genome Quebec, Genome British Columbia, and the McLaughlin Centre. This work was also supported by US NIH grants DK096415, DK075972 and HD042601 (NK); DK072301 and DK096493 (NK and EED). PF received support from the Rare Disease Foundation and the B.C. Children’s Hospital Foundation (P#46). HHA also received support from the Netherlands Organization for Scientific Research (NWO Veni-91613008) and the Dutch Kidney Foundation (CP11.18 ‘KOUNCIL’). MRDB is supported through the Canada Research Chair in Developmental Neuropathology. CSG was supported by a summer studentship from the Children’s Hospital Research Institute of Manitoba. NK is a distinguished Jean and George Brumley Professor.
Competing interests None declared.
Patient consent Obtained.
Ethics approval University of Manitoba. University of Manitoba, University of Ottawa, University of Western Ontario, and McGill University.
Provenance and peer review Not commissioned; externally peer reviewed.
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