Abstract
The exosome is a conserved multi-protein complex that is essential for correct RNA processing. Recessive variants in exosome components EXOSC3, EXOSC8, and RBM7 cause various constellations of pontocerebellar hypoplasia (PCH), spinal muscular atrophy (SMA), and central nervous system demyelination. Here, we report on four unrelated affected individuals with recessive variants in EXOSC9 and the effect of the variants on the function of the RNA exosome in vitro in affected individuals’ fibroblasts and skeletal muscle and in vivo in zebrafish. The clinical presentation was severe, early-onset, progressive SMA-like motor neuronopathy, cerebellar atrophy, and in one affected individual, congenital fractures of the long bones. Three affected individuals of different ethnicity carried the homozygous c.41T>C (p.Leu14Pro) variant, whereas one affected individual was compound heterozygous for c.41T>C (p.Leu14Pro) and c.481C>T (p.Arg161∗). We detected reduced EXOSC9 in fibroblasts and skeletal muscle and observed a reduction of the whole multi-subunit exosome complex on blue-native polyacrylamide gel electrophoresis. RNA sequencing of fibroblasts and skeletal muscle detected significant >2-fold changes in genes involved in neuronal development and cerebellar and motor neuron degeneration, demonstrating the widespread effect of the variants. Morpholino oligonucleotide knockdown and CRISPR/Cas9-mediated mutagenesis of exosc9 in zebrafish recapitulated aspects of the human phenotype, as they have in other zebrafish models of exosomal disease. Specifically, portions of the cerebellum and hindbrain were absent, and motor neurons failed to develop and migrate properly. In summary, we show that variants in EXOSC9 result in a neurological syndrome combining cerebellar atrophy and spinal motoneuronopathy, thus expanding the list of human exosomopathies.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 858-873 |
| Number of pages | 16 |
| Journal | American Journal of Human Genetics |
| Volume | 102 |
| Issue number | 5 |
| DOIs | |
| State | Published - May 3 2018 |
| Externally published | Yes |
Bibliographical note
Funding Information:We thank the families for participating and Christopher Mendoza and Gilberto (“Mike”) Averion for their help in the clinic. We would also like to thank the NIH Intramural Sequencing Center staff and Daniel MacArthur and Fengmei Zhao (Analytic and Translational Genetics Unit at Massachusetts General Hospital in collaboration with the Broad Institute of Harvard and Massachusetts Institute of Technology) for their help with exome analysis. We also thank the Exome Aggregation Consortium and the groups that provided exome variant data for comparison. A full list of contributing groups can be found at http://exac.broadinstitute.org/about . R.H. is a Wellcome Investigator ( 109915/Z/15/Z ) who receives support from the Wellcome Centre for Mitochondrial Research ( 203105/Z/16/Z ), Medical Research Council (UK) ( MR/N025431/1 ), the European Research Council ( 309548 ), the Wellcome Trust Pathfinder Scheme ( 201064/Z/16/Z ), and the Newton Fund (UK/Turkey, MR/N027302/1 ). Work in C.G. Bönnemann’s laboratory is supported by intramural funds from the NIH National Institute of Neurological Disorders and Stroke . Exome sequencing was funded through the Clinical Center Genomics Opportunity , which is sponsored by the National Human Genome Research Institute , the NIH Deputy Director for Intramural Research , and the NIH Clinical Center . Sequencing analysis was provided by the Broad Institute of MIT and Harvard Center for Mendelian Genomics and was funded by the National Human Genome Research Institute , the National Eye Institute , and National Heart, Lung, and Blood Institute grant UM1 HG008900 to Daniel MacArthur and Heidi Rehm. Work in M.S.’s laboratory was supported by the Deutsche Forschungsgemeinschaft (grants SFB 665 TP C4 and NeuroCure Exc 257 ).
Funding Information:
We thank the families for participating and Christopher Mendoza and Gilberto (?Mike?) Averion for their help in the clinic. We would also like to thank the NIH Intramural Sequencing Center staff and Daniel MacArthur and Fengmei Zhao (Analytic and Translational Genetics Unit at Massachusetts General Hospital in collaboration with the Broad Institute of Harvard and Massachusetts Institute of Technology) for their help with exome analysis. We also thank the Exome Aggregation Consortium and the groups that provided exome variant data for comparison. A full list of contributing groups can be found at http://exac.broadinstitute.org/about. R.H. is a Wellcome Investigator (109915/Z/15/Z) who receives support from the Wellcome Centre for Mitochondrial Research (203105/Z/16/Z), Medical Research Council (UK) (MR/N025431/1), the European Research Council (309548), the Wellcome Trust Pathfinder Scheme (201064/Z/16/Z), and the Newton Fund (UK/Turkey, MR/N027302/1). Work in C.G. B?nnemann's laboratory is supported by intramural funds from the NIH National Institute of Neurological Disorders and Stroke. Exome sequencing was funded through the Clinical Center Genomics Opportunity, which is sponsored by the National Human Genome Research Institute, the NIH Deputy Director for Intramural Research, and the NIH Clinical Center. Sequencing analysis was provided by the Broad Institute of MIT and Harvard Center for Mendelian Genomics and was funded by the National Human Genome Research Institute, the National Eye Institute, and National Heart, Lung, and Blood Institute grant UM1 HG008900 to Daniel MacArthur and Heidi Rehm. Work in M.S.'s laboratory was supported by the Deutsche Forschungsgemeinschaft (grants SFB 665 TP C4 and NeuroCure Exc 257).
Publisher Copyright:
© 2018 The Author(s)
Keywords
- cerebellar atrophy
- exosome
- neurodegenerative diseases
- RNA metabolism
- spinal muscular atrophy