Human neurons from Christianson syndrome iPSCs reveal mutation-specific responses to rescue strategies
- 10 February 2021
- journal article
- research article
- Published by American Association for the Advancement of Science (AAAS) in Science Translational Medicine
- Vol. 13 (580)
- https://doi.org/10.1126/scitranslmed.aaw0682
Abstract
Christianson syndrome (CS), an X-linked neurological disorder characterized by postnatal attenuation of brain growth (postnatal microcephaly), is caused by mutations in SLC9A6, the gene encoding endosomal Na+/H+ exchanger 6 (NHE6). To hasten treatment development, we established induced pluripotent stem cell (iPSC) lines from patients with CS representing a mutational spectrum, as well as biologically related and isogenic control lines. We demonstrated that pathogenic mutations lead to loss of protein function by a variety of mechanisms: The majority of mutations caused loss of mRNA due to nonsense-mediated mRNA decay; however, a recurrent, missense mutation (the G383D mutation) had both loss-of-function and dominant-negative activities. Regardless of mutation, all patient-derived neurons demonstrated reduced neurite growth and arborization, likely underlying diminished postnatal brain growth in patients. Phenotype rescue strategies showed mutation-specific responses: A gene transfer strategy was effective in nonsense mutations, but not in the G383D mutation, wherein residual protein appeared to interfere with rescue. In contrast, application of exogenous trophic factors (BDNF or IGF-1) rescued arborization phenotypes across all mutations. These results may guide treatment development in CS, including gene therapy strategies wherein our data suggest that response to treatment may be dictated by the class of mutation.Keywords
Funding Information
- National Institute of Mental Health (R01MH105442, R01MH102418, R21MH115392)
- National Institute of General Medical Sciences (P20GM103641, P20GM103499)
- National Institute of General Medical Sciences (R25GM064118)
- National Institute of General Medical Sciences (R01GM108911)
- Burroughs Wellcome Fund (1006815.01)
- Angelman Syndrome Foundation
- Brown University
- National Institute of Neurological Disorders and Stroke and National Institute on Aging (R01NS113141)
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