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Activating RAC1 variants in the switch II region cause a developmental syndrome and alter neuronal morphology
RAC1 is a highly conserved Rho GTPase critical for many cellular and developmental processes. De novo missense RAC1 variants cause a highly variable neurodevelopmental disorder. Some of these variants have previously been shown to have a dominant negative effect. Most previously reported patients wi...
Autores principales: | , , , , , , , , , , , , , , , , , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Oxford University Press
2022
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9762944/ https://www.ncbi.nlm.nih.gov/pubmed/35139179 http://dx.doi.org/10.1093/brain/awac049 |
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author | Banka, Siddharth Bennington, Abigail Baker, Martin J Rijckmans, Ellen Clemente, Giuliana D Ansor, Nurhuda Mohamad Sito, Hilary Prasad, Pritha Anyane-Yeboa, Kwame Badalato, Lauren Dimitrov, Boyan Fitzpatrick, David Hurst, Anna C E Jansen, Anna C Kelly, Melissa A Krantz, Ian Rieubland, Claudine Ross, Meredith Rudy, Natasha L Sanz, Javier Stouffs, Katrien Xu, Zhuo Luan Malliri, Angeliki Kazanietz, Marcelo G Millard, Tom H |
author_facet | Banka, Siddharth Bennington, Abigail Baker, Martin J Rijckmans, Ellen Clemente, Giuliana D Ansor, Nurhuda Mohamad Sito, Hilary Prasad, Pritha Anyane-Yeboa, Kwame Badalato, Lauren Dimitrov, Boyan Fitzpatrick, David Hurst, Anna C E Jansen, Anna C Kelly, Melissa A Krantz, Ian Rieubland, Claudine Ross, Meredith Rudy, Natasha L Sanz, Javier Stouffs, Katrien Xu, Zhuo Luan Malliri, Angeliki Kazanietz, Marcelo G Millard, Tom H |
author_sort | Banka, Siddharth |
collection | PubMed |
description | RAC1 is a highly conserved Rho GTPase critical for many cellular and developmental processes. De novo missense RAC1 variants cause a highly variable neurodevelopmental disorder. Some of these variants have previously been shown to have a dominant negative effect. Most previously reported patients with this disorder have either severe microcephaly or severe macrocephaly. Here, we describe eight patients with pathogenic missense RAC1 variants affecting residues between Q61 and R68 within the switch II region of RAC1. These patients display variable combinations of developmental delay, intellectual disability, brain anomalies such as polymicrogyria and cardiovascular defects with normocephaly or relatively milder micro- or macrocephaly. Pulldown assays, NIH3T3 fibroblast spreading assays and staining for activated PAK1/2/3 and WAVE2 suggest that these variants increase RAC1 activity and over-activate downstream signalling targets. Axons of neurons isolated from Drosophila embryos expressing the most common of the activating variants are significantly shorter, with an increased density of filopodial protrusions. In vivo, these embryos exhibit frequent defects in axonal organization. Class IV dendritic arborization neurons expressing this variant exhibit a significant reduction in the total area of the dendritic arbour, increased branching and failure of self-avoidance. RNAi knock down of the WAVE regulatory complex component Cyfip significantly rescues these morphological defects. These results establish that activating substitutions affecting residues Q61–R68 within the switch II region of RAC1 cause a developmental syndrome. Our findings reveal that these variants cause altered downstream signalling, resulting in abnormal neuronal morphology and reveal the WAVE regulatory complex/Arp2/3 pathway as a possible therapeutic target for activating RAC1 variants. These insights also have the potential to inform the mechanism and therapy for other disorders caused by variants in genes encoding other Rho GTPases, their regulators and downstream effectors. |
format | Online Article Text |
id | pubmed-9762944 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2022 |
publisher | Oxford University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-97629442022-12-20 Activating RAC1 variants in the switch II region cause a developmental syndrome and alter neuronal morphology Banka, Siddharth Bennington, Abigail Baker, Martin J Rijckmans, Ellen Clemente, Giuliana D Ansor, Nurhuda Mohamad Sito, Hilary Prasad, Pritha Anyane-Yeboa, Kwame Badalato, Lauren Dimitrov, Boyan Fitzpatrick, David Hurst, Anna C E Jansen, Anna C Kelly, Melissa A Krantz, Ian Rieubland, Claudine Ross, Meredith Rudy, Natasha L Sanz, Javier Stouffs, Katrien Xu, Zhuo Luan Malliri, Angeliki Kazanietz, Marcelo G Millard, Tom H Brain Original Article RAC1 is a highly conserved Rho GTPase critical for many cellular and developmental processes. De novo missense RAC1 variants cause a highly variable neurodevelopmental disorder. Some of these variants have previously been shown to have a dominant negative effect. Most previously reported patients with this disorder have either severe microcephaly or severe macrocephaly. Here, we describe eight patients with pathogenic missense RAC1 variants affecting residues between Q61 and R68 within the switch II region of RAC1. These patients display variable combinations of developmental delay, intellectual disability, brain anomalies such as polymicrogyria and cardiovascular defects with normocephaly or relatively milder micro- or macrocephaly. Pulldown assays, NIH3T3 fibroblast spreading assays and staining for activated PAK1/2/3 and WAVE2 suggest that these variants increase RAC1 activity and over-activate downstream signalling targets. Axons of neurons isolated from Drosophila embryos expressing the most common of the activating variants are significantly shorter, with an increased density of filopodial protrusions. In vivo, these embryos exhibit frequent defects in axonal organization. Class IV dendritic arborization neurons expressing this variant exhibit a significant reduction in the total area of the dendritic arbour, increased branching and failure of self-avoidance. RNAi knock down of the WAVE regulatory complex component Cyfip significantly rescues these morphological defects. These results establish that activating substitutions affecting residues Q61–R68 within the switch II region of RAC1 cause a developmental syndrome. Our findings reveal that these variants cause altered downstream signalling, resulting in abnormal neuronal morphology and reveal the WAVE regulatory complex/Arp2/3 pathway as a possible therapeutic target for activating RAC1 variants. These insights also have the potential to inform the mechanism and therapy for other disorders caused by variants in genes encoding other Rho GTPases, their regulators and downstream effectors. Oxford University Press 2022-02-10 /pmc/articles/PMC9762944/ /pubmed/35139179 http://dx.doi.org/10.1093/brain/awac049 Text en © The Author(s) 2022. Published by Oxford University Press on behalf of the Guarantors of Brain. https://creativecommons.org/licenses/by-nc/4.0/This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com |
spellingShingle | Original Article Banka, Siddharth Bennington, Abigail Baker, Martin J Rijckmans, Ellen Clemente, Giuliana D Ansor, Nurhuda Mohamad Sito, Hilary Prasad, Pritha Anyane-Yeboa, Kwame Badalato, Lauren Dimitrov, Boyan Fitzpatrick, David Hurst, Anna C E Jansen, Anna C Kelly, Melissa A Krantz, Ian Rieubland, Claudine Ross, Meredith Rudy, Natasha L Sanz, Javier Stouffs, Katrien Xu, Zhuo Luan Malliri, Angeliki Kazanietz, Marcelo G Millard, Tom H Activating RAC1 variants in the switch II region cause a developmental syndrome and alter neuronal morphology |
title | Activating RAC1 variants in the switch II region cause a developmental syndrome and alter neuronal morphology |
title_full | Activating RAC1 variants in the switch II region cause a developmental syndrome and alter neuronal morphology |
title_fullStr | Activating RAC1 variants in the switch II region cause a developmental syndrome and alter neuronal morphology |
title_full_unstemmed | Activating RAC1 variants in the switch II region cause a developmental syndrome and alter neuronal morphology |
title_short | Activating RAC1 variants in the switch II region cause a developmental syndrome and alter neuronal morphology |
title_sort | activating rac1 variants in the switch ii region cause a developmental syndrome and alter neuronal morphology |
topic | Original Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9762944/ https://www.ncbi.nlm.nih.gov/pubmed/35139179 http://dx.doi.org/10.1093/brain/awac049 |
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