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Wiltrout K, Ferrer A, van de Laar I, Namekata K, Harada T, Klee EW, Zimmerman MT, Cousin MA, Kempainen JL, Babovic-Vuksanovic D, van Slegtenhorst MA, Aarts-Tesselaar CD, Schnur RE, Andrews M, Shinawi M. Variants in DOCK3 cause developmental delay and hypotonia. Eur J Hum Genet 2019; 27:1225-1234. [PMID: 30976111 DOI: 10.1038/s41431-019-0397-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 03/13/2019] [Accepted: 03/26/2019] [Indexed: 01/05/2023] Open
Abstract
The DOCK3 gene encodes the Dedicator of cytokinesis 3 (DOCK3) protein, which belongs to the family of guanine nucleotide exchange factors and is expressed almost exclusively in the brain and spinal cord. We used whole exome sequencing (WES) to investigate the molecular cause of developmental delay and hypotonia in three unrelated probands. WES identified truncating and splice site variants in Patient 1 and compound heterozygous and homozygous missense variants in Patients 2 and 3, respectively. We studied the effect of the three missense variants in vitro by using site-directed mutagenesis and pull-down assay and show that the induction of Rac1 activation was significantly lower in DOCK3 mutant cells compared with wild type human DOCK3 (P < 0.05). We generated a protein model to further examine the effect of the two missense variants within or adjacent to the DHR-2 domain in DOCK3 and this model supports pathogenicity. Our results support a loss of function mechanism but the data on the patients with missense variants should be cautiously interpreted because of the variability of the phenotypes and limited number of cases. Prior studies have described DOCK3 bi-allelic loss of function variants in two families with ataxia, hypotonia, and developmental delay. Here, we report on three patients with DOCK3-related developmental delay, wide-based or uncoordinated gait, and hypotonia, further supporting DOCK3's role in a neurodevelopmental syndrome and expanding the spectrum of phenotypic and genotypic variability.
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Affiliation(s)
- Kimberly Wiltrout
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA
| | - Alejandro Ferrer
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA
| | - Ingrid van de Laar
- Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Kazuhiko Namekata
- Visual Research Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Takayuki Harada
- Visual Research Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Eric W Klee
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA
| | - Michael T Zimmerman
- Genomics Sciences & Precision Medicine Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Margot A Cousin
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA
| | | | | | | | | | | | - Marisa Andrews
- Division of Genetics and Genomic Medicine, Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, USA
| | - Marwan Shinawi
- Division of Genetics and Genomic Medicine, Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, USA.
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