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Kivrak Pfiffner F, Koller S, Ménétrey A, Graf U, Bähr L, Maspoli A, Hackenberg A, Kottke R, Gerth-Kahlert C, Berger W. Homozygosity for a Novel DOCK7 Variant Due to Segmental Uniparental Isodisomy of Chromosome 1 Associated with Early Infantile Epileptic Encephalopathy (EIEE) and Cortical Visual Impairment. Int J Mol Sci 2022; 23:ijms23137382. [PMID: 35806387 PMCID: PMC9266905 DOI: 10.3390/ijms23137382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 06/19/2022] [Accepted: 06/29/2022] [Indexed: 11/16/2022] Open
Abstract
Early infantile epileptic encephalopathy (EIEE) is a severe neurologic and neurodevelopmental disease that manifests in the first year of life. It shows a high degree of genetic heterogeneity, but the genetic origin is only identified in half of the cases. We report the case of a female child initially diagnosed with Leber congenital amaurosis (LCA), an early-onset retinal dystrophy due to photoreceptor cell degeneration in the retina. The first examination at 9 months of age revealed no reaction to light or objects and showed wandering eye movements. Ophthalmological examination did not show any ocular abnormalities. The patient displayed mildly dysmorphic features and a global developmental delay. Brain MRI demonstrated pontine hypo-/dysplasia. The patient developed myoclonic epileptic seizures and epileptic spasms with focal and generalized epileptiform discharges on electroencephalogram (EEG) at the age of 16 months. Genetic screening for a potentially pathogenic DNA sequence variant by whole-exome sequencing (WES) revealed a novel, conserved, homozygous frameshift variant (c.5391delA, p.(Ala1798LeufsTer59)) in exon 42 of the DOCK7 gene (NM_001271999.1). Further analysis by SNP array (Karyomapping) showed loss of heterozygosity (LOH) in four segments of chromosome 1. WES data of the parents and the index patient (trio analysis) demonstrated that chromosome 1 was exclusively inherited from the mother. Four LOH segments of chromosome 1 alternately showed isodisomy (UPiD) and heterodisomy (UPhD). In WES data, the father was a noncarrier, and the mother was heterozygous for this DOCK7 variant. The DOCK7 gene is located in 1p31.3, a region situated in one of the four isodisomic segments of chromosome 1, explaining the homozygosity seen in the affected child. Finally, Sanger sequencing confirmed maternal UPiD for the DOCK7 variant. Homozygous or compound heterozygous pathogenic variants in the DOCK7 (dedicator of cytokinesis 7) gene are associated with autosomal recessive, early infantile epileptic encephalopathy 23 (EIEE23; OMIM #615,859), a rare and heterogeneous group of neurodevelopmental disorders diagnosed during early childhood. To our knowledge, this is the first report of segmental uniparental iso- and heterodisomy of chromosome 1, leading to homozygosity of the DOCK7 frameshift variant in the affected patient.
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Affiliation(s)
- Fatma Kivrak Pfiffner
- Institute of Medical Molecular Genetics, University of Zurich, Wagistrasse 12, 8952 Schlieren, Switzerland; (F.K.P.); (S.K.); (U.G.); (L.B.); (A.M.)
| | - Samuel Koller
- Institute of Medical Molecular Genetics, University of Zurich, Wagistrasse 12, 8952 Schlieren, Switzerland; (F.K.P.); (S.K.); (U.G.); (L.B.); (A.M.)
| | - Anika Ménétrey
- Department of Pediatric Neurology, University Children’s Hospital, University of Zurich, 8032 Zurich, Switzerland; (A.M.); (A.H.)
| | - Urs Graf
- Institute of Medical Molecular Genetics, University of Zurich, Wagistrasse 12, 8952 Schlieren, Switzerland; (F.K.P.); (S.K.); (U.G.); (L.B.); (A.M.)
| | - Luzy Bähr
- Institute of Medical Molecular Genetics, University of Zurich, Wagistrasse 12, 8952 Schlieren, Switzerland; (F.K.P.); (S.K.); (U.G.); (L.B.); (A.M.)
| | - Alessandro Maspoli
- Institute of Medical Molecular Genetics, University of Zurich, Wagistrasse 12, 8952 Schlieren, Switzerland; (F.K.P.); (S.K.); (U.G.); (L.B.); (A.M.)
| | - Annette Hackenberg
- Department of Pediatric Neurology, University Children’s Hospital, University of Zurich, 8032 Zurich, Switzerland; (A.M.); (A.H.)
| | - Raimund Kottke
- Department of Diagnostic Imaging, University Children’s Hospital, University of Zurich, 8032 Zurich, Switzerland;
| | | | - Wolfgang Berger
- Institute of Medical Molecular Genetics, University of Zurich, Wagistrasse 12, 8952 Schlieren, Switzerland; (F.K.P.); (S.K.); (U.G.); (L.B.); (A.M.)
- Neuroscience Center Zurich, University and ETH Zurich, 8057 Zurich, Switzerland
- Center for Integrative Human Physiology, University of Zurich, 8057 Zurich, Switzerland
- Correspondence:
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Kapoor D, Anand A, Siddiqui S, Sharma S. A novel pathogenic variant in DOCK 7 gene in an infant with dysmorphism, epileptic encephalopathy and cortical blindness. Clin Dysmorphol 2022; 31:39-41. [PMID: 34561314 DOI: 10.1097/mcd.0000000000000393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Dipti Kapoor
- Department of Pediatrics, Lady Hardinge Medical College, New Delhi
| | - Aakanksha Anand
- Department of Pediatrics, Lady Hardinge Medical College, New Delhi
| | - Shahyan Siddiqui
- Department of Neuroimaging and Intervention Radiology, STAR Institute of Neurosciences, STAR Hospitals, Hyderabad
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Thompson AP, Bitsina C, Gray JL, von Delft F, Brennan PE. RHO to the DOCK for GDP disembarking: Structural insights into the DOCK GTPase nucleotide exchange factors. J Biol Chem 2021; 296:100521. [PMID: 33684443 PMCID: PMC8063744 DOI: 10.1016/j.jbc.2021.100521] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 03/04/2021] [Accepted: 03/04/2021] [Indexed: 01/16/2023] Open
Abstract
The human dedicator of cytokinesis (DOCK) family consists of 11 structurally conserved proteins that serve as atypical RHO guanine nucleotide exchange factors (RHO GEFs). These regulatory proteins act as mediators in numerous cellular cascades that promote cytoskeletal remodeling, playing roles in various crucial processes such as differentiation, migration, polarization, and axon growth in neurons. At the molecular level, DOCK DHR2 domains facilitate nucleotide dissociation from small GTPases, a process that is otherwise too slow for rapid spatiotemporal control of cellular signaling. Here, we provide an overview of the biological and structural characteristics for the various DOCK proteins and describe how they differ from other RHO GEFs and between DOCK subfamilies. The expression of the family varies depending on cell or tissue type, and they are consequently implicated in a broad range of disease phenotypes, particularly in the brain. A growing body of available structural information reveals the mechanism by which the catalytic DHR2 domain elicits nucleotide dissociation and also indicates strategies for the discovery and design of high-affinity small-molecule inhibitors. Such compounds could serve as chemical probes to interrogate the cellular function and provide starting points for drug discovery of this important class of enzymes.
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Affiliation(s)
- Andrew P Thompson
- Nuffield Department of Medicine, Alzheimer's Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Target Discovery Institute, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Centre for Medicines Discovery, University of Oxford, Oxford, United Kingdom
| | - Christina Bitsina
- Nuffield Department of Medicine, Alzheimer's Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Target Discovery Institute, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Centre for Medicines Discovery, University of Oxford, Oxford, United Kingdom
| | - Janine L Gray
- Nuffield Department of Medicine, Alzheimer's Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Target Discovery Institute, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Centre for Medicines Discovery, University of Oxford, Oxford, United Kingdom
| | - Frank von Delft
- Nuffield Department of Medicine, Alzheimer's Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Centre for Medicines Discovery, University of Oxford, Oxford, United Kingdom; Diamond Light Source, Harwell Science and Innovation Campus, Didcot, United Kingdom; Department of Biochemistry, University of Johannesburg, Auckland Park, South Africa
| | - Paul E Brennan
- Nuffield Department of Medicine, Alzheimer's Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Target Discovery Institute, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Centre for Medicines Discovery, University of Oxford, Oxford, United Kingdom.
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Haberlandt E, Valovka T, Janjic T, Müller T, Blatsios G, Karall D, Janecke AR. Characteristic facial features and cortical blindness distinguish the DOCK7-related epileptic encephalopathy. Mol Genet Genomic Med 2021; 9:e1607. [PMID: 33471954 PMCID: PMC8104163 DOI: 10.1002/mgg3.1607] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 12/26/2020] [Accepted: 01/04/2021] [Indexed: 12/24/2022] Open
Abstract
Background The epileptic encephalopathies display extensive locus and allelic heterogeneity. Biallelic truncating DOCK7 variants were recently reported in five children with early‐onset epilepsy, intellectual disability, and cortical blindness, indicating that DOCK7 deficiency causes a specific type of epileptic encephalopathy. Methods We identified 23‐ and 27‐year‐old siblings with the clinical pattern reported for DOCK7 deficiency, and conducted genome‐wide linkage analysis and WES. The consequences of a DOCK7 variant were analyzed on the transcript and protein level in patients’ fibroblasts. Results We identified a novel homozygous DOCK7 frameshift variant, an intragenic tandem duplication of 124‐kb, previously missed by CGH array, in adult patients. Patients display atrophy in the occipital lobe and pontine hypoplasia with marked pontobulbar sulcus, and focal atrophy of occasional cerebellar folia is a novel finding. Recognizable dysmorphic features include normo‐brachycephaly, narrow forehead, low anterior and posterior hairlines, prominent ears, full cheeks, and long eyelashes. Our patients function on the level of 4‐year‐old children, never showed signs of regression, and seizures are largely controlled with multi‐pharmacotherapy. Studies of patients’ fibroblasts showed nonsense‐mediated RNA decay and lack of DOCK7 protein. Conclusion DOCK7 deficiency causes a definable clinical entity, a recognizable type of epileptic encephalopathy.
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Affiliation(s)
- Edda Haberlandt
- Department of Pediatrics I, Medical University of Innsbruck, Innsbruck, Austria.,Krankenhaus der Stadt Dornbirn, Kinder- und Jugendheilkunde, Dornbirn, Austria
| | - Taras Valovka
- Department of Pediatrics I, Medical University of Innsbruck, Innsbruck, Austria
| | - Tanja Janjic
- Department of Neuroradiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Thomas Müller
- Department of Pediatrics I, Medical University of Innsbruck, Innsbruck, Austria
| | - Georgios Blatsios
- Department of Ophthalmology, Medical University of Innsbruck, Innsbruck, Austria
| | - Daniela Karall
- Department of Pediatrics I, Medical University of Innsbruck, Innsbruck, Austria
| | - Andreas R Janecke
- Department of Pediatrics I, Medical University of Innsbruck, Innsbruck, Austria.,Division of Human Genetics, Medical University of Innsbruck, Innsbruck, Austria
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Lee S, Kim SH, Kim B, Lee ST, Choi JR, Kim HD, Lee JS, Kang HC. Genetic diagnosis and clinical characteristics by etiological classification in early-onset epileptic encephalopathy with burst suppression pattern. Epilepsy Res 2020; 163:106323. [PMID: 32247221 DOI: 10.1016/j.eplepsyres.2020.106323] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/01/2020] [Accepted: 03/20/2020] [Indexed: 01/17/2023]
Abstract
BACKGROUND Early-onset epileptic encephalopathies with burst suppression (EOEE-BS) are a group of neonatal epileptic syndromes characterized by intractable epilepsy and severe psychomotor delay with structural and metabolic factors accounting for major etiologies. However, recent advances in gene sequencing have identified that genetic factors might also play a significant role in the development of EOEE-BS. Herein, we used various genetic tests to identify pathogenic genetic variants in EOEE-BS irrespective of structural malformations and analyzed the clinical features associated with each different etiology. METHODS A total of 48 patients with EOEE-BS were included. Except for patients with severe hypoxic damage, patients with structural malformations were included in our patient cohort. Clinical features of the patients were reviewed, and etiological diagnoses were made based on several genetic tests, metabolic studies, and radiological findings. RESULT A genetic diagnosis was made in 31 (64.6 %) patients, with the most commonly diagnosed gene being STXBP1 (n = 13, 27.1 %), followed by KCNQ2 (n = 5, 10.4 %), SCN2A (n = 5, 10.4 %), DEPDC5 (n = 3, 6.3 %), CASK (n = 1, 2.1 %), CDKL5 (n = 1, 2.1 %), GNAO1 (n = 1, 2.1 %), SLC6A8 (n = 1, 2.1 %), and LIS1 deletion (n = 1, 2.1 %). Other than the classification of epilepsy syndrome, no clinical features were associated with the genetically diagnosed group. Among eight patients with structural malformations, genetic diagnosis was achieved in five (62.5 %), and those patients had pathogenic mutations in DEPDC5 and CASK or LIS1 deletion, indicating the significance of gene sequencing irrespective of structural abnormalities. Treatment responses to a variety of medications and the ketogenic diet differed by etiology, and surgical resection proved to be effective in patients with cortical dysplasia. CONCLUSION Genetic etiologies are an important factor in EOEE-BS irrespective of structural malformations and the treatment options may differ by etiology.
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Affiliation(s)
- Sangbo Lee
- Division of Pediatric Neurology, Epilepsy Research Institute, Severance Children's Hospital, Department of Pediatrics, Yonsei University College of Medicine, Yonsei-ro 50-1, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Se Hee Kim
- Division of Pediatric Neurology, Epilepsy Research Institute, Severance Children's Hospital, Department of Pediatrics, Yonsei University College of Medicine, Yonsei-ro 50-1, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Borahm Kim
- Department of Laboratory Medicine, Severance Hospital, Yonsei University College of Medicine, Yonsei-ro 50-1, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Seung-Tae Lee
- Department of Laboratory Medicine, Severance Hospital, Yonsei University College of Medicine, Yonsei-ro 50-1, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Jong Rak Choi
- Department of Laboratory Medicine, Severance Hospital, Yonsei University College of Medicine, Yonsei-ro 50-1, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Heung Dong Kim
- Division of Pediatric Neurology, Epilepsy Research Institute, Severance Children's Hospital, Department of Pediatrics, Yonsei University College of Medicine, Yonsei-ro 50-1, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Joon Soo Lee
- Division of Pediatric Neurology, Epilepsy Research Institute, Severance Children's Hospital, Department of Pediatrics, Yonsei University College of Medicine, Yonsei-ro 50-1, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Hoon-Chul Kang
- Division of Pediatric Neurology, Epilepsy Research Institute, Severance Children's Hospital, Department of Pediatrics, Yonsei University College of Medicine, Yonsei-ro 50-1, Seodaemun-gu, Seoul, 03722, Republic of Korea.
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