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Bhola PT, Mishra R, Posey JE, Hamilton LE, Graham GE, Punetha J, Lupski JR, Boycott KM, D'Amours D, Kernohan KD. Phenotypic heterogeneity associated with KIF21A: Two new cases and review of the literature. Am J Med Genet A 2024; 194:e63455. [PMID: 37921537 DOI: 10.1002/ajmg.a.63455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 10/06/2023] [Accepted: 10/13/2023] [Indexed: 11/04/2023]
Abstract
Our understanding of genetic and phenotypic heterogeneity associated with the clinical spectrum of rare diseases continues to expand. Thorough phenotypic descriptions and model organism functional studies are valuable tools in dissecting the biology of the disease process. Kinesin genes are well known to be associated with specific disease phenotypes and a subset of kinesin genes, including KIF21A, have been associated with more than one disease. Here we report two patients with KIF21A variants identified by exome sequencing; one with biallelic variants, supporting a novel KIF21A related syndrome with recessive inheritance and the second report of this condition, and another with a heterozygous de novo variant allele representing a phenotypic expansion of the condition described to date. We provide detailed phenotypic information on both families, including a novel neuropathology finding of neuroaxonal dystrophy associated with biallelic variants in KIF21A. Additionally, we studied the dominant variant in Saccharomyces cerevisiae to assess variant pathogenicity and found that this variant appears to impair protein function. KIF21A associated disease has mounting evidence for phenotypic heterogeneity; further patients and study of an allelic series are required to define the phenotypic spectrum and further explore the molecular etiology for each of these conditions.
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Affiliation(s)
- Priya T Bhola
- Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Canada
| | - Radha Mishra
- Department of Cellular and Molecular Medicine, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Canada
| | - Jennifer E Posey
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Leslie E Hamilton
- Department of Pathology and Laboratory Medicine, Children's Hospital of Eastern Ontario and University of Ottawa, Ottawa, Canada
| | - Gail E Graham
- Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Canada
| | - Jaya Punetha
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - James R Lupski
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA
- Texas Children's Hospital, Houston, Texas, USA
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, USA
| | - Kym M Boycott
- Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Canada
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada
| | - Damien D'Amours
- Department of Cellular and Molecular Medicine, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Canada
| | - Kristin D Kernohan
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada
- Newborn Screening Ontario (NSO), Ottawa, Canada
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Puri D, Barry BJ, Engle EC. TUBB3 and KIF21A in neurodevelopment and disease. Front Neurosci 2023; 17:1226181. [PMID: 37600020 PMCID: PMC10436312 DOI: 10.3389/fnins.2023.1226181] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 07/17/2023] [Indexed: 08/22/2023] Open
Abstract
Neuronal migration and axon growth and guidance require precise control of microtubule dynamics and microtubule-based cargo transport. TUBB3 encodes the neuronal-specific β-tubulin isotype III, TUBB3, a component of neuronal microtubules expressed throughout the life of central and peripheral neurons. Human pathogenic TUBB3 missense variants result in altered TUBB3 function and cause errors either in the growth and guidance of cranial and, to a lesser extent, central axons, or in cortical neuronal migration and organization, and rarely in both. Moreover, human pathogenic missense variants in KIF21A, which encodes an anterograde kinesin motor protein that interacts directly with microtubules, alter KIF21A function and cause errors in cranial axon growth and guidance that can phenocopy TUBB3 variants. Here, we review reported TUBB3 and KIF21A variants, resulting phenotypes, and corresponding functional studies of both wildtype and mutant proteins. We summarize the evidence that, in vitro and in mouse models, loss-of-function and missense variants can alter microtubule dynamics and microtubule-kinesin interactions. Lastly, we highlight additional studies that might contribute to our understanding of the relationship between specific tubulin isotypes and specific kinesin motor proteins in health and disease.
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Affiliation(s)
- Dharmendra Puri
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
- F. M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA, United States
- Howard Hughes Medical Institute, Chevy Chase, MD, United States
| | - Brenda J. Barry
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
- F. M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA, United States
- Howard Hughes Medical Institute, Chevy Chase, MD, United States
| | - Elizabeth C. Engle
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
- F. M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA, United States
- Howard Hughes Medical Institute, Chevy Chase, MD, United States
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
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Phenotype, genotype, and management of congenital fibrosis of extraocular muscles type 1 in 16 Chinese families. Graefes Arch Clin Exp Ophthalmol 2023; 261:879-889. [PMID: 36138147 PMCID: PMC9988770 DOI: 10.1007/s00417-022-05830-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 08/18/2022] [Accepted: 09/07/2022] [Indexed: 11/04/2022] Open
Abstract
PURPOSE Congenital fibrosis of extraocular muscles type 1 (CFEOM1), a classical subtype of CFEOM, is characterized by restrictive ophthalmoplegia and ptosis. It is mainly caused by aberrant neural innervation of the extraocular muscles. This study aimed to investigate the genetic characteristics and clinical manifestations of CFEOM1 in Chinese families. METHODS The clinical data, including ocular examinations, magnetic resonance imaging (MRI), and surgical procedures of affected individuals from 16 Chinese CFEOM1 families, were collected. The genomic DNA of 16 probands and their family members were sequenced for causative KIF21A gene mutations. Linkage analysis using microsatellite markers across KIF21A was also conducted. RESULTS Affected individuals were presented with bilateral non-progressive ptosis, restricted horizontal eye movement, fixed infraduction of both eyes, compensatory chin-up head position, and neuromuscular abnormalities. Three heterozygous KIF21A mutations, c.2860C > T (p.R954W) (in eight families), c.2861G > T (p.R954L) (in two families), and c.2861G > A (p.R954Q) (in two families) were identified, which implied that hotspot mutations were common in Chinese CFEOM1 families. Germline Mosaicism was likely to be the cause of affected individuals with asymptomatic parents without KIF21A mutations presented in the eight families. Two affected individuals underwent modified levator muscle complex suspension surgery and achieved a good result without any complications. CONCLUSION Instead of evaluating the whole CFEOM1 gene variant, hotspot mutations could be given priority for screening. The occurrence of germline mosaicism has to be taken into account in genetic counseling. Patients with CFEOM1 who have ptosis may benefit from an innovative surgical procedure called modified levator muscle complex suspension.
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Congenital Fibrosis of the Extraocular Muscles: An Overview from Genetics to Management. CHILDREN 2022; 9:children9111605. [DOI: 10.3390/children9111605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 10/08/2022] [Accepted: 10/19/2022] [Indexed: 11/06/2022]
Abstract
Congenital fibrosis of the extraocular muscles (CFEOM) is a genetic disorder belonging to the congenital cranial dysinnervation disorders and is characterized by nonprogressive restrictive ophthalmoplegia. It is phenotypically and genotypically heterogeneous. At least seven causative genes and one locus are responsible for the five subtypes, named CFEOM-1 to CFEOM-5. This review summarizes the currently available molecular genetic findings and genotype–phenotype correlations, as well as the advances in the management of CFEOM. We propose that the classification of the disorder could be optimized to provide better guidance for clinical interventions. Finally, we discuss the future of genetic-diagnosis-directed studies to better understand such axon guidance disorders.
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Al-Haddad C, Boustany RM, Rachid E, Ismail K, Barry B, Chan WM, Engle E. KIF21A pathogenic variants cause congenital fibrosis of extraocular muscles type 3. Ophthalmic Genet 2020; 42:195-199. [PMID: 33251926 PMCID: PMC7987873 DOI: 10.1080/13816810.2020.1852576] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Background: Congenital fibrosis of the extraocular muscles (CFEOM) is characterized by ptosis and non-progressive restrictive ophthalmoplegia. CFEOM1 is a stereotypical phenotype with isolated bilateral ptosis, bilateral ophthalmoplegia, absent upgaze, and globe infraduction. CFEOM3 is a more variable phenotype that can include unilateral disease, absent ptosis, residual upgaze, and/or orthotropia. Most cases of CFEOM1 result from recurrent heterozygous KIF21A missense mutations and less commonly from recurrent heterozygous TUBB3 missense mutations. While most cases of CFEOM3 result from recurrent heterozygous TUBB3 missense mutations, several pedigrees harbored pathogenic variants in KIF21A. Here, we asked if Lebanese pedigrees with CFEOM3 harbor pathogenic variants in TUBB3 or KIF21A.Materials and Methods: Families affected with congenital cranial dysinnervation disorders were prospectively recruited from the American University of Beirut pediatric ophthalmology clinic and included two probands with CFEOM. KIF21A hotspot exons and TUBB3 coding sequence were sequenced. Available family members were sequenced for co-segregation analysis.Results: Both families were found to have CFEOM3 and to harbor pathogenic variants in KIF21A(OMIM 608283). A simplex proband with CFEOM3 from a consanguineous Iraqi family harbored a de novo heterozygous KIF21A c.2860 C > T variant (p.R954W); this variant accounts for the majority of reported KIF21A mutations but is typically implicated in CFEOM1. A Lebanese father with CFEOM3 and his son with CFEOM1 segregated a heterozygous KIF21A c.2830 G > C variant (p.E944Q), previously reported in an individual with CFEOM1.Conclusions: These results support prior reports of KIF21A mutations as a rare cause of CFEOM3. These families are Middle Eastern or Chinese, supporting a genetic modifier in these populations.
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Affiliation(s)
- Christiane Al-Haddad
- Department of Ophthalmology, American University of Beirut Medical Center, Beirut, Lebanon
| | - Rose-Mary Boustany
- Department of Pediatrics and Adolescent Medicine, Pediatric Neurology Division, American University of Beirut Medical Center, Beirut, Lebanon
| | - Elza Rachid
- Department of Ophthalmology, American University of Beirut Medical Center, Beirut, Lebanon
| | - Karine Ismail
- Department of Ophthalmology, American University of Beirut Medical Center, Beirut, Lebanon
| | - Brenda Barry
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Wai-Man Chan
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Elizabeth Engle
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, USA.,Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, USA
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