DYNC1H1 Mutations Research Articles

Multidisciplinary approach on divergent outcomes in spinal muscular atrophies: comparing DYNC1H1 and SMN1 gene mutations.

Spinal Muscular Atrophy (SMA) emerges as a prominent genetic neuromuscular disorder primarily caused by variants in the survival motor neuron (SMN) gene. However, it is noteworthy that alternative variants impacting DYNC1H1 have also been linked to a subtype known as spinal muscular atrophy lower extremity predominant (SMA-LED). This observation underscores the complexity of SMA and highlights the necessity for tailored, gene-specific management strategies. Our study elucidates how similar approaches to managing SMA can yield distinct outcomes, emphasizing the imperative for personalized gene-based interventions in effectively addressing these conditions.Two patients were referred for further management due to clinical suspicion of type-3 SMA. The definitive diagnosis was confirmed through the polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) technique, as well as whole-exome sequencing (WES).The analysis revealed deletions in exon-7 and 8 of SMN1 in the first patient and a likely pathogenic mutation (NM_001376.5(DYNC1H1):c.1867T > C (NP_001367.2: p.Phe623Leu)) in DYNC1H1 in the second patient. Both patients presented with lower limb muscle weakness. However, while the first patient exhibited a gradual increase in severity over the years, the second patient displayed no progressive symptoms. The management was adjusted accordingly based on the genetic findings.Our observation underscores the complexity of SMA and highlights the necessity for tailored, gene-specific management strategies. Our study elucidates how similar approaches to managing SMA can yield distinct outcomes, emphasizing the imperative for personalized gene-based interventions in effectively addressing these conditions.

A case of a missense DYNC1H1 mutation causing spinal muscular atrophy with lower limb predominance concurrent with germ cell tumor

We report a patient diagnosed with a germ-cell tumor presenting with spinal muscular atrophy with lower limb predominance (SMA-LED) caused by a <i>DYNC1H1</i> genetic variant. His clinical and electrophysiologic phenotype was compatible with SMA-LED. We identified a heterozygous missense variant (c.1793G>T) of <i>DYNC1H1</i>. This report expands the clinical spectrum of <i>DYNC1H1</i>-related disorders, and reinforces the importance of <i>DYNC1H1</i> in both central and peripheral neuronal functions. We suggest that germ-cell tumors should be considered as a possible phenotype of <i>DYNC1H1</i>-related disorders.

Generation of FOUR iPSC lines (CRICKi004-A; CRICKi005-A; CRICKi006-A, CRICKi007-A) from Spinal muscle atrophy patients with lower extremity dominant (SMALED) phenotype

Spinal muscular atrophy with lower extremity dominant (SMALED) is a hereditary neuromuscular disorder characterized by degeneration of spinal cord motor neurons resulting in lower limbs muscle weakness and paralysis. Mutations in DYNC1H1, which encodes BICD2, a multifunctional adaptor for microtubule motor proteins, cause the disorder. Here, we generated four induced pluripotent stem cell (iPSC) lines from patients with SMALED. Dermal fibroblasts were obtained from the MRC neuromuscular disease biobank and reprogrammed using non-integrating mRNA-based protocol. Characterization of the four iPSC lines included karyotyping and Sanger sequencing, while the expression of associated markers confirmed pluripotency and differentiation potential.

VP.93 A novel variant of DYNC1H1 mutations in spinal muscular atrophy lower extremity predominant in an Indonesian patient: a case report

VP.93 A novel variant of DYNC1H1 mutations in spinal muscular atrophy lower extremity predominant in an Indonesian patient: a case report

Expanding the Phenotypic and Genetic Spectrum of Neuromuscular Diseases Caused by DYNC1H1 Mutations.

ObjectivesSpinal muscular atrophy with lower extremity predominance 1 (SMALED1) and Charcot–Marie-Tooth diseasetype 2O (CMT2O) are two kinds of hereditary neuromuscular diseases caused by DYNC1H1 mutations. In this study, we reported two patients with SMALED1 caused by DYNC1H1 mutations. The genotype–phenotype correlations were further analyzed by systematically reviewing previous relevant publications.Materials and MethodsTwo patients' with SMALED1 and their parents' clinical data were collected, and detailed clinical examinations were performed. WES was then applied, which was confirmed by Sanger sequencing. PubMed, Web of Science, CNKI, and Wanfang Data were searched, and all publications that met the inclusion criteria were carefully screened. Any individual patient without a detailed description of clinical phenotypes was excluded.ResultsThe two patients manifested delayed motor milestones and muscle wasting of both lower extremities. The diagnosis was further confirmed as SMALED1. Genetic testing revealed heterozygous DYNC1H1 mutations c.1792C>T and c.790C>G; the latter is a novel dominant mutation. Genotype–phenotype analysis of DYNC1H1 variants and neuromuscular diseases revealed that mutations in the DYN1 region of DYNC1H1 protein were associated with a more severe phenotype, more complicated symptoms, and more CNS involvement than the DHC_N1 region.ConclusionOur study potentially expanded the knowledge of the phenotypic and genetic spectrum of neuromuscular diseases caused by DYNC1H1 mutations. The genotype–phenotype correlation may reflect the pathogenesis underlying the dyneinopathy caused by DYNC1H1 mutations.

Corpus callosum hypoplasia and adult-onset Parkinsonism in DYNC1H1 mutation

Mutations in the cytoplasmic dynein 1 heavy chain 1 (DYNC1H1) gene are associated with autosomal dominant lower extremity-predominant spinal muscular atrophy 1, neuromuscular and neurodevelopmental disorders and hereditary spastic paraplegia. We report a case of adult-onset Parkinson's disease associated to a mutation of DYNC1H1 gene.

Lissencephaly in an epilepsy cohort: Molecular, radiological and clinical aspects.

Lissencephaly is a rare malformation of cortical development due to abnormal transmantle migration resulting in absent or reduced gyration. The lissencephaly spectrum consists of agyria, pachygyria and subcortical band heterotopia. In this study we compared genetic aetiology, neuroradiology, clinical phenotype and response to antiepileptic drugs in patients with epilepsy and lissencephaly spectrum malformations. The study group consisted of 20 patients - 13 males and 7 females, aged 18 months to 21yearsat the time of data collection. Genetic testing was performed by oligonucleotide array comparative genomic hybridization (microarray), multiplex ligation-dependent probe amplification (MLPA), targeted gene panels and whole exome/genome sequencing. All neuroradiological investigations were re-evaluated and the malformations were classified by the same neuroradiologist. Clinical features and response to anti-epileptic drugs (AEDs) were evaluated by retrospective review of medical records. In eleven patients (55%) mutations in PAFAH1B1 (LIS1) or variable microdeletions of 17p13.3 including the PAFAH1B1 gene were detected. Four patients (20%) had tubulin encoding gene mutations (TUBA1A, TUBG1 and TUBGCP6). Mutations in DCX, DYNC1H1, ADGRG1 and WDR62 were identified in single patients. In one patient, a possibly pathogenic intragenic deletion in TRIO was detected. A clear radiologic distinction could be made between tubulinopathies and PAFAH1B1 related lissencephaly. The majority of the patients had therapy resistant epilepsy and epileptic spasms was the most prominent seizure type. The best therapeutic response to seizure control in our cohort was obtained by the ketogenic diet, vigabatrin, clobazam, phenobarbital and valproate. The most common genetic aetiologies in our cohort of 20 individuals with epilepsy and lissencephaly spectrum were intragenic deletions or single nucleotide mutations in PAFAH1B1 or larger deletions in 17p13.3, encompassing PAFAH1B1, followed by mutations in tubulin encoding genes. Radiological findings could reliably predict molecular results only in agyria with a posterior to anterior gradient. Radiological and molecular findings did not correlate consistently with severity of clinical outcome or therapeutic response.

A Database of Caenorhabditis elegans Locomotion and Body Posture Phenotypes for the Peripheral Neuropathy Model.

Inherited peripheral neuropathy is a heterogeneous group of peripheral neurodegenerative disorders including Charcot–Marie–Tooth disease. Many peripheral neuropathies often accompany impaired axonal construction and function. To study the molecular and cellular basis of axon-defective peripheral neuropathy, we explore the possibility of using Caenorhabditis elegans, a powerful nematode model equipped with a variety of genetics and imaging tools. In search of potential candidates of C. elegans peripheral neuropathy models, we monitored the movement and the body posture patterns of 26 C. elegans strains with disruption of genes associated with various peripheral neuropathies and compiled a database of their phenotypes. Our assay showed that movement features of the worms with mutations in HSPB1, MFN2, DYNC1H1, and KIF1B human homologues are significantly different from the control strain, suggesting they are viable candidates for C. elegans peripheral neuropathy models.

Phenotypic Spectrum of DYNC1H1 mutations in Brazilian Patients (P1.460)

Phenotypic Spectrum of DYNC1H1 mutations in Brazilian Patients (P1.460)

Comprehensive investigation of CASK mutations and other genetic etiologies in 41 patients with intellectual disability and microcephaly with pontine and cerebellar hypoplasia (MICPCH).

The CASK gene (Xp11.4) is highly expressed in the mammalian nervous system and plays several roles in neural development and synaptic function. Loss-of-function mutations of CASK are associated with intellectual disability and microcephaly with pontine and cerebellar hypoplasia (MICPCH), especially in females. Here, we present a comprehensive investigation of 41 MICPCH patients, analyzed by mutational search of CASK and screening of candidate genes using an SNP array, targeted resequencing and whole-exome sequencing (WES). In total, we identified causative or candidate genomic aberrations in 37 of the 41 cases (90.2%). CASK aberrations including a rare mosaic mutation in a male patient, were found in 32 cases, and a mutation in ITPR1, another known gene in which mutations are causative for MICPCH, was found in one case. We also found aberrations involving genes other than CASK, such as HDAC2, MARCKS, and possibly HS3ST5, which may be associated with MICPCH. Moreover, the targeted resequencing screening detected heterozygous variants in RELN in two cases, of uncertain pathogenicity, and WES analysis suggested that concurrent mutations of both DYNC1H1 and DCTN1 in one case could lead to MICPCH. Our results not only identified the etiology of MICPCH in nearly all the investigated patients but also suggest that MICPCH is a genetically heterogeneous condition, in which CASK inactivating mutations appear to account for the majority of cases.

Severe cortical malformation and acquired cataract – An unusual presentation of DYNC1H1 mutation in twins

Objective: Cytoplasmatic dynein, a microtubules-associated protein, is crucial for proper neuronal migrations and differentiation. Dominant mutations in the heavy chain1 of the protein (DYNC1H1) are associated with various neurodevelopmental and neurodegenerative diseases such as spinal muscular atrophy with lower extremity dominance (SMA-LED), hereditary motor and sensory neuropathy (HMSN), intellectual disability with neuronal migrations defects and cortical malformations such as posterior predominant pachygyria, lissencephaly and corpus callosum anomalies. We present twin girls with severe congenital cerebral malformations, refractory epilepsy and acquired cataracts due to a de novo mutation in DYNC1H1 identified in girl 1. Methods: Description of twin girls with severe cortical malformation and acquired cataract and family based gene sequencing analysis to identify de novo mutation in DYNC1H1 in girl 1. Results: After prenatal sonographic detection of corpus callosum anomalies in both twins in an otherwise uneventful pregnancy, postnatal cMRI in girl 1 showed partial agenesis of corpus callosum, bilateral polymicrogyria and asymmetric ventricles; in girl 2 subtotal agenesis of corpus callosum, hypoplastic cerebellum and multiple cortical dysplasias. Both girls developed severe intellectual disability, intractable epilepsy since the age of 4 (girl 1) resp. 6 month (girl 2), spastic (1) resp. ataxic (2) cerebral palsy and microcephaly. Cataracts occurred in both girls at the age of 12 months. A gene panel analysis identified a de novo mutation in the DYNC1H1-Gen (c.11015C>T/p.Ser3672Leu) in girl 1 considered pathogenic. Conclusion: Our findings broaden the clinical spectrum and expand the phenotypes associated with DYNC1H1-mutations and suggest a role of dynein in human ocular development. The observation confirms the role of DYNC1H1 in central and peripheral neuronal function and could have implications on molecular diagnostics in complex cortical malformations by adding DYNC1H1 to related genes in microtubule-dependent motor protein pathways.

Expanding the phenotypic spectrum associated with mutations of DYNC1H1

Autosomal dominant mutations of DYNC1H1 cause a range of neurogenetic diseases, including mental retardation with cortical malformations, hereditary spastic paraplegia and spinal muscular atrophy. Using SNP array, linkage analysis and next generation sequencing, we identified two families and one isolated proband sharing a known spinal muscular atrophy, lower extremity predominant (SMALED) causing mutation DYNC1H1 c.1792C>T, p.Arg598Cys, and another family harbouring a c.2327C>T, p.Pro776Leu mutation. Here, we present a detailed clinical and pathological examination of these patients, and show that patients with DYNC1H1 mutations may present with a phenotype mimicking a congenital myopathy. We also highlight features that increase the phenotypic overlap with BICD2, which causes SMALED2. Serial muscle biopsies were available for several patients, spanning from infancy and early childhood to middle age. These provide a unique insight into the developmental and pathological origins of SMALED, suggesting in utero denervation with reinnervation by surrounding intact motor neurons and segmental anterior horn cell deficits. We characterise biopsy features that may make diagnosis of this condition easier in the future.

Severe Cortical Malformation and Acquired Cataract: An Unusual Presentation of DYNC1H1 Mutation in Twins

Severe Cortical Malformation and Acquired Cataract: An Unusual Presentation of DYNC1H1 Mutation in Twins

Whole-exome sequencing identifies a novel de novo mutation in DYNC1H1 in epileptic encephalopathies

Epileptic encephalopathies (EE) are a group of severe childhood epilepsy disorders characterized by intractable seizures, cognitive impairment and neurological deficits. Recent whole-exome sequencing (WES) studies have implicated significant contribution of de novo mutations to EE. In this study, we utilized WES for identifying causal de novo mutations in 4 parent-offspring trios affected by West syndrome. As a result, we found two deleterious de novo mutations in DYNC1H1 and RTP1 in two trios. Expression profile analysis showed that DYNC1H1 and RTP1 are expressed in almost all brain regions and developmental stages. Interestingly, co-expression and genetic interaction network analyses suggested that DYNC1H1 and RTP1 are tightly associated with known epilepsy genes. Furthermore, we observed that the de novo mutations of DYNC1H1 were identified in several different neuropsychiatric disorders including EE, autism spectrum disorders and intellectual disabilities by previous studies, and these mutations primarily occurred in the functional domain of the protein. Taken together, these results demonstrate DYNC1H1 as a strong candidate and RTP1 as a potential candidate on the onset of EE. In addition, this work also proves WES as a powerful tool for the molecular genetic dissection of children affected by sporadic EE.

DYNC1H1 mutations associated with neurological diseases compromise processivity of dynein-dynactin-cargo adaptor complexes.

Mutations in the human DYNC1H1 gene are associated with neurological diseases. DYNC1H1 encodes the heavy chain of cytoplasmic dynein-1, a 1.4-MDa motor complex that traffics organelles, vesicles, and macromolecules toward microtubule minus ends. The effects of the DYNC1H1 mutations on dynein motility, and consequently their links to neuropathology, are not understood. Here, we address this issue using a recombinant expression system for human dynein coupled to single-molecule resolution in vitro motility assays. We functionally characterize 14 DYNC1H1 mutations identified in humans diagnosed with malformations in cortical development (MCD) or spinal muscular atrophy with lower extremity predominance (SMALED), as well as three mutations that cause motor and sensory defects in mice. Two of the human mutations, R1962C and H3822P, strongly interfere with dynein's core mechanochemical properties. The remaining mutations selectively compromise the processive mode of dynein movement that is activated by binding to the accessory complex dynactin and the cargo adaptor Bicaudal-D2 (BICD2). Mutations with the strongest effects on dynein motility in vitro are associated with MCD. The vast majority of mutations do not affect binding of dynein to dynactin and BICD2 and are therefore expected to result in linkage of cargos to dynein-dynactin complexes that have defective long-range motility. This observation offers an explanation for the dominant effects of DYNC1H1 mutations in vivo. Collectively, our results suggest that compromised processivity of cargo-motor assemblies contributes to human neurological disease and provide insight into the influence of different regions of the heavy chain on dynein motility.

A novel de novo mutation in DYNC1H1 gene underlying malformation of cortical development and cataract

Mutations in DYNC1H1, the gene encoding the largest cytoplasmic dynein, have been associated with a wide spectrum of neurodegenerative disorders. In this study, we describe a child in whom a novel de novo likely pathogenic variant in the motor domain of DYCN1H1 was identified through whole exome sequencing. The affected child presented with severe neurological symptoms and more extensive cortical malformations compared to previously reported cases with mutations in this gene, including diffuse pachygyria-lissencephaly and bilateral symmetric subcortical gray matter heterotopia. A more distinct aspect of the phenotype in this child is the presence of cataract in infancy. So far, only acquired bilateral cataract in adulthood has been described in this disorder in a patient with a much milder neurological phenotype. These findings could extend the phenotype associated with defective DYNC1H1 and suggest a possible important role in human ocular development.

Novel mutations in the DYNC1H1 tail domain refine the genetic and clinical spectrum of dyneinopathies.

The heavy chain 1 of cytoplasmic dynein (DYNC1H1) is responsible for movement of the motor complex along microtubules and recruitment of dynein components. Mutations in DYNC1H1 are associated with spinal muscular atrophy (SMA), hereditary motor and sensory neuropathy (HMSN), cortical malformations, or a combination of these. Combining linkage analysis and whole-exome sequencing, we identified a novel dominant defect in the DYNC1H1 tail domain (c.1792C>T, p.Arg598Cys) causing axonal HMSN. Mutation analysis of the tail region in 355 patients identified a de novo mutation (c.791G>T, p.Arg264Leu) in an isolated SMA patient. Her phenotype was more severe than previously described, characterized by multiple congenital contractures and delayed motor milestones, without brain malformations. The mutations in DYNC1H1 increase the interaction with its adaptor BICD2. This relates to previous studies on BICD2 mutations causing a highly similar phenotype. Our findings broaden the genetic heterogeneity and refine the clinical spectrum of DYNC1H1, and have implications for molecular diagnostics of motor neuron diseases.

CNS myelination requires cytoplasmic dynein function.

Cytoplasmic dynein provides the main motor force for minus-end-directed transport of cargo on microtubules. Within the vertebrate central nervous system (CNS), proliferation, neuronal migration, and retrograde axon transport are among the cellular functions known to require dynein. Accordingly, mutations of DYNC1H1, which encodes the heavy chain subunit of cytoplasmic dynein, have been linked to developmental brain malformations and axonal pathologies. Oligodendrocytes, the myelinating glial cell type of the CNS, migrate from their origins to their target axons and subsequently extend multiple long processes that ensheath axons with specialized insulating membrane. These processes are filled with microtubules, which facilitate molecular transport of myelin components. However, whether oligodendrocytes require cytoplasmic dynein to ensheath axons with myelin is not known. We identified a mutation of zebrafish dync1h1 in a forward genetic screen that caused a deficit of oligodendrocytes. Using in vivo imaging and gene expression analyses, we additionally found evidence that dync1h1 promotes axon ensheathment and myelin gene expression. In addition to its well known roles in axon transport and neuronal migration, cytoplasmic dynein contributes to neural development by promoting myelination.

Phenotypic and molecular insights into spinal muscular atrophy due to mutations in BICD2.

Spinal muscular atrophy is a disorder of lower motor neurons, most commonly caused by recessive mutations in SMN1 on chromosome 5q. Cases without SMN1 mutations are subclassified according to phenotype. Spinal muscular atrophy, lower extremity-predominant, is characterized by lower limb muscle weakness and wasting, associated with reduced numbers of lumbar motor neurons and is caused by mutations in DYNC1H1, which encodes a microtubule motor protein in the dynein-dynactin complex and one of its cargo adaptors, BICD2. We have now identified 32 patients with BICD2 mutations from nine different families, providing detailed insights into the clinical phenotype and natural history of BICD2 disease. BICD2 spinal muscular atrophy, lower extremity predominant most commonly presents with delayed motor milestones and ankle contractures. Additional features at presentation include arthrogryposis and congenital dislocation of the hips. In all affected individuals, weakness and wasting is lower-limb predominant, and typically involves both proximal and distal muscle groups. There is no evidence of sensory nerve involvement. Upper motor neuron signs are a prominent feature in a subset of individuals, including one family with exclusively adult-onset upper motor neuron features, consistent with a diagnosis of hereditary spastic paraplegia. In all cohort members, lower motor neuron features were static or only slowly progressive, and the majority remained ambulant throughout life. Muscle MRI in six individuals showed a common pattern of muscle involvement with fat deposition in most thigh muscles, but sparing of the adductors and semitendinosus. Muscle pathology findings were highly variable and included pseudomyopathic features, neuropathic features, and minimal change. The six causative mutations, including one not previously reported, result in amino acid changes within all three coiled-coil domains of the BICD2 protein, and include a possible 'hot spot' mutation, p.Ser107Leu present in four families. We used the recently solved crystal structure of a highly conserved region of the Drosophila orthologue of BICD2 to further-explore how the p.Glu774Gly substitution inhibits the binding of BICD2 to Rab6. Overall, the features of BICD2 spinal muscular atrophy, lower extremity predominant are consistent with a pathological process that preferentially affects lumbar lower motor neurons, with or without additional upper motor neuron involvement. Defining the phenotypic features in this, the largest BICD2 disease cohort reported to date, will facilitate focused genetic testing and filtering of next generation sequencing-derived variants in cases with similar features.

Analysis of dynein intermediate chains, light intermediate chains and light chains in a cohort of hereditary peripheral neuropathies.

The cytoplasmic dynein heavy chain (DYNC1H1) gene has been increasingly associated with neurodegenerative disorders including axonal Charcot-Marie-Tooth disease (CMT2), intellectual disability and malformations of cortical development. In addition, evidence from mouse models (Loa, catabolite repressor-activator (Cra) and Sprawling (Swl)) has shown that mutations in Dync1h1 cause a range of neurodegenerative phenotypes with motor and sensory neuron involvement. In this current study, we examined the possible contribution of other cytoplasmic dynein subunits that bind to DYNC1H1 as a cause of inherited peripheral neuropathy. We focused on screening the cytoplasmic dynein intermediate, light intermediate and light chain genes in a cohort of families with inherited peripheral neuropathies. Nine genes were screened and ten variants were detected, but none was identified as pathogenic, indicating that cytoplasmic dynein intermediate, light intermediate and light chains are not a cause of neuropathy in our cohort.