The clinical-phenotype continuum in DYNC1H1-related disorders-genomic profiling and proposal for a novel classification

Clinical and Genetic Profiles of 5q- and Non-5q-Spinal Muscular Atrophy Diseases in Pediatric Patients

BACKGROUND

Spinal muscular atrophy (SMA) is a genetic disease characterized by loss of motor neurons in the spinal cord and lower brainstem. The term "SMA" usually refers to the most common form, 5q-SMA, which is caused by biallelic mutations in SMN1 (located on chromosome 5q13). However, long before the discovery of SMN1, it was known that other forms of SMA existed. Therefore, SMA is currently divided into two groups: 5q-SMA and non-5q-SMA. This is a simple and practical classification, and therapeutic drugs have only been developed for 5q-SMA (nusinersen, onasemnogene abeparvovec, risdiplam) and not for non-5q-SMA disease.

METHODS

We conducted a non-systematic critical review to identify the characteristics of each SMA disease.

RESULTS

Many of the non-5q-SMA diseases have similar symptoms, making DNA analysis of patients essential for accurate diagnosis. Currently, genetic analysis technology using next-generation sequencers is rapidly advancing, opening up the possibility of elucidating the pathology and treating non-5q-SMA.

CONCLUSION

Based on accurate diagnosis and a deeper understanding of the pathology of each disease, treatments for non-5q-SMA diseases may be developed in the near future.

Patient-specific mutation of Dync1h1 in mice causes brain and behavioral deficits

AIMS

Cytoplasmic dynein heavy chain (DYNC1H1) is a multi-subunit protein complex that provides motor force for movement of cargo on microtubules and traffics them back to the soma. In humans, mutations along the DYNC1H1 gene result in intellectual disabilities, cognitive delays, and neurologic and motor deficits. The aim of the study was to generate a mouse model to a newly identified de novo heterozygous DYNC1H1 mutation, within a functional ATPase domain (c9052C > T(P3018S)), identified in a child with motor deficits, and intellectual disabilities.

RESULTS

P3018S heterozygous (HET) knockin mice are viable; homozygotes are lethal. Metabolic and EchoMRI™ testing show that HET mice have a higher metabolic rate, are more active, and have less body fat compared to wildtype mice. Neurobehavioral studies show that HET mice perform worse when traversing elevated balance beams, and on the negative geotaxis test. Immunofluorescent staining shows neuronal migration abnormalities in the dorsal and lateral neocortex with heterotopia in layer I. Neuron-subtype specific transcription factors CUX1 and CTGF identified neurons from layers II/III and VI respectively in cortical layer I, and abnormal pyramidal neurons with MAP2+ dendrites projecting downward from the pial surface.

CONCLUSION

The HET mice are a good model for the motor deficits seen in the child, and highlights the importance of cytoplasmic dynein in the maintenance of cortical function and dendritic orientation relative to the pial surface. Our results are discussed in the context of other dynein mutant mice and in relation to clinical presentation in humans with DYNC1H1 mutations.

A novel mutation in SORD gene associated with distal hereditary motor neuropathies

BACKGROUND

Distal hereditary motor neuropathy (dHMN) is a heterogeneous group of hereditary diseases caused by the gradual degeneration of the lower motor neuron. More than 30 genes associated with dHMN have been reported, while 70-80% of those with the condition are still unable to receive a genetic diagnosis.

METHODS

A 26-year-old man experiencing gradual weakness in his lower limbs was referred to our hospital, and data on clinical features, laboratory tests, and electrophysiological tests were collected. To identify the disease-causing mutation, we conducted whole exome sequencing (WES) and then validated it through Sanger sequencing for the proband and his parents. Silico analysis was performed to predict the pathogenesis of the identified mutations. A literature review of all reported mutations of the related gene for the disease was performed.

RESULTS

The patient presented with dHMN phenotype harboring a novel homozygous variant c.361G > C (p.Ala121Pro) in SORD, inherited from his parents, respectively. A121 is a highly conserved site and the mutation was categorized as "likely pathogenic" according to the criteria and guidelines of the American College of Medical Genetics and Genomics (ACMG). A total of 13 published articles including 101 patients reported 18 SORD variants. Almost all described cases have the homozygous deletion variant c.757delG (p.A253Qfs*27) or compound heterozygous state of a combination of c.757delG (p.A253Qfs*27) with another variant. The variant c.361G > C (p.Ala121Pro) detected in our patient was the second homozygous variant in SORD-associated hereditary neuropathy.

CONCLUSION

One novel homozygous variant c.361G > C (p.Ala121Pro) in SORD was identified in a Chinese patient with dHMN phenotype, which expands the mutation spectrum of SORD-associated hereditary neuropathy and underscores the significance of screening for SORD variants in patients with undiagnosed hereditary neuropathy patients.

DYNC1H1 variants associated with infant-onset epilepsy without neurodevelopmental disorders

OBJECTIVES

The DYNC1H1 variants are associated with abnormal brain morphology and neuromuscular disorders that are accompanied by epilepsy. This study aimed to explore the relationship between DYNC1H1 variants and epilepsy.

MATERIALS AND METHODS

Trios-based whole-exome sequencing was performed on patients with epilepsy. Previously reported epilepsy-related DYNC1H1 variants were systematically reviewed to analyse genotype-phenotype correlation.

RESULTS

The DYNC1H1 variants were identified in four unrelated cases of infant-onset epilepsy, including two de novo and two biallelic variants. Two patients harbouring de novo missense variants located in the stem and stalk domains presented with refractory epilepsies, whereas two patients harbouring biallelic variants located in the regions between functional domains had mild epilepsy with infrequent focal seizures and favourable outcomes. One patient presented with pachygyria and neurodevelopmental abnormalities, and the other three patients presented with normal development. These variants have no or low frequencies in the Genome Aggregation Database. All the missense variants were predicted to be damaging using silico tools. Previously reported epilepsy-related variants were monoallelic variants, mainly de novo missense variants, and all the patients presented with severe epileptic phenotypes or developmental delay and malformations of cortical development. Epilepsy-related variants were clustered in the dimerization and stalk domains, and generalized epilepsy-associated variants were distributed in the stem domain.

CONCLUSION

This study suggested that DYNC1H1 variants are potentially associated with infant-onset epilepsy without neurodevelopmental disorders, expanding the phenotypic spectrum of DYNC1H1. The genotype-phenotype correlation helps to understand the underlying mechanisms of phenotypic variation.

Structure and Function of Dynein's Non-Catalytic Subunits

Dynein, an ancient microtubule-based motor protein, performs diverse cellular functions in nearly all eukaryotic cells, with the exception of land plants. It has evolved into three subfamilies-cytoplasmic dynein-1, cytoplasmic dynein-2, and axonemal dyneins-each differentiated by their cellular functions. These megadalton complexes consist of multiple subunits, with the heavy chain being the largest subunit that generates motion and force along microtubules by converting the chemical energy of ATP hydrolysis into mechanical work. Beyond this catalytic core, the functionality of dynein is significantly enhanced by numerous non-catalytic subunits. These subunits are integral to the complex, contributing to its stability, regulating its enzymatic activities, targeting it to specific cellular locations, and mediating its interactions with other cofactors. The diversity of non-catalytic subunits expands dynein's cellular roles, enabling it to perform critical tasks despite the conservation of its heavy chains. In this review, we discuss recent findings and insights regarding these non-catalytic subunits.

Comparative Hippocampal Proteome and Phosphoproteome in a Niemann-Pick, Type C1 Mouse Model Reveal Insights into Disease Mechanisms

Niemann-Pick disease, type C (NPC) is a neurodegenerative, lysosomal storage disorder in individuals carrying two mutated copies of either the NPC1 or NPC2 gene. Consequently, impaired cholesterol recycling and an array of downstream events occur. Interestingly, in NPC, the hippocampus displays lysosomal lipid storage but does not succumb to progressive neurodegeneration as significantly as other brain regions. Since defining the neurodegeneration mechanisms in this disease is still an active area of research, we use mass spectrometry to analyze the overall proteome and phosphorylation pattern changes in the hippocampal region of a murine model of NPC. Using 3 week old mice representing an early disease time point, we observed changes in the expression of 47 proteins, many of which are consistent with the previous literature. New to this study, changes in members of the SNARE complex, including STX7, VTI1B, and VAMP7, were identified. Furthermore, we identified that phosphorylation of T286 on CaMKIIα and S1303 on NR2B increased in mutant animals, even at the late stage of the disease. These phosphosites are crucial to learning and memory and can trigger neuronal death by altering protein-protein interactions.

Novel Genetic and Phenotypic Expansion in GOSR2-Related Progressive Myoclonus Epilepsy

Biallelic variants in the Golgi SNAP receptor complex member 2 gene (GOSR2) have been reported in progressive myoclonus epilepsy with neurodegeneration. Typical clinical features include ataxia and areflexia during early childhood, followed by seizures, scoliosis, dysarthria, and myoclonus. Here, we report two novel patients from unrelated families with a GOSR2-related disorder and novel genetic and clinical findings. The first patient, a male compound heterozygous for the GOSR2 splice site variant c.336+1G>A and the novel c.364G>A,p.Glu122Lys missense variant showed global developmental delay and seizures at the age of 2 years, followed by myoclonus at the age of 8 years with partial response to clonazepam. The second patient, a female homozygous for the GOSR2 founder variant p.Gly144Trp, showed only mild fine motor developmental delay and generalized tonic-clonic seizures triggered by infections during adolescence, with seizure remission on levetiracetam. The associated movement disorder progressed atypically slowly during adolescence compared to its usual speed, from initial intention tremor and myoclonus to ataxia, hyporeflexia, dysmetria, and dystonia. These findings expand the genotype-phenotype spectrum of GOSR2-related disorders and suggest that GOSR2 should be included in the consideration of monogenetic causes of dystonia, global developmental delay, and seizures.

Genetic Primary Microcephalies: When Centrosome Dysfunction Dictates Brain and Body Size

Primary microcephalies (PMs) are defects in brain growth that are detectable at or before birth and are responsible for neurodevelopmental disorders. Most are caused by biallelic or, more rarely, dominant mutations in one of the likely hundreds of genes encoding PM proteins, i.e., ubiquitous centrosome or microtubule-associated proteins required for the division of neural progenitor cells in the embryonic brain. Here, we provide an overview of the different types of PMs, i.e., isolated PMs with or without malformations of cortical development and PMs associated with short stature (microcephalic dwarfism) or sensorineural disorders. We present an overview of the genetic, developmental, neurological, and cognitive aspects characterizing the most representative PMs. The analysis of phenotypic similarities and differences among patients has led scientists to elucidate the roles of these PM proteins in humans. Phenotypic similarities indicate possible redundant functions of a few of these proteins, such as ASPM and WDR62, which play roles only in determining brain size and structure. However, the protein pericentrin (PCNT) is equally required for determining brain and body size. Other PM proteins perform both functions, albeit to different degrees. Finally, by comparing phenotypes, we considered the interrelationships among these proteins.

Case report: Genotype and phenotype of DYNC1H1-related malformations of cortical development: a case report and literature review

Background

Mutations in the dynein cytoplasmic 1 heavy chain 1 (DYNC1H1) gene are linked to malformations of cortical development (MCD), which may be accompanied by central nervous system (CNS) manifestations. Here, we present the case of a patient with MCD harboring a variant of DYNC1H1 and review the relevant literature to explore genotype-phenotype relationships.

Case presentation

A girl having infantile spasms, was unsuccessfully administered multiple antiseizure medications and developed drug-resistant epilepsy. Brain magnetic resonance imaging (MRI) at 14 months-of-age revealed pachygyria. At 4 years-of-age, the patient exhibited severe developmental delay and mental retardation. A de novo heterozygous mutation (p.Arg292Trp) in the DYNC1H1 gene was identified. A search of multiple databases, including PubMed and Embase, using the search strategy DYNC1H1 AND [malformations of cortical development OR seizure OR intellectual OR clinical symptoms] up to June 2022, identified 129 patients from 43 studies (including the case presented herein). A review of these cases showed that patients with DYNC1H1-related MCD had higher risks of epilepsy (odds ratio [OR] = 33.67, 95% confidence interval [CI] = 11.59, 97.84) and intellectual disability/developmental delay (OR = 52.64, 95% CI = 16.27, 170.38). Patients with the variants in the regions encoding the protein stalk or microtubule-binding domain had the most prevalence of MCD (95%).

Conclusion

MCD, particularly pachygyria, is a common neurodevelopmental disorder in patients with DYNC1H1 mutations. Literature searches reveales that most (95%) patients who carried mutations in the protein stalk or microtubule binding domains exhibited DYNC1H1-related MCD, whereas almost two-thirds of patients (63%) who carried mutations in the tail domain did not display MCD. Patients with DYNC1H1 mutations may experience central nervous system (CNS) manifestations due to MCD.

DYNC1H1-related epilepsy: Genotype-phenotype correlation

AIM

To explore the phenotypic spectrum and refine the genotype-phenotype correlation of DYNC1H1-related epilepsy.

METHOD

The clinical data of 15 patients with epilepsy in our cohort and 50 patients with epilepsy from 24 published studies with the DYNC1H1 variants were evaluated.

RESULTS

In our cohort, 13 variants were identified from 15 patients (seven males, eight females). Twelve variants were de novo and seven were new. Age at seizure onset ranged from 3 months to 4 years 5 months (median age 1 year). Common seizure types were epileptic spasms, focal seizures, tonic seizures, and myoclonic seizures. Mild-to-severe developmental delay was present in all patients. Six patients were diagnosed with West syndrome and one was diagnosed with epileptic encephalopathy with continuous spikes and waves during slow sleep (CSWS). Collectively, in our cohort and published studies, 17% had ophthalmic diseases, 31% of variants were located in the stalk domain, and 92% patients with epilepsy had a malformation of cortical development (MCD).

INTERPRETATION

The phenotypes of DYNC1H1-related epilepsy included multiple seizure types; the most common epileptic syndrome was West syndrome. CSWS is a new phenotype of DYNC1H1-related epilepsy. One-third of the variants in patients with epilepsy were located in the stalk domain. Most patients had a MCD and developmental delay.

WHAT THIS PAPER ADDS

Nearly 40% of patients with DYNC1H1 variants had epilepsy. Ninety-two percent of patients with DYNC1H1-related epilepsy had malformation of cortical development. More than 10% of patients with DYNC1H1-related epilepsy were diagnosed with West syndrome. Continuous spikes and waves during slow sleep could be a new phenotype of DYNC1H1 variants. One-third of the variants in patients with epilepsy were located in the stalk domain.

A human dynein heavy chain mutation impacts cortical progenitor cells causing developmental defects, reduced brain size and altered brain architecture

Dynein heavy chain (DYNC1H1) mutations can either lead to severe cerebral cortical malformations, or alternatively may be associated with the development of spinal muscular atrophy with lower extremity predominance (SMA-LED). To assess the origin of such differences, we studied a new Dync1h1 knock-in mouse carrying the cortical malformation p.Lys3334Asn mutation. Comparing with an existing neurodegenerative Dync1h1 mutant (Legs at odd angles, Loa, +/p.Phe580Tyr), we assessed Dync1h1's roles in cortical progenitor and especially radial glia functions during embryogenesis, and assessed neuronal differentiation. p.Lys3334Asn /+ mice exhibit reduced brain and body size. Embryonic brains show increased and disorganized radial glia: interkinetic nuclear migration occurs in mutants, however there are increased basally positioned cells and abventricular mitoses. The ventricular boundary is disorganized potentially contributing to progenitor mislocalization and death. Morphologies of mitochondria and Golgi apparatus are perturbed in vitro, with different effects also in Loa mice. Perturbations of neuronal migration and layering are also observed in p.Lys3334Asn /+ mutants. Overall, we identify specific developmental effects due to a severe cortical malformation mutation in Dync1h1, highlighting the differences with a mutation known instead to primarily affect motor function.

Muscle and bone characteristics of a Chinese family with spinal muscular atrophy, lower extremity predominant 1 (SMALED1) caused by a novel missense DYNC1H1 mutation

BACKGROUND

Spinal muscular atrophy, lower extremity predominant (SMALED) is a type of non-5q spinal muscular atrophy characterised by weakness and atrophy of lower limb muscles without sensory abnormalities. SMALED1 can be caused by dynein cytoplasmic 1 heavy chain 1 (DYNC1H1) gene variants. However, the phenotype and genotype of SMALED1 may overlap with those of other neuromuscular diseases, making it difficult to diagnose clinically. Additionally, bone metabolism and bone mineral density (BMD) in patients with SMALED1 have never been reported.

METHODS

We investigated a Chinese family in which 5 individuals from 3 generations had lower limb muscle atrophy and foot deformities. Clinical manifestations and biochemical and radiographic indices were analysed, and mutational analysis was performed by whole-exome sequencing (WES) and Sanger sequencing.

RESULTS

A novel mutation in exon 4 of the DYNC1H1 gene (c.587T > C, p.Leu196Ser) was identified in the proband and his affected mother by WES. Sanger sequencing confirmed that the proband and 3 affected family members were carriers of this mutation. As leucine is a hydrophobic amino acid and serine is hydrophilic, the hydrophobic interaction resulting from mutation of amino acid residue 196 could influence the stability of the DYNC1H1 protein. Leg muscle magnetic resonance imaging of the proband revealed severe atrophy and fatty infiltration, and electromyographic recordings showed chronic neurogenic impairment of the lower extremities. Bone metabolism markers and BMD of the proband were all within normal ranges. None of the 4 patients had experienced fragility fractures.

CONCLUSION

This study identified a novel DYNC1H1 mutation and expands the spectrum of phenotypes and genotypes of DYNC1H1-related disorders. This is the first report of bone metabolism and BMD in patients with SMALED1.

DYNC1H1 variant associated with epilepsy: Expanding the phenotypic spectrum

DYNC1H1 variants are associated with peripheral neuronal dysfunction and brain morphology abnormalities resulting in neurodevelopmental delay. However, few studies have focused on the association between DYNC1H1 variants and epilepsy. Herein, we report a case of drug-resistant focal epilepsy associated with a pathogenic variant of DYNC1H1. We further summarized the clinical, genetic, and neuroimaging characteristics of patients with DYNC1H1 variant-associated epilepsy from the relevant literature. This report expands the phenotypic spectrum of DYNC1H1-related disorder to include early-onset epilepsy, which is frequently associated with neurodevelopmental delay and intellectual disability, malformations of cortical development, and neuromuscular, ophthalmic, and orthopedic involvement.

Alternatives to Gold Standard Diagnostic Tools for Distinguishing "Natural Kinds" on the Autism Spectrum

Next-generation sequencing techniques have accelerated the discovery of rare mutations responsible for autism spectrum disorder (ASD) in genes involved in a large number of physiological processes, including the control of gene expression, chromatin remodeling, signaling pathways, synaptic scaffolding, neurotransmitter receptors, and lipid metabolism. Genetic diagnosis provides subjects with an explanation of the cause of their disorder. However, it does not, or at least does not yet, shed light on the psychopathological phenomena specific to the individual. It could be hypothesized that each physiological impact of a mutation corresponds to a specific psychopathological phenomenon of ASD, i.e., "a psychopathological natural kind". We discuss here the difficulties identifying this specificity of underlying psychopathology in individuals with ASD due to a rare mutation with a major effect. A comparison of Newson's pathological demand avoidance and Wing's Asperger's syndrome with Asperger's autistic psychopathy highlights different ways of approaching psychopathological descriptions and diagnosis, by focusing on either common or unusual features. Such a comparison calls into question the principles of clinical research recommended by Falret for characterizing "disease individuality" of ASD due to a rare mutation.

Association of SORD mutation with autosomal recessive asymmetric distal hereditary motor neuropathy

Background

The aim of this study was to identify the underlying genetic defect in a family segregating autosomal recessive asymmetric hereditary motor neuropathy (HMN). Asymmetric HMN has not been associated earlier with SORD mutations.

Methods

For this study, we have recruited a family and collected blood samples from affected and normal individuals of a family. Detailed clinical examination and electrophysiological studies were carried out. Whole exome sequencing was performed to detect the underlying genetic defect in this family. The potential variant was validated using the Sanger sequencing approach.

Results

Clinical and electrophysiological examination revealed asymmetric motor neuropathy with normal nerve conduction velocities and action potentials. Genetic analysis identified a homozygous mononucleotide deletion mutation (c.757delG) in a SORD gene in a patient. This mutation is predicted to cause premature truncation of a protein (p.A253Qfs*27).

Conclusions

Interestingly, the patient with homozygous SORD mutation demonstrates normal motor and nerve conduction velocities and action potentials. The affected individual describes in this study has a unique presentation of asymmetric motor neuropathy predominantly affecting the right side more than the left as supported by the clinical examination. This is the first report of SORD mutation from Saudi Arabia and this study further expands the phenotypic spectrum of SORD mutation.

Whole-exome sequencing identifies a novel de novo variant in DYNC1H in a patient with intractable epilepsy

DYNC1H1 variants are associated with broad phenotypes including Charcot-Marie-Tooth disease, spinal muscular atrophy, and mental retardation. However, DYNC1H1 variants related intractable epilepsy have not yet been described in detail so far. Herein, we describe the detailed clinical manifestations of a female patient, carrying a novel de novo variant in DYNC1H1 (p.H311Y), who presented with malformation of cortical development (MCD), refractory epilepsy, intellectual disability, and lower motor neuron disease. We provide a review of previously reported patients who presented with epilepsy associated with DYNC1H1 variants. Of the patients with epilepsy, the DYNC1H1 variants were distributed, on average, in the tail, linker, and motor domains, rather than being mainly distributed in the tail domain as previously reported.

Spinal muscular atrophy with predominant lower extremity (SMA-LED) with no signs other than pure motor symptoms at the intersection of multiple overlap syndrome

BACKGROUND

Mutations in the cytoplasmic dynein 1 heavy chain gene (DYNC1H1) have been associated with spinal muscular atrophy with predominant lower extremity involvement (SMA-LED), Charcot-Marie-Tooth 2O (CMT2O) disease, cortical migration anomalies, and autosomal dominant mental retardation13. SMA-LED phenotype-related mutation was found in the DYNC1H1 gene in the patient who applied with the complaint of gait disturbance.

METHODS

Pathogenic heterozygous c.1678G > A (p.Val560Met) mutation was detected in the DYNC1H1 gene by next-generation targeted gene analysis in the patient who had no phenotypic findings except delayed motor milestones, lumbar lordosis, and lower extremity muscle weakness. The patient's creatinine phosphokinase enzyme level and brain magnetic resonance imaging (MRI) were normal. Electromyography (EMG) had pure motor findings.

CONCLUSION

It should be kept in mind that DYNC1H1 mutation, which we are accustomed to seeing with accompanying findings such as orthopedic and ocular dysmorphic findings, sensorineural EMG findings, and intellectual disability, can also observe with pure motor findings such as muscular dystrophy examination findings.

De novo DYNC1H1 mutation causes infantile developmental and epileptic encephalopathy with brain malformations

Background

The human dynein cytoplasmic 1 heavy chain 1 (DYNC1H1) gene encodes a large subunit of the cytoplasmic dynein complex. DYNC1H1 mutations are associated with various neurological diseases involving both the peripheral and central nervous systems.

Methods

The clinical characteristics and genetic data of an infant carrying the de novo DYNC1H1 variant identified by trio exome sequencing were analyzed. Patients with epilepsy with DYNC1H1 mutations were summarized by reviewing the literature.

Results

We first identified an infant presenting with epileptic spasms harboring a de novo missense mutation in DYNC1H1 (c.874C>T; p. Arg292Trp), once reported in an adult case, and further summarized another 54 patients with seizures or epilepsy caused by DYNC1H1 pathogenic variants in the literature. Refractory epilepsy, intellectual disability, and cortical developmental malformations are crucial characteristics of patients with developmental and epileptic encephalopathy (DEE) caused by DYNC1H1 variants. Notably, epileptic spasms in this case were resistant to multiple anti‐seizure medications, corticosteroids, ketogenic diet, and vagus nerve stimulation treatment. The child also showed cortical gyrus malformation and global developmental delay.

Conclusion

DYNC1H1 variants can cause infantile developmental and epileptic encephalopathy, in which Arg292Trp is a mutation hotspot of the DYNC1H1 gene. Epileptic seizures in this type of DYNC1H1‐related DEE are mostly resistant to multiple antiepileptic strategies and need to explore optimized treatments.

De Novo Variants in the DYNC1H1 Gene Associated With Infantile Spasms

Objective: The DYNC1H1 gene is related to a variety of diseases, including spinal muscular atrophy with lower extremity-predominant 1, Charcot-Marie-Tooth disease type 2O, and mental retardation, autosomal dominant13 (MRD13). Some patients with DYNC1H1 variant also had epilepsy. This study aimed to detect DYNC1H1 variants in Chinese patients with infantile spasms (ISs). Methods: We reviewed clinical information, video electroencephalogram (V-EEG), and neuroimaging of a newly identified cohort of five patients with de novo DYNC1H1gene variants. Results: Five patients with four DYNC1H1variants from four families were included. All patients had epileptic spasms (ESs), the median age at seizure onset was 7.5 months (range from 5 months to 2 years 7 months), and the interictal V-EEG results were hypsarrhythmia. Four of five patients had brain magnetic resonance imaging (MRI) abnormalities. Four de novo DYNC1H1 variants were identified, including two novel variants (p.N1117K, p.M3405L) and two reported variants (p.R1962C, p.F1093S). As for the variant site, two variants are located in the tail domain, one variant is located in the motor domain, and one variant is located in the stalk domain. All patients had tried more than five kinds of antiepileptic drugs. One patient has been controlled well by vigabatrin (VGB) for 4 years, and another patient by VGB and steroids for 1.5 years. The other three patients still had frequent ESs. All patients had severe intellectual disability and development delays. Significance: IS was one of the phenotypes of DYNC1H1 variants. Most patients had non-specific brain MRI abnormality. Two of four DYNC1H1 variants were novel, expanding the variant spectrum. The IS phenotype was related to the variant's domains of DYNC1H1 variant sites. All patients were drug-refractory and showed development delays.

Lissencephaly: Update on diagnostics and clinical management

Lissencephaly represents a spectrum of rare malformations of cortical development including agyria, pachygyria and subcortical band heterotopia. The progress in molecular genetics has led to identification of 31 lissencephaly-associated genes with the overall diagnostic yield over 80%. In this review, we focus on clinical and molecular diagnosis of lissencephaly and summarize the current knowledge on histopathological changes and their correlation with the MRI imaging. Additionally we provide the overview of clinical follow-up recommendations and available data on epilepsy management in patients with lissencephaly.

Common and Unique Genetic Background between Attention-Deficit/Hyperactivity Disorder and Excessive Body Weight

Comorbidity studies show that children with ADHD have a higher risk of being overweight and obese than healthy children. This study aimed to assess the genetic alternations that differ between and are shared by ADHD and excessive body weight (EBW). The sample consisted of 743 Polish children aged between 6 and 17 years. We analyzed a unique set of genes and polymorphisms selected for ADHD and/or obesity based on gene prioritization tools. Polymorphisms in the KCNIP1, SLC1A3, MTHFR, ADRA2A, and SLC6A2 genes proved to be associated with the risk of ADHD in the studied population. The COMT gene polymorphism was one that specifically increased the risk of EBW in the ADHD group. Using the whole-exome sequencing technique, we have shown that the ADHD group contains rare and protein-truncating variants in the FBXL17, DBH, MTHFR, PCDH7, RSPH3, SPTBN1, and TNRC6C genes. In turn, variants in the ADRA2A, DYNC1H1, MAP1A, SEMA6D, and ZNF536 genes were specific for ADHD with EBW. In this way, we confirmed, at the molecular level, the existence of genes specifically predisposing to EBW in ADHD patients, which are associated with the biological pathways involved in the regulation of the reward system, intestinal microbiome, and muscle metabolism.

Two cases of DYNC1H1 mutations with intractable epilepsy

BACKGROUND

The DYNC1H1 gene encodes the heavy chain of cytoplasmic dynein 1, a core structure of the cytoplasmic dynein complex. Dominant DYNC1H1 mutations are implicated in Charcot-Marie-Tooth disease, axonal, type 20, spinal muscular atrophy, lower extremity-predominant 1, and autosomal dominant mental retardation 13 with neuronal migration defects. We report two patients with DYNC1H1 mutations who had intractable epilepsy and intellectual disability (ID), one with and one without pachygyria.

CASE REPORTS

Patient 1 had severe ID. At the age of 2 months, she presented myoclonic seizures and tonic seizures, and later experienced atonic seizures and focal impaired-awareness seizures (FIAS). EEG showed slow waves in right central areas during myoclonic seizures. Brain MRI revealed pachygyria, predominantly in the occipital lobe. After callosal transection her atonic seizures disappeared, but FIAS remained. Patient 2 was diagnosed with autism spectrum disorder (ASD) and severe ID. At the age of 7 years, he presented generalized tonic-clonic seizures, myoclonic seizures, and FIAS. Interictal EEG showed generalized spike-and-wave complexes, predominantly in the left frontal area. Brain MRI was unremarkable. Exome sequencing revealed novel de novo mutations in DYNC1H1: c.4691A > T, p.(Glu1564Val) in Patient 1 and c.12536 T > C, p.(Leu4179Ser) in Patient 2.

CONCLUSIONS

DYNC1H1 comprises a stem, stalk, and six AAA domains. Patient 2 is the second report of an AAA6 domain mutation without malformations of cortical development. The p.(Gly4072Ser) mutation in the AAA6 domain was also reported in a patient with ASD. It may be that the AAA6 domain has little effect on neuronal movement of DYNC1H1 along microtubules.