ARF1-related disorder: phenotypic and molecular spectrum.

PURPOSE: ARF1 was previously implicated in periventricular nodular heterotopia (PVNH) in only five individuals and systematic clinical characterisation was not available. The aim of this study is to provide a comprehensive description of the phenotypic and genotypic spectrum of ARF1-related neurodevelopmental disorder. METHODS: We collected detailed phenotypes of an international cohort of individuals (n=17) with ARF1 variants assembled through the GeneMatcher platform. Missense variants were structurally modelled, and the impact of several were functionally validated. RESULTS: De novo variants (10 missense, 1 frameshift, 1 splice altering resulting in 9 residues insertion) in ARF1 were identified among 17 unrelated individuals. Detailed phenotypes included intellectual disability (ID), microcephaly, seizures and PVNH. No specific facial characteristics were consistent across all cases, however microretrognathia was common. Various hearing and visual defects were recurrent, and interestingly, some inflammatory features were reported. MRI of the brain frequently showed abnormalities consistent with a neuronal migration disorder. CONCLUSION: We confirm the role of ARF1 in an autosomal dominant syndrome with a phenotypic spectrum including severe ID, microcephaly, seizures and PVNH due to impaired neuronal migration.

A genome sequencing program for novel undiagnosed diseases.

PURPOSE: The Scripps Idiopathic Diseases of Man (IDIOM) study aims to discover novel gene-disease relationships and provide molecular genetic diagnosis and treatment guidance for individuals with novel diseases using genome sequencing integrated with clinical assessment and multidisciplinary case review. Here we describe the operational protocol and initial results of the IDIOM study. METHODS: A total of 121 cases underwent first-tier review by the principal investigators to determine whether the primary inclusion criteria were satisfied, 59 (48.8%) underwent second-tier review by our clinician-scientist review panel, and 17 patients (14.0%) and their family members were enrolled. RESULTS: 60% of cases resulted in a plausible molecular diagnosis, and 18% of cases resulted in a confirmed molecular diagnosis. Two of three confirmed cases led to the identification of novel gene-disease relationships. In the third confirmed case a previously described but unrecognized disease was revealed. In all three confirmed cases a new clinical management strategy was initiated based on the genetic findings. CONCLUSION: Genome sequencing provides tangible clinical benefit for individuals with idiopathic genetic disease, not only in the context of molecular genetic diagnosis of known rare conditions but also in cases where prior clinical information regarding a new genetic disorder is lacking.

De novo KCNB1 mutations in epileptic encephalopathy.

OBJECTIVE: Numerous studies have demonstrated increased load of de novo copy number variants or single nucleotide variants in individuals with neurodevelopmental disorders, including epileptic encephalopathies, intellectual disability, and autism. METHODS: We searched for de novo mutations in a family quartet with a sporadic case of epileptic encephalopathy with no known etiology to determine the underlying cause using high-coverage whole exome sequencing (WES) and lower-coverage whole genome sequencing. Mutations in additional patients were identified by WES. The effect of mutations on protein function was assessed in a heterologous expression system. RESULTS: We identified a de novo missense mutation in KCNB1 that encodes the KV 2.1 voltage-gated potassium channel. Functional studies demonstrated a deleterious effect of the mutation on KV 2.1 function leading to a loss of ion selectivity and gain of a depolarizing inward cation conductance. Subsequently, we identified 2 additional patients with epileptic encephalopathy and de novo KCNB1 missense mutations that cause a similar pattern of KV 2.1 dysfunction. INTERPRETATION: Our genetic and functional evidence demonstrate that KCNB1 mutation can result in early onset epileptic encephalopathy. This expands the locus heterogeneity associated with epileptic encephalopathies and suggests that clinical WES may be useful for diagnosis of epileptic encephalopathies of unknown etiology.

Gain-of-function ADCY5 mutations in familial dyskinesia with facial myokymia.

OBJECTIVE: To identify the cause of childhood onset involuntary paroxysmal choreiform and dystonic movements in 2 unrelated sporadic cases and to investigate the functional effect of missense mutations in adenylyl cyclase 5 (ADCY5) in sporadic and inherited cases of autosomal dominant familial dyskinesia with facial myokymia (FDFM). METHODS: Whole exome sequencing was performed on 2 parent-child trios. The effect of mutations in ADCY5 was studied by measurement of cyclic adenosine monophosphate (cAMP) accumulation under stimulatory and inhibitory conditions. RESULTS: The same de novo mutation (c.1252C>T, p.R418W) in ADCY5 was found in both studied cases. An inherited missense mutation (c.2176G>A, p.A726T) in ADCY5 was previously reported in a family with FDFM. The significant phenotypic overlap with FDFM was recognized in both cases only after discovery of the molecular link. The inherited mutation in the FDFM family and the recurrent de novo mutation affect residues in different protein domains, the first cytoplasmic domain and the first membrane-spanning domain, respectively. Functional studies revealed a statistically significant increase in ß-receptor agonist-stimulated intracellular cAMP consistent with an increase in adenylyl cyclase activity for both mutants relative to wild-type protein, indicative of a gain-of-function effect. INTERPRETATION: FDFM is likely caused by gain-of-function mutations in different domains of ADCY5-the first definitive link between adenylyl cyclase mutation and human disease. We have illustrated the power of hypothesis-free exome sequencing in establishing diagnoses in rare disorders with complex and variable phenotype. Mutations in ADCY5 should be considered in patients with undiagnosed complex movement disorders even in the absence of a family history.

Autosomal Recessive Cerebellar Atrophy and Spastic Ataxia in Patients With Pathogenic Biallelic Variants in GEMIN5.

The hereditary ataxias are a heterogenous group of disorders with an increasing number of causative genes being described. Due to the clinical and genetic heterogeneity seen in these conditions, the majority of such individuals endure a diagnostic odyssey or remain undiagnosed. Defining the molecular etiology can bring insights into the responsible molecular pathways and eventually the identification of therapeutic targets. Here, we describe the identification of biallelic variants in the GEMIN5 gene among seven unrelated families with nine affected individuals presenting with spastic ataxia and cerebellar atrophy. GEMIN5, an RNA-binding protein, has been shown to regulate transcription and translation machinery. GEMIN5 is a component of small nuclear ribonucleoprotein (snRNP) complexes and helps in the assembly of the spliceosome complexes. We found that biallelic GEMIN5 variants cause structural abnormalities in the encoded protein and reduce expression of snRNP complex proteins in patient cells compared with unaffected controls. Finally, knocking out endogenous Gemin5 in mice caused early embryonic lethality, suggesting that Gemin5 expression is crucial for normal development. Our work further expands on the phenotypic spectrum associated with GEMIN5-related disease and implicates the role of GEMIN5 among patients with spastic ataxia, cerebellar atrophy, and motor predominant developmental delay.

What Is Not in the Name? Dopa-Responsive Dystonia May Respond to More Than L-Dopa.

BACKGROUND: Classic L-dopa-responsive dystonia is characterized by the triad of dystonia, diurnal fluctuation of signs, and dramatic response of signs to low-dose L-dopa therapy. Dopa-responsive dystonia succinctly summarizes the relevant clinical features. However, literal application of this label or consideration of dopa-responsive dystonia as a diagnostic end without molecular and/or biochemical definition may contribute to misdiagnosis and incomplete treatment in dopa-responsive conditions that impair synthesis of monoamine neurotransmitters besides dopamine. PATIENT DESCRIPTION: We describe and provide video for twin patients with a rare form of dopa-responsive dystonia due to sepiapterin reductase deficiency. As is typical in dopa-responsive dystonia, these patients displayed dramatic improvement with L-dopa/carbidopa therapy. However, treatment was suboptimal until 5-hydroxytryptophan was added to address their serotonergic deficit. DISCUSSION: Our report highlights the limitations of the dopa-responsive dystonia label and increases awareness of sepiapterin reductase deficiency and other conditions that may present as dopa-responsive dystonia. We provide a diagnostic and therapeutic approach to guide the clinician in evaluating and treating individuals with dopa-responsive dystonia.

Toward clinical genomics in everyday medicine: perspectives and recommendations.

Precision or personalized medicine through clinical genome and exome sequencing has been described by some as a revolution that could transform healthcare delivery, yet it is currently used in only a small fraction of patients, principally for the diagnosis of suspected Mendelian conditions and for targeting cancer treatments. Given the burden of illness in our society, it is of interest to ask how clinical genome and exome sequencing can be constructively integrated more broadly into the routine practice of medicine for the betterment of public health. In November 2014, 46 experts from academia, industry, policy and patient advocacy gathered in a conference sponsored by Illumina, Inc. to discuss this question, share viewpoints and propose recommendations. This perspective summarizes that work and identifies some of the obstacles and opportunities that must be considered in translating advances in genomics more widely into the practice of medicine.

The Koolen-de Vries syndrome: a phenotypic comparison of patients with a 17q21.31 microdeletion versus a KANSL1 sequence variant.

The Koolen-de Vries syndrome (KdVS; OMIM #610443), also known as the 17q21.31 microdeletion syndrome, is a clinically heterogeneous disorder characterised by (neonatal) hypotonia, developmental delay, moderate intellectual disability, and characteristic facial dysmorphism. Expressive language development is particularly impaired compared with receptive language or motor skills. Other frequently reported features include social and friendly behaviour, epilepsy, musculoskeletal anomalies, congenital heart defects, urogenital malformations, and ectodermal anomalies. The syndrome is caused by a truncating variant in the KAT8 regulatory NSL complex unit 1 (KANSL1) gene or by a 17q21.31 microdeletion encompassing KANSL1. Herein we describe a novel cohort of 45 individuals with KdVS of whom 33 have a 17q21.31 microdeletion and 12 a single-nucleotide variant (SNV) in KANSL1 (19 males, 26 females; age range 7 months to 50 years). We provide guidance about the potential pitfalls in the laboratory testing and emphasise the challenges of KANSL1 variant calling and DNA copy number analysis in the complex 17q21.31 region. Moreover, we present detailed phenotypic information, including neuropsychological features, that contribute to the broad phenotypic spectrum of the syndrome. Comparison of the phenotype of both the microdeletion and SNV patients does not show differences of clinical importance, stressing that haploinsufficiency of KANSL1 is sufficient to cause the full KdVS phenotype.

ADCY5-related dyskinesia: Broader spectrum and genotype-phenotype correlations.

OBJECTIVE: To investigate the clinical spectrum and distinguishing features of adenylate cyclase 5 (ADCY5)-related dyskinesia and genotype-phenotype relationship. METHODS: We analyzed ADCY5 in patients with choreiform or dystonic movements by exome or targeted sequencing. Suspected mosaicism was confirmed by allele-specific amplification. We evaluated clinical features in our 50 new and previously reported cases. RESULTS: We identified 3 new families and 12 new sporadic cases with ADCY5 mutations. These mutations cause a mixed hyperkinetic disorder that includes dystonia, chorea, and myoclonus, often with facial involvement. The movements are sometimes painful and show episodic worsening on a fluctuating background. Many patients have axial hypotonia. In 2 unrelated families, a p.A726T mutation in the first cytoplasmic domain (C1) causes a relatively mild disorder of prominent facial and hand dystonia and chorea. Mutations p.R418W or p.R418Q in C1, de novo in 13 individuals and inherited in 1, produce a moderate to severe disorder with axial hypotonia, limb hypertonia, paroxysmal nocturnal or diurnal dyskinesia, chorea, myoclonus, and intermittent facial dyskinesia. Somatic mosaicism is usually associated with a less severe phenotype. In one family, a p.M1029K mutation in the C2 domain causes severe dystonia, hypotonia, and chorea. The progenitor, whose childhood-onset episodic movement disorder almost disappeared in adulthood, was mosaic for the mutation. CONCLUSIONS: ADCY5-related dyskinesia is a childhood-onset disorder with a wide range of hyperkinetic abnormal movements. Genotype-specific correlations and mosaicism play important roles in the phenotypic variability. Recurrent mutations suggest particular functional importance of residues 418 and 726 in disease pathogenesis.

Myocardial flow regulation in people with mitochondrial myopathy, encephalopathy, lactic acidosis, stroke-like episodes/myoclonic epilepsy and ragged red fibers and other mitochondrial syndromes.

OBJECTIVE: This study tests the hypothesis that elevated levels of rest myocardial blood flow (MBF), indicative of inefficient aerobic metabolism, will be present in some patients with mitochondrial disorders but structurally normal hearts. BACKGROUND: Regulation of MBF is a complex process closely linked to myocardial energy production. Aerobic metabolism in turn depends on normal mitochondrial function and so investigation of patients with mitochondrial disorders may provide important information regarding heritable mechanisms involved in regulation of myocardial flow. METHODS: Rest and adenosine-stimulated MBF was measured by the positron emission tomography (PET) 13NH(3) technique in nine patients with mitochondrial disorders and compared with 15 age-matched control participants. RESULTS: Basal heart rate (beats/min) and rate pressure product (mm Hg/min) were elevated in patients (76+/-13 and 9302+/-1910, mean+/-SD, respectively) compared with control participants (63+/-9 and 7411+/-1531, P<0.01 and P<0.05, respectively). However, rest and adenosine-stimulated MBF (ml/min per g) did not differ significantly between groups (patients, 1.13+/-0.52 and 4.17+/-0.84, respectively; control participants, 0.85+/-0.30 and 3.56+/-0.63, respectively). Normalization of rest MBF to rate pressure product, however, demonstrated three patients whose values exceeded that of all control participants (chi2=5.71, P<0.05, Fisher's exact test). CONCLUSIONS: Elevated basal MBF, in some patients with mitochondrial disorders but structurally normal hearts, suggests the level of basal flow is responsive to efficiency of aerobic metabolism, which closely reflects mitochondrial function. Mitochondrial heteroplasmy with relative sparing of myocardial mitochondria may account for normal basal flow in others with these disorders.

Atypical GLUT1 deficiency with prominent movement disorder responsive to ketogenic diet.

Glucose transport protein deficiency due to mutation in the GLUT1 gene is characterized by infantile onset and chronic seizure disorder, microcephaly, global developmental delays, and hypoglycorrhachia. We describe a 10-year-old normocephalic male with prominent ataxia, dystonia, choreoathetosis, and GLUT1 deficiency whose motor abnormalities improved with a ketogenic diet. We illustrate the motor abnormalities, at baseline and after ketogenic diet, that characterize this unusual case. This case broadens the phenotype of GLUT1 deficiency and illustrates the importance of cerebrospinal fluid (CSF) evaluation in detecting potentially treatable conditions in children with undiagnosed movement disorders.