Cytokine Production by Mononuclear Cells from Patients with Familial Infantile Bilateral Striatal Necrosis

Prompted by findings suggesting immune instability in infantile bilateral striatal necrosis (IBSN), we evaluated levels of proinflammatory (tumor necrosis factor α, interleukin [IL]-1β, IL-6, interferon [IFN]γ) and anti-inflammatory (IL-10 and IL-1ra) cytokines produced by peripheral blood mononuclear cells (PBMC) from 6 children with IBSN and 11 age-matched controls. Compared to controls, non-stimulated PBMC from the IBSN group produced a significantly lower level of IL-1ra (by 38%; p < 0.001) and significantly lower levels of TNFα, IL-1β, and IFNγ (by 36% [p < 0.001], 25% [p = 0.06], and 32% [p < 0.02]) under PBMC stimulation. The severe cachexia manifesting shortly after IBSN onset may impair the immunological state, placing patients at risk of death from hyperpyrexia and sepsis.

Phospholipase A2-activating protein is associated with a novel form of leukoencephalopathy

Leukoencephalopathies are a group of white matter disorders related to abnormal formation, maintenance, and turnover of myelin in the central nervous system. These disorders of the brain are categorized according to neuroradiological and pathophysiological criteria. Herein, we have identified a unique form of leukoencephalopathy in seven patients presenting at ages 2 to 4 months with progressive microcephaly, spastic quadriparesis, and global developmental delay. Clinical, metabolic, and imaging characterization of seven patients followed by homozygosity mapping and linkage analysis were performed. Next generation sequencing, bioinformatics, and segregation analyses followed, to determine a loss of function sequence variation in the phospholipase A₂-activating protein encoding gene (PLAA). Expression and functional studies of the encoded protein were performed and included measurement of prostaglandin E₂ and cytosolic phospholipase A₂ activity in membrane fractions of fibroblasts derived from patients and healthy controls. Plaa-null mice were generated and prostaglandin E₂ levels were measured in different tissues. The novel phenotype of our patients segregated with a homozygous loss-of-function sequence variant, causing the substitution of leucine at position 752 to phenylalanine, in PLAA, which causes disruption of the protein's ability to induce prostaglandin E₂ and cytosolic phospholipase A₂ synthesis in patients' fibroblasts. Plaa-null mice were perinatal lethal with reduced brain levels of prostaglandin E₂ The non-functional phospholipase A₂-activating protein and the associated neurological phenotype, reported herein for the first time, join other complex phospholipid defects that cause leukoencephalopathies in humans, emphasizing the importance of this axis in white matter development and maintenance.

Novel homozygous missense mutation in GAN associated with Charcot-Marie-Tooth disease type 2 in a large consanguineous family from Israel

Background

CMT-2 is a clinically and genetically heterogeneous group of peripheral axonal neuropathies characterized by slowly progressive weakness and atrophy of distal limb muscles resulting from length-dependent motor and sensory neurodegeneration. Classical giant axonal neuropathy (GAN) is an autosomal recessively inherited progressive neurodegenerative disorder of the peripheral and central nervous systems, typically diagnosed in early childhood and resulting in death by the end of the third decade. Distinctive phenotypic features are the presence of “kinky” hair and long eyelashes. The genetic basis of the disease has been well established, with over 40 associated mutations identified in the gene GAN, encoding the BTB-KELCH protein gigaxonin, involved in intermediate filament regulation.

Methods

An Illumina Human CytoSNP-12 array followed by whole exome sequence analysis was used to identify the disease associated gene mutation in a large consanguineous family diagnosed with Charcot-Marie-Tooth disease type 2 (CMT-2) from which all but one affected member had straight hair.

Results

Here we report the identification of a novel GAN missense mutation underlying the CMT-2 phenotype observed in this family. Although milder forms of GAN, with and without the presence of kinky hair have been reported previously, a phenotype distinct from that was investigated in this study. All family members lacked common features of GAN, including ataxia, nystagmus, intellectual disability, seizures, and central nervous system involvement.

Conclusions

Our findings broaden the spectrum of phenotypes associated with GAN mutations and emphasize a need to proceed with caution when providing families with diagnostic or prognostic information based on either clinical or genetic findings alone.

Polymicrogyria and myoclonic epilepsy in autosomal recessive cutis laxa type 2A

Cutis laxa syndromes are rare inherited disorders of skin and connective tissue metabolism associated with variable systemic involvement. The main clinical manifestation is loose, wrinkled, redundant, inelastic skin, hypotonia, typical facies including short nose and down-slanting palpebral fissures, and varying degrees of developmental delay. The aim of this report is to describe two siblings diagnosed with a moderate form of ATP6V0A2-related cutis laxa with polymicrogyria (cobblestone-like brain dysgenesis). One of the patients has myoclonic epilepsy which may have contributed to his more severe clinical presentation. The literature on cutis laxa syndromes is reviewed.

Two novel MYH7 proline substitutions cause Laing Distal Myopathy-like phenotypes with variable expressivity and neck extensor contracture

Background

Human skeletal muscles express three major myosin heavy chain (MyHC) isoforms: MyHCIIx (MYH1) in fast type 2B muscle fibers, MyHCIIa (MYH2) in fast type 2A fibers and MyHCI/β-cardiac MyHC (MYH7) in slow type I skeletal fibers and cardiac ventricles. In line with its expression pattern, MYH7 mutations have been reported in association with hypertrophic or dilated cardiomyopathy, skeletal myopathies or a combination of both. We analyzed the clinical and molecular phenotype of two unrelated families of Jewish Moroccan ancestry that presented with apparently autosomal dominant inheritance of progressive Laing-like distal myopathy with non-specific myopathic changes, but uncommon marked contractures and wasting of the neck extensors.

Methods

Clinical phenotyping, whole exome sequencing and restriction analysis, generation of mutants followed by cell culture transfection and imaging.

Results

Using whole exome sequencing we identified in both families two novel heterozygous proline substitutions located in exon 31 of MYH7 within its rod domain: c.4309G>C (p.Ala1437Pro) and c.4301G>C (p.Arg1434Pro). Here we show that the phenotype caused by these mutations includes marked cervical muscle contracture, and report that the severity of the phenotype varies significantly, to the extent of non-penetrance in one of the families. Finally, we provide evidence that both proline substitutions impair myosin self-assembly in non-muscle cells transfected with β-myosin constructs carrying the mutations, but do not prevent incorporation of the mutant molecules into the sarcomere.

Conclusions

This study expands our clinical and molecular knowledge of MYH7 rod mutations causing skeletal myopathies, and underscores the importance of discussing disease penetrance during genetic counseling.

Acute Cerebellitis in Children: A Many-Faceted Disease

Acute cerebellitis is a rare inflammatory condition. It may have a benign, self-limiting course or present as a fulminant disease resulting in severe cerebellar damage or even sudden death. We present the clinical, laboratory, and radiologic data in 9 children diagnosed with acute cerebellitis, who were identified by database search in our pediatric medical center from January 2000 to November 2014. The main presenting symptom was headache, and the main presenting sign was ataxia. Bilateral diffuse hemispheric involvement was the most common imaging finding at presentation. Mycoplasma pneumoniae was the most common infectious pathogen found. Treatment included steroids in all cases, antibiotics in 4, and intravenous immunoglobulins in 6. Six patients had a full recovery, and 3 had residual neurologic complications. Magnetic resonance imaging (MRI) is the modality of choice for diagnosis. The course of acute cerebellitis varies from a commonly benign and self-limiting disease to an occasionally fulminant disease, resulting in severe cerebellar damage or sudden death.

Multiplex families with epilepsy: Success of clinical and molecular genetic characterization

OBJECTIVE

To analyze the clinical syndromes and inheritance patterns of multiplex families with epilepsy toward the ultimate aim of uncovering the underlying molecular genetic basis.

METHODS

Following the referral of families with 2 or more relatives with epilepsy, individuals were classified into epilepsy syndromes. Families were classified into syndromes where at least 2 family members had a specific diagnosis. Pedigrees were analyzed and molecular genetic studies were performed as appropriate.

RESULTS

A total of 211 families were ascertained over an 11-year period in Israel. A total of 169 were classified into broad familial epilepsy syndrome groups: 61 generalized, 22 focal, 24 febrile seizure syndromes, 33 special syndromes, and 29 mixed. A total of 42 families remained unclassified. Pathogenic variants were identified in 49/211 families (23%). The majority were found in established epilepsy genes (e.g., SCN1A, KCNQ2, CSTB), but in 11 families, this cohort contributed to the initial discovery (e.g., KCNT1, PCDH19, TBC1D24). We expand the phenotypic spectrum of established epilepsy genes by reporting a familial LAMC3 homozygous variant, where the predominant phenotype was epilepsy with myoclonic-atonic seizures, and a pathogenic SCN1A variant in a family where in 5 siblings the phenotype was broadly consistent with Dravet syndrome, a disorder that usually occurs sporadically.

CONCLUSION

A total of 80% of families were successfully classified, with pathogenic variants identified in 23%. The successful characterization of familial electroclinical and inheritance patterns has highlighted the value of studying multiplex families and their contribution towards uncovering the genetic basis of the epilepsies.

A possible genotype-phenotype correlation in Ashkenazi-Jewish individuals with Aicardi-Goutières syndrome associated with SAMHD1 mutation

Aicardi-Goutières syndrome is a genetic neurodegenerative disorder with clinical symptoms mimicking a congenital viral infection. Mutations in 6 genes are known to cause the disease: 3 prime repair exonuclease1, ribonucleases H2A, B, and C, SAM domain and HD domain 1, and most recently ADAR1. HD domain 1 mutations were previously reported in the Ashkenazi-Jewish community. We report an additional patient of Ashkenazi-Jewish descent and review the other 3 cases affected with Aicardi-Goutières syndrome due to SAM domain and HD domain 1 (SAMHD1) mutations described in Israel. We propose that there may be a phenotypic-genotypic correlation in accordance with the type of mutations inherited in the SAMHD1 genotype and suggest that Aicardi-Goutières syndrome may not be a rare disease in the Ashkenazi-Jewish population.

Lethal neonatal rigidity and multifocal seizure syndrome--report of another family with a BRAT1 mutation

We describe two siblings born to consanguineous Arab-Muslim parents who presented in early infancy with myoclonic seizures, hypertonia and contractures, arrested head growth, inability to swallow, and bouts of apnea-bradycardia, culminating in cardiac arrest and death. Whole-genome sequencing yielded a c.1173delG mutation in the BRAT1 gene. Three recent reports identified mutations in the same gene in three infants from three Amish sibships, one Mexican neonate and two Japanese siblings with similar clinical manifestations. The authors speculated that the destabilization of the encoded protein may underlie the catastrophic epilepsy and corticobasal neuronal degeneration. We suggest that BRAT1 be added to the growing list of genes that are related to severe early infantile (neonatal) epileptic encephalopathy.

Characterization of human disease phenotypes associated with mutations in TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR, and IFIH1

Aicardi-Goutières syndrome is an inflammatory disease occurring due to mutations in any of TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR or IFIH1. We report on 374 patients from 299 families with mutations in these seven genes. Most patients conformed to one of two fairly stereotyped clinical profiles; either exhibiting an in utero disease-onset (74 patients; 22.8% of all patients where data were available), or a post-natal presentation, usually within the first year of life (223 patients; 68.6%), characterized by a sub-acute encephalopathy and a loss of previously acquired skills. Other clinically distinct phenotypes were also observed; particularly, bilateral striatal necrosis (13 patients; 3.6%) and non-syndromic spastic paraparesis (12 patients; 3.4%). We recorded 69 deaths (19.3% of patients with follow-up data). Of 285 patients for whom data were available, 210 (73.7%) were profoundly disabled, with no useful motor, speech and intellectual function. Chilblains, glaucoma, hypothyroidism, cardiomyopathy, intracerebral vasculitis, peripheral neuropathy, bowel inflammation and systemic lupus erythematosus were seen frequently enough to be confirmed as real associations with the Aicardi-Goutieres syndrome phenotype. We observed a robust relationship between mutations in all seven genes with increased type I interferon activity in cerebrospinal fluid and serum, and the increased expression of interferon-stimulated gene transcripts in peripheral blood. We recorded a positive correlation between the level of cerebrospinal fluid interferon activity assayed within one year of disease presentation and the degree of subsequent disability. Interferon-stimulated gene transcripts remained high in most patients, indicating an ongoing disease process. On the basis of substantial morbidity and mortality, our data highlight the urgent need to define coherent treatment strategies for the phenotypes associated with mutations in the Aicardi-Goutières syndrome-related genes. Our findings also make it clear that a window of therapeutic opportunity exists relevant to the majority of affected patients and indicate that the assessment of type I interferon activity might serve as a useful biomarker in future clinical trials.

A recurrent de novo mutation in KCNC1 causes progressive myoclonus epilepsy

Progressive myoclonus epilepsies (PMEs) are a group of rare, inherited disorders manifesting with action myoclonus, tonic-clonic seizures and ataxia. We sequenced the exomes of 84 unrelated individuals with PME of unknown cause and molecularly solved 26 cases (31%). Remarkably, a recurrent de novo mutation, c.959G>A (p.Arg320His), in KCNC1 was identified as a new major cause for PME. Eleven unrelated exome-sequenced (13%) and two affected individuals in a secondary cohort (7%) had this mutation. KCNC1 encodes KV3.1, a subunit of the KV3 voltage-gated potassium ion channels, which are major determinants of high-frequency neuronal firing. Functional analysis of the Arg320His mutant channel showed a dominant-negative loss-of-function effect. Ten cases had pathogenic mutations in known PME-associated genes (NEU1, NHLRC1, AFG3L2, EPM2A, CLN6 and SERPINI1). Identification of mutations in PRNP, SACS and TBC1D24 expand their phenotypic spectra to PME. These findings provide insights into the molecular genetic basis of PME and show the role of de novo mutations in this disease entity.

Microcephaly thin corpus callosum intellectual disability syndrome caused by mutated TAF2

BACKGROUND

The combination of microcephaly, pyramidal signs, abnormal corpus callosum, and intellectual disability presents a diagnostic challenge. We describe an autosomal recessive disorder characterized by microcephaly, pyramidal signs, thin corpus callosum, and intellectual disability.

METHODS

We previously mapped the locus for this disorder to 8q23.2-q24.12; the candidate region included 22 genes. We performed Sanger sequencing of 10 candidate genes; to ensure other genes in the candidate region do not harbor mutations, we sequenced the exome of one affected individual.

RESULTS

We identified two homozygous missense changes, p.Thr186Arg and p.Pro416His in TAF2, which encodes a multisubunit cofactor for TFIID-dependent RNA polymerase II-mediated transcription, in all affected individuals.

CONCLUSIONS

We propose that the disorder is caused by the more conserved mutation p.Thr186Arg, with the second sequence change identified, p.Pro416His, possibly further negatively affecting the function of the protein. However, it is unclear which of the two changes, or maybe both, represents the causative mutation. A single missense mutation in TAF2 in a family with microcephaly and intellectual disability was described in a large-scale study reporting on the identification of 50 novel genes. We suggest that a mutation in TAF2 can cause this syndrome.

A novel mutation in the GAN gene causes an intermediate form of giant axonal neuropathy in an Arab-Israeli family

Giant axonal neuropathy is a severe autosomal recessive neurodegenerative disorder of childhood that affects both the peripheral and central nervous systems. It is caused by mutations in the GAN gene linked to chromosome 16q24.1 At least 45 distinct disease-causing mutations have been identified throughout the gene in families of various ethnic origins, with different symptomatologies and different clinical courses. To date, no characteristic mutation or phenotype-genotype correlation has been established. We describe a novel missense mutation in four siblings born to consanguineous parents of Arab original with clinical and molecular features compatible with giant axonal neuropathy. The phenotype was characterized by a predominant motor and sensory peripheral neuropathies and severe skeletal deformities.

Benign neonatal sleep myoclonus: an autosomal dominant form not allelic to KCNQ2 or KCNQ3

Benign neonatal sleep myoclonus is an uncommon, nonepileptic disorder characterized by myoclonic jerks appearing in the neonatal period that occur predominantly during sleep. Although self-limiting, the disorder is frequently confused with epileptic neonatal seizures. A few familial cases have been reported; however the genetics has not been studied. We ascertained 3 families with 2 or more affected individuals and analyzed the pedigrees. We used microsatellite markers to determine if the disorder was possibly linked to KCNQ2 or KCNQ3, the 2 genes that cause most cases of benign familial neonatal seizures, a disorder that it could be easily confused with. The 3 pedigrees, including one with 4 affected individuals, were suggestive of autosomal dominant inheritance. The loci for KCNQ2 and KCNQ3 were excluded in the 2 larger families. We conclude that benign neonatal sleep myoclonus can show autosomal dominant inheritance and is not allelic with benign familial neonatal seizures.

Microcephaly-thin corpus callosum syndrome maps to 8q23.2-q24.12

Postnatal microcephaly is defined as normal head circumference at birth, which progressively declines to more than 2 standard deviations below the average for the patient's age and sex. We describe four patients from three consanguineous families of Arab Bedouin origin who presented with autosomal recessive inheritance of progressive microcephaly, spasticity, thin corpus callosum, pyramidal signs, and intellectual disability. Homozygosity mapping (Human Mapping NspI 250K arrays, Affymetrix, Santa Clara, CA) placed the disease locus at 8q23.2-q24.12. The candidate region includes 22 known or predicted genes, including RAD21, which is related to the cohesion complex EIF3H, which is involved in translation initiation, and TAF2, which may be involved in intellectual disability. Identification of the causative gene in our reported family will shed light on the pathogenesis of this severe condition.

Multiple congenital anomalies-hypotonia-seizures syndrome is caused by a mutation in PIGN

BACKGROUND

This study reports on a hitherto undescribed autosomal recessive syndrome characterised by dysmorphic features and multiple congenital anomalies together with severe neurological impairment, chorea and seizures leading to early death, and the identification of a gene involved in the pathogenesis of the disease.

METHODS

Homozygosity mapping was performed using Affymetrix Human Mapping 250k NspI arrays. Sequencing of all coding exons of the candidate genes was performed with primer sets designed using the Primer3 program. Fluorescence activated cell sorting was performed using conjugated antibody to CD59. Staining, acquisition and analysis were performed on a FACSCalibur flow cytometer.

RESULTS

Using homozygosity mapping, the study mapped the disease locus to 18q21.32-18q22.1 and identified the disease-causing mutation, c.2126G→A (p.Arg709Gln), in PIGN, which encodes glycosylphosphatidylinositol (GPI) ethanolamine phosphate transferase 1, a protein involved in GPI-anchor biosynthesis. Arginine at the position 709 is a highly evolutionarily conserved residue located in the PigN domain. The expression of GPI linked protein CD59 on fibroblasts from patients as compared to that in a control individual showed a 10-fold reduction in expression, confirming the pathogenic consequences of the mutation on GPI dependent protein expression.

CONCLUSIONS

The abundant expression of PIGN in various tissues is compatible with the diverse phenotypic features observed in the patients and with the involvement of multiple body systems. The presence of developmental delay, hypotonia, and epilepsy combined with multiple congenital anomalies, especially anorectal anomalies, should lead a clinician to suspect a GPI deficiency related disorder.

Three sibs with microcephaly, clubfeet and agenesis of corpus callosum: a new genetic syndrome?

Clubfoot is a common birth deformity, and agenesis of the corpus callosum is one of the most prevalent brain malformations. We describe three sibs of Arab origin, who were born with clubfeet, agenesis of corpus callosum, and minor anomalies. Two of them were born with microcephaly. This phenotype may represent a novel autosomal recessive genetic condition.