Marina Michelson

Mutations in TMEM216 perturb ciliogenesis and cause Joubert, Meckel and related syndromes

Joubert syndrome (JBTS), related disorders (JSRDs) and Meckel syndrome (MKS) are ciliopathies. We now report that MKS2 and CORS2 (JBTS2) loci are allelic and caused by mutations in TMEM216, which encodes an uncharacterized tetraspan transmembrane protein. Individuals with CORS2 frequently had nephronophthisis and polydactyly, and two affected individuals conformed to the oro-facio-digital type VI phenotype, whereas skeletal dysplasia was common in fetuses affected by MKS. A single G218T mutation (R73L in the protein) was identified in all cases of Ashkenazi Jewish descent (n = 10). TMEM216 localized to the base of primary cilia, and loss of TMEM216 in mutant fibroblasts or after knockdown caused defective ciliogenesis and centrosomal docking, with concomitant hyperactivation of RhoA and Dishevelled. TMEM216 formed a complex with Meckelin, which is encoded by a gene also mutated in JSRDs and MKS. Disruption of tmem216 expression in zebrafish caused gastrulation defects similar to those in other ciliary morphants. These data implicate a new family of proteins in the ciliopathies and further support allelism between ciliopathy disorders.

Inborn errors of metabolism: A cause of abnormal brain development

Brain malformations are caused by a disruption in the sequence of normal development by various environmental or genetic factors. By modifying the intrauterine milieu, inborn errors of metabolism may cause brain dysgenesis. However, this association is typically described in single case reports. The authors review the relationship between brain dysgenesis and specific inborn errors of metabolism. Peroxisomal disorders and fatty acid oxidation defects can produce migration defects. Pyruvate dehydrogenase deficiency, nonketotic hyperglycinemia, and maternal phenylketonuria preferentially cause a dysgenetic corpus callosum. Abnormal metabolism of folic acid causes neural tube defects, whereas defects in cholesterol metabolism may produce holoprosencephaly. Various mechanisms have been proposed to explain abnormal brain development in inborn errors of metabolism: production of a toxic or energy-deficient intrauterine milieu, modification of the content and function of membranes, or disturbance of the normal expression of intrauterine genes responsible for morphogenesis. The recognition of a metabolic disorder as the cause of the brain malformation has implications for both the care of the patient and for genetic counseling to prevent recurrence in subsequent pregnancies.

Familial partial trisomy 15q11-13 presenting as intractable epilepsy in the child and schizophrenia in the mother.

Various rearrangements involve the proximal long arm of chromosome 15, including deletions, duplications, translocations, inversions and supernumerary marker chromosome of an inverted duplication. The large marker 15, that contains the Prader-Willi syndrome (PWS)/Angelman syndrome (AS) chromosome region, is usually associated with an abnormal phenotype of moderate to severe mental retardation, seizures, poor motor coordination, early-onset central hypotonia, autism and autistic-like behavior, schizophrenia and mild dysmorphic features. We report a ten year-old girl with normal intelligence prior to the onset of seizures, who developed severe intractable epilepsy at the age of seven years. Family history was significant for a mother with recurrent episodes of acute psychosis. The patients and mothers karyotype revealed 47,XX+m. Array comparative genomic hybridization (A-CGH) identified a gain of 13 BAC clones from 15q11.2 through 15q13.1, which was then confirmed by FISH to be part of the marker chromosome. This duplicated region contains the SNRPN/UBE3A locus. This case demonstrates that a duplication of 15q11-13 can present differently in the same family either as intractable epilepsy or as a psychiatric illness and that intelligence can be preserved. We suggest that CGH microarray should be performed in cases with intractable epilepsy or schizophrenia, with or without mental retardation.

Paroxysmal tonic upward gaze as a presentation of de-novo mutations in CACNA1A

OBJECTIVE Paroxysmal tonic upward gaze was initially described as a benign phenomenon with negative investigations and eventual complete resolution of symptoms. Later publications demonstrated that a similar clinical picture may arise from structural brain lesions, channelopathies, neurotransmitter disorders, and epileptic seizures. CACNA1A related disorders manifest as a wide spectrum of paroxysmal neurological disorders: episodic ataxia 2, hemiplegic migraine, benign paroxysmal torticollis of infancy, and paroxysmal vertigo. Paroxysmal tonic upward gaze as a phenomenon in patients with mutations in the CACNA1A gene has only been reported once. METHODS We describe three patients with multiple episodes of paroxysmal tonic upward gaze that appeared during the first months of life. In addition the patients demonstrated motor and language delay and cerebellar ataxia. A sequence analysis of the CACNA1A gene in one patient and whole exome sequencing in the other patients were performed. RESULTS Sequence analysis of the CACNA1A gene in one patient and whole exome sequencing in the two other patients revealed 3 different de-novo mutations in the CACNA1A gene. CONCLUSION CACNA1A mutations should be evaluated in infants and young children with paroxysmal tonic upgaze especially if associated with developmental delay, cerebellar signs, and other types of paroxysmal event.

Congenital Ataxia, Mental Retardation, and Dyskinesia Associated With a Novel CACNA1A Mutation

The CACNA1A gene encodes the pore forming alpha-1A subunit of neuronal voltage-dependant P/Q-type Ca 2+ channels. Mutations in this gene result in clinical heterogeneity, and present with either chronic progressive symptoms, paroxysmal events, or both, with clinical overlap among the different phenotypes. The authors describe a seven year-old boy with mental retardation and congenital cerebellar ataxia that developed dyskinesia at the age of a few months, and recurrent episodes of coma following mild head trauma associated with motor and autonomic signs, from the second year of life. An extensive metabolic evaluation, interictal electroencephalography (EEG), and muscle biopsy were normal. Brain magnetic resonance imaging (MRI) during one of these episodes revealed edema of the right hemisphere and cerebellar atrophy. Genetic testing revealed a R1350Q mutation in the CACNA1A gene. This is a novel de novo mutation.Congenital cerebellar ataxia can be a result of CACNA1A mutations, especially when associated with recurrent unexplained coma.

Delineation of the interstitial 6q25 microdeletion syndrome: Refinement of the critical causative region†

Interstitial deletions of the long arm of chromosome 6 are rare. Clinically, this is a recognizable microdeletion syndrome associated with intellectual disability (ID), acquired microcephaly, typical dysmorphic features, structural anomalies of the brain, and nonspecific multiple organ anomalies. Most of the reported cases have cytogenetically visible interstitial deletions or subtelomeric microdeletions. We report on a boy with global developmental delay, distinct dysmorphic features, dysgenesis of the corpus callosum, limb anomalies, and genital hypoplasia who has a small interstitial deletion of the long arm of chromosome 6 detected by comparative genomic hybridization (CGH). The deleted region spans around 1 Mb of DNA and contains only two coding genes, ARID1B and ZDHHC14. To the best of our knowledge, this case represents the typical phenotype with the smallest deletion reported so far. We discuss the possible role of these genes in the phenotypic manifestations.

Mosaic marker chromosome 16 resulting in 16q11.2–q12.1 gain in a child with intellectual disability, microcephaly, and cerebellar cortical dysplasia†

Proximal duplications of the long arm of chromosome 16 are rare and only a few patients have been reported. Clinically, the patients do not have a distinctive syndromic appearance; however they all show some degree of intellectual disability and most have severely delayed speech development. We report on a child presenting with mild‐to‐moderate intellectual disability, microcephaly, language dyspraxia, and mild dysmorphisms who was found to have a mosaic gain of chromosome 16q (16q11.2–16q12.1). Magnetic resonance imaging done at the age of 4 years demonstrated cerebellar cortical dysplasia involving the vermis and hemispheres. This is the first report of cerebellar anomalies in a patient with partial trisomy 16q. The genes ZNF423 and CBLN1 found in the duplicated region play a role in the development of the cerebellum and may be responsible for the cerebellar cortical dysplasia.

A newly recognized syndrome of severe growth deficiency, microcephaly, intellectual disability, and characteristic facial features

Genetic syndromes with proportionate severe short stature are rare. We describe two sisters born to nonconsanguineous parents with severe linear growth retardation, poor weight gain, microcephaly, characteristic facial features, cutaneous syndactyly of the toes, high myopia, and severe intellectual disability. During infancy and early childhood, the girls had transient hepatosplenomegaly and low blood cholesterol levels that normalized later. A thorough evaluation including metabolic studies, radiological, and genetic investigations were all normal. Cholesterol metabolism and transport were studied and no definitive abnormality was found. No clinical deterioration was observed and no metabolic crises were reported. After due consideration of other known hereditary causes of post-natal severe linear growth retardation, microcephaly, and intellectual disability, we propose that this condition represents a newly recognized autosomal recessive multiple congenital anomaly-intellectual disability syndrome.

Sweet's syndrome in a patient with compound heterozygous mutations in the Mediterranean fever gene (MEFV)

Sweets syndrome (SS) or acute febrile neutrophilic dermatosis is a rare disorder that often occurs in association with other systemic diseases. The disorder is characterized by development of nonpruritic, painful erythematous plaques with pseudovesicles, occasional pustules and rare bullae. SS consists of a triad of erythematous plaques infiltrated by neutrophils in association with fever and leukocytosis. The pathological features of SS involve the dermis. The condition presents in three clinical settings: classic (or idiopathic) SS, malignancy-associated SS and drug-induced SS syndrome. The treatment of choice for SS are systemic corticosteroids, although colchicine and potassium iodide are also considered to be effective for SS. We present an unusual recurrent course of SS in a 38 year old man who carries compound heterogous mutations in the MEFV gene. A 38 year old, generally healthy man from Sephardic Jewish ancestry, had suddenly developed fever, malaise, artralgia and painful erythematous plaques with pustules and bullae on the anterior aspects of the upper extremities. Diagnostic evaluation included moderate leucocytosis, elevated erythrocyte sedimentation and C-reactive protein rate and normal liver functions. antistreptolysin O-titer. Blood cultures and tuberculosis test were negative. Chest radiography was normal. The symptoms exacerbated despite treatment with systemic corticosterids. Clinical improvement appeared after administration of colchicine. Mutational analysis of the MEFV gene revealed compound heterozygous M694V and V726A mutations. Familial Mediterranean fever (FMF) is an autosomal recessive disease characterized by recurrent attacks of fever with serosal inflammation. The FMF gene (MEFV) encodes the protein pyrin that plays an important role in modulating the innate immune response. MEFV mutations have been identified primarily in patients from Mediterranean populations and in Israel the carrier state is as high as1: 5. Sweets syndrome has been described in a patient with classical FMF as a possible new cutaneous feature and has never been described as a presenting sign of FMF. Although various skin lesions have been described with FMF, erysipelas-like erythema (ELE) has been reported the only pathognomonic cutaneous manifestation. Our patient, carrying compound heterozygous mutations in MEFV presented with Sweets syndrome. We suggest, that SS skin lesions might be an only cutaneous presentation of FMF. Written informated consent for publication of their clinical details was obtained from the patient/parent/guardian/relative of the patient.

P145 – 2410: Paroxysmal tonic upward gaze as a presentation of de-novo mutations in CACNA1A

Objective Paroxysmal tonic upward gaze was initially described as a benign phenomenon with negative investigations and eventual complete resolution of symptoms. Later publications demonstrated that a similar clinical picture may arise from structural brain lesions, channelopathies, neurotransmitter disorders, and epileptic seizures. CACNA1A related disorders manifest as a wide spectrum of paroxysmal neurological disorders: episodic ataxia 2, hemiplegic migraine, benign paroxysmal torticollis of infancy, and paroxysmal vertigo. Paroxysmal tonic upward gaze as a phenomenon in patients with mutations in the CACNA1A gene has only been reported once. Methods We describe three patients with multiple episodes of paroxysmal tonic upward gaze that appeared during the first months of life. In addition the patients demonstrated motor and language delay and cerebellar ataxia. A sequence analysis of the CACNA1A gene in one patient and whole exome sequencing in the other patients were performed. Results Sequence analysis of the CACNA1A gene in one patient and whole exome sequencing in the two other patients revealed 3 different de-novo mutations in the CACNA1A gene. Conclusion CACNA1A mutations should be evaluated in infants and young children with paroxysmal tonic upgaze especially if associated with developmental delay, cerebellar signs, and other types of paroxysmal events.