Sedat Işıkay

Human CLP1 Mutations Alter tRNA Biogenesis, Affecting Both Peripheral and Central Nervous System Function

CLP1 is a RNA kinase involved in tRNA splicing. Recently, CLP1 kinase-dead mice were shown to display a neuromuscular disorder with loss of motor neurons and muscle paralysis. Human genome analyses now identified a CLP1 homozygous missense mutation (p.R140H) in five unrelated families, leading to a loss of CLP1 interaction with the tRNA splicing endonuclease (TSEN) complex, largely reduced pre-tRNA cleavage activity, and accumulation of linear tRNA introns. The affected individuals develop severe motor-sensory defects, cortical dysgenesis, and microcephaly. Mice carrying kinase-dead CLP1 also displayed microcephaly and reduced cortical brain volume due to the enhanced cell death of neuronal progenitors that is associated with reduced numbers of cortical neurons. Our data elucidate a neurological syndrome defined by CLP1 mutations that impair tRNA splicing. Reduction of a founder mutation to homozygosity illustrates the importance of rare variations in disease and supports the clan genomics hypothesis.

Molecular etiology of arthrogryposis in multiple families of mostly Turkish origin

BACKGROUND Arthrogryposis, defined as congenital joint contractures in 2 or more body areas, is a clinical sign rather than a specific disease diagnosis. To date, more than 400 different disorders have been described that present with arthrogryposis, and variants of more than 220 genes have been associated with these disorders; however, the underlying molecular etiology remains unknown in the considerable majority of these cases. METHODS We performed whole exome sequencing (WES) of 52 patients with clinical presentation of arthrogryposis from 48 different families. RESULTS Affected individuals from 17 families (35.4%) had variants in known arthrogryposis-associated genes, including homozygous variants of cholinergic γ nicotinic receptor (CHRNG, 6 subjects) and endothelin converting enzyme-like 1 (ECEL1, 4 subjects). Deleterious variants in candidate arthrogryposis-causing genes (fibrillin 3 [FBN3], myosin IXA [MYO9A], and pleckstrin and Sec7 domain containing 3 [PSD3]) were identified in 3 families (6.2%). Moreover, in 8 families with a homozygous mutation in an arthrogryposis-associated gene, we identified a second locus with either a homozygous or compound heterozygous variant in a candidate gene (myosin binding protein C, fast type [MYBPC2] and vacuolar protein sorting 8 [VPS8], 2 families, 4.2%) or in another disease-associated genes (6 families, 12.5%), indicating a potential mutational burden contributing to disease expression. CONCLUSION In 58.3% of families, the arthrogryposis manifestation could be explained by a molecular diagnosis; however, the molecular etiology in subjects from 20 families remained unsolved by WES. Only 5 of these 20 unrelated subjects had a clinical presentation consistent with amyoplasia; a phenotype not thought to be of genetic origin. Our results indicate that increased use of genome-wide technologies will provide opportunities to better understand genetic models for diseases and molecular mechanisms of genetically heterogeneous disorders, such as arthrogryposis. FUNDING This work was supported in part by US National Human Genome Research Institute (NHGRI)/National Heart, Lung, and Blood Institute (NHLBI) grant U54HG006542 to the Baylor-Hopkins Center for Mendelian Genomics, and US National Institute of Neurological Disorders and Stroke (NINDS) grant R01NS058529 to J.R. Lupski.

Prevalence of Celiac Disease in Children With Idiopathic Epilepsy in Southeast Turkey

BACKGROUND We examined the prevalence of celiac disease in children with idiopathic epilepsy. METHODS Patients were screened for celiac disease using the immunoglobulin A anti-tissue transglutaminase antibody. Upper gastrointestinal endoscopy and small intestinal biopsy were offered to all antibody-positive patients. The control group consisted of 400 healthy children. RESULTS A total of 600 patients (332 boys, 268 girls; 8 months-15 years; 9.40 ± 4.09 years) were studied. In 38 patients, the diagnosis was childhood partial epilepsy with occipital paroxysms. Six of the 38 patients with childhood partial epilepsy with occipital paroxysms (15.7%) had positive immunoglobulin A anti-tissue transglutaminase antibody. The frequency of biopsy-proven celiac disease was 15.7% (6/38) among children with childhood partial epilepsy with occipital paroxysms. None of the control patients had positive immunoglobulin A anti-tissue transglutaminase antibody results. CONCLUSIONS These findings suggest that the prevalence of celiac disease in children with partial epilepsy with occipital paroxysms may be higher than with other types of epilepsies. It may be reasonable to screen individuals with this type of epilepsy for celiac disease.

An infant with trisomy 15 mosaicism.

Introduction Conceptions with autosomal trisomies are usually aborted spontaneously in the first trimester of pregnancy. Trisomy 15 accounts for 7.6% of all trisomic abortions and 1.68% of all first-trimester pregnancy losses (Prontera et al., 2006). Few cases of mosaic trisomy 15 in liveborn infants have been reported (Codwell et al., 1981; Stallard and Sommer, 1989; Kuller and Laifer, 1991; Lahdetie and Lakkala, 1992; Fryns et al., 1993; Bühler et al., 1996; Milunsky et al., 1996; Zaslav et al., 1998; Olander et al., 2000; Prontera et al., 2006). We report here the clinical features of an infant with mosaicism for trisomy 15.

Pseudohypoparathyroidism presenting with ventricular arrhythmia: a case report.

Pseudohypoparathyroidism (PHP) is a rare disorder characterized by varying degrees of unresponsiveness to parathyroid hormone. Patients usually present with hypocalcemia-induced seizures or tetany, whereas no case of hypocalcemia-induced cardiac arrhythmia in PHP has been described to date. In this paper, we report the case of a male adolescent with PHP type 1a who presented with hypocalcemia-induced ventricular extrasystoles (bigeminy, trigeminy) and mild corrected QT interval prolongation. The patient had brachydactyly and his second fingers and toes were longer than the others, a finding consistent with PHP. Laboratory tests detected hypomagnesemia, as well as elevated levels of creatine kinase and lactate dehydrogenase. Ventricular arrhythmia and abnormal laboratory tests improved with calcium supplementation and vitamin D treatment. The findings in this patient suggest that hypomagnesemia may make patients with PHP more susceptible to hypocalcemia and may thus prompt a state of hypocalcemia-induced arrhythmia or other cardiac complications. Key words: Pseudohypoparathyroidism, arrhythmia, child Conflict of interest:None declared.

Phenotypic expansion illuminates multilocus pathogenic variation

PurposeMultilocus variation—pathogenic variants in two or more disease genes—can potentially explain the underlying genetic basis for apparent phenotypic expansion in cases for which the observed clinical features extend beyond those reported in association with a “known” disease gene.MethodsAnalyses focused on 106 patients, 19 for whom apparent phenotypic expansion was previously attributed to variation at known disease genes. We performed a retrospective computational reanalysis of whole-exome sequencing data using stringent Variant Call File filtering criteria to determine whether molecular diagnoses involving additional disease loci might explain the observed expanded phenotypes.ResultsMultilocus variation was identified in 31.6% (6/19) of families with phenotypic expansion and 2.3% (2/87) without phenotypic expansion. Intrafamilial clinical variability within two families was explained by multilocus variation identified in the more severely affected sibling.ConclusionOur findings underscore the role of multiple rare variants at different loci in the etiology of genetically and clinically heterogeneous cohorts. Intrafamilial phenotypic and genotypic variability allowed a dissection of genotype–phenotype relationships in two families. Our data emphasize the critical role of the clinician in diagnostic genomic analyses and demonstrate that apparent phenotypic expansion may represent blended phenotypes resulting from pathogenic variation at more than one locus.

Frequency of coeliac disease in children with breath-holding spells

Iron deficiency anaemia (IDA), which is reported very commonly among patients with breath holding spells (BHS), is the most common presentation of coeliac disease (CD). In that aspect, IDA may be a common pathway linking these two diseases. The aim of this study was to evaluate the frequency of CD in patients with BHS.

Imaging Findings Associated With Methylmalonic Aciduria

The conversion of methylmalonic acid to succinic acid tachypnea, tachycardia, lethargy, hypotonia, dehydration, requires both an apoenzyme (methylmalonyl CoA mutase) and a coenzyme (adenosylcobalamin). Deficiency of either entity results in accumulation of methylmalonic acid derivatives in physiologic fluids. The basal ganglia, predominantly globi pallidi, are particularly sensitive to metabolic dysfunction and are thus the main targets for brain injury in this condition. A 7-month-old boy was admitted with a 2-day history of vomiting and lethargy. Clinical examinations revealed

L-2 hydroxyglutaric aciduria presenting with anxiety symptoms.

l-2 Hydroxyglutaric aciduria is a rare autosomal recessively inherited metabolic disorder of organic acid metabolism. Cerebellar and pyramidal signs with progressive neurological syndromes, mental deterioration, tremors, seizures, epilepsy and rarely macrocephaly are clinical findings of the disease. The diagnosis depends on increased levels of l-2 hydroxyglutaric acid in urine, plasma and cerebrospinal fluid. Brain MRI shows peripheral white matter abnormalities in cerebral hemispheres, bilateral symmetrically abnormal signal intensity in basal ganglia and dentate nuclei. In this case report, we present a 13-year-old patient who presented with tremors and anxiety symptoms and was diagnosed as l-2 hydroxyglutaric aciduria after consultation with the child neurology department. We present a patient suffering from psychiatric symptoms with a metabolic disorder.

Two cases of rare cerebral hydatid cyst

Hydatid cyst disease (Echinococcosis) is a parasitic illness that is rarely located in the brain. Primary cerebral hydatid cyst disease is rarely seen. We report here rare two cases presenting with sixth cranial nerve palsy with increased intracranial pressure syndrome due to primary cerebral hydatid cyst. A 5-year-old female and a 13-year-old boy complained of headache, strabismus, nausea, and vomiting. Neurological examination revealed sixth nerve palsy and papilloedema. The diagnosis was cerebral hydatid cyst disease and was confirmed with radiological and pathological investigations. Both cases were operated on. The cysts were removed without rupture, and therapy was completed with albendazole for a period of six months. They were symptom-free during the follow-up period. In conclusion, cerebral hydatid cyst disease should be kept in mind in the differential diagnosis of increased intracranial pressure syndrome.