Disease specific brain capillary angiopathy in schizophrenia, bipolar disorder, and Alzheimer's disease

Schizophrenia (SZ) and bipolar disorder (BD), which are both psychiatric disorders, share some common clinical evidence. We recently discovered that brain capillary angiopathy is another common feature of these psychiatric disorders using fibrin accumulation in vascular endothelial cells as an indicator. This study aimed to characterize the similarities and differences in cerebral capillary injuries in various brain diseases to provide new diagnostic methods for SZ and BD and to develop new therapeutic strategies. We evaluated whether discrepancies exist in the degree of vascular damage among SZ and BD and other brain disorders (amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and Alzheimer's disease (AD)) using postmortem brains. Our results demonstrate that fibrin was strongly accumulated in the capillaries of the grey matter (GM) of brains of patients with SZ and AD and in the capillaries of the white matter (WM) in those of patients with SZ, BD, and AD when compared with control subjects without any psychiatric or neurological disease history. However, ALS and PD brains did not present a significant increase in the amount of accumulated fibrin, either in the capillaries of WM or GM. Furthermore, significant leakage of fibrin into the brain parenchyma, indicating a vascular physical disruption, was observed in the brains of patients with AD but not in the brains of other patients compared with control subjects. In conclusion, our work reveals that Fibrin-accumulation in the brain capillaries are observed in psychiatric disorders, such as SZ, BD, and AD. Furthermore, fibrin-accumulating, nonbreaking type angiopathy is characteristic of SZ and BD, even though there are regional differences between these diseases.

The mouse model of intellectual disability by ZBTB18/RP58 haploinsufficiency shows cognitive dysfunction with synaptic impairment

ZBTB18/RP58 (OMIM *608433) is one of the pivotal genes responsible for 1q43q44 microdeletion syndrome (OMIM #612337) and its haploinsufficiency induces intellectual disability. However, the underlying pathological mechanism of ZBTB18/RP58 haploinsufficiency is unknown. In this study, we generated ZBTB18/RP58 heterozygous mice and found that these mutant mice exhibit multiple behavioral deficits, including impairment in motor learning, working memory, and memory flexibility, which are related to behaviors in people with intellectual disabilities, and show no gross abnormalities in their cytoarchitectures but dysplasia of the corpus callosum, which has been reported in certain population of patients with ZBTB18 haploinsufficiency as well as in those with 1q43q44 microdeletion syndrome, indicating that these mutant mice are a novel model of ZBTB18/RP58 haploinsufficiency, which reflects heterozygotic ZBTB18 missense, truncating variants and some phenotypes of 1q43q44 microdeletion syndrome based on ZBTB18/RP58 haploinsufficiency. Furthermore, these mice show glutamatergic synaptic dysfunctions, including a reduced glutamate receptor expression, altered properties of NMDA receptor-mediated synaptic responses, a decreased saturation level of long-term potentiation of excitatory synaptic transmission, and distinct morphological characteristics of the thick-type spines. Therefore, these results suggest that ZBTB18/RP58 haploinsufficiency leads to impaired excitatory synaptic maturation, which in turn results in cognitive dysfunction in ZBTB18 haploinsufficiency.

High-sucrose diets contribute to brain angiopathy with impaired glucose uptake and psychosis-related higher brain dysfunctions in mice

Metabolic dysfunction is thought to contribute to the severity of psychiatric disorders; however, it has been unclear whether current high–simple sugar diets contribute to pathogenesis of these diseases. Here, we demonstrate that a high-sucrose diet during adolescence induces psychosis-related behavioral endophenotypes, including hyperactivity, poor working memory, impaired sensory gating, and disrupted interneuron function in mice deficient for glyoxalase-1 (GLO1), an enzyme involved in detoxification of sucrose metabolites. Furthermore, the high-sucrose diet induced microcapillary impairments and reduced brain glucose uptake in brains of Glo1-deficient mice. Aspirin protected against this angiopathy, enhancing brain glucose uptake and preventing abnormal behavioral phenotypes. Similar vascular damage to our model mice was found in the brains of randomly collected schizophrenia and bipolar disorder patients, suggesting that psychiatric disorders are associated with angiopathy in the brain caused by various environmental stresses, including metabolic stress.

Pyridoxal in the Cerebrospinal Fluid May Be a Better Indicator of Vitamin B6-dependent Epilepsy Than Pyridoxal 5'-Phosphate

BACKGROUND

We aimed to demonstrate the biochemical characteristics of vitamin B6-dependent epilepsy, with a particular focus on pyridoxal 5'-phosphate and pyridoxal in the cerebrospinal fluid.

METHODS

Using our laboratory database, we identified patients with vitamin B6-dependent epilepsy and extracted their data on the concentrations of pyridoxal 5'-phosphate, pyridoxal, pipecolic acid, α-aminoadipic semialdehyde, and monoamine neurotransmitters. We compared the biochemical characteristics of these patients with those of other epilepsy patients with low pyridoxal 5'-phosphate concentrations.

RESULTS

We identified seven patients with pyridoxine-dependent epilepsy caused by an ALDH7A1 gene abnormality, two patients with pyridoxal 5'-phosphate homeostasis protein deficiency, and 28 patients with other epilepsies with low cerebrospinal fluid pyridoxal 5'-phosphate concentrations. Cerebrospinal fluid pyridoxal and pyridoxal 5'-phosphate concentrations were low in patients with vitamin B6-dependent epilepsy but cerebrospinal fluid pyridoxal concentrations were not reduced in most patients with other epilepsies with low cerebrospinal fluid pyridoxal 5'-phosphate concentrations. Increase in 3-O-methyldopa and 5-hydroxytryptophan was demonstrated in some patients with vitamin B6-dependent epilepsy, suggestive of pyridoxal 5'-phosphate deficiency in the brain.

CONCLUSIONS

Low cerebrospinal fluid pyridoxal concentrations may be a better indicator of pyridoxal 5'-phosphate deficiency in the brain in vitamin B6-dependent epilepsy than low cerebrospinal fluid pyridoxal 5'-phosphate concentrations. This finding is especially helpful in individuals with suspected pyridoxal 5'-phosphate homeostasis protein deficiency, which does not have known biomarkers.

A novel method for isolating lymphatic endothelial cells from lymphatic malformations and detecting PIK3CA somatic mutation in these isolated cells

PURPOSE

Tissue disaggregation and the cell sorting technique by surface markers has played an important role in isolating lymphatic endothelial cells (LECs) from lymphatic malformation (LM). However, this technique may have the drawback of impurities or result in isolation failure because it is dependent on surface marker expressions, the heterogeneity of which has been found in the lymphatic system. We developed a novel method for isolating LM-LECs without using whole tissue disaggregation.

METHODS

Seven LM surgical specimens were collected from seven patients with LMs. LM-LECs were detached from the LM cyst wall by "lumen digestion" and irrigating the cystic cavity with trypsin, and maintained in culture.

RESULTS

The cells formed a monolayer with a cobblestone-like appearance. Immunohistochemistry and quantitative RT-PCR of these cells revealed high expression of lymphatic-specific genes, confirming their identity as LM-LECs. The whole-exome sequencing and PIK3CA sequencing of these cells revealed somatic mutations in PIK3CA in all cases.

CONCLUSIONS

We established a novel technique for isolating LM-LECs from LM tissue by "lumen digestion" without whole-tissue disaggregation. The limited incorporation of non-LM LECs in the isolate in our method could make it an important tool for investigating the heterogeneity of gene expression as well as mutations in LM-LECs.

Cyclocreatine Transport by SLC6A8, the Creatine Transporter, in HEK293 Cells, a Human Blood-Brain Barrier Model Cell, and CCDSs Patient-Derived Fibroblasts

PURPOSE

Cyclocreatine, a creatine analog, is a candidate drug for treating patients with cerebral creatine deficiency syndromes (CCDSs) caused by creatine transporter (CRT, SLC6A8) deficiency, which reduces brain creatine level. The purpose of this study was to clarify the characteristics of cyclocreatine transport in HEK293 cells, which highly express endogenous CRT, in hCMEC/D3 cells, a human blood-brain barrier (BBB) model, and in CCDSs patient-derived fibroblasts with CRT mutations.

METHODS

Cells were incubated at 37°C with [¹⁴C]cyclocreatine (9 μM) and [¹⁴C]creatine (9 μM) for specified periods of times in the presence or absence of inhibitors, while the siRNAs were transfected by lipofection. Protein expression and mRNA expression were quantified using targeted proteomics and quantitative PCR, respectively.

RESULTS

[¹⁴C]Cyclocreatine was taken up by HEK293 cells in a time-dependent manner, while exhibiting saturable kinetics. The inhibition and siRNA knockdown studies demonstrated that the uptake of [¹⁴C]cyclocreatine by both HEK293 and hCMEC/D3 cells was mediated predominantly by CRT as well as [¹⁴C]creatine. In addition, uptake of [¹⁴C]cyclocreatine and [¹⁴C]creatine by the CCDSs patient-derived fibroblasts was found to be largely reduced.

CONCLUSION

The present study suggests that cyclocreatine is a CRT substrate, where CRT is the predominant contributor to influx of cyclocreatine into the brain at the BBB. Our findings provide vital insights for the purposes of treating CCDSs patients using cyclocreatine.

MELAS syndrome with m.4450 G > A mutation in mitochondrial tRNAMet gene

Mutations in the mitochondrial tRNA^Met gene have been reported in only five patients to date, all of whom presented with muscle weakness and exercise intolerance as signs of myopathy. We herein report the case of a 12-year-old girl with focal epilepsy since the age of eight years. At age 11, the patient developed sudden visual disturbances and headaches accompanied by recurrent, stroke-like episodes with lactic acidosis (pH 7.279, lactic acid 11.6 mmol/L). The patient frequently developed a delirious state, exhibited regression of intellectual ability. Brain magnetic resonance imaging revealed high-intensity signals on T2-weighted images of the left occipital lobe. Mitochondrial gene analysis revealed a heteroplasmic m.4450G > A mutation in the mitochondrial tRNA^Met. The heteroplasmic rate of the m.4450G > A mutation in blood, skin, urinary sediment, hair, saliva, and nail samples were 20, 38, 59, 41, 27, and 35%, respectively. The patient's fibroblast showed an approximately 53% reduction in the oxygen consumption rate, compared to a control, and decreased complex I and IV activities. Stroke-like episodes, lactic acidosis, encephalopathy with brain magnetic resonance imaging findings, and declined mitochondrial function were consistent with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome. To our knowledge, the findings associated with this first patient with MELAS syndrome harboring the m.4450G > A mutation in mitochondrial tRNA^Met expand the phenotypic spectrum of tRNA^Met gene.

Mitochondrial DNA 3243A>T mutation in a patient with MELAS syndrome

Approximately 80% of cases of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) harbor a heteroplasmic m.3243A>G transition in the tRNA^{Leu (UUR)} (MTTL1) gene. We report a MELAS case with a rare heteroplasmic m.3243A>T mutation found by direct sequencing of MTTL1. This mutation has been previously reported in 5 cases, of which 2 cases had the MELAS phenotype. Our case also strengthens the hypothesis that the m.3243A>T mutation can cause the MELAS phenotype.

Pelizaeus-Merzbacher disease can be a differential diagnosis in males presenting with severe neonatal respiratory distress and hypotonia

Pelizaeus-Merzbacher disease (PMD; MIM #312080) is a rare X-linked recessive disorder. A male neonate presented with severe respiratory distress that required tracheostomy. After the appearance of nystagmus, PMD was suspected as a diagnosis for the patient, and a missense mutation, p.Phe51Val, was identified in PLP1, the gene responsible for PMD. PMD can be a differential diagnosis in a male neonate presenting severe respiratory distress.

Contiguous gene deletion neighboring TWIST1 identified in a patient with Saethre-Chotzen syndrome associated with neurodevelopmental delay: Possible contribution of HDAC9

Saethre-Chotzen syndrome (SCS) is an autosomal dominant craniosynostotic disorder characterized by coronal synostosis, facial asymmetry, ptosis, and limb abnormalities. Haploinsufficiency of TWIST1, a basic helix-loop-helix transcription factor is responsible for SCS. Here, we report a 15-month-old male patient with typical clinical features of SCS in addition to developmental delay, which is a rare complication in SCS. He showed a de novo 0.9-Mb microdeletion in 7p21, in which TWIST1, NPMIP13, FERD3L, TWISTNB, and HDAC9 were included. In comparison with previously reported patients, HDAC9 was suggested to contribute to developmental delay in SCS patients with 7p21 mirodeletions.

Haploinsufficiency of BCL11A associated with cerebellar abnormalities in 2p15p16.1 deletion syndrome

BACKGROUND

Chromosome 2p15p16.1 deletion syndrome is a rare genetic disorder characterized by intellectual disability (ID), neurodevelopmental delay, language delay, growth retardation, microcephaly, structural brain abnormalities, and dysmorphic features. More than 30 patients with 2p15p16.1 microdeletion syndrome have been reported in the literature.

METHODS

Molecular analysis was performed using microarray-based comparative genomic hybridization (array CGH). Clinical characteristics and brain magnetic resonance imaging features of these patients were also reviewed.

RESULTS

We identified four patients with ID, neurodevelopmental delay, brain malformations, and dysmorphic features; two patients with 2p15p16.1 deletions (3.24 Mb, 5.04 Mb), one patient with 2p16.1 deletion (1.12 Mb), and one patient with 2p14p16.1 deletion (5.12 Mb). Three patients with 2p15p16.1 deletions or 2p16.1 deletions encompassing BCL11A,PAPOLG, and REL showed hypoplasia of the pons and cerebellum. The patient with 2p14p16.1 deletion, which did not include three genes showed normal size and shape of the cerebellar hemispheres and pons.

CONCLUSION

The zinc finger transcription factor BCL11A associated with the BAF chromatin remodeling complex has been identified to be critical for neural development and BCL11A haploinsufficiency is closely related to cerebellar abnormalities.

Mitochonic Acid 5 (MA-5), a Derivative of the Plant Hormone Indole-3-Acetic Acid, Improves Survival of Fibroblasts from Patients with Mitochondrial Diseases

Mitochondria are key organelles implicated in a variety of processes related to energy and free radical generation, the regulation of apoptosis, and various signaling pathways. Mitochondrial dysfunction increases cellular oxidative stress and depletes ATP in a variety of inherited mitochondrial diseases and also in many other metabolic and neurodegenerative diseases. Mitochondrial diseases are characterized by the dysfunction of the mitochondrial respiratory chain, caused by mutations in the genes encoded by either nuclear DNA or mitochondrial DNA. We have hypothesized that chemicals that increase the cellular ATP levels may ameliorate the mitochondrial dysfunction seen in mitochondrial diseases. To search for the potential drugs for mitochondrial diseases, we screened an in-house chemical library of indole-3-acetic-acid analogs by measuring the cellular ATP levels in Hep3B human hepatocellular carcinoma cells. We have thus identified mitochonic acid 5 (MA-5), 4-(2,4-difluorophenyl)-2-(1H-indol-3-yl)-4-oxobutanoic acid, as a potential drug for enhancing ATP production. MA-5 is a newly synthesized derivative of the plant hormone, indole-3-acetic acid. Importantly, MA-5 improved the survival of fibroblasts established from patients with mitochondrial diseases under the stress-induced condition, including Leigh syndrome, MELAS (myopathy encephalopathy lactic acidosis and stroke-like episodes), Leber's hereditary optic neuropathy, and Kearns-Sayre syndrome. The improved survival was associated with the increased cellular ATP levels. Moreover, MA-5 increased the survival of mitochondrial disease fibroblasts even under the inhibition of the oxidative phosphorylation or the electron transport chain. These data suggest that MA-5 could be a therapeutic drug for mitochondrial diseases that exerts its effect in a manner different from anti-oxidant therapy.

Seizure recurrence following pyridoxine withdrawal in a patient with pyridoxine-dependent epilepsy

Pyridoxine-dependent epilepsy (PDE) is an autosomal recessive disorder characterized by early onset and recurrent seizures that can be controlled by a high dose of pyridoxine. PDE is caused by mutations in ALDH7A1, which encodes antiquitin. Antiquitin converts α-aminoadipic semialdehyde to α-aminoadipic acid. Seizure recurrence after pyridoxine withdrawal is a criterion for diagnosis, but PDE can be diagnosed conclusively by genetic testing for mutations in the ALDH7A1 gene. In this case study, we report the long-term follow-up of a patient suspected with PDE. She experienced prolonged generalized tonic seizures and was hospitalized in an intensive care unit following pyridoxine withdrawal. Later, we identified a compound heterozygous mutation, c.1216G>A, p.Gly406Arg, and a novel splice donor site mutation, IVS9+5G>A. Confirmation of these mutations would have prevented an unsafe withdrawal test. This case suggests the importance of the genetic determination of PDE to avoid the diagnostic withdrawal of pyridoxine.

Effect of CYP2C19 polymorphisms on stiripentol administration in Japanese cases of Dravet syndrome

OBJECTIVE

The objective of this study was to investigate stiripentol (STP) administration in cases of Dravet syndrome (DS) by comparing CYP2C19 allelic polymorphisms with the clinical effects of STP, including plasma concentrations of concomitant drugs and adverse effects of STP.

MATERIALS AND METHODS

Eleven cases of DS cases were included. Demographic and clinical characteristics of the cases (age at the study period, body weight, mean dose and plasma concentration of valproate acid (VPA)/clobazam (CLB) off and on STP, mean plasma concentration of norclobazam (N-CLB) off and on STP, degree of seizure reduction, and adverse effects of STP) were examined with each CYP2C19 polymorphism.

RESULTS

There were 3 cases of DS with wild type, 6 with intermediate type, and 2 with poor type of CYP2C19 polymorphisms. The N-CLB concentration/CLB dose ratio and N-CLB/CLB concentration ratio off STP were significantly higher in poor metabolizers. Three (37%) of 8 cases showed no effectiveness of STP regardless of the N-CLB concentration increase, and 1 (33%) of 3 cases showed effectiveness of STP regardless of N-CLB concentration decrease. In total, 6 (54%) of 11 cases with DS had >50% reduction in seizure frequency without significant differences in CYP2C19 polymorphisms.

CONCLUSION

This study demonstrated an effect of CYP2C19 polymorphisms on STP administration in Japanese cases of DS. There were cases of seizure reduction regardless of N-CLB concentration decrease on STP, which suggests a significant anti-convulsant action of STP. N-CLB concentration decrease on STP was observed in 1 case with ketogenic diet and 2 cases with (∗)3 allelic polymorphisms of CYP2C19.

Urine screening for patients with developmental disabilities detected a patient with creatine transporter deficiency due to a novel missense mutation in SLC6A8

Creatine transporter deficiency (CTD) is an example of X-linked intellectual disability syndromes, caused by mutations in SLC6A8 on Xq28. Although this is the second most frequent genetic cause of intellectual disabilities in Europe or America after Fragile X syndrome, information on the morbidity of this disease is limited in Japan. Using the HPLC screening method we have established recently, we examined samples of urine of 105 patients (73 males and 32 females) with developmental disabilities at our medical center. And we have found a family with three ID boys with a novel missense mutation in SLC6A8. This is the second report of a Japanese family case of CTD. A systematic diagnostic system of this syndrome should be established in Japan to enable us to estimate its frequency and treatment.

A novel two-nucleotide deletion in the ATP7A gene associated with delayed infantile onset of Menkes disease

BACKGROUND

Determining the relationship between clinical phenotype and genotype in genetic diseases is important in clinical practice. In general, frameshift mutations are expected to produce premature termination codons, leading to production of mutant transcripts destined for degradation by nonsense-mediated decay. In X-linked recessive diseases, male patients with frameshift mutations typically have a severe or even lethal phenotype.

PATIENT

We report a case of a 17-month-old boy with Menkes disease (NIM #309400), an X-linked recessive copper metabolism disorder caused by mutations in the ATP7A copper transporter gene. He exhibited an unexpectedly late onset and experienced milder symptoms.

STUDY AND RESULT

His genomic DNA showed a de novo two-nucleotide deletion in exon 4 of ATP7A, predicting a translational frameshift and premature stop codon, and a classic severe phenotype. Characterization of his ATP7A mRNA showed no abnormal splicing.

CONCLUSION

We speculate that translation reinitiation could occur downstream to the premature termination codon and produce a partially functional ATP7A protein. Study of the child's fibroblasts found no evidence of translation reinitiation; however, the possibility remains that this phenomenon occurred in neural tissues and influenced the clinical phenotype.

A rapid screening with direct sequencing from blood samples for the diagnosis of Leigh syndrome

Large numbers of genes are responsible for Leigh syndrome (LS), making genetic confirmation of LS difficult. We screened our patients with LS using a limited set of 21 primers encompassing the frequently reported gene for the respiratory chain complexes I (ND1–ND6, and ND4L), IV(SURF1), and V(ATP6) and the pyruvate dehydrogenase E1α-subunit. Of 18 LS patients, we identified mutations in 11 patients, including 7 in mDNA (two with ATP6), 4 in nuclear (three with SURF1). Overall, we identified mutations in 61% of LS patients (11/18 individuals) in this cohort. Sanger sequencing with our limited set of primers allowed us a rapid genetic confirmation of more than half of the LS patients and it appears to be efficient as a primary genetic screening in this cohort.

A three-year-old boy with glucose transporter type 1 deficiency syndrome presenting with episodic ataxia

INTRODUCTION

Glucose transporter type 1 deficiency syndrome is a metabolic encephalopathy that results from impaired glucose transport into the brain as the result of a mutation of the SLC2A1 gene. It has been recognized recently that these patients can present with a much broader clinical spectrum than previously thought. We describe a 3-year-old boy presenting with episodic ataxia.

CASE REPORT

Our patient exhibited periodic abnormal eye movements, including opsoclonus, since he was 4 months of age. At 2 years of age, he experienced acute cerebellar ataxia after a vaccination. Since then, he has had periodic attacks of ataxic gait, repeated vomiting, and abnormal eye movement. He was diagnosed as having episodic ataxia type 2 because the administration of acetazolamide seemed effective. By 3 years and 10 months of age, he exhibited mild mental retardation and mild trunk ataxia. The attacks were more likely to occur when he was hungry. Molecular analysis revealed that the SLC2A1 gene had a de novo mutation of heterozygous seven nucleotide insertion within exon 7, resulting in a frameshift. He has recently begun a modified Atkins diet; the frequency of attacks has been reduced, and his psychomotor and language skills have begun to develop.

DISCUSSION

Glucose transporter type 1 deficiency syndrome should be considered in the differential diagnosis in children with episodic ataxia, even if acetazolamide is effective.

Partial PLP1 deletion causing X-linked dominant spastic paraplegia type 2

BACKGROUND

Proteolipid protein 1 gene (PLP1) mutations result in a continuum of neurological findings characterized by X-linked hypomyelinating leukodystrophies of the central nervous system, from mild spastic paraplegia type 2 to severe Pelizaeus-Merzbacher disease.

PATIENTS

We report spastic paraplegia type 2 in three individuals in one family. A 29-year-old man developed progressive spastic quadriplegia from early childhood with dysarthria, ataxia, dysphagia, and intellectual delay, but he displayed no nystagmus. His mother developed adult-onset mild spastic diplegia with dementia developing in later life, whereas his sister exhibited spastic diplegia from childhood, complicated by motor developmental delay and dysphagia. All three individuals had initially mild but progressive neurological phenotypes, no nystagmus, normal brainstem auditory-evoked potentials, and demyelinating peripheral neuropathy, but with varying clinical severity.

RESULTS

A 33-kb deletion encompassing exon 2 to 7 of PLP1 was identified in all three patients. Cloning of the junction fragment of the genomic recombination revealed a short palindromic sequence at the distal breakpoint, potentially facilitating a double-strand deoxyribonucleic acid break, followed by nonhomologous end joining. X-inactivation study and sequencing of the undeleted PLP1 alleles failed to explain the differences in severity between the two female patients.

CONCLUSIONS

PLP1 partial deletion is a rare cause of spastic paraplegia type 2 and exhibits X-linked dominant inheritance with variable expressivity.

A Japanese adult case of guanidinoacetate methyltransferase deficiency

Guanidinoacetate methyltransferase (GAMT) deficiency is a rare disorder of creatine synthesis resulting in cerebral creatine depletion. We present a 38-year-old patient, the first Japanese case of GAMT deficiency. Developmental delay started after a few months of age with a marked delay in language, which resulted in severe intellectual deficit. She showed hyperactivity and trichotillomania from childhood. Epileptic seizures appeared at 18 months and she had multiple types of seizures including epileptic spasms, brief tonic seizures, atypical absences, complex partial seizures with secondary generalization, and "drop" seizures. They have been refractory to multiple antiepileptic drugs. Although there have been no involuntary movements, magnetic resonance imaging revealed T2 hyperintense lesions in bilateral globus pallidi. Motor regression started around 30 years of age and the patient is now able to walk for only short periods. Very low serum creatinine levels measured by enzymatic method raised a suspicion of GAMT deficiency, which was confirmed by proton magnetic resonance spectroscopy and urinary guanidinoacetate assay. GAMT gene analysis revealed that the patient is a compound heterozygote of c.578A>G, p.Gln193Arg and splice site mutation, c.391G>C, p.Gly131Arg, neither of which have been reported in the literature. We also identified two aberrant splice products from the patient's cDNA analysis. The patient was recently started on supplementation of high-dose creatine and ornithine, the effects of which are currently under evaluation. Although rare, patients with developmental delay, epilepsy, behavioral problems, and movement disorders should be vigorously screened for GAMT deficiency, as it is a treatable disorder.

Two Japanese patients with Leigh syndrome caused by novel SURF1 mutations

We report two patients with Leigh syndrome that showed a combination of facial dysmorphism and MRI imaging indicating an SURF1 deficiency, which was confirmed by sequence analysis. Case 1 is a 3-year-old girl with failure to thrive and developmental delay. She presented with tachypnea at rest and displayed facial dysmorphism including frontal bossing, lateral displacement of inner canthi, esotropia, maxillary hypoplasia, slightly upturned nostril, and hypertrichosis dominant on the forehead and extremities. Case 2 is an 8-year-old boy with respiratory failure. He had been diagnosed as selective complex IV deficiency. Case 2 displayed facial dysmorphism and hypertrichosis. Since both patients displayed characteristic facial dysmorphism and MRI findings, we sequenced the SURF1 gene and identified two heterozygous mutations; c.49+1 G>T and c.752_753del in Case 1, and homozygous c.743 C>A in Case 2. For patients with Leigh syndrome showing these facial dysmorphism and hypertrichosis, sequence analysis of the SURF1 gene may be useful.

Contiguous deletion of SLC6A8 and BAP31 in a patient with severe dystonia and sensorineural deafness

We report here a 6-year-old boy exhibiting severe dystonia, profound intellectual and developmental disability with liver disease, and sensorineural deafness. A deficient creatine peak in brain (1)H-MR spectroscopy and high ratio of creatine/creatinine concentration in his urine lead us to suspect a creatine transporter (solute carrier family 6, member 8; SLC6A8) deficiency, which was confirmed by the inability to take up creatine into fibroblasts. We found a large ~19 kb deletion encompassing exons 5-13 of SLC6A8 and exons 5-8 of the B-cell receptor-associated protein (BAP31) gene. This case is the first report in which the SLC6A8 and BAP31 genes are both deleted. The phenotype of BAP31 mutations has been reported only as a part of Xq28 deletion syndrome or contiguous ATP-binding cassette, sub-family D, member 1 (ABCD1)/DXS1375E (BAP31) deletion syndrome [MIM ID #300475], where liver dysfunction and sensorineural deafness have been suggested to be attributed to the loss of function of BAP31. Our case supports the idea that the loss of BAP31 is related to liver dysfunction and hearing loss.

Paradoxical increase in seizure frequency with valproate in nonketotic hyperglycinemia

Nonketotic hyperglycinemia (NKH), or glycine encephalopathy, is an autosomal recessive disorder caused by a defect in the glycine cleavage enzyme system. In neonatal-onset NKH, patients manifest lethargy, hypotonia, apnea, and intractable epileptic seizures that are not specific to this disease. We experienced a 6-year-old girl with spastic quadriplegia, intractable epilepsy, and mental retardation, all initially regarded as sequelae of neonatal meningitis. The seizure frequency was transiently increased when valproate was started. Head MRI revealed progressive brain atrophy and white matter loss with high intensity signals on T2-weighted and diffusion-weighted images, which prompted us to conduct further metabolic workups. High glycine levels led us to suspect NKH, and we confirmed this diagnosis by the non-invasive, (13)C-glycine breath test. DNA sequencing revealed novel Leu885Pro/Trp897Cys mutations in the glycine decarboxylase gene that were transmitted from both parents. Sodium benzoate and dextromethorphan dramatically decreased her hypertonicity. Our case shows that paradoxical increases in seizure frequency following valproate can be a clue for a diagnosis of NKH, and that a correct diagnosis of NKH can greatly alter the quality of life in such patients.

A simple screening method using ion chromatography for the diagnosis of cerebral creatine deficiency syndromes

Cerebral creatine deficiency syndromes (CCDS) are caused by genetic defects in L-arginine:glycine amidinotransferase, guanidinoacetate methyltransferase or creatine transporter 1. CCDS are characterized by abnormal concentrations of urinary creatine (CR), guanidinoacetic acid (GA), or creatinine (CN). In this study, we describe a simple HPLC method to determine the concentrations of CR, GA, and CN using a weak-acid ion chromatography column with a UV detector without any derivatization. CR, GA, and CN were separated clearly with the retention times (mean ± SD, n = 3) of 5.54 ± 0.0035 min for CR, 6.41 ± 0.0079 min for GA, and 13.53 ± 0.046 min for CN. This new method should provide a simple screening test for the diagnosis of CCDS.

Rapid detection of a mutation causing X-linked leucoencephalopathy by exome sequencing

BACKGROUND

Conventional PCR-based direct sequencing of candidate genes for a family with X-linked leucoencephalopathy with unknown aetiology failed to identify any causative mutations.

OBJECTIVE

To carry out exome sequencing of entire transcripts of the whole X chromosome to investigate a family with X linked leucoencephalopathy.

METHODS AND RESULTS

Next-generation sequencing of all the transcripts of the X chromosome, after liquid-based genome partitioning, was performed on one of the two affected male subjects (the proband) and an unaffected male subject (his brother). A nonsense mutation in MCT8 (c.1102A→T (p.R368X)) was identified in the proband. Subsequent PCR-based direct sequencing of other family members confirmed the presence of this mutation, hemizygous in the other affected brother and heterozygous in the proband's mother and maternal grandmother. MCT8 mutations usually cause abnormal thyroid function in addition to neurological abnormalities, but this proband had normal thyroid function.

CONCLUSION

Single-lane exome next-generation sequencing is sufficient to fully analyse all the transcripts of the X chromosome. This method is particularly suitable for mutation screening of X-linked recessive disorders and can avoid biases in candidate gene choice.

Disrupted SOX10 regulation of GJC2 transcription causes Pelizaeus-Merzbacher-like disease

Mutations in the gap junction protein gamma-2 gene, GJC2, cause a central hypomyelinating disorder; Pelizaeus-Merzbacher-like disease (PMLD; MIM311601). Using a homozygosity mapping and positional candidate gene approach, we identified a homozygous mutation (c.-167A>G) within the GJC2 promoter at a potent SOX10 binding site in a patient with mild PMLD. Functionally, this mutation completely abolished the SOX10 binding and attenuated GJC2 promoter activity. These findings suggest not only that the SOX10-to-GJC2 transcriptional dysregulation is a cause of PMLD, but also that GJC2 may be in part responsible for the central hypomyelination caused by SOX10 mutations.