Shinobu Fukumura

A combination of genetic and biochemical analyses for the diagnosis of PI3K-AKT-mTOR pathway-associated megalencephaly

BackgroundConstitutive activation of the PI3K-AKT-mTOR pathway (mTOR pathway) underlies megalencephaly in many patients. Yet, prevalence of the involvement of the PI3K-AKT-mTOR pathway in patients with megalencephaly remains to be elucidated, and molecular diagnosis is challenging. Here, we have successfully established a combination of genetic and biochemical methods for diagnosis of mTOR pathway-associated megalencephaly, and have attempted to delineate the clinical characteristics of the disorder.MethodsThirteen patients with an increased head circumference and neurological symptoms participated in the study. To evaluate the activation of the mTOR pathway, we performed western blot analysis to determine the expression levels of phosphorylated S6 ribosomal protein (phospho-S6 protein) in lymphoblastoid cell lines from 12 patients. Multiplex targeted sequencing analysis for 15 genes involved in the mTOR pathway was performed on 12 patients, and whole-exome sequencing was performed on one additional patient. Clinical features and MRI findings were also investigated.ResultsWe identified pathogenic mutations in six (AKT3, 1 patient; PIK3R2, 2 patients; PTEN, 3 patients) of the 13 patients. Increased expression of phospho-S6 protein was demonstrated in all five mutation-positive patients in whom western blotting was performed, as well as in three mutation-negative patients. Developmental delay, dysmorphic facial features were observed in almost all patients. Syndactyly/polydactyly and capillary malformations were not observed, even in patients with AKT3 or PIK3R2 mutations. There were no common phenotypes or MRI findings among these patients.ConclusionsA combination of genetic and biochemical methods successfully identified mTOR pathway involvement in nine of 13 (approximately 70%) patients with megalencephaly, indicating a major contribution of the pathway to the pathogenesis of megalencephaly. Our combined approach could be useful to identify patients who are suitable for future clinical trials using an mTOR inhibitor.

Comprehensive investigation of CASK mutations and other genetic etiologies in 41 patients with intellectual disability and microcephaly with pontine and cerebellar hypoplasia (MICPCH)

The CASK gene (Xp11.4) is highly expressed in the mammalian nervous system and plays several roles in neural development and synaptic function. Loss-of-function mutations of CASK are associated with intellectual disability and microcephaly with pontine and cerebellar hypoplasia (MICPCH), especially in females. Here, we present a comprehensive investigation of 41 MICPCH patients, analyzed by mutational search of CASK and screening of candidate genes using an SNP array, targeted resequencing and whole-exome sequencing (WES). In total, we identified causative or candidate genomic aberrations in 37 of the 41 cases (90.2%). CASK aberrations including a rare mosaic mutation in a male patient, were found in 32 cases, and a mutation in ITPR1, another known gene in which mutations are causative for MICPCH, was found in one case. We also found aberrations involving genes other than CASK, such as HDAC2, MARCKS, and possibly HS3ST5, which may be associated with MICPCH. Moreover, the targeted resequencing screening detected heterozygous variants in RELN in two cases, of uncertain pathogenicity, and WES analysis suggested that concurrent mutations of both DYNC1H1 and DCTN1 in one case could lead to MICPCH. Our results not only identified the etiology of MICPCH in nearly all the investigated patients but also suggest that MICPCH is a genetically heterogeneous condition, in which CASK inactivating mutations appear to account for the majority of cases.

Everolimus Treatment for an Early Infantile Subependymal Giant Cell Astrocytoma With Tuberous Sclerosis Complex

Subependymal giant cell astrocytomas are benign tumors often observed with tuberous sclerosis complex. These tumors are rarely diagnosed during fetal life or early infancy. Until recently, the only available treatment has been surgical resection. Current clinical research has demonstrated that everolimus can induce these tumors’ regression. We report a 19-month-old boy with tuberous sclerosis complex. At 2 months of age, he presented with congenital subependymal giant cell astrocytoma that was complicated by refractory epilepsy and severe mental retardation. Treatment with everolimus was started when he was 10 months old. Three months after initiating everolimus, the tumor was significantly reduced in size, and the reduction was subsequently maintained. His seizures decreased and he showed cognitive and developmental improvement. No severe adverse events have been observed to date. Everolimus has promise as an effective alternative to surgery for subependymal giant cell astrocytomas during early infancy.

Compound heterozygous GFM2 mutations with Leigh syndrome complicated by arthrogryposis multiplex congenita.

Defects in the mitochondrial translation apparatus can impair energy production in affected tissues and organs. Most components of this apparatus are encoded by nuclear genes, including GFM2, which encodes a mitochondrial ribosome recycling factor. A few patients with mutations in some of these genes have been reported to date. Here, we present two female siblings with arthrogryposis multiplex congenita, optic atrophy and severe mental retardation. The younger sister had a progressive cerebellar atrophy and bilateral neuropathological findings in the brainstem. Although her cerebrospinal fluid (CSF) levels of lactate and pyruvate were not increased, brain magnetic resonance spectroscopy showed a lactate peak. Additionally, her CSF lactate/pyruvate and serum beta-hydroxybutyrate/acetoacetate ratios were high, and levels of oxidative phosphorylation in skin fibroblasts were reduced. We therefore diagnosed Leigh syndrome. Genomic investigation confirmed the presence of compound heterozygous GFM2 mutations (c.206+4A>G and c.2029-1G>A) in both siblings, causing aberrant splicing with premature stop codons (p.Gly50Glufs*4 and p.Ala677Leufs*2, respectively). These findings suggest that GFM2 mutations could be causative of a phenotype of Leigh syndrome with arthrogryposis multiplex congenita.

Intravenous infusion of mesenchymal stem cells reduces epileptogenesis in a rat model of status epilepticus

OBJECTIVE Status epilepticus (SE) causes neuronal cell death, aberrant mossy fiber sprouting (MFS), and cognitive deteriorations. The present study tested the hypothesis that systemically infused mesenchymal stem cells (MSCs) reduce epileptogenesis by inhibiting neuronal cell death and suppressing aberrant MFS, leading to cognitive function preservation in a rat model of epilepsy. METHODS SE was induced using the lithium-pilocarpine injection model. The seizure frequency was scored using a video-monitoring system and the Morris water maze test was carried out to evaluate cognitive function. Comparisons were made between MSCs- and vehicle-infused rats. Immunohistochemical staining was performed to detect Green fluorescent protein (GFP)+ MSCs and to quantify the number of GAD67+ and NeuN+ neurons in the hippocampus. Manganese-enhanced magnetic resonance imaging (MEMRI) and Timm staining were also performed to assess the MFS. RESULTS MSC infusion inhibited epileptogenesis and preserved cognitive function after SE. The infused GFP+ MSCs were accumulated in the hippocampus and were associated with the preservation of GAD67+ and NeuN+ hippocampal neurons. Furthermore, the MSC infusion suppressed the aberrant MFS in the hippocampus as evidenced by MEMRI and Timm staining. CONCLUSIONS This study demonstrated that the intravenous infusion of MSCs mitigated epileptogenesis, thus advancing MSCs as an effective approach for epilepsy in clinical practice.

A Mutation in the Tubulin-Encoding TUBB3 Gene Causes Complex Cortical Malformations and Unilateral Hypohidrosis

Recent studies have emphasized the association between tubulin gene mutations and developmental abnormalities of the cortex. In this study, the authors identified a mutation in the tubulin-encoding class III β-tubulin (TUBB3) gene in a 4-year-old boy presenting with brain abnormalities and unilateral hypohidrosis. The patient showed a left internal strabismus, moderate developmental delay, and congenital hypohidrosis of the right side of the body. Magnetic resonance imaging disclosed gyral disorganization mainly in the left perisylvian region, dysmorphic and hypertrophic basal ganglia with fusion between the putamen and caudate nucleus without affecting the anterior limb of the internal capsule, and moderate hypoplasia of the right brain stem and cerebellum. Diffusion tensor imaging studies revealed disorganization of the pyramidal fibers. The amplitude of the sympathetic skin response was low in the right arm, which led to a diagnosis of focal autonomic neuropathy. Sequencing the TUBB3 gene revealed a de novo missense mutation, c.862G>A (p.E288K).

Functional recovery after the systemic administration of mesenchymal stem cells in a rat model of neonatal hypoxia-ischemia

The authors intravenously infused mesenchymal stem cells (MSCs) into a rat model of neonatal hypoxia-ischemia and found improvements in functional outcome, increased brain volume, and enhanced synaptogenesis. The results of this animal study suggest that the intravenous administration of MSCs should be further explored as a potential treatment for patients suffering from cerebral palsy after hypoxic-ischemic encephalopathy.

Rapidly progressive fatal idiopathic hypertrophic pachymeningitis with brainstem involvement in a child

BackgroundHypertrophic pachymeningitis (HP) is a rare disorder characterized by diffuse thickening of the dura mater with resultant neurologic deficits. HP develops secondary to various conditions or idiopathically usually in adults but rarely in children.Case reportWe describe a 3-year-old female child with idiopathic HP. Her HP involved the entire central nervous system with progression into the brainstem. The lesion responded poorly to pulsed steroids or any immunosuppressants. The brainstem lesion grew rapidly and formed various nodules that ultimately resulted in brain death. This is the first fatal case of HP in a child.

Distinctive facies, macrocephaly, and developmental delay are signs of a PTEN mutation in childhood

BACKGROUND Germline mutations of the PTEN gene are responsible for several PTEN hamartoma tumor syndromes. They are also implicated as a cause of macrocephaly and mild to severe developmental delay, regardless of the presence or absence of hamartomas in childhood. Nevertheless, because of limited information, the clinical features present during childhood in patients with a PTEN mutation are yet to be elucidated. METHODS PTEN mutations were investigated by multiplex targeted sequencing of genomic DNA from 33 children with increased head circumference (>+2 SD) and developmental delay. The clinical features of all the patients with a PTEN mutation were abstracted by dysmorphologists. RESULTS We have identified six children with a PTEN mutation. Clinical dissection of these six patients, in addition to patient reports in the literature, revealed distinctive facial features that included frontal bossing, dolichocephaly, horizontal eyebrows, and a depressed nasal bridge. Macrocephaly (+3.2 to +6.0 SD) was noticeable compared to their height (-0.8 to +2.1 SD), and the difference in the SD value of head circumference and height was more than 3 SD in all patients. CONCLUSION The presence of distinctive facies, extreme macrocephaly with normal to mildly high stature, and developmental delay may be useful for identifying patients with a PTEN mutation in childhood. Early identification of patients with a PTEN mutation would help uncover the natural course of tumor development in this group of individuals who have a possible predisposition to cancer, and be important for the development of an optimal surveillance strategy.

Subcortical heterotopia appearing as huge midline mass in the newborn brain.

IntroductionWe report the case of a 2-year-old boy who showed a huge midline mass in the brain at prenatal assessment.Case reportAfter birth, magnetic resonance imaging (MRI) revealed a conglomerate mass with an infolded microgyrus at the midline, which was suspected as a midline brain-in-brain malformation. MRI also showed incomplete cleavage of his frontal cortex and thalamus, consistent with lobar holoprosencephaly. The patient underwent an incisional biopsy of the mass on the second day of life. The mass consisted of normal central nervous tissue with gray and white matter, representing a heterotopic brain. The malformation was considered to be a subcortical heterotopia. With maturity, focal signal changes and decreased cerebral perfusion became clear on brain imaging, suggesting secondary glial degeneration. Coincident with these MRI abnormalities, the child developed psychomotor retardation and severe epilepsy focused on the side of the intracranial mass.