The gaze characteristics in preterm children: The appropriate timing for an eye-tracking tool.

BACKGROUND: An objective screening tool for autism spectrum disorder (ASD), also known as an eye-tracking tool, assesses the patient's abnormal gaze patterns and detects the risk of ASD. As this tool is generally used for children born at term, this study aimed to clarify the appropriate timing for using the tool for preterm children, factors that influence the timing, and evaluate their gaze characteristics using the Gazefinder®. METHOD: In 90 preterm children, a total of 125 eye-tracking tasks were completed and analyzed in 3-6, 7-9, 10-12, 13-18, and 19-32 months of corrected age (CA). The Gazefinder® was used to compare the mean fixation time percentage (MFP) in each CA and evaluate the gaze patterns. Perinatal factors associated with low MFP were also analyzed. RESULTS: Only 50% of the children scored ≥70% MFP at 3-6 months of CA. The MFP increased significantly after 7 months of CA (p = 0.0003), reached 90% at 13-18 months, and 100% at 19-32 months of CA. Chronic lung disease (CLD) was a clinical factor associated with low MFP (p = 0.036). Preterm children gazed more at eyes but gazed at mouths when the mouth moved. CONCLUSION: It is necessary for preterm children to begin using Gazefinder® atleast at ≥13 months of age, especially those complicated with CLD. Preterm children prefer gazing at social information just as typically developing children.

Molecular diagnosis of 405 individuals with autism spectrum disorder.

Autism spectrum disorder (ASD) is caused by combined genetic and environmental factors. Genetic heritability in ASD is estimated as 60-90%, and genetic investigations have revealed many monogenic factors. We analyzed 405 patients with ASD using family-based exome sequencing to detect disease-causing single-nucleotide variants (SNVs), small insertions and deletions (indels), and copy number variations (CNVs) for molecular diagnoses. All candidate variants were validated by Sanger sequencing or quantitative polymerase chain reaction and were evaluated using the American College of Medical Genetics and Genomics/Association for Molecular Pathology guidelines for molecular diagnosis. We identified 55 disease-causing SNVs/indels in 53 affected individuals and 13 disease-causing CNVs in 13 affected individuals, achieving a molecular diagnosis in 66 of 405 affected individuals (16.3%). Among the 55 disease-causing SNVs/indels, 51 occurred de novo, 2 were compound heterozygous (in one patient), and 2 were X-linked hemizygous variants inherited from unaffected mothers. The molecular diagnosis rate in females was significantly higher than that in males. We analyzed affected sibling cases of 24 quads and 2 quintets, but only one pair of siblings shared an identical pathogenic variant. Notably, there was a higher molecular diagnostic rate in simplex cases than in multiplex families. Our simulation indicated that the diagnostic yield is increasing by 0.63% (range 0-2.5%) per year. Based on our simple simulation, diagnostic yield is improving over time. Thus, periodical reevaluation of ES data should be strongly encouraged in undiagnosed ASD patients.

Study on the Causes, Types, and Mechanisms of Childhood Injuries-Age and Disease Specificity.

INTRODUCTION: To clarify the causes, types, and mechanisms of injuries in children, we collected injury cases and analyzed their causes. METHODS: During the 3-year period from 2013, we collected injury cases from three sources: nursery schools and kindergartens (A), emergency clinics of hospitals (B), and schools and a clinic for the developmentally disabled (C), using a format designed by Safe Kids Japan. RESULTS: In all, 383 cases were collected during the 3-year period. The causes of the injuries in group A were crashes, falls, and so on. The types of injuries were cuts, bruises, fractures, injuries of teeth, etc. Dislocations and abrasions were prominent in nursery school children (aged less than 3 years) and bone fractures were prominent in kindergarten children aged more than 3 years.Group B consisted of 144 cases. The most common causes of injuries were falls, traffic accidents, and so on, and the types of injuries were fractures, abrasions, sprains, etc. The incidence of fractures was particularly high and 50% of the accidents were bicycle accidents.Group C consisted of 41 cases. Although the age distribution was similar to that of group B, the types of accidents and injuries were similar to those of group A.The Bodygraphic Injury Surveillance System (BISS) analysis showed that groups A and C were similar, that is, injuries occurred mainly to the head, whereas in group B, the extremities were mainly affected. CONCLUSIONS: We analyzed the causes, types, and mechanisms of childhood injuries. The BISS may help to clarify the mechanisms of injuries in childhood.

Human neocortical development as a basis to understand mechanisms underlying neurodevelopmental disabilities in extremely preterm infants.

AIM: Recent advances in perinatal and neonatal medicine have resulted in marked improvements in the survival rates of extremely preterm infants (born before 28 gestational weeks) around the world, and Japan is among the countries with the highest reported survival rates of extremely preterm infants. However, it remains a major concern that many survivors develop neurodevelopmental disabilities, including cognitive dysfunctions and neurodevelopmental disorders later in life. In order to understand the pathophysiological mechanisms underlying the neurodevelopmental disabilities observed in the survivors of extremely preterm births, we reviewed recently reported findings about the development of the human neocortex. METHODS: First, we have summarized the current knowledge about the development of the neocortex, including recently reported human- and/or primate-specific developmental events. Next, we discussed the possible causal mechanisms underlying the development of neurodevelopmental disabilities in extremely preterm infants. RESULTS: Around the birth of extremely preterm infants, neurogenesis and succeeding neuronal migrations are ongoing in the neocortex of human brain. Expansion and maturation of the subplate, which is thought to reflect the axonal wiring in the neocortex, is also prominent at this time. CONCLUSION: Brain injuries that occur around the birth of extremely preterm infants are presumed to affect the dynamic developmental events in the neocortex, such as neurogenesis, neuronal migrations and maturation of the subplate, which could underlie the neurodevelopmental disabilities that often develop subsequently in extremely preterm infants. These possibilities should be borne in mind while considering maternal and neonatal care to further improve the long-term outcomes of extremely preterm infants.

Association of impaired neuronal migration with cognitive deficits in extremely preterm infants.

Many extremely preterm infants (born before 28 gestational weeks [GWs]) develop cognitive impairment in later life, although the underlying pathogenesis is not yet completely understood. Our examinations of the developing human neocortex confirmed that neuronal migration continues beyond 23 GWs, the gestational week at which extremely preterm infants have live births. We observed larger numbers of ectopic neurons in the white matter of the neocortex in human extremely preterm infants with brain injury and hypothesized that altered neuronal migration may be associated with cognitive impairment in later life. To confirm whether preterm brain injury affects neuronal migration, we produced brain damage in mouse embryos by occluding the maternal uterine arteries. The mice showed delayed neuronal migration, ectopic neurons in the white matter, altered neuronal alignment, and abnormal corticocortical axonal wiring. Similar to human extremely preterm infants with brain injury, the surviving mice exhibited cognitive deficits. Activation of the affected medial prefrontal cortices of the surviving mice improved working memory deficits, indicating that decreased neuronal activity caused the cognitive deficits. These findings suggest that altered neuronal migration altered by brain injury might contribute to the subsequent development of cognitive impairment in extremely preterm infants.

Epidemiological, clinical, and genetic landscapes of hypomyelinating leukodystrophies.

To determine the epidemiological, clinical, and genetic characteristics of congenital hypomyelinating leukodystrophies, including Pelizaeus-Merzbacher disease (PMD), we conducted a nationwide epidemiological survey in Japan. A two-step survey targeting all medical institutions specializing in pediatric neurology and childhood disability (919 institutes) in Japan was performed. Detailed information was collected for 101 patients (86 males and 15 females) with congenital hypomyelinating leukodystrophies. The prevalence of congenital hypomyelinating disorders was 0.78 per 100,000 people (0-19 years old), and the incidence was 1.40 per 100,000 live births. Molecular testing was performed in 75 % of patients, and PLP1 gene abnormalities were observed in 62 %. The incidence of PMD with PLP1 mutations was estimated to be 1.45 per 100,000 male live births and that for congenital hypomyelinating disorders with unknown cause to be 0.41 per 100,000 live births. Patients with PLP1 mutations showed a higher proportion of nystagmus and hypotonia, both of which tend to disappear over time. Our results constitute the first nationwide survey of congenital hypomyelinating disorders, and provide the epidemiological, clinical, and genetic landscapes of these disorders.

Effect of curcumin in a mouse model of Pelizaeus-Merzbacher disease.

PLP1 amino acid substitutions cause accumulation of misfolded protein and induce endoplasmic reticulum (ER) stress, causing Pelizaeus-Merzbacher disease (PMD), a hypomyelinating disorder of the central nerve system. Currently no effective therapy is available for PMD. Promoted by its curative effects in other genetic disease models caused by similar molecular mechanisms, we tested if curcumin, a dietary compound, can rescue the lethal phenotype of a PMD mouse model (myelin synthesis deficient, msd). Curcumin was administered orally to myelin synthesis deficit (msd) mice at 180 mg·kg(-1)·day(-1) from the postnatal day 3. We evaluated general and motor status, changes in myelination and apoptosis of oligodendrocytes by neuropathological and biochemical examination, and transcription levels for ER-related molecules. We also examined the pharmacological effect of curcumin in cell culture system. Oral curcumin treatment resulted in 25% longer survival (p<0.01). In addition, oligodendrocytes undergoing apoptosis were reduced in number (p<0.05). However, no apparent improvement in motor function, neurological phenotype, and myelin formation was observed. Curcumin treatment did not change the expression of ER stress markers and subcellular localization of the mutant protein in vitro and/or in vivo. Curcumin partially mitigated the clinical and pathological phenotype of msd mice, although molecular mechanisms underlying this curative effect are yet undetermined. Nonetheless, curcumin may serve as a potential therapeutic compound for PMD caused by PLP1 point mutations.

[Congenital cerebral hypomyelination---Pelizaeus-Merzbacher disease and associated disorders].

Congenital cerebral hypomyelination includes a group of genetic disorders, such as Pelizaeus-Merzbacher disease (PMD), and is characterized by hypomyelination of the cerebral white matter. Until recently, no classification system was available for congenital hypomyelination disorders that are clinically and genetically excluded for PMD. However, the establishment of new disease entities with gene discoveries has generated a clinical need for a new classification and diagnostic criteria for this group of disorders. Here, we review the recent findings on congenital cerebral hypomyelination, which includes 11 diseases, with a novel disease classification and diagnostic criteria with flow charts.

Neurologic phenotype of Schimke immuno-osseous dysplasia and neurodevelopmental expression of SMARCAL1.

Schimke immuno-osseous dysplasia (OMIM 242900) is an uncommon autosomal-recessive multisystem disease caused by mutations in SMARCAL1 (swi/snf-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1), a gene encoding a putative chromatin remodeling protein. Neurologic manifestations identified to date relate to enhanced atherosclerosis and cerebrovascular disease. Based on a clinical survey, we determined that half of Schimke immuno-osseous dysplasia patients have a small head circumference, and 15% have social, language, motor, or cognitive abnormalities. Postmortem examination of 2 Schimke immuno-osseous dysplasia patients showed low brain weights and subtle brain histologic abnormalities suggestive of perturbed neuron-glial migration such as heterotopia, irregular cortical thickness, incomplete gyral formation, and poor definition of cortical layers. We found that SMARCAL1 is highly expressed in the developing and adult mouse and human brain, including neural precursors and neuronal lineage cells. These observations suggest that SMARCAL1 deficiency may influence brain development and function in addition to its previously recognized effect on cerebral circulation.

Spinocerebellar ataxia with axonal neuropathy: consequence of a Tdp1 recessive neomorphic mutation?

Tyrosyl-DNA phosphodiesterase 1 (Tdp1) cleaves the phosphodiester bond between a covalently stalled topoisomerase I (Topo I) and the 3' end of DNA. Stalling of Topo I at DNA strand breaks is induced by endogenous DNA damage and the Topo I-specific anticancer drug camptothecin (CPT). The H493R mutation of Tdp1 causes the neurodegenerative disorder spinocerebellar ataxia with axonal neuropathy (SCAN1). Contrary to the hypothesis that SCAN1 arises from catalytically inactive Tdp1, Tdp1-/- mice are indistinguishable from wild-type mice, physically, histologically, behaviorally, and electrophysiologically. However, compared to wild-type mice, Tdp1-/- mice are hypersensitive to CPT and bleomycin but not to etoposide. Consistent with earlier in vitro studies, we show that the H493R Tdp1 mutant protein retains residual activity and becomes covalently trapped on the DNA after CPT treatment of SCAN1 cells. This result provides a direct demonstration that Tdp1 repairs Topo I covalent lesions in vivo and suggests that SCAN1 arises from the recessive neomorphic mutation H493R. This is a novel mechanism for disease since neomorphic mutations are generally dominant.

Schimke immuno-osseous dysplasia: a cell autonomous disorder?

SMARCAL1 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like protein 1) encodes a SWI/SNF ATP-dependent chromatin remodeling protein. Mutations in SMARCAL1 cause the autosomal-recessive multisystem disorder Schimke immuno-osseous dysplasia (SIOD); this suggests that the SMARCAL1 protein is involved in the development or maintenance of multiple organs. Disease within these many tissues could arise by a cell autonomous or a cell non-autonomous mechanism. Consistent with a cell autonomous mechanism, we did not find any disease recurrence in transplanted organs or protection of other tissues by the organ grafts. In order to better understand the role of SMARCAL1 during normal development and in the pathogenesis of SIOD, we characterized the spatial and temporal expression of the murine homolog (Smarcal1). The Smarcal1 mRNA and protein were expressed throughout development and in all tissues affected in patients with SIOD including the bone, kidney, thymus, thyroid, tooth, bone marrow, hair, eye, and blood vessels. Significantly, the expression profile of Smarcal1 in the mouse has led us to reexamine and identify novel pathology in our patient population resulting in changes in the clinical management of SIOD. The expression of Smarcal1 in affected tissues and the non-recurrence of disease in grafted organs lead us to hypothesize a cell autonomous function for SMARCAL1 and to propose tissue-specific mechanisms for the pathophysiology of SIOD.

Survey of MeCP2 in the Rett syndrome and the non-Rett syndrome brain.

The clinical and neuropathologic aspects of Rett syndrome suggest that an arrest of brain development produces the phenotype, but it is not understood how the gene implicated in Rett syndrome, methyl-CpG protein 2 (MeCP2), is regulated during brain development. In this study, the ontogeny of MeCP2 is examined in the developing human brain and in the female Rett syndrome brain to evaluate the relationship between MeCP2 expression and brain development in health and disease, respectively. Immunocytochemistry using an antibody to the C-terminal region of the protein was performed in paraffin sections of the developing brain to define the age and the sites of MeCP2 protein expression. In development, there is no MeCP2 expression in the germinal matrix or in the progenitor cells. At 10 to 14 weeks' gestation, the neurons of the brain stem and the Cajal-Retzius and subplate neurons of the cortex express MeCP2. By midgestation, some neurons of the basal ganglia express MeCP2, and at late gestation, the most mature cortical neurons in the lower cortical layers are positive. The postnatal cortex continues to increase its expression of neuronal MeCP2. In the Rett syndrome brain, fewer neurons express MeCP2 than in the normal brain. This reduction is most apparent in the brain stem and thalamus. The neurons of the cerebral cortex show the least reduction. We conclude that the regulation of MeCP2 abundance is related to human brain development, being expressed in neurons when they appear mature. In Rett syndrome, however, the expression pattern of MeCP2 does not completely resemble that of the normal immature brain, suggesting that the maintenance of MeCP2 might be determined in specific neurons by factors other than those controlling maturation. In the developing brain, synaptic activity and plasticity could be necessary to maintain MeCP2 in selected neuronal populations.

Reelin and disabled-1 expression in developing and mature human cortical neurons.

In developing mammalian (mouse) brain, Reelin (Reln) is secreted by the Cajal-Retzius (CR) neurons in the marginal zone, binds apolipoprotein E receptor 2 (ApoER2) and very low density lipoprotein receptor (Vldlr), and induces the phosphorylation of the downstream cytoplasmic molecule disabled-1 (Dab1) in cortical plate neurons. Although this is a well-characterized signaling pathway in mice, it has not been well defined in human brain. In this paper we examined the expression of RELN, APOER2, VLDLR, and DAB1 in the developing human brain by RT-PCR. We further determined the cellular expression of the proteins RELN and DAB1 in 50 human brains ranging in age from 10 gestational weeks (GW) to 62 years using immunochemistry. We found that the pattern of expression of RELN and DAB1 in the human brain isnot identical to that observed in the mouse brain. In particular, we report the novel finding that human DAB1and RELN are coexpressed in CR neurons during cortical development and in cortical pyramidal neurons after neuronal migration is complete. Thus, in the human brain, the whole RELN signaling pathway is present within selected populations of cortical neurons throughout life. We speculate that RELN and DAB1 coexpression in these neurons is necessary for both normal cortical development and mature function.