Sachio Takashima

Methyl CpG-Binding Protein 2 (a Mutation of Which Causes Rett Syndrome) Directly Regulates Insulin-Like Growth Factor Binding Protein 3 in Mouse and Human Brains

Rett syndrome (RTT) is a major neurodevelopmental disorder, characterized by mental retardation and autistic behavior. Mutation of the MeCP2 gene, encoding methyl CpG-binding protein 2, causes the disease. The pathomechanism by which MeCP2 dysfunction leads to the RTT phenotype has not been elucidated. We found that MeCP2 directly regulates expression of insulin-like growth factor binding protein 3 (IGFBP3) gene in human and mouse brains. A chromatin immunoprecipitation assay showed that the IGFBP3 promoter contained an MeCP2 binding site. IGFBP3 overexpression was observed in the brains of mecp2-null mice and human RTT patients using real-time quantitative polymerase chain reaction and Western blot analyses. Moreover, mecp2-null mice showed a widely distributed and increased number of IGFBP3-positive cells in the cerebral cortex, whereas wild-type mice at the same age showed fewer IGFBP3-positive cells. These results suggest that IGFBP3 is a downstream gene regulated by MeCP2 and that the previously reported BDNF and DLX5 genes and MeCP2 may contribute directly to the transcriptional expression of IGFBP3 in the brain. Interestingly, the pathologic features of mecp2-null mice have some similarities to those of IGFBP3-transgenic mice, which show a reduction of early postnatal growth. IGFBP3 overexpression due to lack of MeCP2 may lead to delayed brain maturation.

Etiologies and distribution of neonatal leukomalacia

Neonatal leukomalacia was classified into 4 groups: focal (F), widespread (W), diffuse (D), and multicystic encephalomalacia (MCE) according to the distribution of ischemic necrosis in the cerebral hemisphere. The highest and lowest values of PaCO2, PaO2, and pH and the lowest systolic and diastolic blood pressures were compared among each group and controls. The lowest PaCO2 values were significantly lower in MCE than in the F, W, and D (F + W + D) group or controls. The lowest values of systolic and diastolic blood pressures in the W and F + W + D groups were significantly lower than in the controls; therefore, hypocarbia can be an etiologic factor of MCE rather than periventricular leukomalacia. Hypotension may be closely related to a causal factor of neonatal leukomalacia.

Neocortical Layer Formation of Human Developing Brains and Lissencephalies: Consideration of Layer-Specific Marker Expression

To investigate layer-specific molecule expression in human developing neocortices, we performed immunohistochemistry of the layer-specific markers (TBR1, FOXP1, SATB2, OTX1, CUTL1, and CTIP2), using frontal neocortices of the dorsolateral precentral gyri of 16 normal controls, aged 19 gestational weeks to 1 year old, lissencephalies of 3 Miller-Dieker syndrome (MDS) cases, 2 X-linked lissencephaly with abnormal genitalia (XLAG) cases, and 4 Fukuyama-type congenital muscular dystrophy (FCMD) cases. In the fetal period, we observed SATB2+ cells in layers II-IV, CUTL1+ cells in layers II-V, FOXP1+ cells in layer V, OTX1+ cells in layers II or V, and CTIP2+ and TBR1+ cells in layers V and VI. SATB2+ and CUTL1+ cells appeared until 3 months of age, but the other markers disappeared after birth. Neocortices of MDS and XLAG infants revealed SATB2+, CUTL1+, FOXP1+, and TBR1+ cells diffusely located in the upper layers. In fetal FCMD neocortex, neurons labeled with the layer-specific markers located over the glia limitans. The present study provided new knowledge indicating that the expression pattern of these markers in the developing human neocortex was similar to those in mice. Various lissencephalies revealed abnormal layer formation by random migration.

Normal and Abnormal Development of the Human Cerebral Cortex

The functional organization of the developing human brain does not only differ substantially from that of the mature brain, but it also undergoes continuous changes. During fetal brain development, transient neuronal circuitries are formed which are essential for the subsequent development of mature projections. Transitory connections are linked to transient structures which are particularly prominent in the human fetal brain and are susceptible to damage under pathological circumstances. The First International Symposium on Normal and Abnormal Development of the Human Fetal Brain aimed to gather basic information on these transitory organizations and the major developmental events that occur in the fetal brain. This paper summarizes a roundtable discussion at the symposium on transient characteristics and injuries in the developing human cerebral cortex. An overview of cortical development is first presented and then the development of several fetal structures, including the subventricular zone, ganglionic eminence, marginal zone, subplate and cortical plate, is discussed with regard to their important contribution to the formation of the correct fiber projections in the adult. The last section focuses on the anomalies that are commonly found in the premature fetal brain on the one hand and on the other hand are related to the transitory characteristics of the developing brain.

Immunohistochemical Expression of Peroxisomal Enzymes in Developing Human Brain

The immunohistochemistry of peroxisomes was examined in human brains from fetal to adult ages using antibodies against catalase (CAT), acyl-CoA oxidase (AOX), and 3-ketoacyl-CoA thiolase (PT) on conventional formalin-fixed paraffin-embedded sections. Positive staining neurons first appeared in the basal ganglia, thalamus, and cerebellum at 27-28 wk of gestation, and in the frontal cortex at 35-36 wk of gestation. They increased in number with gestational age and the intensity of immunostaining increased with enlargement of perikaryonal size. Positively staining glial cells first appeared in the deep white matter at 31-32 wk of gestation, their appearance showing a shift from the deep to the superficial white matter with increasing age. This developmental change in the peroxisomal immunoreactivities in glial cells corresponds with that in myelination glia. Therefore, the results suggest that peroxisomes are closely related to neuronal growth and myelinogenesis in the developing human brain. Also, our results as to myelinogenesis may explain one pathogenetic factor of dysmyelination in peroxisomal disorders.

Developmental changes in KCNQ2 and KCNQ3 expression in human brain : possible contribution to the age-dependent etiology of benign familial neonatal convulsions

Several mutations of KCNQ2 and KCNQ3 are considered to be associated with benign familial neonatal convulsions (BFNC). BFNC is characterized by seizures starting within several days of life and spontaneous remission within weeks to months. KCNQ channel is a heteromeric voltage-dependent potassium channel consisting of KCNQ2 and KCNQ3 subunits. To clarify the age-dependent etiology of BFNC, we examined the developmental changes in KCNQ2 and KCNQ3 expression in human hippocampus, temporal lobe, cerebellum and medulla oblongata obtained from 23 subjects who died at 22 gestation weeks to adulthood. Formalin-fixed and paraffin-embedded specimens were used for immunohistochemistry. Unique developmental changes in KCNQ2 and KCNQ3 were found in each region. A high expression of KCNQ2 was identified in the hippocampus, temporal cortex, cerebellar cortex and medulla oblongata in fetal life, but such expression decreased after birth. The expression of KCNQ3 increased in late fetal life to infancy. Simultaneous and high expressions of KCNQ2 and KCNQ3 were observed in each region from late fetal life to early infancy, coinciding with the time when BFNC occurs. Such coexpression may contribute to the pathogenesis of BFNC.

A History of Our Understanding of Cerebral Vascular Development and Pathogenesis of Perinatal Brain Damage Over the Past 30 Years

This article reviews our studies focusing on cerebral vascular development, the pathogenesis of subependymal/intraventricular hemorrhage (SEH/IVH), periventricular leukomalacia (PVL), and pontosubicular neuron necrosis (PSN). Their pathogenesis consists of predisposing developmental and causal factors. SEH/IVH may be caused by reperfusion or overperfusion following ischemia in the subependymal germinal matrix with characteristic vasculature. The cause of PVL is multifactorial (ie, ischemia and inflammation), predisposed by the maturational status of the vasculature and oligodendroglia in the white matter. Focal PVL is ischemic necrosis, and diffuse PVL or white matter injury may include cytotoxic damage. PSN has an apoptotic character, and may be induced by ischemic and oxidative stress on specific immature neurons. Further studies on preventive and therapeutic measures are necessary in clinical, pathologic, and experimental fields. The monitoring and control methods of brain hemodynamics and cellular stability should be more developed to prevent brain damages.

From physiology to pathology: arousal deficiency theory in sudden infant death syndrome (SIDS)—with reference to apoptosis and neuronal plasticity

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age (including 26 infant victims of sudden infant death syndrome (SIDS), 5 with congenital cardiac abnormalities, 2 from infected pulmonary dysplasia, 2 from septic shock with multi-organ failure, 1 with a prolonged seizure, 1 from prolonged neonatal hypoxemia, 1 from meningitis and brain infarction). The frequency and duration of sleep apneas recorded some 3-12 weeks before the infants death were analyzed. Brainstem material from these 38 infants was studied in an attempt to elucidate the relationship between sleep apnea and neuronal pathological changes in the arousal pathway. Immunohistochemical analyses included the evaluation of growth-associated phosphoprotein 43 (GAP43) as a marker for synaptic plasticity. The terminal-deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method was used to identify apoptosis. The positive pathological reactions were quantitatively analyzed. The pathological and physiological data were linked for each infant. Akaike Information Criterion (AIC) statistics was calculated to elucidate the relationship between the physiological and the pathological data in the SIDS victims. The findings illustrated the possibility of an organic fragility within the arousal pathway, particularly in the midbrain periaqueductal gray matter, which is associated with the visceral alerting response. This autonomic response occurs within an acetylcholine afferent system and pedunculopontine tegmental nucleus (PPTN). The finding is, in future SIDS infants, associated with repetitive sleep apnea.

Development of ferritin-positive cells in cerebrum of human brain

The distribution and development of ferritin-containing cells were studied immunohistochemically in the cerebrum at ages ranging from human fetuses to adults. The predominant cell type labeled with antiserum to ferritin was the oligodendrocyte. In frontal and occipital lobes, positive cells appeared at 25 weeks gestation in subcortical and periventricular white matter, and increased earlier in the white matter than in the cortex. They also appeared at 25 weeks gestation and increased continuously in infancy in the putamen and globus pallidus, as well as in the frontal and occipital lobes. This development of ferritin-positive glia may be related to the process of myelination and maturation of oligodendrocyte.

Characteristic developmental expression of amyloid β40, 42 and 43 in patients with Down syndrome

We immunohistochemically studied the expression of beta-amyloid precursor protein (APP), Abeta40, Abeta42, and Abeta43 in the frontal lobes of 20 Down syndrome (DS) patients and 13 controls. The immunoreactivity for each antibody was different in the degree of intensity and the chronological pattern of expression. APP and Abeta43 immunoreactivity was increased in neurons initially, and then Abeta43 and 42 immunoreactivity appeared in diffuse plaques from 32 years of age. APP and Abeta43 were characteristically observed in axons around senile plaques. Finally, Abeta40 immunoreactivity was detected in the cores of senile plaques. This time course of immunoreactive expression may be related to the pathogenetic process of Alzheimer-type dementia in DS, and the axonal damage in senile plaques may lead to the formation of neurofibrillary tangles (NFT) or neuronal death through axonal flow disturbance and accumulation of Abeta43 in cortical neurons.