Search

Abstract: T-type Ca2+ channel-dependent long-term potentiation (LTP) occurs predominantly during the critical period of ocular dominance plasticity in rat and cat visual cortex. Noradrenaline and serotonin are known to facilitate ocular dominance plasticity. In this study using rat visual cortical slices, we tested whether this LTP is modulated by these neuromodulators in the same way as ocular dominance plasticity. Extracellular field potentials evoked by layer 4 stimulation were recorded from layer 2/3 and LTP was induced by low-frequency (2Hz) stimulation continued for 15min. The induction of LTP was suppressed by β, but not α, adrenergic receptor antagonists. LTP induction was also inhibited by selective antagonists for 5-HT1A or 5-HT2 receptors. In slices prepared from rats in which noradrenaline or serotonin was depleted by selective neurotoxins, the magnitude of LTP was significantly smaller compared with control slices. These results indicate that the same types of adrenergic and serotonergic receptors facilitate both LTP and ocular dominance plasticity, supporting our hypothesis that T-type Ca2+ channel-dependent LTP mediates experience-dependent enhancement of visual responses of cortical neurons during the critical period. [Copyright &y& Elsevier]

Neocortical neuronal circuits are refined by experience during the critical period of early postnatal life. The shift of ocular dominance in the visual cortex following monocular deprivation has been intensively studied to unravel the mechanisms underlying the experience-dependent modification. Synaptic plasticity is considered to be involved in this process. We previously showed in layer 2/3 pyramidal neurons of rat visual cortex that low-frequency stimulation-induced long-term potentiation (LTP) at excitatory synapses, which requires the activation of Ni2+-sensitive (R-type or T-type) voltage-gated Ca2+ channels (VGCCs) for induction, shared a similar age and experience dependence with ocular dominance plasticity. In this study, we examined whether this LTP is involved in ocular dominance plasticity. In visual cortical slices, LTP was blocked by mibefradil, kurtoxin and R-(−)-efonidipine, T-type VGCC blockers, but not by SNX-482, an R-type VGCC blocker, indicating that LTP induction requires T-type VGCC activation. Mibefradil did not affect synaptic transmission even at a dose about 30 times higher than that required for LTP blockade. Therefore, this drug was used to test the effect of T-type VGCC blockade on ocular dominance shift produced by 6 days of monocular deprivation during the critical period using visual evoked potentials (VEPs). Although this monocular deprivation commonly produced both depression of deprived eye responses and potentiation of nondeprived eye responses, only the former change occurred when mibefradil was infused into the visual cortex during monocular deprivation. Mibefradil infusion produced no acute effects on VEPs. These results suggest that T-type VGCC-dependent LTP contributes to the experience-dependent enhancement of visual responses. [ABSTRACT FROM AUTHOR]

Background: Mowat-Wilson syndrome (MWS; OMIM #235730) is a genetic condition caused by heterozygous mutations or deletions of the ZEB2 gene. It is characterized by moderate-severe intellectual disability, epilepsy, Hirschsprung disease and multiple organ malformations of which congenital heart defects and urogenital anomalies are the most frequent ones. To date, a clear description of the physical development of MWS patients does not exist. The aim of this study is to provide up-to-date growth charts specific for infants and children with MWS. Charts for males and females aged from 0 to 16 years were generated using a total of 2865 measurements from 99 MWS patients of different ancestries. All data were collected through extensive collaborations with the Italian MWS association (AIMW) and the MWS Foundation. The GAMLSS package for the R statistical computing software was used to model the growth charts. Height, weight, body mass index (BMI) and head circumference were compared to those from standard international growth charts for healthy children.Results: In newborns, weight and length were distributed as in the general population, while head circumference was slightly smaller, with an average below the 30th centile. Up to the age of 7 years, weight and height distribution was shifted to slightly lower values than in the general population; after that, the difference increased further, with 50% of the affected children below the 5th centile of the general population. BMI distribution was similar to that of non-affected children until the age of 7 years, at which point values in MWS children increased with a less steep slope, particularly in males. Microcephaly was sometimes present at birth, but in most cases it developed gradually during infancy; many children had a small head circumference, between the 3rd and the 10th centile, rather than being truly microcephalic (at least 2 SD below the mean). Most patients were of slender build.Conclusions: These charts contribute to the understanding of the natural history of MWS and should assist pediatricians and other caregivers in providing optimal care to MWS individuals who show problems related to physical growth. This is the first study on growth in patients with MWS. [ABSTRACT FROM AUTHOR]

High-throughput sequencing has identified vast numbers of variants in genetic disorders. However, the significance of variants at the exon-intron junction remains controversial. Even though most cases of Mowat–Wilson syndrome (MOWS) are caused by heterozygous loss-of-function variants in ZEB2 , the pathogenicity of variants at exon-intron junction is often indeterminable. We identified four intronic variants in 5/173 patients with clinical suspicion for MOWS, and evaluated their pathogenicity by in vitro analyses. The minigene analysis showed that c.73+2T>G caused most of the transcripts skipping exon 2, while c.916+6T>G led to partial skipping of exon 7. No splicing abnormalities were detected in both c.917-21T>C and c.3067+6A>T. The minigene analysis reproduced the splicing observed in the blood cells of the patient with c.73+2T>G. The degree of the exon skipping was concordant with the severity of MOWS; while the patient with c.73+2T>G was typical MOWS, the patient with c.916+6T>G showed milder phenotype which has been seldom reported. Our results demonstrate that mRNA splicing assays using the minigenes are valuable for determining the clinical significance of intronic variants in patients with not only MOWS but also other genetic diseases with splicing aberrations and may explain atypical or milder cases, such as the current patient. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Lamb-Shaffer syndrome (OMIM: 616803 ) is a neurodevelopmental disorder characterized by developmental delay, mild to moderate intellectual disability, speech delay, and mild characteristic facial appearance caused by SOX5 haploinsufficiency on chromosome 12p12.1. There are clinical variabilities among the patients with genomic alterations, such as intragenic deletions, a point mutation, and a chromosomal translocation of t(11;12)(p13;p12.1), in SOX5 . We report herein a 5-year-old Japanese male with a de novo balanced reciprocal translocation t(12;20)(p12.1;p12.3) presenting a mild intellectual disability, speech delay, characteristic facial appearance, and autistic features. We determined the translocation breakpoints of the patient to be in intron 4 of SOX5 and the intergenic region in 20p12.3 via FISH and nucleotide sequence analyses. Thus, the present patient has SOX5 haploinsufficiency affecting 2 long forms of SOX5 and is the second reported case of Lamb-Shaffer syndrome caused by a de novo balanced reciprocal translocation. This report confirmed that haploinsufficiency of the 2 long forms of SOX5 presents common clinical features, including mild intellectual disability and autistic features, which could be useful for the clinical diagnosis of Lamb-Shaffer syndrome. [ABSTRACT FROM AUTHOR]

Abstract: High-frequency stimulation (HFS) induces long-term potentiation (LTP) at inhibitory synapses of layer 5 pyramidal neurons in developing rat visual cortex. This LTP requires postsynaptic Ca2+ rise for induction, while the maintenance mechanism is present at the presynaptic site, suggesting presynaptic LTP expression and the necessity of retrograde signaling. We investigated whether the supposed signal is mediated by brain-derived neurotrophic factor (BDNF), which is expressed in pyramidal neurons but not inhibitory interneurons. LTP did not occur when HFS was applied in the presence of the Trk receptor tyrosine kinase inhibitor K252a in the perfusion medium. HFS produced LTP when bath application of K252a was started after HFS or when K252a was loaded into postsynaptic cells. LTP did not occur in the presence of TrkB-IgG scavenging BDNF or function-blocking anti-BDNF antibody in the medium. In cells loaded with the Ca2+ chelator BAPTA, the addition of BDNF to the medium enabled HFS to induce LTP without affecting baseline synaptic transmission. These results suggest that BDNF released from postsynaptic cells activates presynaptic TrkB, leading to LTP. Because BDNF, expressed activity dependently, regulates the maturation of cortical inhibition, inhibitory LTP may contribute to this developmental process, and hence experience-dependent functional maturation of visual cortex. [Copyright &y& Elsevier]