G(M1)-gangliosidosis is an autosomal recessive lysosomal lipid storage disorder, caused by mutations of the lysosomal beta-galactosidase (beta-gal) and results in the accumulation of G(M1). The underlying mechanisms of neurodegeneration are poorly understood. Here we demonstrate increased autophagy in beta-gal-deficient (beta-gal(-/-)) mouse brains as evidenced by elevation of LC3-II and beclin-1 levels. Activation of autophagy in the beta-gal(-/-) brain was found to be accompanied with enhanced Akt-mTOR and Erk signaling. In addition, the mitochondrial cytochrome c oxidase activity was significantly decreased in brains and cultured astrocytes from beta-gal(-/-) mouse. Mitochondria isolated from beta-gal(-/-) astrocytes were morphologically abnormal and had a decreased membrane potential. These cells were more sensitive to oxidative stress than wild type cells and this sensitivity was suppressed by ATP, an autophagy inhibitor 3-methyladenine and a pan-caspase inhibitor z-VAD-fmk. These results suggest activation of autophagy leading to mitochondrial dysfunction in the brain of G(M1)-gangliosidosis.

Fragile X syndrome (FXS), which is the most common form of familial mental retardation, is caused by the expansion of the CGG repeat in the FMR1 gene on the X chromosome. Previous studies have suggested that as compared to other populations, Japanese have a lower prevalence of FXS. In addition, in the normal population, there are no carriers who have the premutation allele. We analyzed a total of 946 normal Japanese (576 males and 370 females) and attempted to estimate the frequency of the FMR1 allele. Within this population, we found that 1,155 alleles were in the normal range (less than 40 CGG repeats) and had a modal number of 27 repeats (35.75%). No carriers with premutations (55-200 CGG repeats) were observed in this normal population. We also identified six intermediate-sized alleles (40-54 CGG repeats), with a reported incidence of 1 in 103 males and 1 in 324 females. However, this allele frequency was different from that previously reported for the Japanese population. Since data from previous studies has suggested that FXS might possibly be associated with the genetic mechanism of autism, we also analyzed the length of the CGG repeats in 109 autistic patients. In all cases the CGG repeat numbers were within the normal range (16-36 repeats) and no individuals presented with expanded premutation or intermediate alleles. This finding indicates that the length of the CGG repeat within the FMR1 is unlikely to be responsible for autism in Japanese.

Glioma includes astrocytoma, oligodendroglioma, ependymoma and glioblastoma. We previously reported the epigenetic silencing of paternally expressed gene 3 (PEG3) in glioma cell lines. In this study, we investigated methylation of an exonic CpG island in the promoter region and the expression of PEG3 gene in 20 glioma and 5 non-tumor tissue samples. We found wide variations in the methylation level. Hypomethylaiton and hypermethylation was found in 3 and 4 glioma tissue samples, respectively. Monoallelic expression, which is an evidence of an imprinted gene, was maintained in eight out of nine informative cases which have T/C polymorphisms in PEG3. The lower gene expression, which suggested epigenetic silencing of PEG3, was confirmed statistically in glioblastoma using quantitative reverse-transcription polymerase chain reaction. Interestingly, we found higher expression of PEG3 in two out of three oligodendrogliomas. A negative correlation between the methylation level and gene expression was shown by regression analysis. These results suggest that the abnormal regulation of PEG3 is associated with several glioma subtypes and that it plays an important role in tumorigenesis.

The human paternally expressed gene 3 (PEG3) on chromosome 19q13.4 is one of the candidate tumor suppressor genes for glioma. We have previously reported that the epigenetic silencing of PEG3 expression in glioma cell lines is dependent on aberrant DNA methylation of an exonic CpG island. Here, we have identified three expressed sequence tags (ESTs), H80201, H78825 and AW197312, that exhibit paternal allele-specific expression, using human monochromosomal hybrids containing the paternal or maternal origin of PEG3 locus. The EST H80201 was shown to be expressed only from the paternal allele in normal human lymphoblasts by utilizing a single nucleotide polymorphism (SNP). Monoallelic expression of EST H80201 was also detected in non-tumor adult human brain tissues of gliomas. These ESTs were located directly adjacent to PEG3 in a head-to-head orientation. We have named this new transcript, imprinted transcript 1, which is located upstream but oppositely oriented to PEG3 (ITUP1). The ITUP1 showed a similar expression profile with PEG3 in glioma cell lines. Bisulfite genomic sequencing and reverse transcription (RT)-PCR analysis indicated that hypermethylation of the promoter region correlated with the absence of these transcripts. This suggests that ITUP1 and PEG3 are coordinately regulated, and that downregulation of the both genes may be important in the development of glioma.

Autism spectrum disorder (ASD) is gathering concerns in socially developed countries. ASD is a neuropsychiatric disorder of genetic origin with high prevalence of 1%-2%. The patients with ASD characteristically show impaired social skills. Today, many genetic studies identify numerous susceptible genes and genetic loci associated with ASD. Although some genetic factors can lead to abnormal brain function linked to ASD phenotypes, the pathogenic mechanism of ASD is still unclear. Here, we discuss a new mouse model for ASD as an advanced tool to understand the mechanism of ASD. copy number variations, DNA methylation, histone modification, ASD model mouse Citation:Nakai N, Otsuka S, Myung J, Takumi T. Autism spectrum disorder model mice: focus on copy number variation and epigenetics. Sci China Life Sci, 2015Sci, , 58: 976 -984, doi: 10.1007 Autism spectrum disorder (ASD) is diagnosed based on behavioral phenotypes usually by the age of three. The ASD patients show three major phenotypes: deficits in social interaction, impaired communication, and repetitive behavior or restricted interest. In the past two decades, the prevalence has greatly increased from 0.01%-0.02% to 1%-2.6% [1]; but even now, the cause is unknown. Through twin studies, ASD has been recognized as a disorder with genetic etiology. Monozygotic twins (MZ) show over 90% concordance of ASD, while dizygotic twins (DZ) show less than 10%. Because genomic information of MZ completely coincides with each other while the coincidence is only 50% in DZ, the high concordance of ASD must have a genetic origin. Recently, a number of genetic variations in ASD patients were found by cytogenetics and genomics studies ( Figure 1) [2][3][4][5][6][7][8][9][10][11][12][13][14]. The genetic variations include single nucleotide variations (SNVs) and copy number variations (CNVs). In the case of SNV, the mutation causes severe functional loss of the genes. CNV, on the other hand, is a large nucleotide change in chromosomal complement and can affect dosage of gene function in various ways (e.g. deletion or duplication). As it stands now, SNV and CNV are responsible for 5%-7% and 10%-20% of all ASD cases, respectively, while other causes of genetic variation remain unknown. A higher rate of CNV mutation is consistent within psychiatric disorders including schizophrenia. Incidentally, it is found that a greater enrichment of CNVs in individuals diagnosed with intellectual disability (ID) have severe craniofacial anomalies and cardiovascular defects compared to those with epilepsy or ASD [15]. CNVs in ASD can have comparatively milder effect than diseases with lethal pathology. In SNV cases, many of the causative genes identified code for cell adhesion molecules or scaffolding proteins (NLGN3, NLGN4, NRXN1, CNTNAP2, and SHANK3) [16]. These genes are important for organization of synaptic connections, which play a fundamental role in neuronal function. Not a few psychiatric syndromes show features of ASD.