Investigation of Gene Regulatory Networks Associated with Autism Spectrum Disorder Based on MiRNA Expression in China

<div><p>Autism spectrum disorder (ASD) comprise a group of neurodevelopmental disorders characterized by deficits in social and communication capacities and repetitive behaviors. Increasing neuroscientific evidence indicates that the neuropathology of ASD is widespread and involves epigenetic regulation in the brain. Differentially expressed miRNAs in the peripheral blood from autism patients were identified by high-throughput miRNA microarray analyses. Five of these miRNAs were confirmed through quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis. A search for candidate target genes of the five confirmed miRNAs was performed through a Kyoto encyclopedia of genes and genomes (KEGG) biological pathways and Gene Ontology enrichment analysis of gene function to identify gene regulatory networks. To the best of our knowledge, this study provides the first global miRNA expression profile of ASD in China. The differentially expressed miR-34b may potentially explain the higher percentage of male ASD patients, and the aberrantly expressed miR-103a-3p may contribute to the abnormal ubiquitin-mediated proteolysis observed in ASD.</p></div

qRT-PCR confirmation of the expression of selected miRNAs.

<p>The levels of the five differentially expressed five miRNAs were statistically significant. The miR-34b expression level was significantly increased, whereas the levels of miR-let-7a, miR-let-7d, miR-103a, and miR-1228 were decreased.</p

Importance of target genes and transcription factor genes.

<p>The horizontal axis indicates the names of target genes and transcription factor genes, and the vertical axis indicates the numbers of associated genes. The ranking was performed according to the number of associated genes, more than 10 of which could be shown.</p

Prediction of target genes.

<p>Four databases were used for the prediction of target genes: TargetScan, miRanda, CLIP-Seq, and miRDB. Venn Diagrams A, B, C, D, and E show the intersection of each miRNA target gene predicted by various databases, and intersection of the target genes obtained from at least three databases. F indicates the total number of candidate target genes for each miRNA.</p

Distribution of the GGGGCC repeats size in SCA3/MJD patients and controls.

<p>There was no significant difference in the distribution of the GGGGCC repeats length between SCA3/MJD patients and controls.</p

Demographic information and average number of repeats between SCA3/MJD patients and controls.

<p>^a x ² test.</p><p>^b t-tests.</p><p>^c Mann-Whitney U test.</p><p>Demographic information and average number of repeats between SCA3/MJD patients and controls.</p

Frequencies of C9orf72 genotypes.

<p>A presents the frequencies in SCA3/MJD patients. B presents the frequencies in controls.</p

The association of expanded CAG repeats in the expanded <i>ATXN3</i> gene with age at onset (AO) in SCA3/MJD patients.

<p>The X-axis indicates the expanded CAG repeat lengths and the Y-axis denotes AO in years. AO of SCA3/MJD is inversely correlated with the length of CAG repeat (<i>r</i> = －0.694, <i>p</i> = 0.000).</p

Analysis of the GGGGCC Repeat Expansions of the <i>C9orf72</i> Gene in SCA3/MJD Patients from China

<div><p>Neurodegenerative disorders are a heterogeneous group of chronic progressive diseases and have pathological mechanisms in common. A certain causative gene identified for a particular disease may be found to play roles in more than one neurodegenerative disorder. We analyzed the GGGGCC repeat expansions of <i>C9orf72</i> gene in patients with SCA3/MJD from mainland China to determine whether the <i>C9orf72</i> gene plays a role in the pathogenesis of SCA3/MJD. In our study, there were no pathogenic repeats (>30 repeats) detected in either the patients or controls. SCA3/MJD patients with intermediate/intermediate or short/intermediate genotype (short: <7 repeats; intermediate: 7-30 repeats) of the GGGGCC repeats had an earlier onset compared with those with short/short genotype. The presence of the intermediate allele of the GGGGCC repeats in the patients decreased the age at onset by nearly 3 years. Our study firstly demonstrate that the development of SCA3/MJD may involve some physiological functions of the <i>C9orf72</i> gene and provide new evidence to the hypothesis that a specific mutation identified in one of the neurodegenerative disorders may be a modulator in this class of diseases.</p></div