RESUMEN
Rett syndrome (RTT) is a rare neurodevelopmental disorder characterized by severe cognitive, social, and physical impairments resulting from de novo mutations in the X-chromosomal methyl-CpG binding protein gene 2 (MECP2). While there is still no cure for RTT, exploring up-to date neurofunctional diagnostic markers, discovering new potential therapeutic targets, and searching for novel drug efficacy evaluation indicators are fundamental. Multiple neuroimaging studies on brain structure and function have been carried out in RTT-linked gene mutation carriers to unravel disease-specific imaging features and explore genotype-phenotype associations. Here, we reviewed the neuroimaging literature on this disorder. MRI morphologic studies have shown global atrophy of gray matter (GM) and white matter (WM) and regional variations in brain maturation. Diffusion tensor imaging (DTI) studies have demonstrated reduced fractional anisotropy (FA) in left peripheral WM areas, left major WM tracts, and cingulum bilaterally, and WM microstructural/network topology changes have been further found to be correlated with behavioral abnormalities in RTT. Cerebral blood perfusion imaging studies using single-photon emission CT (SPECT) or PET have evidenced a decreased global cerebral blood flow (CBF), particularly in prefrontal and temporoparietal areas, while magnetic resonance spectroscopy (MRS) and PET studies have contributed to unraveling metabolic alterations in patients with RTT. The results obtained from the available reports confirm that multimodal neuroimaging can provide new insights into a complex interplay between genes, neurotransmitter pathway abnormalities, disease-related behaviors, and clinical severity. However, common limitations related to the available studies include small sample sizes and hypothesis-based and region-specific approaches. We, therefore, conclude that this field is still in its early development phase and that multimodal/multisequence studies with improved post-processing technologies as well as combined PET-MRI approaches are urgently needed to further explore RTT brain alterations.
RESUMEN
Autism is known as a severe neurobehavioral syndrome, with males affected more often than females. Previous studies have revealed that microRNAs (miRNAs) play a critical role in the search for novel therapeutic strategies for autism. Therefore, we evaluate the ability of miR-153 to influence brain-derived neurotrophic factor (BDNF) of autism as well as proliferation and apoptosis of hippocampal neuron through the janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway by targeting leptin receptor (LEPR). Firstly, the autistic mice models were established and Morris water maze was employed for the analysis of the learning ability and memory of the mice. Besides, in vitro experiments were conducted with the transfection of different mimic, inhibitor, or siRNA into the hippocampal neuron cells, after which the effect of miR-153 on LEPR and the JAK-STAT signaling pathway-related factors was investigated. Next, 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay and flow cytometry assay were conducted to evaluate cell proliferation, cell cycle, and apoptosis respectively following transfection. The results revealed that there was a significant decrease in learning ability and memory in the autistic mice along with a reduction in the positive expression rate of BDNF and serious inflammatory reaction. LEPR was confirmed as a target gene of miR-153 by the dual luciferase reporter gene assay. After transfection of overexpressed miR-153, LEPR and the JAK-STAT signaling pathway were inhibited followed by an increase in BDNF and enhancement of cell proliferation. In conclusion, the high expression of miR-153 can inhibit activation of JAK-STAT signaling pathway by LEPR, thus improving BDNF expression and the proliferative ability of hippocampal neurons.