Mutually exclusive splicing is a regulated means to generate protein diversity, but the underlying mechanisms are poorly understood. Here comparative genome analysis revealed the built-in intronic elements for controlling mutually exclusive splicing of the 14-3-3ξ pre-mRNA. These elements are clade specific but are evolutionarily conserved at the secondary structure level. Combined evidence revealed the triple functions of these inter-intronic RNA pairings in synergistically ensuring the selection of only one of multiple exons, through activation of the proximal variable exon outside the loop by the approximation of cis elements, and simultaneous repression of the exon within the loop, in combination with the physical competition of RNA pairing. Additionally, under this model, we also deciphered a similar structural code in exon clusters 4 and 9 of Dscam (38,016 isoforms) and Mhc (480 isoforms). Our findings suggest a broadly applicable mechanism to ensure mutually exclusive splicing.

Glioma is a worldwide malignancy, which displays significantly active metastasis and angiogenesis. Interaction between long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) has been shown to play crucial role in regulating tumor properties. However, the potential of lncRNA X-inactive specific transcript (XIST) to function as a miRNA regulator and its relevance in glioma tumorigenicity and angiogenesis have so far remained unclear. Expression analysis of lncRNA XIST in glioma cells revealed its significant up-regulation. Interestingly, silencing of XIST repressed both metastatic and pro-angiogenic ability in vitro as well as in vivo. Subsequent studies revealed that lncRNA XIST expression inversely correlated with miR-429 expression in glioma cells; miR-429 modulated XIST expression by directly targeting the XIST gene sequence. In addition, miR-429 inhibitor restored metastatic and pro-angiogenic ability of gliomas abolished by silencing XIST. Our data provide insight into the key roles of the lncRNA-miRNA functional network in gliomas, which can aid in developing new therapeutic strategies for gliomas through clinical trials.

BackgroundRNA editing and alternative splicing play an important role in expanding protein diversity and this is well illustrated in studies of nicotinic acetylcholine receptors (nAChRs).ResultsHere, we compare the RNA editing and alternative splicing of the nAChR alpha6 subunit genes from different insects spanning ~300 million years of evolution– Drosophila melanogaster, Anopheles gambiae, Bombyx mori, Tribolium castaneum and Apis mellifera. The conserved and species-specific A-to-I RNA editing occurred across all species except A. gambiae, which displayed extraordinarily short flanking intronic sequences. Interestingly, some A-to-I editing sites were a genomically encoded G in other species. A combination of the experimental data and computational analysis of orthologous alpha6 genes from different species indicated that RNA editing and alternative splicing predated at least the radiation of insect orders spanning ~300 million years of evolution; however, they might have been lost in some species during subsequent evolution. The occurrence of alternative splicing was found to be regulated in distinct modes and, in some cases, even correlated with RNA editing.ConclusionOn the basis of comparative analysis of orthologous nAChR alpha6 genes from different insects spanning ~300 million years of evolution, we have documented the existence, evolutionary conservation and divergence, and also regulation of RNA editing and alternative splicing. Phylogenetic analysis of RNA editing and alternative splicing, which can create a multitude of functionally distinct protein isoforms, might have a crucial role in the evolution of complex organisms beyond nucleotide and protein sequences.

An increasing number of experiments have found anomalies in mitochondria in the brains of psychotics, which suggests that mitochondrial dysfunction or abnormal cerebral energy metabolism might play an important role in the pathophysiology of schizophrenia (SCZ). We adopted a proteomic approach to identify the differential effects on the cerebral cortex and hippocampus mitochondrial protein expression of Sprague-Dawley (SD) rats by comparing exposure to typical and atypical antipsychotic medications. Differential mitochondrial protein expressions were assessed using two-dimensional (2D) gel electrophoresis for three groups with Chlorpromazine (CPZ), Clozapine (CLZ), quetiapine (QTP) and a control group. A total of 14 proteins, of which 6 belong to the respiratory electron transport chain (ETC) of oxidative phosphorylation (OXPHOS), showed significant changes in quantity including NADH dehydrogenase (ubiquinone) 1 alpha subcomplex 10 (Ndufa10), NADH dehydrogenase (ubiquinone) flavoprotein 2 (Ndufv2), NADH dehydrogenase (ubiquinone) Fe-S protein 3 (Ndufs3), F1-ATPase beta subunit (Atp5b), ATPase, H+ transporting, lysosomal, beta 56/58 kDa, isoform 2 (Atp6v1b2) and ATPase, H+ transporting, V1 subunit A, isoform 1 (Atp6v1a1). The differential proteins subjected to 2D were assessed for levels of mRNA using quantitative real time PCR (Q-RT-PCR), and we also made partial use of Western blotting for assessing differential expression. The results of our study may help to explain variations in SD rats as well as in human response to antipsychotic drugs. In addition, they should improve our understanding of both the curative effects and side effects of antipsychotics and encourage new directions in SCZ research.