Page 113 - Molecular features of low-grade developmental brain tumours

THE CODING AND NON-CODING TRANSCRIPTIONAL LANDSCAPE OF SEGA
is well established, the role of this complex in human pathology has rarely been studied. In the present study, we identified the Ragulator complex (LAMTOR1 – LAMTOR5) to be over- expressed in SEGAs compared to control tissue. RNA-Seq on tubers did not find an over- expression of LAMTOR genes in tubers, suggesting that over-expression of this complex is unique to SEGA 23,70. While we found weak expression of LAMTOR1 in a subset of tubers, expression of LAMTOR1 was also seen in neurons of healthy control tissue, which could explain why no difference was found on RNA level between tubers and cortex control in previous studies 23,70. Furthermore, we show that LAMTOR1-5 co-express with pERK and pS6 suggesting that the Ragulator complex might be involved with the activation of these two pathways in SEGA and could be an interesting target for therapy. However, further research is needed to show the direct link between the Ragulator complex and SEGA development.
So far, research on small non-coding RNAs in SEGA has been limited to miRNA expression using microarray analysis or direct RT-qPCR 62,90. In this study we mapped the whole small non-coding RNA profile in SEGAs relative to control tissue and found that miRNAs, snRNAs, snoRNAs and vtRNAs were amongst the differentially expressed small RNAs. We identified miRNAs as the largest group of differentially expressed small RNAs. Since miRNAs are known regulators of gene expression we used a bioinformatics approach to identify miRNAs that could potentially modulate the enriched pathways found in this study. In doing so, we identified miRNA-20a-5p as a potential regulator of several LAMTOR genes. We also identified a high number of unannotated small transcripts. Although these unannotated small RNAs still need to be validated and functionally characterized, they could potentially harbor novel small RNAs and therefore be interesting for further research.
Taken together, this study shows an activation of ERK in SEGAs and suggest that the MAPK/ERK pathway could be used as a target for treatment independent of, or in combination with mTORC1 inhibitors for TSC patients with SEGAs. Furthermore, we are the first to identify the over-expression of the Ragulator complex in human pathology, linking the constitutive activated mTORC1 pathway and MAPK/ERK activation seen in SEGAs, highlighting the Ragulator complex as a promising novel therapeutic target.
Author Contributions
EA, JM and AM conceived the study and participated in its design and coordination. FJ, WS, WD, VG, TS,SS, JH, MF, KK, SJ, WG, AMB, CC, FG, LG, RC, IB, PK, JZ, LM, AM and EA contributed to the collection and selection of tissue samples and/or clinical data. AB, JM, and BS performed the bioinformatics. RT-qPCR, immunohistochemistry, western blotting and cell culture experiments were performed by AB supported by AK, CM and JA. Flow cytometry was performed by AB and JS. Analysis of the data was performed by AB, JS, JM and AM. AB, JM, BS, AS, AM and EA wrote the paper. All authors read and approved the final manuscript.
Acknowledgements
The authors thank all supporters of the TSC brain bank (Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland: J. Jaworski, A Tempes; The Service d’ Anatomie Pathologique, CHI de Creteil and Inserm
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