Circular RNAs are a large group of RNAs whose cellular functions are still being investigated. We recently proposed that circSMARCA5 acts as sponge for the splicing factor Serine and Arginine Rich Splicing Factor 1 (SRSF1) in glioblastoma multiforme (GBM). After demonstrating by RNA immunoprecipitation a physical interaction between SRFS1 and circSMARCA5, we assayed by real-time PCR in a cohort of 31 GBM biopsies and 20 unaffected brain parenchyma controls (UC) the expression of total, pro-angiogenic (Iso8a) and anti-angiogenic (Iso8b) mRNA isoforms of Vascular Endothelial Growth Factor A (VEGFA), a known splicing target of SRSF1. The Iso8a to Iso8b ratio: (i) increased in GBM biopsies with respect to UC (p-value < 0.00001); (ii) negatively correlated with the expression of circSMARCA5 (r-value = −0.46, p-value = 0.006); (iii) decreased in U87-MG overexpressing circSMARCA5 with respect to negative control (p-value = 0.0055). Blood vascular microvessel density, estimated within the same biopsies, negatively correlated with the expression of circSMARCA5 (r-value = −0.59, p-value = 0.00001), while positively correlated with that of SRSF1 (r-value = 0.38, p-value = 0.00663) and the Iso8a to Iso8b ratio (r-value = 0.41, p-value = 0.0259). Kaplan-Meier survival analysis showed that GBM patients with low circSMARCA5 expression had lower overall and progression free survival rates than those with higher circSMARCA5 expression (p-values = 0.033, 0.012, respectively). Our data convincingly suggest that circSMARCA5 is an upstream regulator of pro- to anti-angiogenic VEGFA isoforms ratio within GBM cells and a highly promising GBM prognostic and prospective anti-angiogenic molecule.

https://www.mdpi.com/2072-6694/11/2/194/pdf

CircSMARCA5 Regulates VEGFA mRNA Splicing and Angiogenesis in Glioblastoma Multiforme Through the Binding of SRSF1.

Background Cryopreservation is now considered as an efficient way to store human oocytes to preserve fertility. However, little is known about the effects of this technology on oocyte gene expression. The aim of this study was to examine the effect of the two cryopreservation procedures, slow freezing and vitrification, on the gene expression profile of human metaphase II (MII) oocytes. Methods Unfertilized MII oocytes following ICSI failure were cryopreserved either by slow freezing or by the Cryotip method for vitrification. After thawing, total RNA was extracted and analyzed using Affymetrix Human Genome U133 Plus 2.0 GeneChip arrays. The gene expression profiles and associated biological pathways in slowly frozen/thawed and vitrified MII oocytes were determined and compared with those of non-cryopreserved MII oocytes used as controls. Results Both cryopreservation procedures negatively affected the gene expression profile of human MII oocytes in comparison with controls. However, slowly frozen and vitrified MI oocytes displayed specific gene expression signatures. Slow freezing was associated with down-regulation of genes involved in chromosomal structure maintenance (KIF2C and KIF3A) and cell cycle regulation (CHEK2 and CDKN1B) that may lead to a reduction in the oocyte developmental competence. In vitrified oocytes, many genes of the ubiquitination pathway were down-regulated, including members of the ubiquitin-specific peptidase family and subunits of the 26S proteasome. Such inhibition of the degradation machinery might stabilize the maternal protein content that is necessary for oocyte developmental competence. Conclusions The low pregnancy rates commonly observed when using human MII oocytes after slow freezing-thawing may be explained by the alterations of the oocyte gene expression profile.

https://www.hal.inserm.fr/inserm-00726705/document

Slow freezing and vitrification differentially modify the gene expression profile of human metaphase II oocytes

In this study, for the first time, we demonstrated the presence of microRNAs and extracellular vesicles in human blastocoel fluid. The bioinformatic and comparative analyses identified the biological function of blastocoel fluid microRNAs and suggested a potential role inside the human blastocyst. We found 89 microRNAs, expressed at different levels, able to regulate critical signaling pathways controlling embryo development, such as pluripotency, cell reprogramming, epigenetic modifications, intercellular communication, cell adhesion and cell fate. Blastocoel fluid microRNAs reflect the miRNome of embryonic cells and their presence, associated with the discovery of extracellular vesicles, inside blastocoel fluid, strongly suggests their important role in mediating cell communication among blastocyst cells. Their characterization is important to better understand the earliest stages of embryogenesis and the complex circuits regulating pluripotency. Moreover, blastocoel fluid microRNA profiles could be influenced by blastocyst quality, therefore, microRNAs might be used to assess embryo potential in IVF cycles.

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Elisa Minutolo

Papers

Molecular profiling of human oocytes after vitrification strongly suggests that they are biologically comparable with freshly isolated gametes