Anti-HSPA5 monoclonal antibody, clone 20D4

Although it is well established that maturation conditions have a clear influence on oocyte developmental competence, it is not known whether this could be due to downstream effects of perturbation of the transcript profile of the oocyte's adjacent cumulus cells. Therefore, the aim of the present study was to compare the transcript profiles of cumulus cells derived from cumulus-oocyte complexes (COCs) matured in vitro or in vivo. Using a previously validated combined synchronisation and superstimulation protocol, COCs were recovered from beef heifer ovaries just before the expected time of the LH surge and matured in vitro, while in vivo-matured COCs were recovered just before ovulation (20 h after the LH surge). A custom-made cDNA microarray containing 2278 granulosa/cumulus transcripts was used for target and dye-swap hybridisations. In all, 64 genes were differentially expressed between the two groups. Transcript abundance of key genes associated with cumulus expansion (TNFAIP6) and regulation of oocyte maturation (INHBA and FST) were upregulated in in vivo-derived cumulus cells. However, cumulus cells derived from IVM COCs were enriched with genes involved in response to stress (HSPA5 and HSP90AB1). Quantitative real-time polymerase chain reaction confirmed the array results for eight of 10 genes selected for validation. The data presented here reveal that differences in oocyte developmental capacity after maturation in vitro or in vivo are accompanied by distinct differences in transcript abundance of the surrounding cumulus cells.

Epithelial-to-Mesenchymal Transition (EMT) is a key process contributing to the aggressiveness of cancer cells. EMT is triggered by activation of different transcription factors collectively known as EMT-TFs. Different cellular cues and cell signalling networks activate EMT at transcriptional and posttranscriptional level in different biological and pathological situations. Among them, overexpression of LOXL2 (lysyl oxidase-like 2) induces EMT independent of its catalytic activity. Remarkably, perinuclear/cytoplasmic accumulation of LOXL2 is a poor prognosis marker of squamous cell carcinomas and is associated to basal breast cancer metastasis by mechanisms no yet fully understood. Here, we report that overexpression of LOXL2 promotes its accumulation in the Endoplasmic Reticulum where it interacts with HSPA5 leading to activation of the IRE1-XBP1 signalling pathway of the ER-stress response. LOXL2-dependent IRE1-XBP1 activation induces the expression of several EMT-TFs: SNAI1, SNAI2, ZEB2 and TCF3 that are direct transcriptional targets of XBP1. Remarkably, inhibition of IRE1 blocks LOXL2-dependent upregulation of EMT-TFs thus hindering EMT induction.