Biology subjects

Crespo, A.

Publications and source records attributed to Crespo, A..

3 recordsLinked to original sources

bioRxiv2022

Rapid presynaptic maturation in naturally regenerating axons

Successful neuronal regeneration requires the re-establishment of synaptic connectivity. Crucial to this process is the reconstitution of presynaptic machinery responsible for controlling neurotransmitter release. In the mammalian adult CNS post-injury regeneration is usually only possible after extensive experimental intervention, and it is unknown how presynaptic function is re-established, let alone how it might be optimised to promote functional recovery. Here we addressed these questions by studying presynaptic maturation during a regenerative process that occurs entirely naturally. After toxin-induced injury, olfactory sensory neurons in the adult mouse olfactory epithelium can regenerate fully, sending axons to the brain to re-establish synaptic contact with postsynaptic partners in the olfactory bulb. Using electrophysiological recordings in acute slices, we found that after initial re-contact, functional connectivity in this system was rapidly established. Moreover, re-connecting presynaptic terminals had almost mature functional properties, including high release probability and a strong capacity for presynaptic inhibition. Release probability then matured quickly, rendering re-established terminals functionally indistinguishable from controls just one week after initial contact. These data show that successful synaptic regeneration in the adult mammalian brain is not quite a plug-and-play process; instead, almost-mature presynaptic terminals undergo a rapid phase of functional maturation to re-integrate into established target networks.

neuroscience↗

bioRxiv2021

LRH-1/NR5A2 regulates the PTGS2-PGE2-PTGER1 signalling axis contributing to islet survival and antidiabetic actions of the agonist BL001

We have previously described a role of LRH-1/NR5A2 in islet morphogenesis during postnatal development and reported that the treatment with BL001, an agonist of LRH-1/NR5A2, protects islets against-stress induced apoptosis and reverts hyperglycemia in 3 mouse models of Type 1 Diabetes Mellitus (T1DM). Islet transcriptome profiling revealed that most differentially expressed genes after BL001 treatment are involved in immunomodulation, among them, the increase in PTGS2/COX2 expression. Herein, we dissected the cellular and molecular branches of the BL001/LRH-1/NR5A2 signalling axis in order to chart the mode of action confering beta cell protection and hyperglycaemia reversion. We found that constitutive LRH-1/NR5A2 ablation within the insulin expression domain (RIP-Cre mouse model) caused a significant beta cell mass reduction characterized by blunted proliferation correlating with animal growth retardation, weight loss and hypoglycemia, leading to lethality before weaning. Using an inducible approach (pdx1PBCreER mouse model), specific deletion of LRH-1/NR5A2 in adult beta cells abolished the anti diabetic effect of BL001 in streptozotocin treated mice, correlating with complete beta-cell mass destruction. Additionally, BL001 induced Ptgs2 expression, was blunted in islets lacking LRH-1/NR5A2. The combined BL001/cytokine treatment did not further stimulate Ptgs2 expression above levels detected with cytokine alone yet secreted PGE2 levels were increased 5-fold. Inactivation of PTGS2 blunted induction of the target and its product PGE2 in islets treated with cytokines alone or with BL001. Importantly, PTGS2 inactivated islets were refractory to the BL001 protective effect under cytokine attack as evidenced by increased Bax expression levels, cytochrome C release and cleaved PARP. The PTGER1 antagonist ONO-8130, but not the PTGER4 antagonist L-161,982, negated BL001-mediated islet survival. Our results establish that the beneficial properties of BL001 against stress-induced cell death are specifically conveyed by LRH-1/NR5A2 activation in beta cells and downstream stimulation of the PTGS2-PGE2/PTGER1 signalling axis.

physiology↗

bioRxiv2021

Cell lineage as a predictor of immune response in neuroblastoma

Immunotherapy for patients with neuroblastoma has met with limited success, partly due to an incomplete understanding of the mechanisms underlying immune responsiveness in this clinically and genetically heterogenic tumor. Here, we undertook an unbiased analysis using dimension reduction and UMAP visualization of transcriptional signatures derived from 498 primary neuroblastoma tumors. Four distinct clusters based on differentially expressed genes emerged, of which one, representing about 30% and comprising mainly of MYCN-nonamplified tumors, was notable for the high expression of genes associated with both immune response activation and suppression. This capacity to elicit a productive immune response resided exclusively in tumors with dominant populations of undifferentiated, neural crest-like or mesenchymal cells; by contrast, tumors comprising primarily of committed, adrenergic neuron-like cells were less immunogenic. Mesenchymal neuroblastoma cells were enriched for innate and adaptive immune gene signatures, demonstrated engagement with cytotoxic T and natural killer cells, and induced immune cell infiltration in an immunocompetent mouse model. Transcriptional or targeted therapy-induced reprogramming of adrenergic cells to the mesenchymal state led to reactivation of tumor cell-intrinsic immune genes. Key immune response genes in adrenergic tumor cells were found to be epigenetically silenced by the PRC2 complex, and such repression could be relieved by either mesenchymal cell state reprogramming or EZH2 inhibition, leading to increased activation of natural killer cells by the tumor cells. These data identify cell lineage as a major determinant of the immunogenic potential in neuroblastoma that could be used to stratify patients who are most likely to benefit from immunotherapy.

cancer biology↗