Aging‐associated genes and
            <i>let‐7</i>
            microRNAs: a contribution to myogenic program dysregulation in oculopharyngeal muscular dystrophy

Abella-Quintana

et al. 2020

Preprint

The axolotl (Ambystoma mexicanum) is a caudate amphibian, which has an extraordinary ability to restore a wide variety of damaged structures by a process denominated epimorphosis. While the origin and potentiality of progenitor cells that take part during epimorphic regeneration are known to some extent, the metabolic changes experienced and their associated implications, remain unexplored.However, a circuit with a potential role as a modulator of cellular metabolism along regeneration is that formed by Lin28/let-7. In this study, we report two Lin28 paralogs and eight mature let-7 microRNAs encoded in the axolotl genome. Particularly, in the proliferative blastema stage amxLin28B is more abundant in the nuclei of blastemal cells, while the microRNAs amx-let-7c and amx-let-7a are most downregulated. Functional inhibition of Lin28 factors increase the levels of most mature let-7 microRNAs, consistent with an increment of intermediary metabolites of the Krebs cycle, and phenotypic alterations in the outgrowth of the blastema. In summary, we describe the primary components of the Lin28/let-7 circuit and their function during axolotl regeneration, acting upstream of metabolic reprogramming events.The Axolotl Lin28/let-7 Circuit 3 Pioneer studies have related some components of the Lin28/let-7 circuit with regenerative processes, as those that report a high regenerative plasticity in juvenile stages of Caenorhabditis elegans, where immature neurons with low levels of mature let-7 retain a robust regeneration at the axon disruption site, nearby to neural body (Nix and Bastiani, 2013;Zou et al., 2013). Similarly, the transient overexpression of Lin28 in postnatal sensory neurons of mouse after injury, induce an axonal regeneration in vivo through changes in the balance of the AKT-mTOR pathway (Wang et al., 2018).Therefore, an adequate cell metabolic state is relevant for regeneration, since the AKT-mTOR pathway acts as an important mediator between anabolic and catabolic cell reactions (Altomare and Khaled, 2012;Saxton and Sabatini, 2017). In this sense, it has been shown that the inducible overexpression of Lin28A in mouse neonatal tissues, improves regeneration by a rewiring of the primary energetic metabolism, where the glycolysis is favored to increase intermediary metabolites of the Krebs cycle (Shyh-Chang et al., 2013). However, such metabolic reprogramming of the cell bioenergetics differs from other metabolic profiles also achieved with overexpression of Lin28A, but in the context of embryonic development, or during active proliferation of primed pluripotent stem cells and malignant neoplastic cells (Ma et al., 2014;Miyazawa et al., 2017;Zhang et al., 2016).Since the role of the Lin28/let-7 circuit has not been directly studied in the context of epimorphosis, using an amphibian model with a high and innate regenerative capacity, we decided to characterize its behavior and function during forelimb regeneration in axolotl (Ambystoma mexicanum). In this study, we describe the spatio-temporal expression dynamics of ...

Section: Discussionsupporting

confidence: 55%

Functional Characterization of the Lin28/let-7 Circuit during Forelimb Regeneration inAmbystoma mexicanumand its Influence on Metabolic Reprogramming

Abella-Quintana

et al. 2020

Preprint

“…Certain miRNAs possess an immunostimulatory motif (UGUGU) and/or serve as TLR7/8 ligands, and some of them are represented in our results: let-7, one of the most highly represented miRNAs in our results for all stimuli; miR-34, also common for all the PAMPs; and miR-133, differentially downregulated after poly I:C challenge. All these miRNAs are related to innate immunity, development, ageing and senescence in molluscs (89), insects (90,91), fish (92), and mammals, including humans (93)(94)(95)(96)(97).…”

Section: Discussionmentioning

confidence: 99%

Stimulation of Mytilus galloprovincialis Hemocytes With Different Immune Challenges Induces Differential Transcriptomic, miRNomic, and Functional Responses

et al. 2020

Mediterranean mussels (Mytilus galloprovincialis) are marine bivalve molluscs with high resilience to biotic and abiotic stress. This resilience is one of the reasons why this species is such an interesting model for studying processes such as the immune response. In this work, we stimulated mussel hemocytes with poly I:C, β-glucans, and LPS and then sequenced hemocyte mRNAs (transcriptome) and microRNAs (miRNome) to investigate the molecular basis of the innate immune responses against these pathogen-associated molecular patterns (PAMPs). An immune transcriptome comprising 219,765 transcripts and an overview of the mussel miRNome based on 5,175,567 non-redundant miRNA reads were obtained. The expression analyses showed opposite results in the transcriptome and miRNome; LPS was the stimulus that triggered the highest transcriptomic response, with 648 differentially expressed genes (DEGs), while poly I:C was the stimulus that triggered the highest miRNA response, with 240 DE miRNAs. Our results reveal a powerful immune response to LPS as well as activation of certain immunometabolism- and ageing/senescence-related processes in response to all the immune challenges. Poly I:C exhibited powerful stimulating properties in mussels, since it triggered the highest miRNomic response and modulated important genes related to energy demand; these effects could be related to the stronger activation of these hemocytes (increased phagocytosis, increased NO synthesis, and increased velocity and accumulated distance). The transcriptome results suggest that after LPS stimulation, pathogen recognition, homeostasis and cell survival processes were activated, and phagocytosis was induced by LPS. β-glucans elicited a response related to cholesterol metabolism, which is important during the immune response, and it was the only stimulus that induced the synthesis of ROS. These results suggest a specific and distinct response of hemocytes to each stimulus from a transcriptomic, miRNomic, and functional point of view.

“…In this sense, it has been shown that the proliferation capacity of muscle cells, and the regeneration failure in aged muscles, are modulated by let-7 action (Drummond et al, 2011). The increase of amx-pax-7 transcripts after Lin28-1632 treatments could represent a response to a differentiation-inducing stimulus, as occurs in human oculopharyngeal muscular dystrophy, where satellite cells enter to an early proliferative arrest with overexpression of Pax7, MyoG, and Hmgb1, also accompanied by high levels of mature let-7 (Cappelletti et al, 2019). In turn, the increase of amx-myf-4 transcripts after Lin28 inhibition also supports the notion of an induced muscle differentiation, since the disorganization of muscle fibers was affected, a necessary event for mobilization of satellite cells and interstitial fibroblast cells.…”

Section: Discussionmentioning

confidence: 99%

Functional Characterization of the Lin28/let-7 Circuit During Forelimb Regeneration in Ambystoma mexicanum and Its Influence on Metabolic Reprogramming

Abella-Quintana

Espinal-Centeno

et al. 2020

Front. Cell Dev. Biol.