Biology subjects

Jamet, S.

Publications and source records attributed to Jamet, S..

2 recordsLinked to original sources

bioRxiv2020

Satellite cell expansion is mediated by P-eIF2α dependent Tacc3 translation

Translational control of gene expression is an important regulator of adult stem cell quiescence, activation and self-renewal. In skeletal muscle, quiescent satellite cells maintain low levels of protein synthesis, mediated in part through the phosphorylation of eIF2 (P-eIF2). Pharmacological inhibition of the eIF2 phosphatase with the small molecule sal003 maintains P-eIF2 and permits the expansion of satellite cells ex vivo. Paradoxically, P-eIF2 also increases the translation of specific mRNAs, which is mediated by P-eIF2 dependent readthrough of inhibitory upstream open reading frames (uORFs). Here, we ask whether P-eIF2 dependent mRNA translation enables expansion of satellite cells. Using transcriptomic and proteomic analyses, we show a number of genes associated with the assembly of the spindle pole to be upregulated at the level of protein, without corresponding change in mRNA levels, in satellite cells expanded in the presence of sal003. We show that uORFs in the 5UTR of mRNA for the mitotic spindle stability gene Tacc3 direct P-eIF2 dependent translation. Satellite cells deficient for TACC3 exhibit defects in expansion, self-renewal and regeneration of skeletal muscle. SignificanceTranslational control of gene expression has emerged as an important regulator of adult stem cell populations, which maintain low levels of protein synthesis. In adult muscle stem cells, or satellite cells, a portrait of translational control has emerged whereby multiple repression mechanisms prevent the translation of specific mRNAs. It remains unclear how other mRNAs escape repression and are efficiently translated. We show that within the context of low global rates of protein synthesis, satellite cell expansion occurs through the selective translation of Tacc3 mRNA. Tacc3 deficient satellite cells expand poorly, leading to defects in skeletal muscle regeneration. Our study provides a more complete picture of translational control of gene expression in adult stem cell populations.

cell biology↗

bioRxiv2019

Ex vivo expansion of skeletal muscle stem cells with a novel small compound inhibitor of eIF2α dephosphorylation

BACKGROUNDRegeneration of adult tissues requires the activity of rare, mitotically quiescent somatic stem cells. These features are illustrated by the muscle stem cell (MuSC), also known as the satellite cell for its satellite position underneath the basal lamina of the myofiber. Isolation of MuSCs results in their rapid activation of the myogenic program and their subsequent culture ex vivo leads to loss of stem cell regenerative capacity. These shortcomings make MuSCs difficult to study, manipulate and prevent cell based therapies. We have previously shown that muscle stem cells (MuSCs) require tightly regulated protein synthesis through the phosphorylation of eIF2. Sal003, an analog of salubrinal that blocks eIF2 dephosphorylation, promotes ex vivo expansion of MuSCs retaining regenerative capacity after engraftment into the Dmdmdx mouse model of Duchenne muscular dystrophy.\n\nMETHODSSince micromolar concentrations of sal003 (10M) are required to expand MuSCs ex vivo, we undertook a structure relations study to identify novel sal003 analogs with efficacy at lower concentrations. We demonstrate ex vivo expansion of MuSCs isolated from wild-type and mdx mice using new compounds, and use CRISPR/Cas9 genome editing tools to restore dystrophin expression in cultured MuSCs.\n\nRESULTSHere, we have synthesized and screened chemical analogs of sal003 to identify a novel compound promoting the ex vivo expansion of MuSCs. The novel compound expands wild-type and mdx MuSCs more efficiently than sal003 and also prolongs culture of primary myoblasts from isolated MuSCs.\n\nCONCLUSIONSWe identify a novel sal003 analog, C10, with increased potency at lower concentrations. Culture conditions including sal003 or C10 can extend culture of primary myoblasts from isolated MuSCs, which we predict will enable their further study, genetic manipulation and cell based therapies.

cell biology↗