You are here : Version anglaise > Training > Doctoral studies

Publié le October 5, 2020 | Updated on October 8, 2020

Rôle du récepteur gp130 et de ses effecteurs dans la reprogrammation à l’état naïf des cellules souches embryonnaires pluripotentes humaines

Claire SANTAMARIA - Under the supervision of Pierre Savatier

 Pluripotency exist in at least two different states, naïve and primed. Mouse pluripotent stem cells (PSCs) self-renew in the naive state of pluripotency under the action of the LIF/GP130 signalling pathway. In contrast, human PSCs self-renew in the primed state of pluripotency under the action of both the Activin/Smads and FGF2/MAPK signalling pathways. Naïve and primed states differ by a number of key parameters including self-renewal stability, chromatin opening, energy metabolism, cell-cycle regulation and genome stability. Thus, human PSCs are seemingly more prone to genomic rearrangements and spontaneous differentiation. The ultimate goal of this study is to generate human PSCs capable of long-term self-renewal in the naïve state of pluripotency, similar to mouse PSCs. Specifically, the study aimed to study the role of transcription factors, phosphatases and kinases, which are recruited to the GP130 receptor, in reprogramming conventional human PSCs to the naive state. 

We used G-CSFR:GP130 chimeric receptors composed of the extracellular domain of the G-CSF receptor and the cytoplasmic domain of the GP130 signal transducer. Five mutant receptors were generated. Three of them harbour point mutations that prevent tyrosine phosphorylation and subsequent recruitment of transcription factor STAT3, phosphatase SHP2, or both. The other two mutants harbour small deletions that prevent recruitment and activation of the Src-related kinases HCK and YES. Human PSCs stably expressing a tamoxifen-activable STAT3, namely STAT3-ER, were used in all subsequent experiments. Indeed, we previously reported that the synergistic action of tamoxifen-activated STAT3-ER and LIF is necessary for sustaining self-renewal of human PSCs in the absence pf FGF2 (Chen et al., Nat Commun, 6:7095, 2015). Human PSCs expressing both STAT3-ER and each one of the 6 G-CSF:GP130 receptors were generated. Their ability to self-renew under the action of G-CSF and tamoxifen was explored. 

Human PSCs expressing either wild-type, STAT3-binding deficient, SHP2-binding-deficient, or HCK-binding-deficient G-CSFR:GP130 chimeric receptor responded to G-CSF stimulation and self-renewed in the absence of FGF2. In contrast, human PSCs expressing the YES-binding deficient receptor lost this ability and differentiated. 

This result strongly suggests that the YES kinase is essential to sustain pluripotency in human FGF2-deprived PSCs. This approach makes it possible to identify key factors for reprogramming human PSCs to naïve-state pluripotency.