Metabolic Control over mTOR-Dependent Diapause-like State

Abstract

Regulation of embryonic diapause, dormancy that interrupts the tight connection between developmental stage and time, is still poorly understood. Here, we characterize the transcriptional and metabolite profiles of mouse diapause embryos and identify unique gene expression and metabolic signatures with activated lipolysis, glycolysis, and metabolic pathways regulated by AMPK. Lipolysis is increased due to mTORC2 repression, increasing fatty acids to support cell survival. We further show that starvation in pre-implantation ICM-derived mouse ESCs induces a reversible dormant state, transcriptionally mimicking the in vivo diapause stage. During starvation, Lkb1, an upstream kinase of AMPK, represses mTOR, which induces a reversible glycolytic and epigenetically H4K16Ac-negative, diapause-like state. Diapause furthermore activates expression of glutamine transporters SLC38A1/2. We show by genetic and small molecule inhibitors that glutamine transporters are essential for the H4K16Ac-negative, diapause state. These data suggest that mTORC1/2 inhibition, regulated by amino acid levels, is causal for diapause metabolism and epigenetic state. In BriefHussein et al. report that, during starvation, mTOR is repressed through LKB1-AMPK, inducing a reversible metabolically active but epigenetically silenced embryonic diapause-like state that upregulates expression of the glutamine transporters SLC38A1/2. These transporters are required for the H4K16ac-negative, diapause state.

microRNAs Regulating Human and Mouse Naïve Pluripotency

“…Importantly, we propose that the dynamics of the paused stage, embryonic diapause are affected by microRNA regulated stress and inflammation response genes. This is interesting in the light of recent publications that have revealed importance of stress response and inflammation in regulation of embryonic diapause and stem cell quiescence [35,88,89], and calls for further analysis on microRNA contribution in stress induced regulation of pause in development.…”

“…The transition from pre-to-post-implantation can be suspended in an intermediate state called diapause. To obtain a more complete picture of microRNAs potentially involved in regulating the diapause state, we combined a publicly available microarray-based profiling of diapause and re-activated embryos [37] with our RNA-seq of diapause and post-implantation embryos [35], using the strategy outlined in Figure 1A. We identified 379 consistent connections between 38 microRNA and 274 target genes, where a microRNA is up (down)-regulated, and its target gene is down (up)-regulated (Table S7).…”

“…In the past few years it has become clear that pluripotency is a very dynamic stage and cells progress through a continuum of pluripotent states with unique properties for each state [30,33,34]. The pre-to-post-implantation transition can be suspended under certain conditions, and this stage is called diapause [35] (Figure 1A). Let-7 has been previously shown to be a potential regulator of diapause [36,37].…”

“…In addition, we combined existing datasets in mouse pluripotent cells [38,39,40] in order to find microRNAs regulating important pathways during the naïve to primed transition, and in naïve and primed states. We also identified 38 microRNAs as potential regulators of diapause by combining existing microRNA expression data [37] with our RNA-seq of diapause and post-implantation embryos [35].…”

p38-MAPK mediated rRNA processing and translation regulation enables PrE differentiation during mouse blastocyst maturation

“…The mTOR signalling pathway (integrated by two mTOR containing complexes, mTORC1 and mTORC2) is a global regulator of translation, and maintains cellular energy homeostasis in response to extra-cellular stimuli such as growth factors and nutrient availability 47 . As part of mTORC1, mTOR specifically controls transcription and translation of ribosomal proteins, synthesis and processing of rRNAs and ribosome biogenesis, assembly and availability, that ultimately dictates general translation of all mRNA transcripts (mTORC2 is associated with co-translational protein degradation and lipolysis) 47,[63][64][65][66] . It was recently demonstrated that a prolonged state of in vitro developmental diapause (lasting 9-12 days) can be chemically induced in early stage (E3.5) mouse blastocysts upon dual inhibition of the mTORC1 and mTORC2, mimicking naturally occurring in vivo diapause 41 .…”