Ribosome biogenesis dysfunction leads to p53-mediated apoptosis and goblet cell differentiation of mouse intestinal stem/progenitor cells

Abstract

International audienceRibosome biogenesis is an essential cellular process. Its impairment is associated with developmental defects and increased risk of cancer. The in vivo cellular responses to defective ribosome biogenesis and the underlying molecular mechanisms are still incompletely understood. In particular, the consequences of impaired ribosome biogenesis within the intestinal epithelium in mammals have not been investigated so far. Here we adopted a genetic approach to investigate the role of Notchless (NLE), an essential actor of ribosome biogenesis, in the adult mouse intestinal lineage. Nle deficiency led to defects in the synthesis of large ribosomal subunit in crypts cells and resulted in the rapid elimination of intestinal stem cells and progenitors through distinct types of cellular responses, including apoptosis, cell cycle arrest and biased differentiation toward the goblet cell lineage. Similar observations were made using the rRNA transcription inhibitor CX-5461 on intestinal organoids culture. Importantly, we found that p53 activation was responsible for most of the cellular responses observed, including differentiation toward the goblet cell lineage. Moreover, we identify the goblet cell-specific marker Muc2 as a direct transcriptional target of p53. Nle-deficient ISCs and progenitors disappearance persisted in the absence of p53, underlying the existence of p53-independent cellular responses following defective ribosome biogenesis. Our data indicate that NLE is a crucial factor for intestinal homeostasis and provide new insights into how perturbations of ribosome biogenesis impact on cell fate decisions within the intestinal epithelium

Notchless defines a stage-specific requirement for ribosome biogenesis during lineage progression in adult skeletal myogenesis

“…Perturbations in this process can result in tissue-specific defects (Kondrashov et al, 2011). Among these, Nle participates in the formation of the large 60S subunit and has specific roles in proliferating and differentiating cells (Le Bouteiller et al, 2013;Stedman et al, 2015). Here, we show that Nle expression is rapidly upregulated at the transcriptional and protein level, during the quiescence-to-activation transition of satellite cells following muscle damage.…”

“…Conditional ablation of Nle in adult mouse haematopoietic stem cells (HSCs) results in their loss (Le Bouteiller et al, 2013) yet deletion of Nle in B lymphocytes showed that this regulator is not required for their maintenance. In another context, conditional ablation of Nle with an inducible Villin-CreERT2 resulted in the loss of intestinal stem and progenitor cells (Stedman et al, 2015).…”

The Crystal Structure of the Ubiquitin-like Domain of Ribosome Assembly Factor Ytm1 and Characterization of Its Interaction with the AAA-ATPase Midasin

“…Moreover, elevated levels of the proteins associated with the PeBoW complex have been found in many different types of human cancers, including neuroblastoma, hepatocellular carcinoma, and breast, colon, and ovarian cancers (42, 49 -55). Nle1 was also recently shown to be a crucial factor for intestinal homeostasis and a requirement for organogenesis, especially in axial skeleton formation in mice (13,56). Further investigations into the roles of WDR12 and Nle1 are needed to determine the mechanisms by which they are involved in cardiac function and intestinal homeostasis, but our work identifies that the interactions between the UBL domains of WDR12 and Nle1 with midasin are both evolutionarily conserved interactions important for the synthesis of eukaryotic ribosomes.…”

The R2TP chaperone assembles cellular machineries in intestinal CBC stem cells and progenitors

“…First, -galactosidase knock-in models showed that Rpap3 mRNA is expressed in the crypts where CBCs reside. Second, some R2TP clients are themselves preferentially active in the intestinal proliferative compartment: (i) under homeostatic conditions, ATR is required to signal defective DNA replication in the intestinal proliferative compartment (Ruzankina et al, 2007); (ii) markers of RNAPolI activity have been detected preferentially in the crypts and TA compartment with decreasing levels along the crypt-villus axis (Stedman et al, 2015); (iii), a recent transcriptomic analysis along the cryptvillus axis detected mRNAs encoding ribosomal, splicing and transcription components at the very bottom of the villus, but not along the villus or at the tip (Moor et al, 2018). All this supports a model in which ribosomal biogenesis, transcription machineries and PIKK complexes are built in the rapidly proliferating stem cells and progenitors.…”