Nod1-dependent NF-kB activation initiates hematopoietic stem cell specification in response to small Rho GTPases

Abstract

SummaryThe possibility of specifying functional hematopoietic stem and progenitor cells (HSPCs) from human pluripotent stem cells (hPSCs) would overcome current limitations related to HSPC transplantation. However, generating hPSC-derived HSPCs has been elusive, necessitating a better understanding of the native developmental mechanisms that trigger HSPC specification. Here, we revealedin vivoan intrinsic inflammatory mechanism triggered by Nod1 that drives early hemogenic endothelium (HE) patterning to specify HSPCs. Our genetic and chemical experiments showed that HSPCs failed to specify in the absence of Nod1 and its downstream kinase Ripk2. Rescue experiments demonstrated that Nod1 and Ripk2 acted through NF-kB, and that small Rho GTPases are at the apex of this mechanism. Manipulation of NOD1 in a human system of hPSCs differentiation towards the definitive hematopoietic lineage indicated functional conservation. This work establishes the RAC1-NOD1-RIPK2-NFkB axis as the earliest inflammatory inductor that intrinsically primes the HE for proper HSPC specification. Manipulation of this pathway could help derive a competent HE amenable to specify functional patient specific HSPCs for the treatment of blood disorders.HighlightsNod1 specifies HSPCsin vivothrough the early induction of hemogenic endothelium.Nod1-Ripk2 controls HSPC specification by activating the inflammatory master TF NF-kB.Nod1 links small Rho GTPases with pro-inflammatory signaling during the genesis of HSPCs.The function of NOD1 is conserved in the development of definitive human HSPCs.