ASCL2 reciprocally controls key trophoblast lineage decisions during hemochorial placenta development

Abstract

Invasive trophoblast cells are critical to spiral artery remodeling in hemochorial placentation. Insufficient trophoblast cell invasion and vascular remodeling can lead to pregnancy disorders including preeclampsia, preterm birth, and intrauterine growth restriction. Previous studies in mice identified achaete-scute homolog 2 (ASCL2) as essential to extraembryonic development. We hypothesized that ASCL2 is a critical and conserved regulator of invasive trophoblast cell lineage development. In contrast to the mouse, the rat possesses deep intrauterine trophoblast cell invasion and spiral artery remodeling similar to human placentation. In this study, we investigated invasive/extravillous trophoblast (EVT) cell differentiation using human trophoblast stem (TS) cells and a loss-of-function mutant Ascl2 rat model. ASCL2 transcripts are expressed in the EVT column and junctional zone, which represent tissue sources of invasive trophoblast progenitor cells within human and rat placentation sites, respectively. Differentiation of human TS cells into EVT cells resulted in significant up-regulation of ASCL2 and several other transcripts indicative of EVT cell differentiation. Disruption of ASCL2 impaired EVT cell differentiation, as indicated by cell morphology and transcript profiles. RNA sequencing analysis of ASCL2-deficient trophoblast cells identified both down-regulation of EVT cell-associated transcripts and up-regulation of syncytiotrophoblast-associated transcripts, indicative of dual activating and repressing functions. ASCL2 deficiency in the rat impacted placental morphogenesis, resulting in junctional zone dysgenesis and failed intrauterine trophoblast cell invasion. ASCL2 acts as a critical and conserved regulator of invasive trophoblast cell lineage development and a modulator of the syncytiotrophoblast lineage.

Early Human Trophoblast Development: From Morphology To Function

“…Uterine spiral artery remodeling is an essential process for a successful pregnancy. Recently, achaete-scute family BHLH transcription factor 2 (ASCL2) was con rmed as a critical and conserved regulator of the invasive trophoblast cell lineage and ASCL2 expression was especially prominent in the endovascular EVT population [145]. In this study the authors did not stratify/differentiate between endoarterial, endovenous and endolymphatic trophoblasts.…”

Modeling Trophoblast Cell-Guided Uterine Spiral Artery Transformation in the Rat

“…Global-LOF Junctional zone dysgenesis and failed intrauterine trophoblast cell invasion [176] Ahr Global-LOF Maternal AHR regulates TCDD-induced endovascular trophoblast cell invasion [125] Tfpi Trophoblast-LOF Inhibition of endovascular and interstitial trophoblast cell invasion [48] a LOF, loss of function.…”

“…It is important to appreciate that all in vitro analyses are artificial and potentially misleading without complementary in vivo physiological assessments [ 5 ]. Invasive trophoblast cells can be effectively tracked in vivo [ 46 , 173 ] and the importance of a gene in a physiological context can be evaluated using lentiviral-mediated trophectoderm gene manipulation [ 174 , 175 ] and global genome edited rat models [ 48 , 64 , 125 , 176 ]. Roles for phosphoinositide 3-kinase (PI3K)/AKT/fos-related antigen 1 (FOSL1)/JUNB proto-oncogene (JUNB), HIF/KDM3A/MMP12, achaete-scute family bHLH transcription factor 2 (ASCL2), and tissue factor pathway inhibitor (TFPI) as conserved regulators of the invasive trophoblast cell lineage have been demonstrated using this strategy [ 47 , 48 , 64 , 176 , 177 , 178 , 179 , 180 ] ( Table 2 ).…”

“…Invasive trophoblast cells can be effectively tracked in vivo [ 46 , 173 ] and the importance of a gene in a physiological context can be evaluated using lentiviral-mediated trophectoderm gene manipulation [ 174 , 175 ] and global genome edited rat models [ 48 , 64 , 125 , 176 ]. Roles for phosphoinositide 3-kinase (PI3K)/AKT/fos-related antigen 1 (FOSL1)/JUNB proto-oncogene (JUNB), HIF/KDM3A/MMP12, achaete-scute family bHLH transcription factor 2 (ASCL2), and tissue factor pathway inhibitor (TFPI) as conserved regulators of the invasive trophoblast cell lineage have been demonstrated using this strategy [ 47 , 48 , 64 , 176 , 177 , 178 , 179 , 180 ] ( Table 2 ). PI3K/AKT signaling regulates FOSL1, which cooperates with JUNB, to form a heterodimer and a functional activator protein 1 (AP-1) transcription factor that facilitates endovascular trophoblast cell development during early stages of placentation [ 177 , 178 , 179 , 180 ].…”

“…As discussed above, the HIF/KDM3A/MMP12 regulatory circuit contributes to invasive trophoblast cell lineage decisions in response to hypoxia [ 47 , 64 ]. ASCL2, a transcription factor, and TFPI, a regulator of hemostasis, act independently to promote invasive trophoblast cell differentiation [ 48 , 176 ]. Results from the experimentation establish the feasibility of the outlined research strategy and identify key nodes of regulation impacting the invasive trophoblast cell lineage and trophoblast-guided uterine spiral artery remodeling.…”