CITED2 is a conserved regulator of deep placentation (Rat I)

Establishment of the hemochorial placentation site requires the exodus of trophoblast cells from the placenta and their transformative actions on the uterine vasculature, which is a critical but poorly understood developmental process. CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxyl terminal domain 2 (CITED2) is a member of the CITED protein family of co-regulators and has been shown to possess roles in embryogenesis, including placenta development. We examined the involvement of CITED2 in the rat, which exhibits deep hemochorial placentation, a feature it shares with the human. CITED2 is distinctively expressed in the junctional zone compartment of the rat placentation site and in intrauterine invasive trophoblast cells. Homozygous disruption of the rat Cited2 locus resulted in placental and fetal growth restriction and abnormalities in heart and lung development, which are also characteristic of the CITED deficient mouse model. However, other features of the mouse Cited2 null phenotype, including exencephaly, adrenal gland agenesis, and prenatal lethality were not associated with CITED2 deficiency in the rat. Trophoblast-specific lentiviral CITED2 knockdown in the rat yielded a growth arrested placental phenotype. Smaller Cited2 null placentas were associated with a growth restricted junctional zone and coincided with a delay in intrauterine trophoblast cell invasion. Invasive trophoblast cells arise from the junctional zone. Transcriptomes of the junctional zone, the invasive trophoblast cell lineage, and differentiating trophoblast stem cells were affected by CITED2 disruption, as were placental adaptations to hypoxia and exposure to viral mimetics. Evidence for the conservation of CITED2 expression in human placental tissue and conserved actions in invasive/extravillous trophoblast cell development were demonstrated. We conclude that CITED2 is a conserved regulator of deep hemochorial placentation.血绒毛膜胎盘形成位点（hemochorial placentation site）的建立，需要滋养层细胞（trophoblast cell）从胎盘迁出并对子宫血管进行重塑，这是一个关键但目前尚未完全阐明的发育过程。含富谷氨酸/天冬氨酸羧基末端结构域的CBP/p300相互作用反式激活因子2（CITED2）属于共调节因子CITED蛋白家族，已被证实参与胚胎发生（embryogenesis）过程，包括胎盘发育。本研究以具有深层血绒毛膜胎盘形成特性（该特性与人类共有）的大鼠为模型，探究了CITED2的相关作用：CITED2在大鼠胎盘形成位点的交界区（junctional zone）区域以及宫内侵袭性滋养层细胞中特异性表达。大鼠Cited2基因座（locus）的纯合破坏会导致胎盘与胎儿生长受限，以及心脏和肺发育异常，这与CITED2缺陷小鼠模型的表型特征一致；然而，小鼠Cited2纯合缺失表型的其他特征，如露脑畸形（exencephaly）、肾上腺发育不全（adrenal gland agenesis）及产前致死（prenatal lethality），在大鼠CITED2缺陷模型中并未出现。在大鼠中进行滋养层细胞特异性慢病毒（lentiviral）介导的CITED2敲低，可导致胎盘生长停滞的表型。纯合缺失Cited2的胎盘体积更小，伴随交界区生长受限，且与宫内滋养层细胞侵袭延迟相关，而侵袭性滋养层细胞正起源于交界区。CITED2破坏会影响交界区、侵袭性滋养层细胞谱系以及分化中滋养层干细胞的转录组（transcriptome），胎盘对缺氧（hypoxia）及病毒模拟物（viral mimetic）暴露的适应性反应也受其影响。本研究证实了CITED2在人类胎盘组织中表达保守，且其在侵袭性/绒毛外滋养层细胞（extravillous trophoblast cell）发育中的功能同样具有保守性。综上，CITED2是深层血绒毛膜胎盘形成的保守调节因子。