Cell Polarity Regulator PARD6B Is Essential for Trophectoderm Formation in the Preimplantation Mouse Embryo
Cell Polarity Regulator PARD6B Is Essential for Trophectoderm Formation in the Preimplantation Mouse Embryo
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DOI：
10.1095/biolreprod.110.084400
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发表时间：
2010-09-01
影响因子：
3.6
通讯作者：
Alarcon, Vernadeth B.
中科院分区：
文献类型：
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作者：
Alarcon, Vernadeth B.
在植入前小鼠发育中，首先建立的细胞谱系是滋养外胚层（TE）和内细胞团。TE具有上皮特征，包括顶端-基底细胞极性和细胞间连接，这对于在胚泡中产生充满液体的腔至关重要。秀丽隐杆线虫中的分配缺陷（par）基因同源物是细胞极性的关键调节因子。然而，它们在调节TE分化和囊胚形成中的作用仍不清楚。在这里，小鼠Pard 6 b，一个同源的PAR-6基因和PAR-非典型蛋白激酶C（aPKC）复合物的组成部分，的作用进行了研究。通过显微注射RNA干扰构建体到受精卵中来敲低Pard 6 b表达。Pard 6 b基因敲除的胚胎正常分裂和致密，但未能形成囊胚腔。空化失败可能是细胞间连接缺陷的结果，因为Pard 6 b敲低导致肌动蛋白丝和TJP 1（ZO-1）紧密连接（TJ）蛋白的异常分布，并干扰含有正常胚胎细胞的嵌合体中的空化。缺陷性TJ形成可能是由异常细胞极化引起的，因为在Pard 6 b敲低胚胎中不存在PRKCZ（aPKCzeta）的顶端定位。Pard 6 b敲除还减少了外细胞中TE谱系转录因子CDX 2的表达。TEAD 4是Cdx 2表达和空腔形成所需的转录激活因子，对Pard 6 b的转录不是必需的。两者合计，Pard 6 b是必要的囊胚形态发生，特别是TE-特定功能的发展，即，顶-基底细胞极性，形成TJ细胞旁渗透性密封，和上调Cdx 2的表达。
In preimplantation mouse development, the first cell lineages to be established are the trophectoderm (TE) and inner cell mass. TE possesses epithelial features, including apical-basal cell polarity and intercellular junctions, which are crucial to generate a fluid-filled cavity in the blastocyst. Homo logs of the partitioning defective (par) genes in Caenorhabditis elegans are critical regulators of cell polarity. However, their roles in regulating TE differentiation and blastocyst formation remain unclear. Here, the role of mouse Pard6b, a homolog of par-6 gene and a component of the PAR-atypical protein kinase C (aPKC) complex, was investigated. Pard6b expression was knocked down by microinjecting RNA interference construct into zygotes. Pard6b-knockdown embryos cleaved and compacted normally but failed to form the blastocyst cavity. The cavitation failure is likely the result of defective intercellular junctions, because Pard6b knockdown caused abnormal distribution of actin filaments and TJP1 (ZO-1) tight junction (TJ) protein and interfered with cavitation in chimeras containing cells from normal embryos. Defective TJ formation may be caused by abnormal cell polarization, because the apical localization of PRKCZ (aPKCzeta) was absent in Pard6b-knockdown embryos. Pard6b knockdown also diminished the expression of CDX2, a TE-lineage transcription factor, in the outer cells. TEAD4, a transcriptional activator that is required for Cdx2 expression and cavity formation, was not essential for the transcription of Pard6b. Taken together, Pard6b is necessary for blastocyst morphogenesis, particularly the development of TE-specific features-namely, the apical-basal cell polarity, formation of TJ paracellular permeability sealing, and up-regulated expression of Cdx2.