Lin T P, Labosky P A, Grabel L B, Kozak C A, Pitman J L, Kleeman J, MacLeod C L
Department of Medicine, University of California at San Diego, La Jolla 92093-0961.
Dev Biol. 1994 Nov;166(1):170-9. doi: 10.1006/dbio.1994.1305.
We previously reported the isolation of a cDNA clone for a homeobox-containing gene designated Pem, shown by Northern analysis of Day 7 through Day 16 mouse embryos to be expressed in extraembryonic tissues. In this study, Pem gene expression was further examined using in situ hybridization and immunocytochemistry to determine the spatial distribution of Pem transcripts and protein in peri-implantation embryos and in embryoid bodies (EBs). Low amounts of Pem mRNA were detected in undifferentiated EBs. When EBs were induced to differentiate, the outer cell layer of visceral or parietal endoderm expressed both Pem mRNA and protein. In developing embryos, no Pem protein was detectable in the uncompacted morula; 12% of the nuclei in compacted morulae were Pem positive, while 25% of the blastocyst trophectoderm and 15% of inner cell mass cells expressed Pem protein. Shortly after implantation, in 5.5 and 6.5 d.p.c. embryos, Pem expression was limited to extraembryonic tissues and was present in distal and proximal visceral endoderm, parietal endoderm, and ectoplacental cone. By 7.5-8.5 d.p.c. neither Pem RNA nor protein was found in the distal squamous visceral endoderm, which surrounds the embryonic region of the egg cylinder, nor in the parietal endoderm. Expression was retained in the proximal columnar epithelium of the visceral endoderm. Prominent Pem expression was observed in the chorion, in trophoblast-derived cells of the ectoplacental cone, and in secondary giant cells, localized in the nuclear compartment. Pem was localized to the X chromosome and found to be expressed in cell lineages where only the maternal X chromosome is active. The data indicate a possible role for Pem in regulating genes involved in the differentiation of extraembryonic tissues.
我们之前报道了一个含有同源异型框基因的cDNA克隆的分离，该基因命名为Pem，通过对第7天至第16天小鼠胚胎的Northern分析表明，它在胚外组织中表达。在本研究中，使用原位杂交和免疫细胞化学进一步检测了Pem基因的表达，以确定Pem转录本和蛋白质在着床前胚胎和胚状体（EBs）中的空间分布。在未分化的EBs中检测到少量的Pem mRNA。当EBs被诱导分化时，脏层或壁层内胚层的外层细胞同时表达Pem mRNA和蛋白质。在发育中的胚胎中，未紧实的桑椹胚中未检测到Pem蛋白；紧实桑椹胚中12%的细胞核为Pem阳性，而囊胚滋养外胚层中25%的细胞和内细胞团中15%的细胞表达Pem蛋白。着床后不久，在妊娠5.5天和6.5天的胚胎中，Pem表达仅限于胚外组织，存在于远端和近端脏层内胚层、壁层内胚层和外胎盘锥中。到妊娠7.5 - 8.5天时，在围绕卵柱胚胎区域的远端鳞状脏层内胚层和壁层内胚层中均未发现Pem RNA和蛋白质。在内脏层近端柱状上皮中仍保留表达。在绒毛膜、外胎盘锥的滋养层来源细胞以及位于核区的次级巨细胞中观察到显著的Pem表达。Pem定位于X染色体，并且发现在仅母本X染色体活跃的细胞谱系中表达。数据表明Pem在调节参与胚外组织分化的基因方面可能发挥作用。
