Allen N D, Barton S C, Hilton K, Norris M L, Surani M A
AFRC Babraham Institute, Cambridge, UK.
Development. 1994 Jun;120(6):1473-82. doi: 10.1242/dev.120.6.1473.
A detailed analysis of the developmental potential of parthenogenetic embryonic stem cells (PGES) was made in vivo and in vitro, and a comparison was made with the development of cells from parthenogenetic embryos (PG). In vivo, in chimeras with normal host cells (N), PGES cells showed a restricted tissue distribution consistent with that of PG cells, suggesting faithful imprinting in PGES cells with respect to genes involved in lineage allocation and differentiation. Restricted developmental potential was also observed in teratomas formed by ectopic transfer under the kidney capsule. In contrast, the classic phenotype of growth retardation normally observed in PG<==>N chimeras was not seen, suggesting aberrant regulation in PGES cells of genes involved in growth regulation. We also analysed the expression of known imprinted genes after ES cell differentiation. Igf2, H19 and Igf2r were all appropriately expressed in the PGES derived cells following induction of differentiation in vitro with all-trans retinoic acid or DMSO, when compared with control (D3) and androgenetic ES cells (AGES). Interestingly, H19 was found to be expressed at high levels following differentiation of the AGES cells. Due to the unexpected normal growth regulation of PGES<==>N chimeras we also examined Igf2 expression in PGES derived cells differentiated in vivo and found that this gene was still repressed. Our studies show that PGES cells provide a valuable in vitro model system to study the effects of imprinting on cell differentiation and they also provide invaluable material for extensive molecular studies on imprinted genes. In addition, the aberrant growth phenotype observed in chimeras has implications for mechanisms that regulate the somatic establishment and maintenance of some imprints. This is of particular interest as aberrant imprinting has recently been invoked in the etiology of some human diseases.
对孤雌生殖胚胎干细胞（PGES）的发育潜能进行了体内和体外的详细分析，并与孤雌生殖胚胎（PG）细胞的发育情况进行了比较。在体内，在与正常宿主细胞（N）形成的嵌合体中，PGES细胞显示出与PG细胞一致的受限组织分布，这表明PGES细胞在参与谱系分配和分化的基因方面存在忠实的印记。在肾包膜下异位移植形成的畸胎瘤中也观察到了受限的发育潜能。相比之下，在PG<==>N嵌合体中通常观察到的生长迟缓的经典表型并未出现，这表明PGES细胞中参与生长调节的基因存在异常调控。我们还分析了ES细胞分化后已知印记基因的表达情况。与对照（D3）和雄核发育胚胎干细胞（AGES）相比，在用全反式维甲酸或二甲基亚砜体外诱导分化后，Igf2、H19和Igf2r在PGES衍生细胞中均得到了适当表达。有趣的是，发现AGES细胞分化后H19表达水平较高。由于PGES<==>N嵌合体出现了意外的正常生长调节情况，我们还检测了在体内分化的PGES衍生细胞中的Igf2表达，发现该基因仍然受到抑制。我们的研究表明，PGES细胞为研究印记对细胞分化的影响提供了一个有价值的体外模型系统，同时也为印记基因的广泛分子研究提供了宝贵的材料。此外，在嵌合体中观察到的异常生长表型对调节某些印记的体细胞建立和维持的机制具有重要意义。这一点特别有趣，因为最近在一些人类疾病的病因学中提到了异常印记。
