Baizabal José-Manuel, Covarrubias Luis
Department of Developmental Genetics and Molecular Physiology, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mor., Mexico.
Dev Biol. 2009 Jan 1;325(1):49-59. doi: 10.1016/j.ydbio.2008.09.024. Epub 2008 Oct 2.
Specific neuronal differentiation of Embryonic Stem Cells (ESCs) depends on their capacity to interpret environmental cues. At present, it is not clear at which stage of differentiation ESCs become competent to produce multiple neuronal lineages in response to the niche of the embryonic brain. To unfold the developmental potential of ESC-derived precursors, we transplanted these cells into the embryonic midbrain explants, where neurogenesis occurs as in normal midbrain development. Using this experimental design, we show that the transition from ESCs to Embryoid Body (EB) precursors is necessary to differentiate into Lmx1a(+)/Ptx3(+)/TH(+) dopaminergic neurons around the ventral midline of the midbrain. In addition, EB cells placed at other dorsal-ventral levels of the midbrain give rise to Nkx6.1(+) red nucleus (RN) neurons, Nkx2.2(+) ventral interneurons and Pax7(+) dorsal neurons at the correct positions. Notably, differentiation of ESCs into Neural Precursor Cells (NPCs) prior to transplantation markedly reduces specification at the Lmx1a, Nkx6.1 and Pax7 expression domains, without affecting neuronal differentiation. Finally, exposure to Fgf8 and Shh in vitro promotes commitment of some ESC-derived NPCs to differentiate into putative Lmx1a(+) dopaminergic neurons in the midbrain. Our data demonstrate intrinsic developmental potential differences among ESC-derived precursor populations.
胚胎干细胞（ESCs）的特异性神经元分化取决于它们解读环境信号的能力。目前尚不清楚胚胎干细胞在分化的哪个阶段能够响应胚胎脑的微环境而产生多种神经元谱系。为了揭示胚胎干细胞来源的前体细胞的发育潜能，我们将这些细胞移植到胚胎中脑外植体中，这里的神经发生过程与正常中脑发育相同。通过这种实验设计，我们发现从胚胎干细胞向胚状体（EB）前体细胞的转变对于在中脑腹侧中线周围分化为Lmx1a(+)/Ptx3(+)/TH(+)多巴胺能神经元是必要的。此外，置于中脑其他背腹水平的EB细胞在正确位置产生Nkx6.1(+)红核（RN）神经元、Nkx2.2(+)腹侧中间神经元和Pax7(+)背侧神经元。值得注意的是，移植前胚胎干细胞向神经前体细胞（NPCs）的分化显著降低了Lmx1a、Nkx6.1和Pax7表达域的特异性，但不影响神经元分化。最后，体外暴露于Fgf8和Shh可促进一些胚胎干细胞来源的NPCs定向分化为中脑假定的Lmx1a(+)多巴胺能神经元。我们的数据证明了胚胎干细胞来源的前体细胞群体之间存在内在的发育潜能差异。
