Walsh C, Reid C
Neurogenetics Laboratory, Beth Israel Hospital/Harvard Medical School, Boston, MA 02115, USA.
Ciba Found Symp. 1995;193:21-40; discussion 59-70. doi: 10.1002/9780470514795.ch2.
Knowledge of cell lineage in the cortex is important for understanding normal development as well as brain malformations. We studied cell lineage in rats by injecting a library of up to 3400 retroviruses, distinguishable by PCR analysis and encoding alkaline phosphatase, at E14-19. Histological analysis at P15 revealed normal cell morphology and allowed identification of about 80% of all labelled cells. PCR amplification of DNA tags allowed clonal analysis. Cortical cells labelled at E15 formed clustered or widespread clones with equal frequency. Clustered clones contained one to four cells within about 1 mm that had similar morphology and laminar location. However, 48% of cortical clones contained multiple cell types with widely different locations (2.1-6.7 mm; mean, 3.8 mm). Widespread clones contained two to four 'subunits' (one to five neurons each), spaced at apparent intervals of 2-3 mm, with each subunit morphologically indistinguishable from a clustered clone. Distinct subunits in the same clone usually differed in laminar location suggesting sequential formation. Clones labelled at E17 contained fewer neurons and up to two subunits. Clustered clones seem to be produced by stationary progenitors, whereas progenitors of clusters may themselves be produced by migratory, multipotential cells.
了解皮质中的细胞谱系对于理解正常发育以及脑畸形至关重要。我们在E14 - 19期通过注射一个包含多达3400种逆转录病毒的文库来研究大鼠的细胞谱系，这些逆转录病毒可通过PCR分析区分并编码碱性磷酸酶。在P15期进行的组织学分析揭示了正常的细胞形态，并能够识别所有标记细胞中的约80%。对DNA标签进行PCR扩增可进行克隆分析。在E15期标记的皮质细胞形成聚集或广泛分布的克隆，频率相同。聚集的克隆在约1毫米范围内包含一到四个细胞，这些细胞具有相似的形态和层状位置。然而，48%的皮质克隆包含多种位置差异很大的细胞类型（2.1 - 6.7毫米；平均为3.8毫米）。广泛分布的克隆包含两到四个“亚单位”（每个亚单位有一到五个神经元），间隔约2 - 3毫米，每个亚单位在形态上与聚集的克隆无法区分。同一克隆中的不同亚单位通常在层状位置上有所不同，表明是顺序形成的。在E17期标记的克隆包含较少的神经元和最多两个亚单位。聚集的克隆似乎由静止的祖细胞产生，而聚集克隆的祖细胞本身可能由迁移的多能细胞产生。
