Genetic and genomic analysis in Drosophila suggests that hematopoietic progenitors likely transition into terminal fates via intermediate progenitors (IPs) with some characteristics of either, but perhaps maintaining IP-specific markers. In the past, IPs have not been directly visualized and investigated due to lack of appropriate genetic tools. Here we report a split-GAL4 construct, CHIZ-GAL4, that identifies IPs as cells physically juxtaposed between true progenitors and differentiating hemocytes. IPs comprise a distinct cell type with a unique cell-cycle profile and they remain multipotent for all blood cell fates. Additionally, through their dynamic control of the Notch ligand, Serrate, IPs specify the fate of direct neighbors. The Ras pathway controls the number of IP cells and promotes their transition into differentiating cells. The split-GAL4 strategy is amenable for adoption in mammalian systems and would be invaluable in assigning trajectories that stem and progenitor populations follow as they develop into mature blood cells.

中文翻译：

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中间祖细胞在造血祖细胞及其分化后代之间提供过渡

果蝇的遗传和基因组分析表明，造血祖细胞可能会通过中间祖细胞（IP）转变为最终命运，而中间祖细胞则具有其中任一特征，但可能会保留IP特异性标记。过去，由于缺乏适当的遗传工具，无法对IP进行直接可视化和调查。在这里，我们报告一个split-GAL4结构CHIZ-GAL4，将IPs识别为在真正的祖细胞和分化的血细胞之间并列的细胞。IP包含具有独特细胞周期特征的独特细胞类型，并且对于所有血细胞命运都具有多能作用。此外，通过对Notch配体Serrate的动态控制，IP可以确定直接邻居的命运。Ras途径控制IP细胞的数量，并促进其向分化细胞的转变。GAL4分裂策略适合在哺乳动物系统中采用，并且在分配干和祖细胞发育成成熟血细胞时所遵循的轨迹方面将是无价的。