Naylor Richard W, Han Hwa In, Hukriede Neil A, Davidson Alan J
Department of Molecular Medicine and Pathology, University of Auckland, Auckland 1142, New Zealand.
Department of Developmental Biology, Center for Critical Care Nephrology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Dev Biol. 2017 May 15;425(2):130-141. doi: 10.1016/j.ydbio.2017.03.027. Epub 2017 Mar 28.
During zebrafish embryogenesis the pronephric kidney arises from a small population of posterior mesoderm cells that then undergo expansion during early stages of renal organogenesis. While wnt8 is required for posterior mesoderm formation during gastrulation, it is also transiently expressed in the post-gastrula embryo in the intermediate mesoderm, the precursor to the pronephros and some blood/vascular lineages. Here, we show that knockdown of wnt8a, using a low dose of morpholino that does not disrupt early mesoderm patterning, reduces the number of kidney and blood cells. For the kidney, wnt8a deficiency decreases renal progenitor growth during early somitogenesis, as detected by EdU incorporation, but has no effect on apoptosis. The depletion of the renal progenitor pool in wnt8a knockdown embryos leads to cellular deficits in the pronephros at 24 hpf that are characterised by a shortened distal-most segment and stretched proximal tubule cells. A pulse of the canonical Wnt pathway agonist BIO during early somitogenesis is sufficient to rescue the size of the renal progenitor pool while longer treatment expands the number of kidney cells. Taken together, these observations indicate that Wnt8, in addition to its well-established role in posterior mesoderm patterning, also plays a later role as a factor that expands the renal progenitor pool prior to kidney morphogenesis.
在斑马鱼胚胎发育过程中，前肾起源于一小群后中胚层细胞，这些细胞随后在肾器官发生的早期阶段进行增殖。虽然Wnt8在原肠胚形成过程中对后中胚层的形成是必需的，但它在原肠胚后期的胚胎中，在中间中胚层（前肾和一些血液/血管谱系的前体）中也短暂表达。在这里，我们表明，使用低剂量的吗啉代寡核苷酸敲低Wnt8a，该剂量不会破坏早期中胚层的模式，会减少肾脏和血细胞的数量。对于肾脏，通过EdU掺入检测发现，Wnt8a缺乏会在早期体节发生期间降低肾祖细胞的生长，但对细胞凋亡没有影响。Wnt8a敲低胚胎中肾祖细胞池的耗尽导致24 hpf时前肾出现细胞缺陷，其特征是最远端节段缩短和近端小管细胞拉长。在早期体节发生期间给予经典Wnt信号通路激动剂BIO脉冲足以挽救肾祖细胞池的大小，而更长时间的处理会增加肾脏细胞的数量。综上所述，这些观察结果表明，Wnt8除了在后部中胚层模式形成中已确立的作用外，在肾脏形态发生之前作为一种扩大肾祖细胞池的因子也发挥了后期作用。
