Removal of nuclei in lens fiber cells is required for organelle-free zone (OFZ) formation during lens development. Defect in degradation of nuclear DNA leads to cataract formation. DNase2β degrades nuclear DNA of lens fiber cells during lens differentiation in mouse. Hsf4 is the principal heat shock transcription factor in lens and facilitates the lens differentiation. Knockout of Hsf4 in mouse and zebrafish resulted in lens developmental defect that was characterized by retaining of nuclei in lens fiber cells. In previous in vitro studies, we found that Hsf4 promoted DNase2β expression in human and mouse lens epithelial cells. In this study, it was found that, instead of DNase2β, DNase1l1l is uniquely expressed in zebrafish lens and was absent in Hsf4-/- zebrafish lens. Using CRISPR-Cas9 technology, a DNase1l1l knockout zebrafish line was constructed, which developed cataract. Deletion of DNase1l1l totally abrogated lens primary and secondary fiber cell denucleation process, whereas had little effect on the clearance of other organelles. The transcriptional regulation of DNase1l1l was dramatically impaired in Hsf4-/- zebrafish lens. Rescue of DNase1l1l mRNA into Hsf4-/- zebrafish embryos alleviated its defect in lens fiber cell denucleation. Our results in vivo demonstrated that DNase1l1l is the primary DNase responsible for nuclear DNA degradation in lens fiber cells, and Hsf4 can transcriptionally activate DNase1l1l expression in zebrafish.

中文翻译：

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剔除DNase11l1可消除晶状体脱核过程，并导致斑马鱼白内障。

晶状体发育过程中无细胞器区（OFZ）形成需要晶状体纤维细胞中的核去除。核DNA降解的缺陷导致白内障形成。DNase2β在小鼠晶状体分化过程中降解晶状体纤维细胞的核DNA。Hsf4是晶状体中主要的热激转录因子，可促进晶状体分化。Hsf4在小鼠和斑马鱼中的敲除导致晶状体发育缺陷，其特征是晶状体纤维细胞中保留了核。在先前的体外研究中，我们发现Hsf4促进了人和小鼠晶状体上皮细胞中DNase2β的表达。在这项研究中，发现DNase11l代替DNase2β在斑马鱼晶状体中独特表达，而在Hsf4-/-斑马鱼晶状体中不存在。使用CRISPR-Cas9技术，构建了DNase11l1敲除斑马鱼品系，该品系发展为白内障。DNase11l1的删除完全废除了晶状体初级和次级纤维细胞的去核过程，而对其他细胞器的清除几乎没有影响。在Hsf4-/-斑马鱼晶状体中，DNase11l1的转录调控显着受损。将DNase11l1 mRNA拯救为Hsf4-/-斑马鱼胚胎可减轻其在晶状体纤维细胞去核中的缺陷。我们的体内研究结果表明，DNase11l是负责晶状体纤维细胞中核DNA降解的主要DNase，而Hsf4可以转录激活斑马鱼中的DNase11l表达。在Hsf4-/-斑马鱼晶状体中，DNase11l1的转录调控显着受损。将DNase11l1 mRNA拯救为Hsf4-/-斑马鱼胚胎可减轻其在晶状体纤维细胞去核中的缺陷。我们的体内研究结果表明，DNase11l是负责晶状体纤维细胞中核DNA降解的主要DNase，而Hsf4可以转录激活斑马鱼中的DNase11l表达。在Hsf4-/-斑马鱼晶状体中，DNase11l1的转录调控显着受损。将DNase11l1 mRNA拯救为Hsf4-/-斑马鱼胚胎可减轻其在晶状体纤维细胞去核中的缺陷。我们的体内研究结果表明，DNase11l是负责晶状体纤维细胞中核DNA降解的主要DNase，而Hsf4可以转录激活斑马鱼中的DNase11l表达。