Zbtb48 is a regulator of Mtfp1 expression in zebrafish

ZBTB48 (also known as TZAP) is a transcription factor that has previously been reported to bind to telomeres and act as a negative regulator of telomere length in human cell lines. To explore whether transcription factor activity and telomere length regulation are conserved at the organismal level in vertebrates, we generated a zbtb48-/- zebrafish line via CRISPR‒Cas genome editing. The zbtb48-/- mutants displayed no obvious physical or behavioral abnormalities in the first two generations. We found no statistically significant changes in telomere length in first-generation adults. However, for the gene regulatory aspect of Zbtb48, similar to that in human cancer cell lines, we observed downregulation of mtfp1 at both the mRNA and protein levels in the zbtb48-/- mutants. This suggests that mtfp1 is an evolutionarily conserved regulatory target of Zbtb48. Further investigation of the spatiotemporal expression of zbtb48 in previously published zebrafish data revealed low transcript expression in diverse tissues, except in germline stem cells and gametocytes of the gonads. Notably, Mtfp1 protein downregulation was detected in the ovaries of 40 dpf zbtb48-/- mutants and in the testes of both 40 dpf and 10.5-month-old zbtb48-/- mutants.

ZBTB48（又称TZAP）是一种转录因子，既往研究已报道其可结合端粒，并在人类细胞系中作为端粒长度的负调控因子发挥功能。为探究转录因子活性与端粒长度调控在脊椎动物个体水平是否具有进化保守性，我们通过CRISPR-Cas基因组编辑技术构建了zbtb48-/-斑马鱼品系。前两代zbtb48-/-突变体未表现出明显的外观或行为异常；第一代成年个体的端粒长度未出现具有统计学意义的显著改变。然而在Zbtb48的基因调控层面，与人类癌细胞系中的观测结果一致，我们在zbtb48-/-突变体中发现mtfp1的mRNA及蛋白水平均出现下调。这表明mtfp1是Zbtb48在进化上保守的调控靶标。对已发表的斑马鱼数据中zbtb48的时空表达谱进行进一步分析后发现，除生殖系干细胞与性腺内的配子细胞外，zbtb48在其他多种组织中的转录本表达水平较低。值得注意的是，我们在40 dpf (days post fertilization)的zbtb48-/-突变体卵巢，以及40 dpf和10.5月龄的zbtb48-/-突变体精巢中，均检测到Mtfp1蛋白表达下调。