Zhao Rong, Fan Yali, Li Jieyan, Li Lin, Yin Chenghong
Department of Obstetrics, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, Chaoyang, Beijing, 100026, China.
Central Laboratory, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, Dongcheng, Beijing, 100006, China.
Orphanet J Rare Dis. 2025 Jun 7;20(1):289. doi: 10.1186/s13023-025-03833-x.
SALL4 is a transcription factor that plays a crucial role in early embryonic development and organogenesis, particularly in kidney development, although its specific regulatory mechanisms remain unclear.
We performed whole-exome sequencing (WES) to identify pathogenic variants in a fetus with unilateral renal agenesis and confirmed a variant in SALL4 using Sanger sequencing. The expression of wild-type or mutant SALL4 proteins in cells was used to determine whether the level and localization of the proteins were altered by the SALL4 variant. RNA sequencing was used to identify differentially expressed genes at the transcriptome level due to the SALL4 mutant protein. Finally, key differentially expressed proteins were verified using quantitative PCR and western blotting.
A novel truncating mutation in SALL4 was identified through WES in a fetus with unilateral renal agenesis. Expression of the truncated SALL4 protein in cells revealed its predominant cytoplasmic localization, unlike the wild-type SALL4 protein, which was localized to the nucleus. Further RNA sequencing analysis indicated that the mutant SALL4 protein lost its transcriptional activation ability, with 1047 genes markedly downregulated compared to cells expressing wild-type SALL4. These downregulated genes were primarily enriched in biological processes such as cell activation, salt transmembrane transporter activity, and calcium ion binding. Additionally, we found that these differentially expressed genes mainly regulated fetal ureteric bud cells, suggesting that SALL4 mutations may ultimately lead to unilateral renal agenesis by affecting the development and function of fetal ureteric bud cells. Among these genes, two proteins crucial for kidney development, WNT11 and PAX2, were significantly downregulated in cells expressing the truncated SALL4 protein, suggesting that WNT11 and PAX2 may mediate the regulatory role of SALL4 in kidney development.
This study elucidated the molecular mechanism by which SALL4 mutations lead to renal agenesis.
SALL4是一种转录因子，在早期胚胎发育和器官形成中发挥关键作用，尤其是在肾脏发育中，但其具体调控机制仍不清楚。
我们对一名单侧肾缺如胎儿进行了全外显子测序（WES）以鉴定致病变异，并使用桑格测序法确认了SALL4中的一个变异。通过在细胞中表达野生型或突变型SALL4蛋白，来确定SALL4变异是否改变了蛋白的水平和定位。利用RNA测序来鉴定由于SALL4突变蛋白导致的转录组水平上差异表达的基因。最后，使用定量PCR和蛋白质印迹法对关键的差异表达蛋白进行验证。
通过对一名单侧肾缺如胎儿进行WES，鉴定出SALL4中一个新的截短突变。截短的SALL4蛋白在细胞中的表达显示其主要定位于细胞质，这与定位于细胞核的野生型SALL4蛋白不同。进一步的RNA测序分析表明，突变的SALL4蛋白失去了转录激活能力，与表达野生型SALL4的细胞相比，有1047个基因显著下调。这些下调的基因主要富集在细胞激活、盐跨膜转运体活性和钙离子结合等生物学过程中。此外，我们发现这些差异表达的基因主要调节胎儿输尿管芽细胞，这表明SALL4突变可能最终通过影响胎儿输尿管芽细胞的发育和功能导致单侧肾缺如。在这些基因中，对肾脏发育至关重要的两种蛋白WNT11和PAX2，在表达截短SALL4蛋白的细胞中显著下调，这表明WNT11和PAX2可能介导SALL4在肾脏发育中的调控作用。
本研究阐明了SALL4突变导致肾缺如的分子机制。
