| Description |
Axenfeld-Rieger syndrome (ARS) is a rare developmental anomaly with genetic heterogeneity. However, the variants in the currently known ARS causative genes PITX2 and FOXC1 explain only about 40% of ARS, leaving close to 60% of ARS patients with unknown genetic etiology. Here we performed genome-wide linkage analysis and whole-genome sequencing in a Chinese ARS family and then identified the presence of a heterozygous deletion approximately 570 kb (named LOH-1) in the intergenic sequence upstream of PITX2. Knockout of homologous sequences of LOH-1 in mice revealed the phenotype of ARS. RNA-seq and RT-qPCR showed a significant decrease in Pitx2 gene expression levels in LOH-1-/- mice, while Foxc1 expression was not altered. Potential enhancer region (named LOH-E1) was found in LOH-1 by bioinformatics analysis and CHIP-seq, and deletion of LOH-E1 resulted in significant downregulation of the PITX2 gene. Mechanistically, we found that RAD21, a critical component of the cohesin complex which loops chromatin to bring enhancer and promoter together, can be recruited by LOH-E1. And knocking down RAD21 reduces PITX2 expression. Taken together, these findings suggest that the potential enhancer region LOH-E1 may remotely regulate the expression of PITX2 through cohesin-mediated loop domains and causes ARS when it is lacking. |
