Missense mutations in CRX homeodomain cause dominant retinopathies through two distinct mechanisms

• Published in: eLife Vol. 12
• Main Authors: Zheng, Yiqiao, Sun, Chi, Zhang, Xiaodong, Ruzycki, Philip A, Chen, Shiming
• Format: Journal Article
• Language: English
• Published: 14.11.2023
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.87147.4

Homeodomain transcription factors (HD TFs) are instrumental to vertebrate development. Mutations in HD TFs have been linked to human diseases, but their pathogenic mechanisms remain elusive. Here, we use Cone-Rod Homeobox ( CRX ) as a model to decipher the disease-causing mechanisms of two HD mutations, p.E80A and p.K88N, that produce severe dominant retinopathies. Through integrated analysis of molecular and functional evidence in vitro and in knock-in mouse models, we uncover two novel gain-of-function mechanisms: p.E80A increases CRX-mediated transactivation of canonical CRX target genes in developing photoreceptors; p.K88N alters CRX DNA-binding specificity resulting in binding at ectopic sites and severe perturbation of CRX target gene expression. Both mechanisms produce novel retinal morphological defects and hinder photoreceptor maturation distinct from loss-of-function models. This study reveals the distinct roles of E80 and K88 residues in CRX HD regulatory functions and emphasizes the importance of transcriptional precision in normal development.