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

Area of Science:

• Molecular Biology
• Genetics
• Developmental Biology

Background:

• Homeodomain transcription factors (HD TFs) are crucial for vertebrate development.
• Mutations in HD TFs are linked to human diseases, but their pathogenic mechanisms are not fully understood.
• Cone-Rod Homeobox (CRX) is an HD TF implicated in photoreceptor development and inherited retinal diseases.

Approach:

• Investigated two CRX mutations (p.E80A and p.K88N) linked to dominant retinopathies using in vitro and knock-in mouse models.
• Analyzed molecular and functional evidence to elucidate the pathogenic mechanisms.
• Focused on CRX-mediated transactivation and DNA-binding specificity.

Key Points:

• The p.E80A mutation enhances CRX-mediated transactivation of target genes in developing photoreceptors.
• The p.K88N mutation alters CRX DNA-binding specificity, leading to ectopic binding and disrupted gene expression.
• Both mutations cause distinct retinal defects and impair photoreceptor maturation, differing from loss-of-function models.

Conclusions:

• Elucidated two novel gain-of-function mechanisms for CRX-associated retinopathies.
• Demonstrated the critical roles of specific CRX residues (E80 and K88) in transcriptional regulation.
• Highlighted the importance of precise transcriptional control by HD TFs for normal retinal development.