Analysis of Disease-Causing Mutations in Photoreceptor Transcription Factors

Authors: Julia Medicis, Barry Knox

SUNY Campus: Purchase College

Presentation Type: Poster

Location: Old Union Hall

Presentation #: 14

Timeslot: Session C 1:45-2:45 PM

Abstract: Cone-Rod Homeobox (CRX) and Neural Leucine Zipper (NRL) are two key transcription factors that regulate many genes in photoreceptors and are required for detecting light. Mutations in CRX and NRL can cause many inherited retinal disorders such as Retinitis Pigmentosa, Cone-Rod Dystrophy and Leber's Congenital Amaurosis. CRX is a paired-like homeodomain transcription factor. Previous work has shown that point-mutations in CRX can cause alterations in transcriptional activation and DNA binding. However, there is a difference between the severity of the disease phenotype and the various point mutations in the DNA binding domain. To clarify whether protein stability or cellular localization contribute to these differences, western blots and fluorescence microscopy were performed using transiently transfected cells. We found the R41Q, E80A, K88N and R90W variants were expressed to similar levels and nuclear localization. These findings indicate that more complex interactions of CRX with transcriptional complexes may be needed to explain the severity of the mutant phenotypes. NRL is a basic leucine zipper transcription factor required for rod differentiation and gene expression which functions as a dimer. To investigate whether mutants with low activity could function with wildtype molecules in a heterodimer, co-transfection experiments were performed. The variant L160P, which was not able to activate the rhodopsin promoter alone, was able to activate transcription in the presence of wild type molecules. Future work to understand the structural basis for pathogenesis of CRX and NRL mutations is required.