Description
Retinitis Pigmentosa (adRP) is the most common Inherited Retinal Dystrophy (IRD). The autosomal-dominant form (adRP) accounts for 25-30% of the cases. adRP primarily affects rod photoreceptors and can progress into the central retina, affecting cone photoreceptor function and survival. We recently identified multiple genomic structural variants (SVs) at the previously unsolved RP17 locus on Chr17q22. These SVs are the cause of IRD in a growing number of families affected by adRP, although the mechanism of disease is currently unknown. These complex SVs have the potential to reorganise the 3D structure of the genome. This study aims to uncover mechanisms of disease for adRP caused by SVs at the RP17 locus by producing and characterising mouse models with similar SVs.
Genetically altered (GA) mice were generated using CRISMERE to recreate a patient SV in the syntenic region of the mouse genome (Chr11qC), that contains conserved genes and regulatory regions, including Gdpd1, Ypel2 and a retinal enhancer. This resulted in several different genomic rearrangements, including deletions, duplications and inversions. The RP17 mice were characterised on a genomic, transcriptomic, proteomic and visual functional level. Optical Genome Mapping (OGM) was used to validate the genomic rearrangements. RT-qPCR, RNAseq and Western Blots were used to create transcriptomic and proteomic profiles on each line, and mice were tested for visual functionality by Electroretinography (ERG) and Optical Coherence Tomography (OCT).
The data show that the mouse model recapitulates key molecular changes observed in patient-derived retinal cells, including dysregulation of genes within the locus. Despite these molecular alterations, however, the mice do not exhibit overt retinal degeneration. Importantly, differences in genomic organisation led to variable effects on Gdpd1 expression. Despite carrying equivalent gene copy numbers, the duplication and duplicated inversion have different levels of Gdpd1 matching the predicted effects on the 3D folding of the genome, repositioning genes relative to their regulatory elements and thereby dysregulating their expression. In contrast, Ypel2 expression remains largely stable. These findings support disrupted TAD boundaries as a potential disease model and provide a framework for designing small molecule therapies to correct aberrant gene expression.
Lay Abstract
Autosomal-dominant Retinitis Pigmentosa (adRP) is a genetic eye disease affecting the retina, the tissue at the back of your eye that senses light. RP initially causes night blindness and tunnel vision but progresses into central vision loss. Complex genetic changes in a DNA region on chromosome 17 have been linked to adRP in a number of patient families. These changes, called structural variants (SV), involve missing, duplicated or rearranged pieces of DNA that disrupt how genes work together and may drive disease.
To understand how these changes lead to vision loss, disease models were created to replicate the same SVs found in patients. These models were assessed for changes at the level of DNA, proteins and visual function. The SVs had different effects on the activity of nearby genes: one gene was switched on, while the other remained unaffected. These changes are thought to be due to the rearrangement of DNA which can change the way the genome folds, shifting genes closer to or further away from the ‘molecular switches’ that control their activity.
This work provides a valuable platform for studying how disruption of DNA organisation can cause disease and allows for the design and testing of retinal therapies.
| Lay Title | Using new mouse models to investigate a genetic cause of autosomal-dominant Retinitis Pigmentosa. |
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| Role | PhD Student |