Speaker
Description
Ciliopathies are a group of disorders associated with pathogenic variants in genes that result in abnormal formation or dysfunction of cilia. Retinal degeneration is a common feature in ciliopathies. Pathogenic variants in Intraflagellar transport 140 (IFT140) are associated to syndromic and non-syndromic ciliopathies. Yet, the different effects of IFT140 variants in different tissues, especially in the retina, is not fully understood. The lack of appropriate human retinal models limited the investigation of IFT140 function in the retina and the development of targeted therapeutic strategies.
We investigated patient fibroblasts carrying different IFT140 variants, and identified variations in cilia length between these lines, that was accompanied by mislocalisation of IFT components, suggesting defective retrograde transport. These defects were visualised using ultrastructure expansion microscopy (U-ExM), which confirmed disrupted IFT transport.
To investigate the retinal consequences associated with IFT140 dysfunction, we characterized induced pluripotent stem cell (iPSC)-derived retinal pigment epithelium (RPE) and retinal organoids (ROs) models, from CRISPR/Cas9 IFT140 knockout (IFT140-KO), patient-derived c.1451C>T (p.T484M) and isogenic control (WT) lines. The results showed that loss of IFT140 led to shorter cilia and IFT88 accumulation at the cilia tip in iPSC-RPE. In iPSC-ROs, the IFT140-KO line displayed a thinner brush border corresponding to the photoreceptor outer segments, while the T484M line showed a phenotype intermediate between WT and IFT140-KO.
These results suggested that IFT140 deficiency disrupts cilia trafficking in human retinal cells and impairs photoreceptor development, providing mechanistic insight into retinal degeneration associated with IFT140-related ciliopathies.
Lay Abstract
Cilia are tiny hair-like structures in most cells, but in light sensitive cells (photoreceptors) in the retina they form a special light sensing organelle called the outer segment. Inherited changes (variants) in the IFT140 gene can cause ciliopathies, a group of conditions in which cilia do not work properly. These disorders lead to a range of health problems including vision loss. The reasons why IFT140 variants cause blindness remains unknown. The lack of appropriate human models limited the understanding of IFT140 function in the retina.
In this study, we examined human skin cells carrying different IFT140 variants and discovered these variants had shorter cilia and key proteins required for cilia function were misplaced. Using an advanced imaging method called ultrastructure expansion microscopy, we were able to visualize these tiny structures in detail.
We then focused on a specific IFT140 variant called T484M, using ‘retina in a dish’ models. We found that cells completely lacking IFT140 had very short cilia and problems in light-sensing cell development, while the T484M variant caused milder but noticeable defects. This ‘retina in a dish’ model allows us to study why IFT140 variants cause vision loss and explore therapeutic strategies in the future.
| Lay Title | Studying Vision Loss Caused by IFT140 Variants |
|---|---|
| Role | PhD Student |