New Approaches in the Genetic Diagnosis of Inherited Retinal Dystrophies and Future Therapeutic Insights
- Autores: Belén García‑Bohórquez
- Directores de la Tesis: José María Millán Salvador (dir. tes.), Gema García Garcia (dir. tes.), Joaquín Cañizares Sales (tut. tes.)
- Lectura: En la Universitat Politècnica de València ( España ) en 2025
- Idioma: inglés
- Tribunal Calificador de la Tesis: Rosa Coco Martín (presid.), María José Herrero Cervera (secret.), Eduardo José Gil Duarte Silva (voc.)
- Programa de doctorado: Programa de Doctorado en Biotecnología por la Universitat Politècnica de València
- Materias:
- Enlaces
- Tesis en acceso abierto en: RiuNet
- Resumen
Inherited retinal dystrophies (IRD) are genetic disorders affecting photoreceptors and retinal pigment epithelium cells, leading to progressive vision loss. Their genetic diagnosis is challenging due to significant genetic and clinical heterogeneity, with over 280 associated genes. High-throughput sequencing (HTS) has revolutionized the diagnostic process, improving variant identification and providing patients with genetic counseling and access to gene therapy trials.
The first study analyzed 92 IRD patients using custom gene panels, identifying the genetic cause in 57.6% of cases. Among them, 13% had only one mutation in autosomal recessive genes, while 29.3% remained undiagnosed. A total of 120 pathogenic or likely pathogenic variants were found, including 30 novel ones. ABCA4 was the most frequently mutated gene in cone-rod dystrophy, whereas USH2A mutations were most common in retinitis pigmentosa (RP). The inclusion of non-coding regions allowed the identification of deep-intronic variants in ABCA4 and CEP290, reinforcing the importance of these regions in genetic diagnostics. This approach enabled molecular diagnosis for many patients, helping them make reproductive decisions and access gene therapy clinical trials.
The second study focused on deep-intronic variants in USH2A in unresolved Usher syndrome (USH) and autosomal recessive RP cases. Five previously reported pathogenic variants were screened in monoallelic patients, leading to a complete diagnosis in 30.95% of them. Further sequencing of USH2A or all USH genes revealed 16 variants affecting splicing, of which four were confirmed functionally. Two newly discovered variants caused pseudoexon (PE) inclusion in pre-mRNA, while two others affected a regulatory cis-element. Antisense oligonucleotides (ASOs) were designed to correct PE inclusion in three deep-intronic USH2A variants, successfully restoring normal splicing in vitro, demonstrating the therapeutic potential of ASOs.
The third study examined oro-facial-digital syndrome (OFD) type IX, a ciliopathy linked to TBC1D32 mutations. A patient presenting OFD type IX features, RP, and bilateral sensorineural hearing loss (SNHL) underwent clinical exome sequencing, which identified two heterozygous TBC1D32 variants in trans. As this was the first reported case of SNHL associated with TBC1D32 mutations, additional analyses of SNHL-related genes were conducted, but no disease-causing variants were found. Given the role of ciliary dysfunction in hearing loss, SNHL could be considered an additional symptom of OFD type IX. This highlights the importance of genetic and clinical evaluations in complex phenotypes.
In conclusion, this research underscores the need to analyze both coding and non-coding regions to improve IRD diagnosis. It also demonstrates how HTS and tools like ASOs can advance personalized treatments, offering hope for patients with ultra-rare variants. A thorough clinical anamnesis and case review are essential for achieving accurate genetic diagnoses and ensuring proper patient follow-up.
