Zebrafish and mouse models for studying deubiquitinating enzyme genes as candidates for retinal dystrophies

dc.contributor
Universitat de Barcelona. Departament de Genètica, Microbiologia i Estadística
dc.contributor.author
Toulis, Vasileios
dc.date.accessioned
2022-04-08T09:04:38Z
dc.date.available
2022-04-08T09:04:38Z
dc.date.issued
2020-07-20
dc.identifier.uri
http://hdl.handle.net/10803/674031
dc.description
Programa de Doctorat en Genètica
en_US
dc.description.abstract
The retina consists of several structured layers of highly specialized neurons that capture and process light stimuli enabling vision. Such a fine architecture turns retinal differentiation into an extremely complex event that must be accurately regulated. The ubiquitin-proteasome system (UPS) is considered one of the most dynamic and versatile mechanisms of protein regulation in eukaryotic cells. As ubiquitination is reversible, deubiquitinating enzymes (DUBs) play a major regulatory role in the UPS. Despite the importance of proteostasis and the UPS in health and disease, a more comprehensive in-depth analysis of DUB expression and function on particular tissues or organs, such as the retina, is still missing. Combining expression quantification, mRNA localization assays and functional analyses in animal and cellular models, we analyzed the function of several DUB genes in the retina to identify DUBs that regulate important retinal cell mechanisms, explore their relevance in retinal function in health and disease, and finally, posit them as new potential candidate genes for retinal dystrophies. Taking into consideration our results in the expression levels and pattern of DUBs in the retina, we first selected USP45 to perform functional assays in animal models in order to define its role and function in the retina. By morpholino-knockdown of usp45 in zebrafish embryos, our results showed moderate to severe eye morphological defects, eye size reduction, small body size with small tail or without tail, and disruption in notochord formation. There is also defective lamination and formation of the retinal structures, with no distinguishable layers and smaller retinas. Overall, our results supported the relevance of USP45 in the normal development and formation of the vertebrate retina, and we proposed this gene as a good candidate for causing hereditary retinal dystrophies, as later confirmed by other authors in several families. We also selected ATXN3, a DUB gene that causes the dominant polyQ disease Spinocerebellar ataxia type 3 (SCA3), and we aimed to analyze its function in the retina. We showed that depletion of Atxn3 in zebrafish and mice caused retinal morphological and functional alterations with photoreceptor outer segment elongation, cone opsin mislocalization, and cone hyperexcitation upon light stimuli. A pool of ATXN3 resides at the basal body and axoneme of the photoreceptor cilium, where it controls the levels and recruitment of the regulatory proteins KEAP1 and HDAC6. Abrogation of Atxn3 expression causes delayed phagosome maturation in the retinal pigment epithelium. We propose that ATXN3 regulates two relevant biological processes in the retina, ciliogenesis and phagocytosis, by modulating microtubule polymerization and microtubule-dependent retrograde transport, and propose ATXN3 as a causative or modifier gene in retinal/macular dystrophies. We further aimed to explore whether the SCA3 humanized mouse model showed specific retinal phenotype traits. We showed that polyQ-expanded ATXN3 protein formed a high number of progressive pathogenic aggregates in the retinal layers of transgenic Atxn3Q84 mice, and caused a decrease in the number of cone photoreceptors. Optical coherence tomography revealed a general decrease in the thickness of the retinal layers whereas retinal electrophysiological analyses showed a strong decrease in photoreceptor response to light, thus supporting severe retinal dysfunction in Atxn3Q84 mice. Similar analyses in human patients detected a correlation of retinal alterations with the number of CAG repeats and the age of onset of SCA3 symptoms. We propose that retinal alterations detected by non-invasive eye examination and electroretinography tests in SCA3 patients could serve as a valuable early-onset symptom and a biological marker of disease progression. As a conclusion, our work posits several DUB genes as candidates for inherited retinal dystrophies, but further investigation is needed to dissect the function of DUBs in retinal cell differentiation, photoreceptor function, and retinal homeostasis.
en_US
dc.format.extent
451 p.
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dc.format.mimetype
application/pdf
dc.language.iso
eng
en_US
dc.publisher
Universitat de Barcelona
dc.rights.license
L'accés als continguts d'aquesta tesi queda condicionat a l'acceptació de les condicions d'ús establertes per la següent llicència Creative Commons: http://creativecommons.org/licenses/by-nc/4.0/
dc.rights.uri
http://creativecommons.org/licenses/by-nc/4.0/
*
dc.source
TDX (Tesis Doctorals en Xarxa)
dc.subject
Retina
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dc.subject
Enzims
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dc.subject
Enzimas
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dc.subject
Enzymes
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dc.subject
Cicle cel·lular
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dc.subject
Ciclo celular
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dc.subject
Cell cycle
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dc.subject
Models animals en la investigació
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dc.subject
Modelos animales en investigación
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dc.subject
Animal models in research
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Fotoreceptors
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dc.subject
Fotorreceptores
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dc.subject
Photoreceptors
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dc.subject.other
Ciències Experimentals i Matemàtiques
en_US
dc.title
Zebrafish and mouse models for studying deubiquitinating enzyme genes as candidates for retinal dystrophies
en_US
dc.type
info:eu-repo/semantics/doctoralThesis
dc.type
info:eu-repo/semantics/publishedVersion
dc.subject.udc
575
en_US
dc.contributor.director
Marfany i Nadal, Gemma
dc.contributor.tutor
Marfany i Nadal, Gemma
dc.embargo.terms
cap
en_US
dc.rights.accessLevel
info:eu-repo/semantics/openAccess


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