Die Rolle von Nicastrin in der Pigmentierung
The role of Nicastrin in pigmentation
Doctoral thesis
Date of Examination:2022-12-20
Date of issue:2022-12-19
Advisor:Prof. Dr. Jorge Alberto Frank
Referee:Prof. Dr. Jorge Alberto Frank
Referee:Dr. Ivan Prof Bogeski
Referee:Prof. Dr. Ralf Dressel
Files in this item
Name:Hermasch_Matthias_Andreas_Dissertation (ohne...pdf
Size:29.6Mb
Format:PDF
Abstract
English
The regulation of melanocyte function in the context of pigmentation is a complex biological process involving several molecular signaling pathways whose specific role is largely unknown. Recently, it was shown that a variant of the hereditary disease Dowling-Degos is characterized by dysfunction of melanocyte migration, proliferation and differentiation. This manifests clinically with a pigmentation disorder and is caused by mutations in the PSENEN gene, which encodes PEN-2, a protein of the 𝛾-secretase protease complex. The 𝛾-secretase comprises the three other subunits nicastrin, presenilin, and Aph-1 and occupies a central position in the NOTCH signaling pathway, which plays a crucial role especially in pigment cell development. In this project, we investigated the function of the γ-secretase subunit nicastrin in relation to zebrafish pigmentation. We demonstrated that morpholino-mediated ncstn deficiency leads to hypo/depigmentation based on changes in melanophore morphology, proliferation, migration, and differentiation. We were able to reverse the resulting hypopigmentation phenotype by co-injection of both human and zebrafish RNA. In this context, we also cloned the four NCSTN mutations described in humans, c.497C>A, c.278delC, c.1101+1C>G, and c.632C>G, and examined their effects on pigmentation in vivo in reversion experiments. We showed that the three mutations resulting in a preterminal stop codon c.497C>A, c.278delC, c.1101+1C>G have deleterious effects on zebrafish pigmentation and do not lead to phenotype reversion, as they presumably cause nonsense-mediated RNA degradation. In comparison, the functional consequences of the missense mutation c.632C>G do not appear to be equally deleterious, as we were able to reverse the hypopigmentation phenotype by treating ncstn-deficient zebrafish with an RNA containing this mutation. These results illustrate the potential for therapy of pigmentation disorders using siRNA interference in the zebrafish model. Since this technology has now also been successfully used in humans, models such as the one used here may hold the key to a better understanding of complex biological processes and a possibility for the first evaluation of targeted causal therapeutic strategies in patients with pigmentation disorders.
Keywords: Nicastrin; Pigmentation; Dowling-Degos disease