Dokument: Molecular mechanisms of RASopathy-associated hypertrophic cardiomyopathy
| Titel: | Molecular mechanisms of RASopathy-associated hypertrophic cardiomyopathy | |||||||
| Weiterer Titel: | Molekulare Mechanismen der RASopathieassoziierten hypertrophen Kardiomyopathie | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=68498 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20250402-132830-3 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Bazgir, Farhad [Autor] | |||||||
| Dateien: |
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| Beitragende: | Ahmadian, Mohammad Reza [Betreuer/Doktorvater] Prof. Urlacher, Vlada [Betreuer/Doktorvater] | |||||||
| Stichwörter: | Biology | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie | |||||||
| Beschreibung: | The RAS family of GTPases (Guanosine triphosphatases) act as molecular switches to control several key processes in all eukaryotic cells, existing in an active (GTP-bound) or inactive (GDPbound) state with Guanine nucleotide exchange factors (GEFs) enabling the release of GDP leading to the activation of the protein and GTPase activating proteins (GAPs) facilitating the return to the inactive state by accelerating the intrinsic GTPase activity. RAS proteins link modifications in the surrounding environment of the cell to internal signal transduction pathways by interacting with a wide range of target proteins controlling many cellular processes, including proliferation, differentiation, survival, and migration. The most prevalent among RASopathies, Noonan syndrome (NS), is brought on by germline mutations in genes that encode RAS-MAPK pathway elements. Some variations, such as the frequent Ser257Leu substitution in RAF1, are connected to severe hypertrophic cardiomyopathy (HCM). In a relevant study, I used threedimensional cardiac bodies and bioartificial cardiac tissues made from patient-derived induced
pluripotent stem cells (iPSCs) with the aforementioned pathogenic RAF1 mutation to evaluate the molecular relationship between NS-associated RAF1S257L and HCM. Vastly elevated levels of the heart failure marker BNP and an ultrastructural shortening of the I-bands along the Z-line region of sarcomere in both patient specific iPSC-derived RAF1S257L cardiomyocytes were found upon molecular, structural, and functional evaluation of the differentiated cardiac models. These modifications coincided with titin's isoform shift from a longer (N2BA) to a shorter (N2B) variant, which also had an impact on the active force generation and contractile tensions. In this model, hyperactivation of the ERK, p38, and YAP signaling pathways were observed as contributing factors in the development of the HCM phenotypes. By employing both MEK inhibition and a CRISPR-Cas9 gene-corrected isogenic cell line, the disease phenotype was largely reversed, adding important and novel mechanistic insights into the disorder's pathophysiology. RIT1, another member of the RAS-MAPK pathway, is highly associated with development of HCM upon germline mutations in NS patients and Arteriovenous malformation syndrome (AVM) upon somatic alterations. Molecular evaluation of three novel RIT1 indels in patients with AVM indicated a massive hyperactivation status of ERK which was shown to be rescued upon MEK inhibition but not SHP2 inhibition, providing critical insights into available clinical options of the subject patients. The complex developmental condition Costello syndrome is mainly linked to HRAS germline mutations, namely the Gly12Ser substitution, which is a frequently mutated residue in several cancer types, locking HRAS in a constitutively active state. HRAS has been known to interact with RIN1 and boosts the activation of RAB5 GTPases and ABL1/2 tyrosine kinases affecting endosomal sorting and cytoskeletal dynamics. Investigating into this, I contributed to find that the HRASG12S boosts the RIN1-dependent RAB5A activation and subsequently disrupts the membrane availability and trafficking of integrins in keratinocytes, which highlights critical molecular events in etiology of the dermatological symptoms in Costello syndrome. Patients with various degrees of neurodegeneration events were found to have novel ARF3 GTPase mutations. Our structural-functional investigations of ARF3 mutations revealed a significant increase in their nucleotide exchange rates. The study was able to demonstrate that the identified variations are sited in the nucleotide-binding pocket, interfering with the protein's ability to function by maintaining the protein in GTP-bound state and ultimately disrupting the integrity of the Golgi. These findings collectively provide critical mechanistic understanding into the pathogenesis and treatment options of several patient-specific MAPK-associated disorders in various proteins and mutation profiles. | |||||||
| Lizenz: |  Dieses Werk ist lizenziert unter einer Creative Commons Namensnennung 4.0 International Lizenz | |||||||
| Fachbereich / Einrichtung: | Medizinische Fakultät » Institute » Institut für Biochemie und Molekularbiologie II | |||||||
| Dokument erstellt am: | 02.04.2025 | |||||||
| Dateien geändert am: | 02.04.2025 | |||||||
| Promotionsantrag am: | 28.02.2023 | |||||||
| Datum der Promotion: | 27.10.2023 |
