Moyamoya Disease 5 (MYMY5) Cell Models for Research

Moyamoya disease (MMD) is a rare, progressive cerebrovascular disorder characterized by stenosis of the intracranial internal carotid arteries and the development of a fragile collateral vascular network. The global incidence is estimated at 0.35–0.94 per 100,000 person-years, with higher prevalence in East Asian populations (Japan, Korea, China). The disease can manifest in childhood (ischemic strokes) or adulthood (hemorrhagic strokes), leading to significant morbidity and mortality. Five-year survival rates vary, but with revascularization surgery, outcomes improve; however, without treatment, recurrent strokes can be disabling. (WHO, NCI).

Moyamoya Disease 5 (MYMY5) is a genetic subtype linked to mutations in the RNF213 gene. Studying MYMY5 provides insights into vascular biology, angiogenesis, and stroke mechanisms. The disease offers a unique model to investigate the role of RNF213 in endothelial cell function and smooth muscle cell proliferation. Public datasets, such as those in NCBI and ClinVar, provide genetic variants, while cell models enable functional validation. Open questions include the precise molecular pathways leading to vascular stenosis and the development of targeted therapies.

• • Although Moyamoya is not a cancer, the disease involves aberrant cell proliferation and angiogenesis. Key pathways include:
• • RNF213-related signaling: RNF213 is a ubiquitin ligase involved in angiogenesis and inflammation. Mutations lead to dysregulation of NF-κB and VEGF signaling.
• • Inflammatory pathways: Chronic inflammation contributes to intimal thickening.
• • Hypoxia-inducible factor (HIF) pathway: HIF-1α upregulation in response to ischemia promotes angiogenesis but also abnormal vascular remodeling.
• • Notch signaling: Involved in arterial specification and smooth muscle cell differentiation.

Data from TCGA and COSMIC are not directly applicable as MYMY5 is not a cancer, but ClinVar and NCBI Gene provide variant frequencies.

• • Key signaling networks implicated in MYMY5:
• • NF-κB pathway: RNF213 mutations lead to increased NF-κB activity, promoting inflammation.
• • VEGF signaling: Upregulated, leading to aberrant angiogenesis.
• • TGF-β pathway: Involved in vascular remodeling.
• • MAPK/ERK pathway: Enhanced proliferation of smooth muscle cells.
• • PI3K/AKT pathway: Promotes cell survival and migration.

Key nodes: RNF213, NF-κB, VEGF, TGF-β, MAPK1, AKT1.

Organoids: 3D vascular organoids can recapitulate vessel formation and are useful for studying RNF213 function.

• • RNF213 knockout mice: Show abnormal vascular remodeling and reduced angiogenesis.
• • RNF213 p.R4810K knock-in mice: Mimic human mutation, display moyamoya-like features.
• • Induced models: Carotid artery ligation in mice induces moyamoya-like changes.
• • PDX models: Not applicable for non-cancer disease, but patient-derived xenografts of vascular tissue can be used.

• • CRISPR-Cas9 gene editing enables the creation of isogenic cell lines with specific RNF213 mutations. For example:
• • RNF213 knockout in HUVECs: Loss-of-function model to study angiogenesis.
• • RNF213 p.R4810K knock-in in HUVECs: Mimics patient mutation, allowing functional studies.
• • RNF213 knockout in smooth muscle cells: Investigates proliferative phenotypes.

These models are commercially available and sequence-verified, accelerating research. They are ideal for drug screening and functional genomics.

Knockout and knock-in lines validate the role of RNF213 in endothelial function, angiogenesis, and inflammation. For example, RNF213 knockout in HUVECs leads to increased tube formation and altered gene expression of angiogenic factors. Knock-in of p.R4810K recapitulates patient phenotypes, enabling mechanistic studies.

Isogenic pairs (wild-type vs. mutant) are used for high-throughput screening to identify compounds that rescue mutant phenotypes. Resistance models can be generated by exposing cells to drugs and selecting for resistant clones, aiding in understanding drug resistance mechanisms.

CRISPR synthetic lethality screens can identify genes that are essential in RNF213-mutant cells but not wild-type, revealing potential therapeutic targets. Biomarkers can be discovered by comparing transcriptomes and proteomes of isogenic lines.