MYCBP2, also known as PAM or Phr1, is an E3 ubiquitin ligase and a large signalling hub involved in diverse biological processes. It participates in neuronal connectivity, synaptic growth, cell division, neuronal survival, and protein ubiquitination. It is also associated with multiple signalling pathways like the mTOR signalling pathway and is involved in the regulation of lipid metabolism and immune responses [3,4,5,6,7,8]. Genetic models such as Caenorhabditis elegans are valuable for studying MYCBP2 [1].

In humans, loss-of-function variants in MYCBP2 cause a neurodevelopmental disorder. Eight patients with such variants presented with corpus callosum abnormalities, developmental delay, intellectual disability, epilepsy, and autistic features. Nuclease technology-mediated introduction of disease-associated variants into the C. elegans MYCBP2 orthologue, RPM-1, led to axonal and behavioural abnormalities, including altered habituation, and abnormal axonal accumulation of the autophagy marker LGG-1/LC3 in variants affecting RPM-1 ubiquitin ligase activity. This indicates that MYCBP2 variants likely result in loss of function and are linked to a neurodevelopmental spectrum disorder [1].

In spinal cord injury, ginsenoside Rg1-pretreated neuronal cell-derived extracellular vesicles (Rg1-EVs) with enriched MYCBP2 improve motor function, regulate immune responses, and enhance neural tissue repair. MYCBP2 knockdown counteracts these beneficial effects, as MYCBP2 promotes microglial M2-phenotype polarization and reduces oxidative stress by ubiquitinating and degrading S100A9 [2].

In thyroid cancer, MYCBP2 expression is correlated with inflammatory cell infiltration, prognosis, and ICI efficacy. MYCBP2-high patients have increased infiltration of multiple immune cell types, higher expression of immune-related genes, and better prognosis [3].

In MASH-associated hepatocellular carcinoma, MYCBP2 acts as a potential tumor suppressor. It inhibits HCC cell proliferation, migration, and invasion by modulating lipid metabolism pathways through promoting the ubiquitination and degradation of HNF4α [4].

In breast cancer, MYCBP2 dysfunction is associated with decreased disease-free survival, resistance to cisplatin-induced apoptosis, and cell cycle changes [8].

In conclusion, MYCBP2 is a crucial E3 ubiquitin ligase and signalling hub involved in a wide range of biological functions. Model-based research, especially the use of gene-editing techniques in in vivo models, has revealed its significance in neurodevelopmental disorders, spinal cord injury, thyroid cancer, hepatocellular carcinoma, and breast cancer. Understanding MYCBP2's functions provides insights into the mechanisms of these diseases and potential therapeutic targets.