Arnt, also known as HIFβ, is a crucial protein in various biological processes. It is the obligate binding partner of HIFα subunits and is necessary for HIFα's transcriptional activity. Arnt is involved in multiple pathways, such as hypoxia response, angiogenesis, and regulation of inflammatory cytokine production. It plays an essential role in the development of the cardiovascular system, and also participates in processes like the cellular response to xenobiotic compounds when complexed with AhR [2,3].

In glioblastoma, higher Arnt expression is associated with the mesenchymal subtype and poorer survival. Silencing Arnt attenuated the proliferative, invasive, and stem-like capabilities of GBM cell lines, while overexpression enhanced these malignant phenotypes. Arnt activates p38 MAPK signaling to promote chemoresistance in GBM cells [1]. In melanoma, ARNT deficiency represses pyruvate dehydrogenase kinase 1 (PDK1), leading to increased ROS production and melanoma metastasis [4]. In skeletal muscle, the loss of Arnt in old mice was associated with decreased levels of Notch1 intracellular domain (N1ICD) and impaired regenerative response to injury. Knockdown of Arnt in a primary muscle cell line impaired differentiation in vitro, and skeletal muscle-specific Arnt deletion in young mice limited muscle regeneration [5].

In conclusion, Arnt is essential for multiple biological functions, including cardiovascular development, hypoxia response, and cell-specific functions in various tissues. Studies using gene-knockdown or knockout models in different diseases, such as glioblastoma, melanoma, and in the context of skeletal muscle aging, have revealed its significance in disease pathogenesis. These models contribute to understanding how Arnt influences disease-related biological processes, providing potential therapeutic targets for these diseases.