The ACVR2B gene encodes the activin A type IIB receptor, a transmembrane protein belonging to the transforming growth factor-β (TGF-β) superfamily. It is widely expressed in various human tissues, with particularly critical expression levels in tissues closely related to physiological functions, such as muscle, bone, and gonads. The protein encoded by ACVR2B is a type II serine/threonine kinase receptor, consisting of three core domains: an extracellular ligand-binding domain, a transmembrane domain, and a cytoplasmic kinase domain. It can initiate signal transduction by binding to ligands like activin and myostatin. Functionally, ACVR2B is a key molecule regulating multiple physiological processes. In muscle, it inhibits muscle growth by mediating myostatin signaling and serves as a core target for the regulation of muscle atrophy and growth ^[1]. In the reproductive system, it participates in processes such as folliculogenesis and spermatogenesis by regulating gonadal hormone secretion ^[2-3]. Additionally, it is involved in energy metabolism, influencing fat accumulation and the development of metabolic syndrome. Abnormal ACVR2B function or signal imbalance is associated with various diseases: in cancer cachexia, overactivation of its mediated signaling pathways accelerates muscle breakdown ^[4]. In metabolic syndrome and obesity, abnormal expression of this gene may lead to disordered fat metabolism. Furthermore, defects in this gene are linked to congenital diseases such as left-right axis malformations ^[5].

The B6-huACVR2B mouse is a humanized model constructed using gene-editing technology. The sequence from exon 2 to 3'UTR of the mouse Acvr2b gene is in situ replaced with the sequence from exon 2 to 3'UTR of the human ACVR2B gene. This model can be used for research related to muscle atrophy and growth regulation, cancer cachexia intervention, and reproductive and gonadal functions, as well as the development of ACVR2B-targeted drugs.