2541-P: Generation of Humanized ALK7 Mice for Obesity Preclinical Research and Small Nucleic Acid Drug Evaluation

Introduction and Objective: ACVR1C (Activin receptor-like kinase 7, ALK7) is a type I receptor of the TGF-β superfamily. Activin E serves as its ligand, mediating activation of the Smad2/3 signaling pathway and regulating the expression of energy metabolism-associated genes. ALK7 modulates fat storage by suppressing lipolysis. Rare variant analysis using UK Biobank datasets shows that ALK7 loss-of-function is associated with favorable fat distribution patterns and lipid profiles. To date, small nucleic acid drugs—particularly siRNAs—represent the primary focus of ALK7-targeted drug development.To support preclinical research on obesity and siRNA drug evaluation, Biocytogen developed a humanized mouse model (B-hALK7 mice) for in vivo efficacy. Methods: To generate a humanized ALK7 mouse model (B-hALK7 mice), the part of exon 2 to exon 9 of the mouse Alk7 gene, including 3’UTR, was replaced by the human full coding sequence (CDS) and human 3’UTR in B-hALK7 mice. The promoter and 5’UTR region of the mouse gene are retained. mRNA expression of human and mouse ALK7 was validated by RT-PCR and RT-qPCR. To evaluate the inhibitory efficiency of the nucleic acid drugs against human ALK7, B-hALK7 mice were treated with siRNA drugs (synthesized according to patents), and the adipose tissue was collected to detect the expression level of human ALK7 mRNA by RT-qPCR. B-hALK7 mice and wild-type mice were fed with a high-fat diet (HFD) to induce obesity. Results: Human ALK7 mRNA was detected exclusively in B-hALK7 mice, whereas mouse Alk7 mRNA was restricted to wild-type mice. SiRNA treatment significantly reduced human ALK7 mRNA expression in adipose tissues compared to the control group. Under a high-fat diet (HFD) induction, the body weight growth of B-hALK7 mice was similar to the wild-type mice. Conclusion: B-hALK7 mice can successfully express human but not mouse ALK7. Based on in vivo efficacy data, this model is suitable for preclinical studies of obesity and small nucleic acid drug evaluation.