Gas1, short for Growth Arrest Specific 1, is a gene with diverse functions. It is a member of the alpha receptors (GFRα) for the GDNF ligands (GFL) family. Gas1 is involved in multiple signaling pathways, such as Wnt, Hedgehog (Hh), and NOTCH, and plays a crucial role in various biological processes including embryonic development, cell growth regulation, and apoptosis [2,4,6]. Genetic models, like gene knockout (KO) mouse models, have been instrumental in studying its functions.

In mice with Gas1 loss-of-function mutation, there are variations in tooth number, morphology, and size within the molar dentition. Gas1 in cranial neural crest cells regulates tooth number by restricting Wnt and downstream FGF signaling in odontogenic epithelium through facilitating Shh signal transduction [3]. In the context of colorectal cancer, Bifidobacterium adolescentis can suppress tumorigenesis by regulating Gas1 via the Wnt signaling pathway, inducing a new subset of CD143+ cancer-associated fibroblasts [1]. Also, in gastric adenocarcinoma, loss of ATOH1 activates the AKT/mTOR signaling pathway through down-regulating Gas1 [5].

In conclusion, Gas1 is a pleiotropic regulator involved in embryonic development, especially in tooth patterning. In disease conditions, it plays a role in cancers such as colorectal and gastric adenocarcinoma. Studies using KO mouse models have significantly contributed to understanding Gas1's functions in these biological processes and disease areas.