Lmbr1l, or limb region 1-like gene, encodes a membrane-spanning protein. It is essential for proper regulation of Wnt/β-catenin and Norrin/β-catenin signaling pathways, playing a significant role in lymphopoiesis, angiogenesis, and potentially other biological processes [1,2]. Genetic models, such as gene knockout mouse models, have been crucial in studying its functions.

In gene-knockout mouse models, Lmbr1l deficiency leads to severely impaired development of all lymphoid lineages, with Lmbr1l-deficient T cells showing hallmarks of Wnt/β-catenin activation and undergoing apoptotic cell death in response to proliferative stimuli. This indicates its role as a negative regulator of the Wnt/β-catenin pathway during lymphopoiesis and lymphoid activation [1]. In another study, a global knockout mouse model showed that Lmbr1l is essential for retinal vascular development. Depletion of Lmbr1l in vitro leads to aberrant activation of the Norrin/β-catenin signaling pathway, causing abnormal endothelial cell proliferation and migration [2].

In conclusion, Lmbr1l is vital for lymphopoiesis and angiogenesis, acting as a regulator of the Wnt/β-catenin and Norrin/β-catenin signaling pathways. The use of gene-knockout mouse models has significantly contributed to understanding its functions in these biological processes, which may have implications for related diseases such as immune-system disorders and retinal vascular diseases [1,2].

References:

1. Choi, Jin Huk, Zhong, Xue, McAlpine, William, Moresco, Eva Marie Y, Beutler, Bruce. . LMBR1L regulates lymphopoiesis through Wnt/β-catenin signaling. In Science (New York, N.Y.), 364, . doi:10.1126/science.aau0812. https://pubmed.ncbi.nlm.nih.gov/31073040/

2. Liu, Wenjing, Jiang, Xiaoyan, Li, Xiao, Li, Shujin, Zhu, Xianjun. 2022. LMBR1L regulates the proliferation and migration of endothelial cells through Norrin/β-catenin signaling. In Journal of cell science, 135, . doi:10.1242/jcs.259468. https://pubmed.ncbi.nlm.nih.gov/35146515/