Generation and characterization of Tmeff2 mutant mice

► A Tmeff2 knock-in/null mouse line is generated (Tmeff2PLAP/PLAP). ► Tmeff2 mutant mice show growth retardation and die around weaning age. ► Tmeff2PLAP allele enables visualization of neuronal innervation with PLAP-staining. ► Tmeff2 mutant mice have normally developed central and peripheral nervous system. ► No in vivo evidence was found for a role of TMEFF2 as a tumor suppressor. TMEFF2 is a single-transmembrane protein containing one EGF-like and two follistatin-like domains. Some studies implicated TMEFF2 as a tumor suppressor for prostate and other cancers, whereas others reported TMEFF2 functioning as a growth factor for neurons and other cells. To gain insights into the apparently conflicting roles of TMEFF2, we generated a null allele of Tmeff2 gene by replacing its first coding exon with human placental alkaline phosphatase cDNA (Tmeff2PLAP). Tmeff2PLAP/PLAP homozygous mutant mice are born normal, but show growth retardation and die around weaning age. Tmeff2 is widely expressed in the nervous system, and the Tmeff2PLAP knock-in allele enables the visualization of neuronal innervations of skin and internal organs with a simple alkaline phosphatase staining. Tmeff2 is also highly expressed in prostate gland and white adipose tissues (WAT). However, with the exception of reduced WAT mass, extensive anatomical and molecular analyses failed to detect any structural or molecular abnormalities in the brain, the spinal cord, the enteric nervous system, or the prostate in the Tmeff2 mutants. No tumors were found in Tmeff2-mutant mice. The Tmeff2PLAP/PLAP knock-in mouse is an useful tool for studying the in vivo biological functions of TMEFF2.