A tension-sensing module has been inserted into the coding sequence of the endogenous shg locus, in the cytoplasmic domain between the transmembrane domain and the β-catenin binding domain. The tension-sensing module consists of ECFP (FRET donor) and mEYFP (FRET acceptor) connected by an elastic linker (GPGGA)[[8]], derived from spider silk. If the tension is low, the two fluorophores are close enough to allow FRET. With increased tension, the elastic linker stretches, increasing the distance between the two fluorophores and reducing FRET.