Molecular and functional analysis of Popeye genes: A novel family of transmembrane proteins preferentially expressed in heart and skeletal muscle

Popeye (Pop) genes encode novel transmembrane proteins, of which three family members are present in vetebrates, while in Drosophila a single gene is found. By northern blot analysis a restricted expression pattern is observed; Pop genes predominantly expressed in the heart, skeletal and smooth muscle. Using homologous recombination, a null mutation was generated in the case of Pop1. The homozygous mutants are viable and do not display any obvious phenotype. They display an impaired ability to regenerate skeletal muscle while the hypertropic response of the heart rate isoproterenol infusion revealed no difference between genotypes. Recently a function of Pop1 as a prototype of a novel class of cell adhesion molecules was proposed. Further work is required to substantiate these findings and to extend it to other members of the family.