The TMPRSS3 (also known as ECHOS1) gene, which encodes a transmembrane serine protease, has been found to be responsible for two non-syndromic recessive deafness loci located on human chromosome 21q22.3, DFNB8 and DFNB10.TMPRSS3, a 437 amno acid membrane bound serine protease and a member of the S1 peptidase family. TMPRSS3 contains an amino-terminal signalanchor sequence and a glycosylated extracellular region containing the serine protease domain. Two novel missense mutations of TMPRSS3, W251C and P404L, alter the highly conserved amino acids of the serine protease domain. TMPRSS3 is expressed in many tissues, including fetal cochlea, a subset of pancreatic cancer and various other cancer tissues. TMPRSS3 is also overexpressed in cancer, suggesting that it may be important for processes in metastasis formation and tumor invasion.