FAM9B (Family With Sequence Similarity 9 Member B, also known as TEX39B) is located on human chromosome Xp22.31. The FAM9B gene contains 9 exons and spans about 9 kb. FAM9B shares 65% amino acid identity with FAM9C, 46% identity with FAM9A, and about 30% identity with rodent Sycp3. The encoded protein may be localized to the nucleus as the protein contains several nuclear localization signals, and has similarities to a synaptonemal complex protein. FAM9B is associated with some diseases, including Epithelial Basement Membrane Dystrophy and Epithelial And Subepithelial Dystrophy.