While investigating radiation-induced gene expression in mouse hepatocellular carcinoma cells, Fukuda et al. isolated a clone showing similarity to Sdf2, and they obtained the full-length mouse cDNA. The deduced human and mouse proteins contain 221 amino acids and share 88% sequence identity. SDF2L1 has an N-terminal hydrophobic signal sequence and an endoplasmic reticulum retention-like motif at the C terminus. SDF2 and SDF2L1 show significant similarity to the central hydrophilic regions of POMT1 , POMT2 , the O-mannosyltransferase family of S. cerevisiae and C. albicans, and the rt protein of Drosophila. Northern blot analysis detected ubiquitous expression of Sdf2l1 in mouse tissues, with strong expression in testis, ovary, and uterus, and weak expression in heart and skeletal muscle.