We have identified PAP1 gene, a novel member of the immunoglobulin superfamily (IGSF) from U251-pTet-p53 cell line, which carried a wild-type p53 transgene. The gene has been localised to chromosome 16p12-13. Alignment of the predicted protein sequence for Human, Pan troglodytes, Canis, Mus musculus and Gallus gallus revealed it was highly conserved. Its homologue, IGSF6, possible involves in mouse embryonic development. The presence of IGSF6 specific transcript was detected by Northern blot in the RNAs extracted from 11 to 14 day postconception. IGSF6 expression is different in mouse embryos of the different ages. In situ hybridization performed on mice embryos sections showed the differential presence of IGSF6 in developing lung and kidney. This structure and differential expression suggests a function involvement in embryonic development, perhaps involvement in cell proliferation.