Immunoglobulin superfamily members are implicated in immune responses,
growth factor signaling, and cell adhesion. IGSF4 (IGSF4A), homologous to IGSF4B, IGSF4C, IGSF4D, PVR,
PVRL1, PVRL2, PVRL3 and PVRL4, is down-regulated in
lung cancer. IGSF11, homologous to CXADR (CAR), ESAM and ASAM, is up-regulated in the intestinal-type
gastric cancer. Here, we identified and characterized a novel member of the
immunoglobulin superfamily, TMEM25, by using bioinformatics. BC042896 and AY358919 cDNAs were derived from human TMEM25 gene, while AK002841
cDNA was derived from mouse Tmem25 gene. TMEM25
isoform 1 (BC042896), consisting of exons 1-9, encoded a 366-aa transmembrane
protein. TMEM25
isoform 2 (AY358919), consisting of exons 1-4 and 6-9, encoded a 322-aa secreted
protein. Human TMEM25 gene was found to encode transmembrane-type as well as secreted-type
proteins due to alternative splicing of exon-skipping type. TMEM25
mRNA was expressed in brain, including cerebellar cortex and hippocampus, as well as in
neuroblastoma,
brain tumors, and
gastric cancer. Human TMEM25
isoform 1 showed 91.0% total-
amino-acid identity with mouse Tmem25. TMEM25 was identified as a member of
immunoglobulin superfamily, because
codon 42-112 of TMEM25 was the C-2 type immunoglobulin domain homologous to Hemicentin (Fibulin-6, FIBL6),
Titin (TTN),
Sialoadhesin (SN) and
Nephrin (NEPHS1). Human TMEM25 gene was located at the 11q23.3 oncogenomic recombination hotspot around the MLL amplicon and the
neuroblastoma deleted region. TMEM25 is a target of pharmacogenomics in the field of oncology and regenerative medicine.