Cloning and characterization of a type II integral transmembrane protein gene, Itm2c, that is highly expressed in the...

An Itm2C cDNA encoding a member of the mouse type II integral transmembrane protein (Itm2) was cloned from a mouse 13.5 days' post-coitum (dpc) embryonic head cDNA library. The nucleotide sequence and protein prediction analyses indicate that the membrane topology of the mouse Itm2c is a type II integral transmembrane protein with the N-terminus being intracellular and C-terminus, which is considered as either an extracellular or a luminal organelle domain. The predicted protein consists of 269 amino acids with a calculated Mr of 30,482 and a theoretical pI of 8.83. A putative N-glycosylation site was identified at amino acid 171, Asn. The single N-glycosylation site is conserved in the three members of the family in both mice and humans. The amino acid sequence of Itm2C is 41 and 49% identical to those of mouse Itm2A and Itm2B, respectively. A single approximately 2.1 kb transcript was detected with different levels in all of the tissues examined by Northern blot analysis. The Itm2c was highly expressed in both adult and postimplantation embryonic brains, although weak or moderate signals were also detected in other adult tissues. Among the tissues examined, RT-PCR analyses in various adult tissue shows that the Itm2c expression is highest in the adult brain. The results from this study suggest that the cloned Itm2c is a member of the Itm2 family that is specifically expressed in adult brains, unlike other members.