Genomic Organization and Chromosomal Localization of the Itm2a Gene

Itm2A is a novel type II integral membrane protein that is involved in osteo- and chondrogenic differentiation. Itm2a cDNA was originally isolated from a cDNA library of organ cultures from prenatal mouse mandibular condyles, by subtractive hybridization and differential screening. The Itm2a gene was isolated from a BALB/c liver genomic library. In total, 9.4 kb of the gene were sequenced, of which 2649 bp are 5' flanking sequences. The Itm2a gene contains six exons and five introns. The splice sites conform to the GT/AG rule. The 5' flanking region, which contains the presumed promoter sequence, lacks the common TATAA and CCAAT sequences, but contains consensus binding sites for various transcription factors. Several of these transcription factors are known to play a role in transcriptional regulation of cartilage- or bone-specific genes (e.g. Cbfa1, Cart-1, MHox, HES-1, and CIIS1). Itm2a was mapped to mouse chromosome position XA2-XA3 by fluorescent in situ hybridization (FISH) analysis. The human homolog, ITM2A, was mapped to chromosome position Xq13.3-Xq21.2.