Alpha10beta1 is a collagen-binding integrin expressed by chondrocytes [Camper et al. (1998) J. Biol. Chem. 273: 20383-20389]. In the present study, the mouse alpha10 gene was isolated from a sCos1 SVJ library and the genomic structure and chromosomal localization was determined. The alpha10 gene consists of 30 translated exons spanning a region of approximately 18 kb genomic DNA. The sequences of all exon/intron borders follow the consensus "gt-ag" rule. A transcription start site, determined by primer extension analysis, was located 38 nucleotides upstream of the initiation ATG site. The 5' flanking region of the transcription start site lacked a TATA-box. The first exon contained, in addition to 38 untranslated nucleotides, the ATG translation start site and the major part of the signal peptide. The alpha10 gene was mapped to mouse chromosome 3 by fluorescence in situ hybridization and is the only integrin subunit localized to this chromosome. When we investigated the expression of alpha10 by PCR we found that both mouse and human articular chondrocytes express extracellular splice variants of the alpha10 subunit. In mouse, exon 26 was extended into the intron by 62 nt, generating a truncated alpha10-chain. In human, exon 25 consisted of 114 nt which were alternately spliced in or out.