Sequence, structure and chromosomal localization of Crtm gene encoding mouse cartilage matrix protein and its exclusion as a candidate for murine achondroplasia.

The mouse cartilage matrix protein gene (Crtm) was isolated from a cosmid library using a mouse Crtm cDNA fragment as probe. Crtm spans 12.2 kb from the start of translation to the polyadenylation signal sequence and comprises eight exons. Sequencing of the 1.9 kb 5' flanking region revealed a TATA-like box 72 bp upstream from the initiator Met codon as well as several cis-acting motifs known to bind eukaryotic transcription factors. Analysis of the exon-intron junctions demonstrated that the last intron does not follow the gt/ag rule but belongs to the minor class of pre-mRNA introns that contain "at" and "ac" at their 5'and 3' ends, respectively. Single-strand conformation polymorphism analysis was used to map Crtm to the distal part of chromosome 4 between the microsatellite markers D4Mit16 and D4Mit339. Achodroplasia (cn), a recessive skeletal disorder in mice, has already been mapped to this region. Immunostaining for CMP and sequence of Crtm in cn/cn mice failed to reveal any disease-specific mutations, suggesting that mutations in Crtm do not cause achondroplasia.