HGNC Approved Gene Symbol: CILP2
Cytogenetic location: 19p13.11 Genomic coordinates (GRCh38): 19:19,538,265-19,546,659 (from NCBI)
By searching databases for sequences similar to CILP1 (CILP; 603489), followed by screening an osteoarthritic joint cartilage chondrocyte cDNA library, Johnson et al. (2003) cloned full-length CILP2. The deduced CILP2 protein shares 50.6% identity with CILP1, and both proteins have a central furin (FUR; 136950) endoprotease consensus cleavage site predicted to cause release of N- and C-terminal peptides. The N-terminal halves of CILP1 and CILP2 contain a thrombospondin (see 188060) type-1 repeat and an immunoglobulin C2-type domain, but the N-terminal half of CILP2 lacks the putative aldehyde dehydrogenase (see 100640) cysteine active site and the ATP-binding site found in CILP1. RT-PCR analysis detected both CILP1 and CILP2 in cultured normal hyaline cartilage articular chondrocytes, but not in osteoblasts, fibroblasts, or vascular smooth muscle cells. Only CILP1 was detected in normal knee meniscal fibrocartilage chondrocytic cells.
Bernardo et al. (2011) showed that mouse Cilp2 mRNA is distributed at the surface of the articular cartilage during development and localizes to the intermediate zone of articular cartilage and meniscal cartilage with maturity. The Cilp2 protein is more localized in the deeper intermediate zone of the articular cartilage than Cilp1. The human CILP2 protein was found in articular cartilage and shown to be proteolytically processed and N-glycosylated. Bernardo et al. (2011) found that Cilp2 protein was reduced in mouse osteoarthritic cartilage. RT-PCR analysis detected Cilp1 and Cilp2 transcripts in heart and skeletal muscle, indicating that these genes are not exclusively expressed by chondrocytes.
By genomic sequence analysis, Johnson et al. (2003) mapped the CILP2 gene to chromosome 9p13.11. However, Gross (2012) mapped the CILP2 gene to chromosome 19p13.11 based on an alignment of the CILP2 sequence (GenBank AF542080) with the genomic sequence (GRCh37).
Bernardo, B. C., Belluoccio, D., Rowley, L., Little, C. B., Hansen, U., Bateman, J. F. Cartilage intermediate layer protein 2 (CILP-2) is expressed in articular and meniscal cartilage and down-regulated in experimental osteoarthritis. J. Biol. Chem. 286: 37758-37767, 2011. [PubMed: 21880736] [Full Text: https://doi.org/10.1074/jbc.M111.248039]
Gross, M. B. Personal Communication. Baltimore, Md. 9/10/2012.
Johnson, K., Farley, D., Hu, S.-I., Terkeltaub, R. One of two chondrocyte-expressed isoforms of cartilage intermediate-layer protein functions as an insulin-like growth factor 1 antagonist. Arthritis Rheum. 48: 1302-1314, 2003. [PubMed: 12746903] [Full Text: https://doi.org/10.1002/art.10927]