Other entities represented in this entry:
HGNC Approved Gene Symbol: OC90
Cytogenetic location: 8q24.22 Genomic coordinates (GRCh38): 8:132,024,216-132,059,382 (from NCBI)
Using a differential hybridization strategy, Feuchter-Murthy et al. (1993) isolated AF-5, a human teratocarcinoma cell line cDNA representing a chimeric transcript in which an endogenous retrovirus-like element, RTVL-H, is spliced to downstream cellular sequences. AF-5 contains an open reading frame beginning within RTVL-H sequences and continuing with a region from an adjacent gene that encodes 2 domains homologous to PLA2 (see 172411). The authors designated the adjacent gene PLA2L (PLA2-like gene). PLA2s generally have only a single PLA2 domain; neither PLA2L phospholipase domain could be classified definitively as a member of a known PLA2 group. Using Southern blots, the authors determined that the RTVL-H element is a normal part of the PLA2L locus in humans. Northern blot analysis revealed that PLA2L is expressed only in teratocarcinoma cell lines.
Kowalski et al. (1997) argued that PLA2L has substitutions in several conserved residues shared by functional PLA2s; hence, it is not likely to be a true phospholipase.
The ability to sense orientation relative to gravity requires dense particles, called otoconia, which are localized in the vestibular macular organs. In mammals, otoconia are composed of proteins known as otoconins and calcium carbonate crystals in a calcite lattice. It is thought that matrix proteins are required for the nucleation and growth of the crystals. Otoconin-90 (OC90) accounts for more than 90% of total mouse otoconial protein. Wang et al. (1998) determined a partial protein sequence for mouse and guinea pig otoconin-90 (OC90) and found that it corresponded to the PLA2L gene. The authors isolated additional mouse cDNAs and genomic clones and determined that the predicted mature OC90 protein contains 453 amino acids. Although OC90 has a predicted molecular mass of 49 kD and pI of 4.4, it has an apparent molecular mass of 83 kD and pI of 2.9. The authors attributed the discrepancy to nonhomogeneous glycosylation. RT-PCR analysis demonstrated that OC90 is specifically expressed in the developing mouse otocyst. Kowalski et al. (1999) determined that the precursor OC90 protein contains a 17-amino acid signal peptide that is cleaved to yield mature OC90.
Kowalski et al. (1999) reported that the PLA2L transcript represents a tripartite fusion event in which transcription initiates from the retroviral element's long terminal repeat and then splices together exons from a novel gene, HHLA1 (604109), and OC90. They hypothesized that human HHLA1 and OC90 are normally expressed independently from different promoters, and that the intergenic splicing event is specific to teratocarcinoma tumor cells.
The human OC90 gene contains at least 14 exons and is located less than 10 kb downstream of HHLA1.
Using fluorescence in situ hybridization and radiation hybrid mapping techniques, Meyer et al. (1996) assigned the PLA2L gene to 8q24-qter. Kowalski et al. (1997) confirmed the mapping of PLA2L to 8q24.
Feuchter-Murthy, A. E., Freeman, J. D., Mager, D. L. Splicing of a human endogenous retrovirus to a novel phospholipase A2 related gene. Nucleic Acids Res. 21: 135-143, 1993. [PubMed: 8382789] [Full Text: https://doi.org/10.1093/nar/21.1.135]
Kowalski, P. E., Freeman, J. D., Mager, D. L. Intergenic splicing between a HERV-H endogenous retrovirus and two adjacent human genes. Genomics 57: 371-379, 1999. [PubMed: 10329003] [Full Text: https://doi.org/10.1006/geno.1999.5787]
Kowalski, P. E., Freeman, J. D., Nelson, D. T., Mager, D. L. Genomic structure and evolution of a novel gene (PLA2L) with duplicated phospholipase A(2)-like domains. Genomics 39: 38-46, 1997. [PubMed: 9027484] [Full Text: https://doi.org/10.1006/geno.1996.4471]
Meyer, A. H., Schmuck, K., Morel, C., Wishart, W., Lubbert, H., Engels, P. Localization of a gene coding for the phospholipase A2-L subtype (PLA2L) to human chromosome 8q24-qter. Genomics 38: 435-437, 1996. [PubMed: 8975724] [Full Text: https://doi.org/10.1006/geno.1996.0650]
Wang, Y., Kowalski, P. E., Thalmann, I., Ornitz, D. M., Mager, D. L., Thalmann, R. Otoconin-90, the mammalian otoconial matrix protein, contains two domains of homology to secretory phospholipase A(2). Proc. Nat. Acad. Sci. 95: 15345-15350, 1998. [PubMed: 9860971] [Full Text: https://doi.org/10.1073/pnas.95.26.15345]