Alternative titles; symbols
HGNC Approved Gene Symbol: CAPRIN2
Cytogenetic location: 12p11.21 Genomic coordinates (GRCh38): 12:30,709,553-30,754,951 (from NCBI)
By searching for cDNAs encoding large proteins expressed in brain, Nagase et al. (2001) identified a partial cDNA from adult brain encoding C1QDC1, which they called KIAA1873. RT-PCR analysis detected expression in all adult and fetal tissues and specific brain regions examined.
By searching an EST database for genes expressed during erythropoiesis, followed by PCR of bone marrow and erythroid progenitor cell cDNA libraries, Aerbajinai et al. (2004) cloned long and short variants of C1QDC1, which they called EEG1. The long variant, EEG1L, lacks exon 13 and encodes a 1,077-amino acid protein containing an N-terminal nuclear localization sequence, a C-terminal C1q (see 120550)-like domain, and several phosphorylation sites. The short variant, EEG1S, lacks exon 5, resulting in a frameshift and a truncated protein of 279 amino acids. RT-PCR analysis detected low, ubiquitous expression of EEG1, with highest expression of EEG1L and EEG1S in brain and spleen, respectively. Immunofluorescence confocal microscopy demonstrated cytoplasmic expression of EEG1L, whereas EEG1S was associated with aggregated mitochondria.
By database analysis, Grill et al. (2004) identified C1QDC1, which they called caprin-2, as a paralog of caprin-1 (GPIAP1; 601178). The predicted 1,126-amino acid caprin-2 protein shares 2 conserved regions, termed homology region-1 (HR1) and HR2, with caprin-1. Caprin-2 also has a C-terminal C1q-related domain not present in caprin-1. The authors identified multiple caprin-2 splice variants by database analysis.
By immunoblot analysis of mouse tissues, Shiina and Tokunaga (2010) found that Caprin2, which they called Rng140, was highly expressed in adult brain only. In contrast, its paralog, Rng105 (Caprin2), was primarily expressed in embryonic mouse brain. Immunofluorescence analysis showed that Rng140 and Rng105 localized to distinct RNA granules in both cultured cells and rat neuronal dendrites.
Aerbajinai et al. (2004) found that transfection of EEG1L and EEG1S was associated with increased apoptosis in Chinese hamster ovary cells. They proposed that EEG1 is involved in the regulation of growth occurring as erythroblasts shift from a highly proliferative state toward the terminal phase of differentiation.
Shiina and Tokunaga (2010) reported that rat Rng140 and Rng105 both bound to mRNA, inhibited translation, and induced formation of RNA granules. Knockdown of either protein in cultured mouse neurons resulted in reduced dendrite length and spine density, and there was no compensatory rescue activity of one protein for the other.
Aerbajinai et al. (2004) and Grill et al. (2004) determined that the C1QDC1 gene contains at least 18 exons and spans 45 kb.
By genomic sequence analysis, Aerbajinai et al. (2004) mapped the C1QDC1 gene to chromosome 12p11.21.
Aerbajinai, W., Lee, Y. T., Wojda, U., Barr, V. A., Miller, J. L. Cloning and characterization of a gene expressed during terminal differentiation that encodes a novel inhibitor of growth. J. Biol. Chem. 279: 1916-1921, 2004. [PubMed: 14593112] [Full Text: https://doi.org/10.1074/jbc.M305634200]
Grill, B., Wilson, G. M., Zhang, K.-X., Wang, B., Doyonnas, R., Quadroni, M., Schrader, J. W. Activation/division of lymphocytes results in increased levels of cytoplasmic activation/proliferation-associated protein-1: prototype of a new family of proteins. J. Immun. 172: 2389-2400, 2004. [PubMed: 14764709] [Full Text: https://doi.org/10.4049/jimmunol.172.4.2389]
Nagase, T., Nakayama, M., Nakajima, D., Kikuno, R., Ohara, O. Prediction of the coding sequences of unidentified human genes. XX. The complete sequences of 100 new cDNA clones from brain which code for large proteins in vitro. DNA Res. 8: 85-95, 2001. [PubMed: 11347906] [Full Text: https://doi.org/10.1093/dnares/8.2.85]
Shiina, N., Tokunaga, M. RNA granule protein 140 (RNG140), a paralog of RNG105 localized to distinct RNA granules in neuronal dendrites in the adult vertebrate brain. J. Biol. Chem. 285: 24260-24269, 2010. [PubMed: 20516077] [Full Text: https://doi.org/10.1074/jbc.M110.108944]