Alternative titles; symbols
HGNC Approved Gene Symbol: JCHAIN
Cytogenetic location: 4q13.3 Genomic coordinates (GRCh38): 4:70,655,541-70,666,508 (from NCBI)
J chain is a 137-amino acid protein that is synthesized in B lymphocytes and serves 2 known functions: linking immunoglobulin monomers (IgM to pentamers, IgA to dimers) and binding these immunoglobulins to secretory component (Koshland, 1985).
Using probes from J chain clones, Max et al. (1986) assigned the J chain gene to 4q21 by Southern analysis of somatic cell hybrids and by in situ hybridization. This band is the site of translocations with chromosome 11 in some acute lymphocytic leukemias. In the mouse, JCH maps to chromosome 5 which carries 4 other genes that are also on human chromosome 4 (PGM2, PEPS, ALB, and AFP).
Max et al. (1986) also discovered genetic variation in the number of repeats of a 27-bp sequence that is tandemly reduplicated 5-prime of the human J chain gene. They suggested that this polymorphism may be 'useful in genetic linkage studies in a region of chromosome 4 heretofore relatively barren of markers definitively localized to a particular subband.' (The J chain gene is not to be confused with the J region gene of immunoglobulins; see 146970, 147010, and 147230 for the J region genes of kappa, heavy, and lambda chains, respectively.)
Lim et al. (2006) showed that the CRLZ1 (UTP3; 611614) and IgJ genes are adjacent but divergently transcribed in human and mouse. By chromatin immunoprecipitation and FACS analysis of sorted mouse pre-B cells and plasma cells, Lim et al. (2006) found that IgJ was expressed in the plasma cell stage, whereas Crlz1 was expressed in the pre-B cell stage. The stage-specific expression of IgJ and Crlz1 was regulated by chromatin accessibility and acetylation. DNase I hypersensitive site 1 on the IgJ promoter was opened in plasma cells, but hypersensitive sites 9 and 10 on the Crlz1 promoter were opened in pre-B cells. H3 (see 602810) and H4 (see 602822) histones were hyperacetylated in the chromatin of Crlz1 in pre-B cells, whereas those in the chromatin of IgJ were hyperacetylated in plasma cells. Lim et al. (2006) concluded that the CRLZ1-IgJ locus shows stage-specific gene expression regulation, and they proposed that additional regulatory elements may exist between the genes to coordinate chromatin accessibility and histone acetylation over the locus.
Koshland, M. E. The coming of age of the immunoglobulin J chain. Annu. Rev. Immun. 3: 425-453, 1985. [PubMed: 2415140] [Full Text: https://doi.org/10.1146/annurev.iy.03.040185.002233]
Lim, J.-H., Cho, S.-J., Park, S.-K., Kim, J., Cho, D., Lee, W. J., Kang, C.-J. Stage-specific expression of two neighboring Crlz1 and IgJ genes during B cell development is regulated by their chromatin accessibility and histone acetylation. J. Immun. 177: 5420-5429, 2006. [PubMed: 17015728] [Full Text: https://doi.org/10.4049/jimmunol.177.8.5420]
Max, E. E., McBride, O. W., Morton, C. C., Robinson, M. A. Human J chain gene: chromosomal localization and associated restriction fragment length polymorphisms. Proc. Nat. Acad. Sci. 83: 5592-5596, 1986. [PubMed: 3016707] [Full Text: https://doi.org/10.1073/pnas.83.15.5592]