JCHAIN (Joining Chain of Multimeric IgA and IgM)
A key component of the adaptive immune system, essential for the polymerization and mucosal transport of IgA and IgM antibodies.
Gene Information Card
| Symbol | JCHAIN |
|---|---|
| Full Name | Joining chain of multimeric IgA and IgM |
| Gene Type | Protein coding |
| Chromosomal Location | 4q13.3 |
| NCBI Gene ID | 3512 ncbi.nlm.nih.gov/gene/3512 |
| Ensembl ID | ENSG00000132465 |
| UniProt ID | P01591 |
| OMIM ID | 147790 |
| HGNC ID | 6169 |
| Aliases | IGJ, JCH, J chain, immunoglobulin J chain |
Description
The JCHAIN gene encodes the joining (J) chain, a 15-16 kDa polypeptide that is a critical component of polymeric immunoglobulins. It is synthesized by plasma cells and facilitates the polymerization of IgA into dimers and IgM into pentamers. The J chain is also essential for the binding of these immunoglobulins to the polymeric immunoglobulin receptor (pIgR), enabling their transcytosis across mucosal epithelial cells into secretions such as saliva, tears, and intestinal fluid. This gene is highly expressed in lymphoid tissues and plasma cells.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Multiple myeloma | JCHAIN is frequently expressed in multiple myeloma cells and is used as a marker of plasma cell differentiation. Its expression correlates with disease progression and prognosis. | ClinVar, COSMIC |
| IgA nephropathy | Dysregulation of JCHAIN expression may contribute to aberrant IgA1 glycosylation and polymerization, leading to mesangial deposition. | OMIM, NCBI |
| Immunodeficiency with hyper-IgM | Mutations affecting JCHAIN or its regulatory elements can impair IgM polymerization and mucosal immunity, though direct evidence is limited. | ClinVar |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Lymph node | 12.5 | High |
| Spleen | 10.8 | High |
| Bone marrow | 8.2 | Medium |
| Small intestine | 6.1 | Medium |
| Colon | 4.3 | Low |
| Salivary gland | 3.9 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| RPMI-8226 (multiple myeloma) | 15.2 | High expression; used as positive control |
| U266 (multiple myeloma) | 12.8 | High expression |
| MCF7 (breast cancer) | 0.5 | Very low expression |
| HeLa (cervical cancer) | 0.3 | Very low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1A>G (p.Met1Val) | Missense | <0.01% | Potential loss of start codon; predicted to affect translation initiation |
| c.214C>T (p.Arg72Cys) | Missense | <0.01% | May disrupt disulfide bond formation; uncertain significance |
| c.325_326insA | Frameshift | <0.01% | Predicted to cause premature truncation; likely loss of function |
Mutation functional classification
Loss of Function (LOF)
Frameshift and nonsense mutations that truncate the J chain protein, impairing IgA/IgM polymerization and mucosal transport.
Gain of Function (GOF)
Not described in the literature; no known gain-of-function mutations.
Dominant Negative (DN)
Not reported; JCHAIN is typically expressed from a single allele and dominant-negative effects are not documented.
View complete mutation data：
Gene Ontology (GO)
Pathways
• hsa04672 (Intestinal immune network for IgA production)
• hsa04640 (Hematopoietic cell lineage)
• hsa04662 (B cell receptor signaling pathway)
• hsa05150 (Staphylococcus aureus infection)
• hsa05320 (Autoimmune thyroid disease)
Protein Summary
The J chain protein (UniProt P01591) is a 137-amino-acid polypeptide that contains 8 cysteine residues involved in disulfide bonding with the tailpieces of IgA and IgM heavy chains. It is synthesized as a precursor with a 22-amino-acid signal peptide. The mature protein is highly conserved across mammals. Its structure includes a single immunoglobulin-like domain. The J chain is essential for the formation of secretory IgA and IgM, which are critical for mucosal immunity. It also plays a role in the intracellular transport of polymeric immunoglobulins.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| JCHAIN Knockout HEK293 Cell Line | EDJ-KQ2316 | Human | 3512 | Details Get a Quote |
| JCHAIN Knockout HeLa Cell Line | EDJ-KQ22707 | Human | 3512 | Details Get a Quote |
| JCHAIN Knockout A-549 Cell Line | EDJ-KQ62098 | Human | 3512 | Details Get a Quote |
| JCHAIN Knockout HCT 116 Cell Line | EDJ-KQ70585 | Human | 3512 | Details Get a Quote |
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