| Symbol | JAM2 |
|---|---|
| Full Name | Junctional Adhesion Molecule 2 |
| Chromosome | 21 |
| Location | 21q21.3 |
| NCBI Gene ID | JAM2 |
| OMIM | 607215 |
| Ensembl ID | ENSG00000176182 |
| UniProt ID | Q9UJF4 |
| Associated Diseases | Autism spectrum disorder, intellectual disability |
JAM3 is a human gene whose product jAM2 mediates homophilic (JAM2-JAM2) and heterophilic (JAM2-JAM3) interactions at cell junctions:. This page covers the gene's normal function, disease associations, expression patterns, and key research findings relevant to neurodegeneration.
JAM2 (Junctional Adhesion Molecule 2) is a tight junction protein expressed at the blood-brain barrier (BBB), neuronal synapses, and germ cell junctions. It plays critical roles in maintaining BBB integrity, regulating synaptic transmission, and controlling immune cell trafficking. JAM2 deficiency leads to disrupted BBB function, increased neuroinflammation, and synaptic abnormalities. Common variants in JAM2 have been associated with autism spectrum disorder and intellectual disability, while altered expression is observed in multiple sclerosis and Alzheimer's disease.[1][2]
JAM2 mediates homophilic (JAM2-JAM2) and heterophilic (JAM2-JAM3) interactions at cell junctions:
Blood-Brain Barrier Integrity: JAM2 is a core component of tight junctions in brain endothelial cells. It recruits signaling proteins (ZO-1, cingulin) and maintains barrier properties. Loss of JAM2 increases BBB permeability to immune cells and toxins.
Synaptic Function: Postsynaptic JAM2 interacts with PSD-95 and regulates excitatory synapse formation and function. It modulates AMPA receptor trafficking and synaptic plasticity.
Immune Cell Trafficking: JAM2 controls lymphocyte migration across the BBB by interacting with integrin α4β1 (VLA-4) on immune cells. This regulates neuroinflammation in MS and autoimmune encephalitis.
Neuronal Polarity: JAM2 helps establish axonal polarity by localizing to the axon initial segment, where it interacts with ankyrin-G.
Epileptogenesis: Altered JAM2 expression contributes to BBB breakdown during seizures, creating a feedforward loop for neuroinflammation.[3][4]
Autism spectrum disorder, intellectual disability[5][6]
JAM2 is highly expressed in brain endothelial cells forming the blood-brain barrier, with lower expression in neurons (particularly in the hippocampus and cortex). Postsynaptic expression is enriched in dendritic spines. Expression is inducible by inflammatory cytokines (TNF-α, IFN-γ).[7]
Target Rationale: JAM2's central role in BBB integrity makes it attractive for neuroinflammatory and neurodegenerative diseases.
Potential Approaches:
Research Status: JAM2-Fc is in preclinical development for multiple sclerosis; AAV-mediated JAM2 expression being explored for BBB repair.[8]