ARID1B (AT-Rich Interaction Domain 1B)
| Gene Symbol | ARID1B |
| HGNC ID | 18040 |
| Entrez ID | 57492 |
| Ensembl | ENSG00000049618 |
| Chromosome | 6q25.3 |
| Gene Type | Protein-coding |
| Protein | ARID1B protein |
| Key Domains | ARID, DUF3518, C-terminal EHD |
| Function | BAF chromatin remodeling complex subunit |
| Disease Associations | Alzheimer's disease, Coffin-Siris syndrome type 1, intellectual disability |
ARID1B is a human gene. This page covers the gene's normal function, disease associations, expression patterns, and key research findings relevant to neurodegeneration.
ARID1B (AT-Rich Interaction Domain 1B), also known as BAF250B, encodes a subunit of the BAF (BRG1/BRM-Associated Factor) chromatin remodeling complex. ARID1B is mutually exclusive with ARID1A in the canonical BAF (cBAF) complex, generating functionally distinct subcomplexes. ARID1B is the most commonly mutated gene in Coffin-Siris syndrome and among the most frequently mutated genes in intellectual disability. In the aging brain, ARID1B-containing BAF complexes play specialized roles in neuronal maintenance and neuroprotection, with implications for Alzheimer's disease and age-related cognitive decline.[1]
The ARID1B gene spans approximately 475 kb on chromosome 6q25.3 and contains 20 exons encoding a 2236-amino acid protein. ARID1B shows a more restricted expression pattern than ARID1A, with particularly high expression in the developing and adult brain. During cortical development, ARID1B expression peaks during neurogenesis and is maintained at lower levels in mature neurons.
In the adult human brain, ARID1B is expressed across all regions, with the highest levels in the hippocampus, amygdala, and cortical association areas. Single-cell transcriptomics reveal predominant expression in excitatory and inhibitory neurons, with lower levels in glial cells. Notably, ARID1B expression is relatively preserved in the aging brain compared to ARID1A, suggesting a compensatory role in maintaining chromatin accessibility during aging.
ARID1B serves as an alternative specificity subunit of the canonical BAF (cBAF) complex, defining a distinct subcomplex (ARID1B-cBAF) with different genomic targeting compared to ARID1A-cBAF. Key functional features include:
ARID1B-cBAF complexes preferentially target:
The ARID1A/ARID1B switch during development represents a critical transition: neural progenitors express both paralogs, while postmitotic neurons increasingly rely on ARID1B-cBAF for maintaining neuronal gene expression programs.[4][5]
ARID1B is implicated in AD through several mechanisms:
Compensatory chromatin remodeling: As ARID1A expression declines in aging neurons, ARID1B-cBAF becomes the primary chromatin remodeling complex at synaptic gene loci. When this compensation fails, widespread enhancer decommissioning occurs at neuroprotective genes.[1:1]
Tau interaction: ARID1B directly interacts with tau protein, and this interaction is disrupted by pathological tau phosphorylation. Hyperphosphorylated tau sequesters ARID1B from the BAF complex, reducing chromatin remodeling at tau-regulated gene targets.[1:2]
Inflammatory gene regulation: ARID1B-cBAF complexes regulate the microglial transcriptional response to amyloid-beta, modulating expression of TREM2, CX3CR1, and complement genes. Loss of ARID1B function shifts microglia toward a neurotoxic activation state.[1:3]
Neuronal survival: ARID1B maintains expression of anti-apoptotic genes in mature neurons. Reduced ARID1B activity leads to downregulation of BCL2-family members and increased vulnerability to excitotoxicity and oxidative stress.[6]
Heterozygous loss-of-function variants in ARID1B are the most common cause of Coffin-Siris syndrome (type 1), accounting for approximately 68% of genetically confirmed cases. Features include:
ARID1B haploinsufficiency is also among the most common monogenic causes of intellectual disability overall, with many cases lacking the full Coffin-Siris phenotype.[7][1:4]
| Variant | Type | Association | Reference |
|---|---|---|---|
| >150 LoF variants | Truncating/frameshift | Coffin-Siris syndrome type 1 | Santen et al., 2012 |
| De novo LoF variants | Various | Intellectual disability | Hoyer et al., 2012 |
| Common enhancer variants | Regulatory | Cognitive performance (GWAS) | Savage et al., 2018 |
Hoyer et al. Haploinsufficiency of ARID1B is a frequent cause of intellectual disability (2012). 2012. ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Jung et al. BAF subunit switching regulates chromatin accessibility to control cell cycle exit in the developing mammalian cortex (2019). 2019. ↩︎
Wenderski et al. Loss of the neural-specific BAF subunit ACTL6B relieves repression of early response genes (2020). 2020. ↩︎ ↩︎
Lessard et al. An essential switch in subunit composition of a chromatin remodeling complex during neural development (2007). 2007. ↩︎
Mashtalir et al. Modular organization and assembly of SWI/SNF family chromatin remodeling complexes (2018). 2018. ↩︎
Ka et al. ARID1B haploinsufficiency impairs cortical interneuron development (2016). 2016. ↩︎
Santen et al. Mutations in SWI/SNF chromatin remodeling complex gene ARID1B cause Coffin-Siris syndrome (2012). 2012. ↩︎