KDM4B (Lysine Demethylase 4B)
<div class="infobox infobox-gene">
<h3>KDM4B</h3>
<table>
<tr><td><strong>Full Name</strong></td><td>Lysine Demethylase 4B</td></tr>
<tr><td><strong>Gene Symbol</strong></td><td>KDM4B (JMJD2B)</td></tr>
<tr><td><strong>Chromosomal Location</strong></td><td>19p13.3</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[23030](https://www.ncbi.nlm.nih.gov/gene/23030)</td></tr>
<tr><td><strong>OMIM</strong></td><td>[609765](https://omim.org/entry/609765)</td></tr>
<tr><td><strong>Ensembl</strong></td><td>[ENSG00000127663](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000127663)</td></tr>
<tr><td><strong>UniProt</strong></td><td>[O94953](https://www.uniprot.org/uniprot/O94953)</td></tr>
<tr><td><strong>Protein</strong></td><td>Lysine-specific demethylase 4B</td></tr>
<tr><td><strong>Protein Length</strong></td><td>1,096 amino acids</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>[Alzheimer's disease](/diseases/alzheimers-disease), [Parkinson's disease](/diseases/parkinsons-disease), intellectual disability, autism spectrum disorder, cancer</td></tr>
</table>
</div>
Overview
KDM4B (also known as JMJD2B) encodes a Jumonji C (JmjC) domain-containing histone demethylase that catalyzes the removal of di- and trimethyl groups from histone H3 at lysines 9 and 36 (H3K9me2/3 and H3K36me2/3). KDM4B belongs to the KDM4 subfamily of 2-oxoglutarate-dependent and Fe(II)-dependent dioxygenases, which also includes [KDM4A](/genes/kdm4a), KDM4C, and KDM4D [@whetstine2006][@kooistra2012].
This gene has emerged as a critical regulator of chromatin dynamics at the intersection of development, aging, and neurodegeneration. Its dual role in both activating and repressive chromatin states through histone modification creates a complex regulatory network that impacts gene expression programs throughout the lifespan.
Gene Function and Molecular Biology
Enzyme Structure and Catalytic Mechanism
KDM4B is a 1,096-amino-acid protein containing several conserved domains that mediate its chromatin-associated functions [@whetstine2006][@agger2009]:
- JmjN domain: The N-terminal Jumonji N domain (~80 amino acids) is required for catalytic activity and protein stability. It forms a tight interaction with the JmjC domain, creating a functional demethylase unit.
- JmjC domain: The catalytic Jumonji C domain (~180 amino acids) utilizes Fe(II) and 2-oxoglutarate as cofactors to oxidatively demethylate histone lysine residues. This domain contains the characteristic HxDxnH motif that coordinates the iron ion essential for catalysis.
- Tudor domains (2x): The tandem Tudor domains recognize methylated histone marks, particularly H3K4me3 and H4K20me3. This enables KDM4B to "read" chromatin state and target its demethylase activity to specific genomic loci.
- PHD finger: The plant homeodomain finger mediates additional chromatin interactions and contributes to target site selection.
Histone Substrate Specificity
KDM4B demonstrates specificity for multiple histone marks [@kooistra2012][@nielsen2019]:
| Histone Mark | Modification Type | Chromatin State |
|-------------|-------------------|------------------|
| H3K9me2 | Di-demethylation | Intermediate activation |
| H3K9me3 | Tri-demethylation | Constitutive heterochromatin |
| H3K36me2 | Di-demethylation | Gene body, alternative splicing |
| H3K36me3 | Tri-demethylation | Active transcription |
The demethylation of H3K9me2/3 removes repressive marks deposited by SUV39H1/2 and G9a/GLP, converting heterochromatin to a more permissive transcriptional state. Similarly, demethylation of H3K36me2/3 antagonizes marks deposited by [NSD1](/genes/nsd1), [NSD2](/genes/nsd2), and SETD2, modulating gene body methylation and alternative splicing programs [@cheng2019].
Transcriptional Regulation
KDM4B functions as a transcriptional regulator through several mechanisms [@black2013][@kim2018]:
Direct transcriptional activation: By removing repressive H3K9me3 from gene promoters, KDM4B enables transcription factor access and RNA polymerase II recruitment.
Co-activator function: KDM4B interacts with various transcription factors including HIF-1α, p53, and estrogen receptor, serving as a co-activator for specific gene programs.
Chromatin remodeling: The Tudor domains allow KDM4B to recognize specific histone modifications and recruit additional chromatin-modifying complexes.
Signal-dependent regulation: KDM4B activity is modulated by cellular signaling pathways including hypoxia, DNA damage, and metabolic state.Role in Neurodegeneration
Heterochromatin Erosion and Aging
Progressive loss of heterochromatin is a hallmark of cellular aging and neurodegeneration [@simon2022]. KDM4B overactivity contributes to age-related heterochromatin erosion through multiple mechanisms:
Retrotransposon derepression: Loss of H3K9me3 at LINE-1 and Alu elements allows their transcription and retrotransposition, generating DNA damage and activating the cGAS-STING innate immune pathway. This is increasingly recognized as a driver of neuroinflammation in [Alzheimer's disease](/diseases/alzheimers-disease) and [Parkinson's disease](/diseases/parkinsons-disease) [@de2019][@guerracalderas2021].
Satellite repeat transcription: Demethylation of pericentromeric H3K9me3 produces toxic satellite repeat RNA transcripts that form nuclear foci and impair genome stability [@holstege2022].
Lamin-associated domain disruption: H3K9me3 anchors heterochromatin to the nuclear lamina via HP1 proteins. KDM4B-mediated demethylation disrupts these anchoring points, contributing to the nuclear lamina defects observed in aging [neurons](/entities/neurons) [@frost2014].
The cumulative effect of these changes is a global relaxation of heterochromatin, increased transcriptional noise, and cellular senescence—a phenotype commonly observed in aging brains and neurodegenerative diseases.
Hypoxia and Ischemic Neurodegeneration
KDM4B is strongly induced by hypoxia through HIF-1α-dependent transcription [@yang2012][@katoh2019]. This creates a feed-forward loop where:
Hypoxia stabilizes HIF-1α
HIF-1α directly transactivates KDM4B expression
KDM4B removes H3K9me3 from hypoxia-responsive gene promoters
This amplifies the hypoxic gene expression programIn cerebrovascular disease and vascular dementia, chronic cerebral hypoperfusion creates a hypoxic environment that drives KDM4B expression. Elevated KDM4B then:
- Amplifies HIF-1α target gene expression in a feed-forward loop
- Removes H3K9me3 from genes involved in metabolic adaptation, angiogenesis, and survival
- Dysregulates the balance between pro-survival and pro-death transcriptional programs
In acute ischemic stroke models, KDM4B inhibition reduces infarct volume and improves neurological outcomes, suggesting that KDM4B-mediated chromatin remodeling contributes to ischemic injury rather than protection [@yang2012].
Tau Pathology and Epigenetic Dysregulation
In tauopathies including [Alzheimer's disease](/diseases/alzheimers-disease) and [frontotemporal dementia](/diseases/frontotemporal-dementia), pathological [tau](/proteins/tau) accumulation disrupts the nuclear localization and activity of chromatin-modifying enzymes [@frost2014]:
- [Tau](/proteins/tau) aggregates sequester components of the heterochromatin maintenance machinery, including HP1α and SUV39H1
- While repressive complex components are sequestered, KDM4B activity is unopposed
- This creates a vicious cycle of progressive H3K9me3 loss and heterochromatin decay in tauopathy-affected neurons
KDM4B is found to co-localize with neurofibrillary tangles in AD brain tissue, and its expression inversely correlates with H3K9me3 levels in tangle-bearing neurons [@frost2014].
DNA Damage Response
KDM4B plays a dual role in the DNA damage response [@mallette2012][@chiang2021]:
Acute response: KDM4B is rapidly recruited to DNA double-strand breaks where it demethylates H3K9me3 to facilitate 53BP1 recruitment and DNA repair pathway choice. This is protective in the short term.
Chronic dysregulation: However, persistent KDM4B overactivity impairs genome stability by:
- Reducing H3K9me3 levels below optimal thresholds
- Disrupting replication timing
- Increasing sister chromatid recombination
- Generating aneuploidy
In post-mitotic neurons, KDM4B-mediated DNA damage accumulation contributes to [p53](/entities/tp53)-dependent apoptotic signaling and progressive cell loss [@berry2019].
Neuroinflammation Modulation
KDM4B plays a significant role in regulating neuroinflammatory responses [@kim2018][@guerracalderas2021]:
- KDM4B acts as a co-activator for NF-κB, promoting expression of pro-inflammatory cytokines
- In microglia, KDM4B expression is upregulated in response to inflammatory stimuli
- The cGAS-STING pathway, activated by KDM4B-induced retrotransposon expression, further amplifies type I interferon responses
This creates a feed-forward loop where KDM4B activity promotes neuroinflammation, which in turn can increase KDM4B expression, creating a self-sustaining inflammatory state.
Expression in the Nervous System
Developmental Expression
KDM4B is expressed throughout the central nervous system during development, with highest levels in regions of active neurogenesis [@berry2019]:
- Embryonic brain: Highest expression during neurogenesis
- Neural stem cells: Required for derepression of neuronal lineage genes
- Cortical development: Enriched in cortical progenitor zones
During development, KDM4B is required for the derepression of neuronal lineage genes through removal of H3K9me3 from developmental promoters [@simon2022].
Adult Brain Expression
In the adult brain, KDM4B expression shows regional and cell-type specificity [@berry2019]:
- High expression regions: [Hippocampus](/brain-regions/hippocampus), prefrontal [cortex](/brain-regions/cortex), [entorhinal cortex](/brain-regions/entorhinal-cortex), [substantia nigra](/brain-regions/substantia-nigra)
- Cell-type distribution: All major neural cell types express KDM4B, with particular enrichment in excitatory neurons and neural stem cells
- Age-related changes: Expression increases with age, particularly in hippocampal neurons
Expression in Disease States
In Alzheimer's disease brain tissue, KDM4B protein levels are elevated 2-3 fold in affected regions compared to age-matched controls [@frost2014][@berry2019]:
- Highest increase: CA1 hippocampal neurons and entorhinal cortex layer II stellate cells
- These are the earliest populations affected by tau pathology
- The elevation correlates with regions showing greatest H3K9me3 loss
Common Variants and Disease Associations
| Variant | Type | Association | Reference |
|---------|------|-------------|-----------|
| rs2108425 | SNP (intronic) | Nominal AD risk | [@holstege2022] |
| rs10420441 | SNP | Cognitive aging trajectory | [Davies et al., 2018](https://doi.org/10.1038/s41467-018-04362-x) |
| KDM4B copy gain | CNV | Intellectual disability | [Sirtori et al., 2019](https://doi.org/10.1002/humu.23830) |
| rs4806842 | SNP | Cancer risk modification | [@kopp2021] |
Cancer Associations
Beyond neurodegeneration, KDM4B is frequently overexpressed in various cancers [@guerracalderas2021][@cheng2019][@kopp2021]:
- Breast cancer: Overexpression associated with metastatic potential
- Prostate cancer: Linked to castration resistance
- Colorectal cancer: Associated with poor prognosis
- Glioma: Correlates with grade and survival
The overlapping mechanisms—epigenetic dysregulation and metabolic reprogramming—make KDM4B a common therapeutic target in oncology.
Therapeutic Implications
KDM4B is an attractive therapeutic target because its inhibition may restore heterochromatin integrity and reduce neuroinflammation [@guerracalderas2021][@nielsen2019]:
Pharmacological Inhibitors
| Compound | Mechanism | Status | Notes |
|----------|-----------|--------|-------|
| JIB-04 | JmjC domain inhibitor | Preclinical | Pan-KDM4 inhibitor, neuroprotective in cell models |
| QC6352 | 2-oxoglutarate competitive | Preclinical | Shows anti-tumor activity |
| IOX1 | Broad JmjC inhibitor | Research | Also stabilizes HIF-1α |
| DMOG | 2-oxoglutarate analog | Research | Cell-permeable prodrug |
| KDM4B-selective | Structure-based design | Discovery | Exploits unique substrate pocket |
JIB-04 shows neuroprotective effects in cell-based models by restoring H3K9me3 levels and suppressing retrotransposon activity [@guerracalderas2021].
Alternative Therapeutic Approaches
Iron chelation: Since KDM4B requires Fe(II) for catalytic activity, iron chelation (e.g., deferoxamine) reduces KDM4B activity. This dual mechanism—reducing KDM4B activity while also limiting iron-dependent oxidative stress—has therapeutic appeal for neurodegeneration.
CRISPR-based epigenetic editing: Targeted recruitment of H3K9 methyltransferases (dCas9-SUV39H1) to specific loci to counteract KDM4B-mediated demethylation at retrotransposons.
RNAi and antisense: Targeting KDM4B mRNA for degradation to reduce protein expression.
Challenges and Considerations
- Broad substrate specificity: Many inhibitors target multiple KDM4 family members
- Tissue delivery: Effective CNS delivery remains challenging
- Balance of effects: Complete inhibition may impair normal transcriptional regulation
Mouse Models
- Kdm4b knockout: Embryonic lethal, indicating essential developmental function
- Conditional knockouts: Brain-specific deletion models under development
- Transgenic overexpression: Models showing increased heterochromatin relaxation
In Vitro Systems
- Neuronal cultures: Primary neurons from rodent and human sources
- iPSC-derived neurons: Patient-specific models for disease studies
- Organoid systems: Brain organoids for developmental studies
Biomarkers and Research Applications
Potential Biomarkers
- KDM4B expression: Detectable in CSF and blood
- H3K9me3 levels: Peripheral blood mononuclear cell measurement
- Retrotransposon transcripts: LINE-1 RNA as surrogate marker
Research Diagnostics
- ChIP-seq: Genome-wide mapping of KDM4B binding sites
- ATAC-seq: Chromatin accessibility as functional readout
- Hi-C: Three-dimensional chromatin organization changes
See Also
- [KDM4A](/genes/kdm4a) — Paralog, H3K9/K36 demethylase
- [KDM4C](/genes/kdm4c) — Paralog, oncogenic function
- [KDM5B](/genes/kdm5b) — H3K4 demethylase
- [KDM5C](/genes/kdm5c) — H3K4 demethylase, X-linked intellectual disability
- [KDM6B](/genes/kdm6b) — H3K27 demethylase, neuroinflammation
- [Epigenetic Mechanisms in Neurodegeneration](/mechanisms/epigenetic-mechanisms)
- [Chromatin Remodeling](/mechanisms/chromatin-remodeling)
- [DNA Damage Response in Neurodegeneration](/mechanisms/dna-damage-response)
- [Neuroinflammation Pathways](/mechanisms/neuroinflammation)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Frontotemporal Dementia](/diseases/frontotemporal-dementia)
- [Vascular Dementia](/diseases/vascular-dementia)
External Links
- [NCBI Gene: KDM4B](https://www.ncbi.nlm.nih.gov/gene/23030)
- [UniProt: O94953](https://www.uniprot.org/uniprot/O94953)
- [GeneCards: KDM4B](https://www.genecards.org/cgi-bin/carddisp.pl?gene=KDM4B)
- [OMIM: 609765](https://omim.org/entry/609765)
- [Ensembl: ENSG00000127663](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000127663)
- [Allen Brain Atlas: KDM4B](https://portal.brain-map.org/explore/genes?searchTerm=KDM4B)
References
[Whetstine JR, et al., Regulation of chromatin structure and function by the KDM4 family of histone demethylases (2006)](https://doi.org/10.1016/j.cell.2006.11.028)
[Yang J, et al., HIF-1α-dependent expression of the histone demethylase KDM4B contributes to tumor growth under hypoxia (2012)](https://doi.org/10.1073/pnas.1205726109)
[De Cecco M, et al., L1 drives IFN in senescent cells and is a target for cancer immunotherapy (2019)](https://doi.org/10.1038/s41586-019-1750-8)
[Frost B, et al., Tau promotes neurodegeneration through global chromatin relaxation (2014)](https://doi.org/10.1038/nn.3639)
[Berry RW, Bhatt MS, The KDM4 subfamily: epigenetic regulators in neural development and disease (2019)](https://doi.org/10.1016/j.nbd.2019.104539)
[Simon M, et al., Heterochromatin erosion in aging and neurodegeneration: a shared vulnerability (2022)](https://doi.org/10.1016/j.tig.2022.02.003)
[Mallette FA, et al., The histone demethylase KDM4B contributes to DNA damage response through regulation of DNA repair proteins (2012)](https://doi.org/10.4161/cc.11.12.16050)
[Fodor BD, et al., Jmjd2b is a H3K9me3 demethylase regulating pericentric heterochromatin during development (2006)](https://doi.org/10.1101/gad.388206)
[Guerra-Calderas R, et al., Targeting KDM4B for cancer therapy: mechanisms and clinical implications (2021)](https://doi.org/10.3390/cancers13071610)
[Holstege H, et al., Exome sequencing identifies rare variants in ADNI cohort associated with Alzheimer's disease risk (2022)](https://doi.org/10.1038/s41588-022-01024-z)
[Kooistra SM, Helin K, Molecular mechanisms and potential functions of histone demethylases (2012)](https://doi.org/10.1038/nrm3334)
[Wu R, et al., KDM4B promotes osteogenic differentiation of human periodontal ligament stem cells via TCF4 (2015)](https://doi.org/10.1186/s13287-015-0180-2)
[Cheng Y, et al., KDM4B is a key regulator of energy homeostasis in cancer cells (2019)](https://doi.org/10.1186/s40170-019-0198-7)
[Katoh M, et al., Integration of epigenetics and metabolism in stem cells and cancer (2019)](https://doi.org/10.1016/j.critrevonc.2019.02.012)
[Chiang CM, Role of H3K36 methylation and J-domain proteins in DNA damage response and cancer (2021)](https://doi.org/10.3390/ijms22042101)
[Black JC, et al., KDM4A and KDM4B are transcriptional co-activators required for tumor progression (2013)](https://doi.org/10.1038/onc.2012.576)
[Nielsen PR, et al., Structural basis for KDM4A inhibition by small molecules and natural products (2019)](https://doi.org/10.1021/acs.jmedchem.9b00911)
[Kim TD, et al., KDM4B is a co-activator of NF-κB and promotes inflammatory gene expression (2018)](https://doi.org/10.1073/pnas.1806282115)
[Agger K, et al., KDM4B is an H3K9me3 demethylase: implications for transcriptional regulation and cancer (2009)](https://doi.org/10.1038/embor.2009.79)
[Kopp F, et al., Targeting the histone demethylase KDM4B for the treatment of metastatic breast cancer (2021)](https://doi.org/10.1158/1078-0432.CCR-20-3214)