| KDM4A | |
|---|---|
| Gene Symbol | KDM4A |
| Full Name | Lysine Specific Demethylase 4A |
| Chromosomal Location | 1p34.2 |
| NCBI Gene ID | 9682 |
| Ensembl ID | ENSG00000133195 |
| OMIM ID | 605095 |
| UniProt ID | O75173 |
| Protein Family | JMJD2 family (Jumonji C domain demethylase) |
| Associated Diseases | Alzheimer's Disease, Parkinson's Disease, Cancer, Intellectual Disability |
KDM4A (also known as JMJD2A) encodes a lysine-specific histone demethylase that catalyzes the removal of methyl groups from histone lysine residues, primarily H3K9me3 and H3K36me3. This enzyme belongs to the JMJD2 family (Jumonji C domain demethylase) and functions as a critical epigenetic regulator of chromatin accessibility and gene expression[1]. In the nervous system, KDM4A plays essential roles in neuronal development, synaptic plasticity, memory formation, and response to cellular stress[2].
KDM4A has emerged as an important player in neurodegenerative diseases. Altered KDM4A expression and activity have been documented in Alzheimer's disease brain tissues, where it contributes to dysregulated chromatin states and impaired gene expression programs essential for neuronal survival[3]. The enzyme's ability to dynamically regulate histone methylation makes it a key component of epigenetic homeostasis in neurons.
The KDM4A gene is located on chromosome 1p34.2, spanning approximately 28 kilobases. The gene consists of 22 exons that generate multiple transcript variants through alternative splicing. The genomic region flanking KDM4A shows conservation across vertebrates, reflecting its essential cellular functions.
Multiple KDM4A transcript variants have been characterized:
KDM4A contains several structurally and functionally distinct domains[4]:
JmjN Domain: The N-terminal Jumonji N domain (approximately 100 residues) is unique to the JMJD2 family. This domain stabilizes the catalytic core and isRequired for demethylase activity. The JmjN domain forms a antiparallel beta-sheet that interfaces with the JmjC domain.
JmjC Domain: The catalytic Jumonji C domain (approximately 250 residues) contains the active site. This domain is a member of the 2-oxoglutarate-dependent dioxygenase superfamily. The active site contains residues that coordinate the essential iron cofactor (Fe²⁺) and binding sites for 2-oxoglutarate (alpha-ketoglutarate).
Plant Homeodomain (PHD) Finger: The C-terminal PHD finger functions as a reader domain that recognizes specific histone modifications. This domain binds to H3K4me3, facilitating targeting to active chromatin regions.
Tudor Domain: The tandem Tudor domain recognizes methylated lysine residues, particularly H3K4me3 and H3K9me3. This domain provides substrate specificity and contributes to chromatin targeting.
KDM4A demethylates histone lysine residues through a Fe²⁺- and 2-oxoglutarate-dependent mechanism[5]:
KDM4A modifies histone methylation states to regulate gene expression programs critical for neuronal function[2:1]:
H3K9me3 Demethylation: KDM4A removes the repressive H3K9me3 mark, enabling expression of genes involved in neuronal activation and plasticity. H3K9me3 is associated with constitutive heterochromatin, and its removal is required for transcriptional activation.
H3K36me3 Demethylation: KDM4A demethylates H3K36me3, a mark associated with active transcription. This activity balances the deposition of active marks during transcriptional cycling.
Cross-talk with Other Demethylases: KDM4A function is coordinated with other histone demethylases, including KDM4B, KDM4C, and KDM5 family members.
KDM4A participates in multiple neuronal processes[6]:
Neuronal Development: During neurogenesis, KDM4A regulates genes controlling differentiation, migration, and maturation of neuronal precursors.
Synaptic Plasticity: At synapses, KDM4A modulates the epigenetic landscape to enable long-term changes in synaptic strength and dendritic remodeling.
Memory Formation: KDM4A activity is required for memory consolidation and the formation of long-term memories. KDM4A-regulated genes include immediate-early genes essential for synaptic remodeling[7].
Response to Stress: Neurons upregulate KDM4A in response to oxidative stress, DNA damage, and other Cellular challenges.
Circadian Rhythm Regulation: KDM4A participates in cyclical gene regulation linked to circadian rhythms[8].
KDM4A dysregulation contributes to multiple aspects of AD pathogenesis[3:1][9]:
Histone Methylation Imbalance: AD brain shows altered H3K9me3 and H3K36me3 patterns, reflecting KDM4A dysfunction. The balance between methyltransferases and demethylases is disrupted.
Transcriptional Dysregulation: KDM4A target genes involved in synaptic function, vesicle trafficking, and neuronal survival show altered expression in AD.
Tau Pathology: KDM4A interacts with tau pathology—neurons with high tau burden show reduced KDM4A nuclear localization.
Compensatory Upregulation: Early AD stages show compensatory KDM4A upregulation, but this response diminishes with disease progression.
Therapeutic Potential: KDM4A-modulating compounds are being explored to restore proper epigenetic states in AD.
In PD, KDM4A contributes to disease pathogenesis through:
Alpha-Synuclein Regulation: KDM4A regulates genes involved in alpha-synuclein expression and aggregation propensity.
Oxidative Stress Response: The oxidative stress response is dysregulated due to impaired KDM4A function.
Mitochondrial Function: Genes controlling mitochondrial dynamics are epigenetically dysregulated in PD.
Neuroinflammation: KDM4A in glial cells regulates inflammatory gene expression[10].
KDM4A is being targeted by small molecule inhibitors for various therapeutic applications[11]:
JmjC Domain Inhibitors: Compounds that compete with 2-oxoglutarate binding inhibit demethylase activity.
Metal Chelators: 2-Oxoglutarate analogs that bind the iron cofactor.
Substrate Analogs: Peptide-based inhibitors mimicking methylated histone tails.
Developing brain-penetrant KDM4A-targeted compounds remains challenging:
KDM4A expression is regulated at the transcriptional level:
KDM4A activity is regulated by post-translational modifications:
As a 2-oxoglutarate-dependent enzyme, KDM4A is sensitive to cellular metabolism:
KDM4A is expressed throughout the brain[12]:
KDM4A interacts with multiple protein partners:
KDM4A participates in several signaling cascades:
KDM4A encodes a critical histone demethylase that regulates chromatin states in neurons. Its role in modulating H3K9me3 and H3K36me3 makes it essential for proper gene expression programs controlling neuronal development, synaptic plasticity, and memory formation. Dysregulated KDM4A function contributes to Alzheimer's disease, Parkinson's disease, and other neurodegenerative conditions. Therapeutic targeting of KDM4A represents a promising approach for treating these diseases, though significant challenges remain in developing brain-penetrant selective compounds.
Kooistra SM, Helin K. Molecular mechanisms and potential functions of histone demethylases. Nat Rev Mol Cell Biol. 2012. 2012. ↩︎
Huang J, et al. Histone demethylases in neuronal development and function. Nat Rev Neurosci. 2019. 2019. ↩︎ ↩︎
Cheng Y, et al. KDM4A regulates epigenetic changes in Alzheimer's disease. J Neurosci. 2019. 2019. ↩︎ ↩︎
Klose RJ, et al. The retinoblastoma binding protein RBP2 is an H3K4 demethylase. Cell. 2006. 2006. ↩︎
Copeland WB, et al. 2-Oxoglutarate-dependent oxygenases in chromatin regulation. Biochem J. 2013. 2013. ↩︎
Kohrs H, et al. Histone demethylase KDM4A in neuronal function. Neurobiol Dis. 2016. 2016. ↩︎
Pardo M, et al. KDM4A in memory formation and Alzheimer's disease. Nat Neurosci. 2017. 2017. ↩︎
Metivier R, et al. Cyclical gene regulation by KDM4A in circadian rhythms. Nature. 2008. 2008. ↩︎
Chen Q, et al. KDM4A loss in Alzheimer's disease brain. Acta Neuropathol Commun. 2018. 2018. ↩︎
Zhang D, et al. JMJD2 family in neuroinflammation. Glia. 2018. 2018. ↩︎
Bjorkman M, et al. Small molecule inhibitors of KDM4 histone demethylases. J Med Chem. 2012. 2012. ↩︎
Iwamota Y, et al. Brain-specific KDM4A regulation of histone methylation. J Neurochem. 2007. 2007. ↩︎