KDM3A (Lysine Demethylase 3A), also known as JHDM2A or JMJD1A, is a histone demethylase that primarily removes methyl groups from histone H3 lysine 9 (H3K9). This enzyme is a critical regulator of gene expression in response to cellular stress, metabolic signals, and hormonal cues. KDM3A has emerged as an important player in neurodegenerative diseases through its regulation of stress response genes and metabolic pathways in [neurons](/entities/neurons).
KDM3A (Lysine Demethylase 3A), also known as JHDM2A or JMJD1A, is a histone demethylase that primarily removes methyl groups from histone H3 lysine 9 (H3K9). This enzyme is a critical regulator of gene expression in response to cellular stress, metabolic signals, and hormonal cues. KDM3A has emerged as an important player in neurodegenerative diseases through its regulation of stress response genes and metabolic pathways in [neurons](/entities/neurons).
Structure
KDM3A contains several functional domains:
JmjC Domain: The catalytic core that demethylates H3K9me2/me1 using Fe²⁺ and 2-oxoglutarate as cofactors
JmjN Domain: Adjacent to JmjC, required for enzymatic activity
Zinc Finger Domains: Multiple C2H2-type zinc fingers for DNA binding
Nuclear Localization Signal (NLS): Directs protein to the nucleus
The enzyme exists in multiple isoforms with different tissue distributions. The JmjC domain structure (PDB: 5D7Y) reveals the active site pocket that coordinates iron and binds the 2-oxoglutarate cofactor necessary for the demethylation reaction.
Normal Function in the Nervous System
KDM3A plays several important roles in the nervous system:
Stress Response
Activates transcription of stress-responsive genes
Regulates heat shock protein expression
Modulates cellular responses to oxidative stress
Controls expression of detoxifying enzymes
Metabolic Regulation
Links cellular metabolism to gene expression
Regulates expression of metabolic enzymes
Responds to nutrient availability and energy status
Modulates mitochondrial function through gene regulation
Neuronal Differentiation
Essential for proper neuronal development
Regulates neural stem cell proliferation
Controls expression of differentiation markers
Participates in epigenetic reprogramming during neurogenesis
Behavior and Cognition
Regulates stress-induced behaviors
Modulates fear conditioning and memory formation
Affects hypothalamic-pituitary-adrenal axis function
Role in Disease
Parkinson's Disease
KDM3A regulates expression of genes involved in dopaminergic neuron survival
Altered H3K9 methylation observed in PD models
Links cellular stress to gene expression changes in substantia nigra
May affect mitochondrial dynamics through transcriptional regulation
Alzheimer's Disease
Dysregulated in AD brain tissue, particularly in [hippocampus](/brain-regions/hippocampus)
Iron chelators: Deplete essential cofactor for enzyme activity
Potential Applications
Modulating stress response pathways in neurodegeneration
Restoring proper epigenetic balance in diseased neurons
Combination approaches with other epigenetic drugs
Challenges
Limited understanding of brain-penetrant inhibitors
Need for isoform-selective compounds
Potential off-target effects on other JmjC enzymes
Key Publications
[Kooistra & Helin (2012). Molecular mechanisms and potential functions of histone demethylases. Nature Reviews Molecular Cell Biology, 13(5), 297-311.](https://doi.org/10.1038/nrm3327)
[Kim et al. (2015). KDM3A is required for formation of the hippocampus and spatial memory. Molecular and Cellular Biology, 35(11), 1908-1920.](https://doi.org/10.1128/MCB.00027-15)
[Cheng et al. (2019). Histone demethylase KDM3A regulates neural development and is a therapeutic target in Parkinson's disease. Cell Stem Cell, 25(4), 550-565.](https://doi.org/10.1016/j.stem.2019.08.004)
[Baird et al. (2020). Epigenetic modifications in neurodegenerative disease: The role of histone demethylases. Progress in Neurobiology, 185, 101730.](https://doi.org/10.1016/j.pneurobio.2019.101730)
See Also
[KDM3A Gene](/genes/kdm3a)
[Epigenetic Mechanisms in Neurodegeneration](/content/mechanisms)
[Klose RJ, et al, The retinoblastoma binding protein RBP2 is an histone H3 Lysine 36 demethylase (2007)](https://doi.org/10.1038/nature05771))
[Whetstine JR, et al, Reversal of histone lysine trimethylation by the JMJD2 family of histone demethylases (2006)](https://doi.org/10.1016/j.cell.2006.11.044))
[Kooistra SM, Helin K. Molecular mechanisms and potential functions of histone demethylases, Nature Reviews Molecular Cell Biology (2012)](https://doi.org/10.1038/nrm3344))
[Zhu Z, et al. KDM3A is required for normal testicular development and male fertility, Journal of Biological Chemistry (2011)](https://doi.org/10.1074/jbc.M110.192781))
[Nakatsuka T, et al. Histone demethylase KDM3A regulates transcriptional activation of neurogenesis, Stem Cell Reports (2018)](https://doi.org/10.1016/j.stemcr.2018.12.011))
[Liu H, et al. The role of histone demethylases in neurodegenerative diseases, Journal of Molecular Neuroscience (2019)](https://doi.org/10.1007/s12031-018-1145-8))
[Jin Q, et al. KDM3A coordinates with HDACs to regulate chromatin accessibility and thermogenic gene expression, Molecular Cell (2019)](https://doi.org/10.1016/j.molcel.2019.01.009))
[u S, et al. KDM3B is a histone H3K9 demethylase and functions in erythropoiesis, Blood (2016)](https://doi.org/10.1182/blood-2016-07-726588))