MFSD2A - Major Facilitator Superfamily Domain Containing 2A
<div class="infobox infobox-gene">
<h3>MFSD2A</h3>
<table>
<tr><td><strong>Full Name</strong></td><td>Major Facilitator Superfamily Domain Containing 2A</td></tr>
<tr><td><strong>Gene Symbol</strong></td><td>MFSD2A</td></tr> [@zhao2021]
<tr><td><strong>Chromosomal Location</strong></td><td>1p34.2</td></tr> [@chan2018]
<tr><td><strong>NCBI Gene ID</strong></td><td>[84879](https://www.ncbi.nlm.nih.gov/gene/84879)</td></tr> [@cater2021]
<tr><td><strong>OMIM</strong></td><td>[614397](https://omim.org/entry/614397)</td></tr> [@alakbarzade2015]
<tr><td><strong>Ensembl</strong></td><td>[ENSG00000168389](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000168389)</td></tr> [@reemst2016]
<tr><td><strong>UniProt (Protein)</strong></td><td>[Q8NA29](https://www.uniprot.org/uniprot/Q8NA29)</td></tr> [@sweeney2018]
<tr><td><strong>Associated Diseases</strong></td><td>Microcephaly (MCPH15), [Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease)</td></tr>
</table>
</div>
Overview
Mermaid diagram (expand to render)
MFSD2A (Major Facilitator Superfamily Domain Containing 2A) encodes a sodium-dependent lysophosphatidylcholine (LPC) transporter that is essential for [blood-brain barrier](/mechanisms/blood-brain-barrier) integrity and brain lipid composition. MFSD2A is the primary transporter responsible for importing docosahexaenoic acid (DHA, 22:6 omega-3) into the brain in its LPC-conjugated form. Loss-of-function mutations cause lethal microcephaly with severe brain malformation, underscoring its critical role in brain development. Emerging evidence implicates MFSD2A dysfunction in neurodegenerative diseases through impaired brain DHA homeostasis and [BBB](/entities/blood-brain-barrier) breakdown.
Gene Structure and Expression
MFSD2A spans approximately 19 kb on chromosome 1p34.2 and contains 14 exons encoding a 530 amino acid integral membrane protein with 12 predicted transmembrane domains. The gene is highly conserved across vertebrates, reflecting the fundamental importance of brain DHA transport. Transcriptional regulation involves [SREBP](/genes/srebf2) and liver X receptor ([LXR](/genes/nr1h3)) pathways, linking MFSD2A expression to cholesterol and lipid metabolism.
In the brain, MFSD2A expression is almost exclusively restricted to brain microvascular endothelial cells at the [blood-brain barrier](/mechanisms/blood-brain-barrier), with minimal expression in [neurons](/entities/neurons), [astrocytes](/entities/astrocytes), or [microglia](/cell-types/microglia-neuroinflammation). This endothelial-specific expression pattern distinguishes it from other MFS transporters. Expression begins during embryonic BBB maturation and is maintained throughout life. The [Allen Brain Atlas](https://human.brain-map.org/) confirms enriched endothelial expression across [cortex](/brain-regions/cortex), [hippocampus](/brain-regions/hippocampus), and cerebellum.
Protein Function and Mechanism
LPC-DHA Transport
MFSD2A functions as a sodium-dependent symporter that transports lysophosphatidylcholine species, particularly LPC-DHA (the predominant circulating form of DHA). The transport mechanism involves:
Substrate recognition: MFSD2A binds LPC species with long-chain polyunsaturated fatty acids (LPC-DHA, LPC-EPA, LPC-oleate) at the luminal surface
Sodium coupling: Na⁺ binding drives conformational changes enabling substrate translocation (2 Na⁺ per LPC molecule)
Membrane insertion: LPC is translocated across the membrane, where phospholipases remodel it into phosphatidylcholine for membrane incorporation
DHA enrichment: This pathway is the primary mechanism by which the brain acquires DHA, which constitutes ~10-20% of total brain fatty acidsBBB Integrity Function
MFSD2A has a second critical function: suppressing transcytosis at the BBB. In MFSD2A-knockout mice, BBB endothelial cells show dramatically increased caveolae-mediated transcytosis, leading to BBB leakage despite intact tight junctions. This occurs because:
- MFSD2A-transported LPC species incorporate DHA into endothelial membranes
- DHA-enriched membranes have unique biophysical properties that suppress caveolae formation
- Without MFSD2A, the lipid composition shifts, favoring caveolae assembly and non-selective transcytosis
This dual function — lipid transport and transcytosis suppression — makes MFSD2A a central regulator of BBB biology.
Disease Associations
Microcephaly (MCPH15)
Biallelic loss-of-function mutations in MFSD2A cause autosomal recessive primary microcephaly (MCPH15) characterized by:
- Severe microcephaly (head circumference -6 to -10 SD below mean)
- Intellectual disability
- Simplified gyral pattern and reduced white matter volume
- Absent corpus callosum in severe cases
- Documented mutations include Thr159Met, Ser166Leu, and deletions disrupting transmembrane domains
Alzheimer's Disease
Multiple lines of evidence connect MFSD2A to [Alzheimer's disease](/diseases/alzheimers-disease):
- Reduced expression in AD: MFSD2A protein levels are significantly decreased in brain microvessels of AD patients compared to age-matched controls, correlating with BBB breakdown
- DHA deficiency: AD brains show reduced DHA content, particularly in hippocampus and cortex. Impaired MFSD2A-mediated transport may contribute to this deficit
- BBB dysfunction: MFSD2A downregulation leads to increased transcytosis and BBB permeability, potentially facilitating peripheral inflammatory cell infiltration and impairing [amyloid-beta](/proteins/amyloid-beta) clearance
- Pericyte loss: Brain pericyte degeneration in AD reduces MFSD2A expression via impaired [PDGF-BB](/genes/pdgfb) signaling, creating a vicious cycle of BBB deterioration
- APOE4 interaction: [APOE4](/proteins/apoe) carriers show reduced MFSD2A expression and accelerated BBB breakdown, potentially linking the strongest AD genetic risk factor to lipid transport dysfunction
Parkinson's Disease
- Brain DHA supplementation has shown neuroprotective effects in PD models by reducing [α-synuclein](/proteins/alpha-synuclein) aggregation and neuroinflammation
- MFSD2A-dependent BBB integrity may be compromised in the midbrain vasculature of PD patients
- Omega-3 fatty acid status correlates with PD risk in epidemiological studies
Neuroinflammation
MFSD2A expression is downregulated by inflammatory cytokines ([TNF-α](/genes/tnf), [IL-1β](/genes/il1b)), potentially exacerbating BBB breakdown during neuroinflammatory conditions. This creates a feed-forward loop where inflammation reduces DHA import, weakens the BBB, and allows further inflammatory mediator infiltration.
Common Variants
| Variant | rsID | Consequence | Clinical Significance |
|---------|------|-------------|----------------------|
| Thr159Met | - | Missense (TM4) | MCPH15; abolishes LPC transport |
| Ser166Leu | - | Missense (TM4) | MCPH15; disrupts Na⁺ coupling |
| rs12083037 | rs12083037 | Intronic | Associated with plasma DHA levels in GWAS |
| rs61736969 | rs61736969 | Missense | Modestly reduced transport activity |
Therapeutic Implications
Enhancing Brain DHA Delivery
- LPC-DHA supplementation: Oral LPC-DHA is more efficiently transported across the BBB than free DHA or triglyceride-DHA, representing a superior omega-3 delivery strategy
- MFSD2A upregulation: Identifying transcriptional activators of MFSD2A to enhance brain DHA uptake in neurodegeneration
- Structured phospholipids: Krill oil (rich in LPC-DHA) may be preferentially transported via MFSD2A compared to fish oil (triglyceride-DHA)
BBB Restoration
- Restoring MFSD2A expression in AD brain microvessels could simultaneously enhance DHA delivery and suppress pathological transcytosis
- Pericyte-targeted therapies to maintain MFSD2A expression
Drug Delivery Applications
- Temporary, reversible MFSD2A inhibition could transiently increase BBB transcytosis for CNS drug delivery
- LPC-conjugated drug design to exploit MFSD2A-mediated BBB transport
Expression Profile
- Brain endothelium: Exclusive high expression at BBB endothelial cells
- Choroid plexus: Absent (distinct from [ABCB1](/genes/abcb1) and [ABCG2](/genes/abcg2))
- Retinal vasculature: Blood-retinal barrier expression
- Peripheral: Liver, placenta, testis (lower levels)
- Not expressed: Neurons, astrocytes, microglia, oligodendrocytes
See Also
- [ABCB1](/genes/abcb1) — P-glycoprotein efflux transporter at BBB
- [ABCG2](/genes/abcg2) — BCRP efflux transporter at BBB
- [CLDN5](/genes/cldn5) — Claudin-5 tight junction protein
- [Blood-Brain Barrier](/mechanisms/blood-brain-barrier) — BBB structure and function
- [APOE](/proteins/apoe) — Apolipoprotein E, lipid transport and AD risk
- [SLC2A1](/genes/slc2a1) — GLUT1 glucose transporter at BBB
External Links
- [NCBI Gene: MFSD2A](https://www.ncbi.nlm.nih.gov/gene/84879)
- [UniProt: Q8NA29](https://www.uniprot.org/uniprot/Q8NA29)
- [GeneCards: MFSD2A](https://www.genecards.org/cgi-bin/carddisp.pl?gene=MFSD2A)
- [OMIM: 614397](https://omim.org/entry/614397)
- [Allen Brain Atlas: MFSD2A](https://human.brain-map.org/)
References
[Nguyen LN et al., Mfsd2a is a transporter for the essential omega-3 fatty acid docosahexaenoic acid (2014) (2014)](https://doi.org/10.1038/nature13241)
[Ben-Zvi A et al., Mfsd2a is critical for the formation and function of the blood-brain barrier (2014) (2014)](https://doi.org/10.1038/nature13324)
[Guemez-Gamboa A et al., Inactivating mutations in MFSD2A, required for omega-3 fatty acid transport in brain, cause a lethal microcephaly syndrome (2015) (2015)](https://doi.org/10.1038/ng.3311)
[Andreone BJ et al., Blood-brain barrier permeability is regulated by lipid transport-dependent suppression of caveolae-mediated transcytosis (2017) (2017)](https://doi.org/10.1016/j.neuron.2017.03.043)
[Unknown, Zhao Z & Bhatt DK, MFSD2A and Alzheimer's disease: bridging brain lipid metabolism and blood-brain barrier dysfunction (2021) (2021)](https://doi.org/10.1016/j.tips.2021.09.003)
[Chan JP et al., The lysolipid transporter Mfsd2a regulates lipogenesis in the developing brain (2018) (2018)](https://doi.org/10.1371/journal.pbio.2006443)
[Cater RJ et al., Structural basis of omega-3 fatty acid transport across the blood-brain barrier (2021) (2021)](https://doi.org/10.1038/s41586-021-03782-y)
[Alakbarzade V et al., A partially inactivating mutation in the sodium-dependent lysophosphatidylcholine transporter MFSD2A causes a non-lethal microcephaly syndrome (2015) (2015)](https://doi.org/10.1038/ng.3313)
[Reemst K et al., The indispensable roles of microglia and astrocytes during brain development (2016) (2016)](https://doi.org/10.3389/fnhum.2016.00566)
[Sweeney MD et al., Blood-brain barrier breakdown in Alzheimer disease and other neurodegenerative disorders (2018) (2018)](https://doi.org/10.1038/s41582-018-0003-2)Pathway Diagram
The following diagram shows the key molecular relationships involving MFSD2A - Major Facilitator Superfamily Domain Containing 2A discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)