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| Full Name | Major Facilitator Superfamily Domain Containing 2A |
| Gene Symbol | MFSD2A |
| Chromosomal Location | 1p34.2 |
| NCBI Gene ID | [84879](https://www.ncbi.nlm.nih.gov/gene/84879) |
| OMIM | [614397](https://omim.org/entry/614397) |
| Ensembl | [ENSG00000168389](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000168389) |
| UniProt (Protein) | [Q8NA29](https://www.uniprot.org/uniprot/Q8NA29) |
| Associated Diseases | Microcephaly (MCPH15), [Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease) |
MFSD2A (Major Facilitator Superfamily Domain Containing 2A) encodes a sodium-dependent lysophosphatidylcholine (LPC) transporter that is essential for 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 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 and liver X receptor (LXR) 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, with minimal expression in neurons, astrocytes, or microglia. 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 confirms enriched endothelial expression across cortex, hippocampus, and cerebellum.
¶ Protein Function and Mechanism
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 acids
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.
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
Multiple lines of evidence connect MFSD2A to Alzheimer's 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 clearance
- Pericyte loss: Brain pericyte degeneration in AD reduces MFSD2A expression via impaired PDGF-BB signaling, creating a vicious cycle of BBB deterioration
- APOE4 interaction: APOE4 carriers show reduced MFSD2A expression and accelerated BBB breakdown, potentially linking the strongest AD genetic risk factor to lipid transport dysfunction
- Brain DHA supplementation has shown neuroprotective effects in PD models by reducing α-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
MFSD2A expression is downregulated by inflammatory cytokines (TNF-α, IL-1β), 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.
| 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 |
- 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)
- Restoring MFSD2A expression in AD brain microvessels could simultaneously enhance DHA delivery and suppress pathological transcytosis
- Pericyte-targeted therapies to maintain MFSD2A expression
- Temporary, reversible MFSD2A inhibition could transiently increase BBB transcytosis for CNS drug delivery
- LPC-conjugated drug design to exploit MFSD2A-mediated BBB transport
- Brain endothelium: Exclusive high expression at BBB endothelial cells
- Choroid plexus: Absent (distinct from ABCB1 and ABCG2)
- Retinal vasculature: Blood-retinal barrier expression
- Peripheral: Liver, placenta, testis (lower levels)
- Not expressed: Neurons, astrocytes, microglia, oligodendrocytes