Major facilitator superfamily domain-containing protein 2 (MFSD2 or MFSD2A) -- also known as sodium-dependent lysophosphatidylcholine symporter 1 -- is a protein that in humans is encoded by the MFSD2A gene. MFSD2A is a membrane transport protein that is expressed in the endothilium of the blood–brain barrier (BBB) and has an essential role in BBB formation and function.Genetic ablation of MFSD2A results in leaky BBB and increases central nervous system endothelial cell vesicular transcytosis without otherwise affecting tight junctions. MFSD2A is an atypical SLC, thus a predicted SLC transporter. It clusters phylogenetically to AMTF8.