[5] Genetic ablation of MFSD2A results in leaky BBB and increases central nervous system endothelial cell vesicular transcytosis without otherwise affecting tight junctions.

[9][10][11] Complete loss of MFSD2A in human leads to a recessive lethal microcephaly syndrome consisting of enlarged lateral ventricles and underdevelopment of the cerebellum and brainstem.

This is presumably due to loss of uptake of essential polyunsaturated fatty acids by the brain endothelial cells, which utilize MFSD2A as a transporter for these fats.

Serum from patients showed elevated levels of essential polyunsaturated fatty acids, presumably due to the inability of vascular cells to uptake these lipids in the absence of protein function.

This was demonstrated in a zebrafish model by intracardiac injection of dye, which was found to extravasate into the brain parenchyma following inactivating one of the paralogues of MSFD2A known as mfsd2aa.