TEK and microcephaly: To determine if Mfsd2a deficiency at the BBB endothelium is responsible for microcephaly reported in 2aKO mice, an endothelial-specific deletion of Mfsd2a was generated using a floxed allele of Mfsd2a (2afl/fl) crossed to the endothelial cre-driver line Tie2 (2aECKO).