May be involved in angiogenesis. May play a role in activity-dependent changes of brain vasculature. May affect blood-brain permeability. Present at low levels in brain vascular cells (at protein level). Expressed at high levels in vessels from developing heart from E12 to P12. Expression decreases markedly from P12 to P17, and is no longer detectable at P30. In the brain, by electrical or chemical seizures (at protein level). Belongs to the apolipoprotein L family.