"Molecular biology" . "Ligands (biochemistry)" . "Cell signaling" . "Genes on human chromosome 7" . "Proteins" . "Sonic the Hedgehog" . "Pharmacokinetics" . "HINT domain" . "Neurology" . "Glial cells" . "Central nervous system" . "Human cells" . "Interleukins" . "Circulatory system" . "Brain" . "Morphogens" . "Animal physiology" .