Receptor tyrosine kinases (RTKs) are cell surface proteins that tightly regulate 
a variety of downstream intra-cellular processes; ligand-receptor interactions 
result in cascades of signaling events leading to growth, proliferation, 
differentiation and migration. There are 58 described RTKs, which are further 
categorized into 20 different RTK families. When dysregulated or overexpressed, 
these RTKs are implicated in disordered growth, development, and oncogenesis. 
The TAM family of RTKs, consisting of Tyro3, Axl, and MerTK, is prominently 
expressed during the development and function of the central nervous system 
(CNS). Aberrant expression and dysregulated activation of TAM family members has 
been demonstrated in a variety of CNS-related disorders and diseases, including 
the most common but least treatable brain cancer in children and adults: 
glioblastoma multiforme.