+------------SUBJ:V-N------------+                                  
      +-------COMP:N-N(of)-------+     +-------COMP:V-N(in)-------+       
      |           +-MOD_ATT:N-ADJ+     |        +---MOD_ATT:N-N---+       
      |           |       +MOD_AT+     |        |        +MOD_ATT:+       
      |           |       |      |     |        |        |        |       
 Expression of __SP__ __NODE__ mRNA occurs in grade 2 __SP__ astrocytoma .
COMP:N-N(of) (expression,mRNA)
MOD_ATT:N-ADJ (mRNA,__SP__)
MOD_ATT:N-ADJ (mRNA,__NODE__)
SUBJ:V-N (occur,expression)
COMP:V-N(in) (occur,astrocytoma)
MOD_ATT:N-N (astrocytoma,grade)
MOD_ATT:N-ADJ (astrocytoma,__SP__)