+------------SUBJ:V-N------------+                               
      +-------COMP:N-N(of)-------+     +-------COMP:V-N(in)-------+    
      |           +-MOD_ATT:N-ADJ+     |         +--MOD_ATT:N-ADJ-+    
      |           |       +MOD_AT+     |         |       +MOD_ATT:+    
      |           |       |      |     |         |       |        |    
 Expression of __SP__ __NODE__ mRNA occurs in __SP__ placental tissue .
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,toilet)
MOD_ATT:N-ADJ (toilet,__SP__)
MOD_ATT:N-ADJ (toilet,placental)