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