+-------------SUBJ:V-N------------+--------COMP:V-N(in)--------+      
      +----COMP:N-N(of)---+             |           +--MOD_ATT:N-ADJ-+      
      |            +MOD_AT+        +-NEG+           |       +MOD_ATT:+      
      |            |      |        |    |           |       |        |      
 Expression of __NODE__ mRNA does not occur in peripheral blood leukocytes .
COMP:N-N(of) (expression,mRNA)
MOD_ATT:N-ADJ (mRNA,__NODE__)
SUBJ:V-N (occur,expression)
NEG (occur,not)
COMP:V-N(in) (occur,leukocytes)
MOD_ATT:N-ADJ (leukocytes,peripheral)
MOD_ATT:N-N (leukocytes,blood)