MicroRNA-Mediated Suppression of Glial Cell Line-Derived Neurotrophic Factor Expression
Is Modulated by a Schizophrenia-Associated Non-Coding Polymorphism
Plasma levels of glial cell line-derived neurotrophic factor (GDNF), a pivotal regulator
of differentiation and survival of dopaminergic neurons, are reportedly decreased
in schizophrenia. To explore the involvement of GDNF in the pathogenesis of the disease,
a case–control association analysis was performed between five non-coding single nucleotide
polymorphisms (SNP) across the GDNF gene and schizophrenia. Of them, the ‘G’ allele
of the rs11111 SNP located in the 3′ untranslated region (3′-UTR) of the gene was
found to associate with schizophrenia. In silico analysis revealed that the rs11111
‘G’ allele might create binding sites for three microRNA (miRNA) species. To explore
the significance of this polymorphism, transient co-transfection assays were performed
in human embryonic kidney 293T (HEK293T) cells with a luciferase reporter construct
harboring either the ‘A’ or ‘G’ allele of the 3′-UTR of GDNF in combination with the
hsa-miR-1185-1-3p pre-miRNA. It was demonstrated that in the presence of the rs11111
‘G’ (but not the ‘A’) allele, hsa-miR-1185-2-3p repressed luciferase activity in a
dose-dependent manner. Deletion of the miRNA binding site or its substitution with
the complementary sequence abrogated the modulatory effect. Our results imply that
the rs11111 ‘G’ allele occurring more frequently in patients with schizophrenia might
downregulate GDNF expression in a miRNA-dependent fashion.