Colony stimulating factor 2 receptor, beta (CSF2RB) is the shared subunit of receptors for interleukin 3 (IL3), colony stimulating factor 2 (CSF2) and IL5, and is responsible for the initiation of signal transduction triggered by ligand binding. In our previous study, we showed the evidence that the IL3 gene is associated with schizophrenia and the associations observed are sex-specific and dependent on family history (FH). In this article, we studied 10 singlenucleotide polymorphisms in the CSF2RB gene in the Irish Study of High-Density Schizophrenia Families (ISHDSF) and the Irish Case -Control Study of Schizophrenia (ICCSS), and tested allele and haplotype associations with schizophrenia. Using the pedigree disequilibrium test, we found that two markers (rs11705394 and rs7285064) reached nominal significance. In sex-stratified analyses, for both the markers the association signals were mainly derived from male subjects. In the ICCSS sample, we found that several markers (rs2072707, rs2284031 and rs909486) showed sex-specific and FH-dependent associations with schizophrenia. In multimarker haplotype analyses, both ISHDSF and ICCSS samples showed globally significant associations in multiple linkage disequilibrium (LD) blocks sharing minimal LD. Since CSF2RB is essential for IL3 signaling, the findings that both IL3 and CSF2RB showed sex-specific and FH-dependent associations suggest that the IL3 pathway is involved in schizophrenia.

The histidine triad nucleotide-binding protein-1 gene (HINT1) is implicated in schizophrenia and in the behavioral effects of morphine and amphetamine. Because nicotine dependence (ND) is highly comorbid with schizophrenia and other substance abuse, we examined the association of HINT1 with ND. Association analyses from two independent samples show that HINT1 gene variants are associated with ND phenotypes. Furthermore, human postmortem mRNA expression shows that smoking status and genotype influence HINT1 expression in the brain. In animal studies, western blot analyses show an increase of HINT1 protein level in the mouse nucleus accumbens (NAc) after chronic nicotine exposure. This increase was reduced after treatment with the nicotinic-receptor antagonist mecamylamine, and 24 and 72 h after cessation of nicotine treatment. These results indicate a genetic association between HINT1 variants and ND, and indicate that nicotine-induced modulation of HINT1 level may be involved in mechanisms of excess smoking.