Evidence for association of schizophrenia with genetic variation in the 8p21.3 gene, PPP3CC, encoding the calcineurin gamma subunit

Abstract

Schizophrenia is a severe psychiatric disorder characterized by a complex mode of inheritance. Forebrain-specific CNB knockout mice display a spectrum of behavioral abnormalities related to altered behaviors observed in schizophrenia patients. To examine whether calcineurin dysfunction is involved in schizophrenia etiology, we undertook studies of an initial subset of calcineurin-related genes, prioritizing ones that map to loci previously implicated in schizophrenia by linkage studies. Transmission disequilibrium studies in a large sample of affected families detected association of the PPP3CC gene, which encodes the calcineurin gamma catalytic subunit, with disease. Our results identify PPP3CC, located at 8p21.3, as a potential schizophrenia susceptibility gene and support the proposal that alterations in calcineurin signaling contribute to schizophrenia pathogenesis.

Fig. 1.

PPP3CC gene locus. (A) The location of the PPP3CC gene in the 8p21.3 region is depicted in relation to relevant markers from linkage studies. D8S136 (13); D8S1771 (15, 16); D8S1752 (15); and D8S1715 and D8S133 (14). (B) An expanded view of the PPP3CC gene is presented, including the exon/intron structure and the locations of the SNPs used for our association studies and of the coding sequence mutation identified in exon 5. This mutation changes a G to an A at position 824 of the mRNA (GenBank accession no. NM_005605). Distances and positions in this figure are according to the November 2002 human draft sequence. (C) Haplotype distribution and transmission at the PPP3CC locus. Only four haplotypes with frequencies ≥5% were observed in both U.S. and SA samples and are shown here. The most common PPP3CC haplotype is consistently overtransmitted in both samples. T/nT, transmitted/nontransmitted.

Fig. 2.

PPP3CC expression in human brain. (A) PCR amplification of cDNA from human adult total brain, fetal total brain, and testis. PCR was performed on ≈0.25 ng of cDNA with two primer pairs. Primer pair 1 amplifies a 218-bp fragment extending from exon 1 to exon 2. Primer pair 2 amplifies a 298-bp fragment from exon 14 consisting of 3′ UTR sequence. Lane 1, 100-bp marker; lane 2, adult brain, primer pair 1; lane 3, adult brain, primer pair 2; lane 4, fetal brain, primer pair 1; lane 5, fetal brain, primer pair 2; lane 6, testis, primer pair 1; lane 7, testis, primer pair 2; lane 8, no DNA control, primer pair 1; lane 9, no DNA control, primer pair 2. The products <100 bp in size are present in lanes 8 and 9 and are most likely primer-related amplification artifacts. (B) PCR amplification of cDNA from human adult brain regions. PCR was performed on ≈1.0 ng of cDNA with primer pair 1. Lane 1, 100-bp marker; lane 2, frontal lobe; lane 3, temporal lobe; lane 4, cerebellum; lane 5, hippocampus; lane 6, substantia nigra; lane 7, caudate nucleus; lane 8, amygdala; lane 9, thalamus; lane 10, hypothalamus; lane 11, pons; lane 12, medulla; lane 13, spinal cord.