Eric Shink

Genome-wide search for linkage of bipolar affective disorders in a very large pedigree derived from a homogeneous population in quebec points to a locus of major effect on chromosome 12q23-q24.

We completed a genome-wide scan for susceptibility loci for bipolar affective disorders in families derived from a rather homogeneous population in the Province of Québec. The genetic homogeneity of this population stems from the migration of founding families into this relatively isolated area of Québec in the 1830s. A possible founder effect, combined with a prevalence of very large families, makes this population ideal for linkage studies. Genealogies for probands can be readily constructed from a population database of acts of baptism and marriage from the early 1830s up to the present time (the BALSAC register). We chose probands with a DSM III diagnosis of bipolar affective disorder and who may be grouped within large families having genealogical origins with the founding population of the Saguenay-Lac-St-Jean area. Living members (n approximately 120) of a very large pedigree were interviewed using the Structured Clinical Interview for DSM III (SCID I), SCID II, and with a family history questionnaire. A diagnostic panel evaluated multisource information (interview, medical records, family history) and pronounced best-estimate consensus diagnoses on all family members. Linkage, SimAPM, SimIBD, and sib-pair analyses have been performed with 332 microsatellite probes covering the entire genome at an average spacing of 11 cM. GENEHUNTER and haplotype analyses were performed on regions of interest. Analysis of a second large pedigree in the same regions of interest permitted confirmation of presumed linkages found in the region of chromosome 12q23-q24.

Analysis of single nucleotide polymorphisms in genes in the chromosome 12Q24.31 region points to P2RX7 as a susceptibility gene to bipolar affective disorder

Previous results from our genetic analyses using pedigrees from a French Canadian population suggested that the interval delimited by markers on chromosome 12, D12S86 and D12S378, was the most probable genomic region to contain a susceptibility gene for affective disorders. Association studies with microsatellite markers using a case/control sample from the same population (n = 427) revealed significant allelic associations between the bipolar phenotype and marker NBG6. Since this marker is located in intron 9 of the P2RX7 gene, we analyzed the surrounding genomic region for the presence of polymorphisms in regulatory, coding and intron/exon junction sequences. Twenty four (24) SNPs were genotyped in a case/control sample and 12 SNPs in all pedigrees used for linkage analysis. Allelic, genotypic or family‐based association studies suggest the presence of two susceptibility loci, the P2RX7 and CaMKK2 genes. The strongest association was observed in bipolar families at the non‐synonymous SNP P2RX7‐E13A (rs2230912, P‐value = 0.000708), which results from an over‐transmission of the mutant G‐allele to affected offspring. This Gln460Arg polymorphism occurs at an amino acid that is conserved between humans and rodents and is located in the C‐terminal domain of the P2X7 receptor, known to be essential for normal P2RX7 function.

Analysis of microsatellite markers and single nucleotide polymorphisms in candidate genes for susceptibility to bipolar affective disorder in the chromosome 12Q24.31 region.

Previous results from our genetic analyses using pedigrees from a French Canadian population suggested that the interval delimited by markers D12S86 and D12S378 on chromosome 12 was the most probable genomic region to contain a susceptibility gene for affective disorders. Here we present a more detailed genetic analysis of a 7.7 Mb genomic region located on 12q24.31. This region was saturated with 20 microsatellite markers to refine the candidate region and linkage analysis performed in 41 families from the Saguenay‐Lac‐St‐Jean (SLSJ) region of Quebec. The results of two point parametric analysis using MFLINK supported the presence of a susceptibility locus on chromosome 12q24.31. Association studies with microsatellite markers using a case/control sample from the same population (n = 401) and analyzed with CLUMP revealed significant allelic associations between the bipolar phenotype and markers NBG6 (P = 0.008) and NBG12 (P < 10−3). According to these results, we investigated candidate genes in the NBG12 area. We analyzed 32 genes for the presence of polymorphisms in coding sequences and intron/exon junctions and genotyped 22 non‐synonymous SNPs in the SLSJ case/control sample. Two uncommon polymorphisms (minor allele frequency ≤ 0.03) found in KIAA1595 and FLJ22471 genes, gave P‐values below 0.05 with the T1 statistic. Moreover, using haplotype analysis, a nearly significant haplotypic association was observed at the HM74 gene. These results do not give strong support for a role in the susceptibility to bipolar disorder of any of these genes analyzed. However, the significance of rare polymorphisms should be explored by further analyses.

Support for the presence of bipolar disorder susceptibility loci on chromosome 5: heterogeneity in a homogeneous population in Quebec.

A very large pedigree derived from the Saguenay-Lac-St-Jean region of Quebec contains a branch where a distal chromosome 5q haplotype seems to cosegregate with bipolar affective disorder. The authors used a diagnosis model where Bipolar Types I and II and schizoaffective disorder bipolar type were considered as affected, while single or recurrent episode major depression was classified as unknown and all the others diagnoses as unaffected. Model-free two-point LOD score values of 3.41 and 2.21 were observed at D5S432 in the 5p region with sib_ibd and sib_phase from the ASPEX package, but simulation studies did not permit the conclusion of a significant linkage because associated empirical P values were equal to .0026 and .0037. A parametric LOD score value of 2.15 was obtained at locus D5S412 in the distal chromosome 5q area. In order to investigate heterogeneity in the single multigenerational family, the pedigree was divided into five branches. Our simulation study suggested that the five branches of the Saguenay-Lac-St-Jean bipolar pedigree had low power to detect linkage under intrapedigree heterogeneity in this region.

Protein tyrosine phosphatase inhibition induces anti-tumor activity: Evidence of Cdk2/p27kip1 and Cdk2/SHP-1 complex formation in human ovarian cancer cells

The protein tyrosine phosphatase (PTP) superfamily of enzymes functions with protein tyrosine kinases to regulate a broad spectrum of fundamental physiological processes. Addition of the PTP inhibitor potassium bisperoxo(1,10-phenanthroline)oxo-vanadate(V) [bpV(phen)] to the culture medium of human ovarian cancer cells (OVCAR-3) resulted in a dose-dependent decrease in the formation of tumors in a 3-D culture system. An evaluation of the potency of bpV(phen) in vivo confirmed the anti-tumor activity. Further study of the mechanism of action revealed a 40% decrease in Cdk2 kinase activity, an elevated level of Cdk2/p27(kip1), and the appearance of Cdk2/SHP-1 complexes. Therefore, a cytostatic dose of a PTP inhibitor increases the intracellular levels of Cdk2/p27(kip) and Cdk2/SHP-1 complexes, which indicate the presence of additional mechanisms underlying the anti-tumor activity.

Genetic heterogeneity in a very large bipolar affective disorder pedigree from Quebec

We previously reported a genome‐wide scan for bipolar affective disorder based on a multigenerational family sampled from a relatively homogeneous population derived from founding families that migrated to an isolated area of Quebec from the early 1830s onwards. For the genome scan, the pedigree was split into five branches to facilitate calculation and a second family was added to more specifically analyze chromosome 12 results. In the present study, we reanalyzed the undivided pedigree after genealogical links were reconstructed over ten generations to investigate a founder effect using an algorithm in the SIMWALK2 package. Our results do not lend support to the presence of a common haplotype shared among affected individuals.

Exclusion of non‐synonymous SNPs and a polyglutamine tract in SMRT/N‐CoR2 as common deleterious mutation for bipolar disorder in the Sagnenay‐Lac‐St‐Jean population

Bipolar disorder (BP) is a psychiatric illness with both genetic and environmental components occurring with a prevalence of slightly more than 1%. Our previous linkage and case/control studies have pointed to a susceptibility locus for BP in the 12q24.31 chromosomal region. Here, we investigated the possible involvement of the SMRT/N‐CoR2 gene, which encodes for the nuclear receptor co‐repressor 2. SMRT/N‐CoR2 was retained as a candidate gene for BP because of its location within our candidate gene region and its interactions with thyroid hormone receptors. We screened SMRT/N‐CoR2 for the presence of polymorphism/mutation in coding sequences and exon–intron junctions. Four non‐synonymous SNPs and a polyglutamine tract (CAG repeat) in the coding exon 14 were analyzed in a case/control sample from the Saguenay‐Lac‐St‐Jean (SLSJ) area of Quebec (213 cases and 214 controls). Our data indicated no significant allelic/genotypic association between any of the five mutations and bipolar phenotype when they were considered either individually or as haplotypes. Finally, the CAG repeat observed in SMRT/N‐CoR2 did not demonstrate allelic instability and consequently it is unlikely that this polymorphism could be involved in the anticipation phenomenon reported for BP.

Analysis of a variable number tandem repeat polymorphism in the huntingtin interacting protein-1 related gene for anticipation in bipolar affective disorder.

The anticipation phenomenon, described as either an increase in disease severity, a decrease in age at onset, or both, in successive generations, has been suggested as a possibility of genetic transmission for bipolar affective disorder. We report here investigation of the stability of intergenerational transmission of a variable number tandem repeat (VNTR) polymorphism, found in the Huntingtin interacting protein-1 related gene (HIP12/HIP1R) that is mapped to the chromosome 12q24.31 region, in nine pedigrees showing decreased age at onset in successive generations. We did not observe any allelic instability but we report a deletion that includes this VNTR polymorphism. Allelic and genotypic association studies should be undertaken to verify the involvement of HIP12/HIP1R in bipolar disorder.