Bernard Gagné

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.

Effects of chronic estrogen treatment on dopamine concentrations and turnover in discrete brain nuclei of ovariectomized rats

We investigated the effects of chronic estrogen treatment in ovariectomized rats on the concentration of dopamine in 33 discrete brain nuclei. In order to assess estrogens influence on dopamine turnover, some of the rats were administered alpha-methyl-p-tyrosine. Estrogen treatment reduced the concentrations of dopamine in the nucleus accumbens septi, striatum, median eminence, nucleus anterior hypothalami, nucleus suprachiasmaticus, nucleus arcuate IV-V, area ventralis tegmenti, interpeduncular nucleus and nucleus interstitialis striae terminalis. Treatment was without effect on dopamine turnover in all areas studied.

Corticotropin-releasing factor stimulates adenylate cyclase activity in the anterior pituitary gland

Abstract Ovine corticotropin-releasing factor (CRF) stimulates adenylate cyclase activity in rat anterior pituitary homogenate at an ED 50 value of 70 nM. GTP increases the stimulatory effect of CRF on [ 32 P] cyclic AMP formation in a rat adenohypophysial particulate fraction and in bovine anterior pituitary plasma membranes. The present data show that CRF stimulates adenylate cyclase activity in the anterior pituitary gland at least partly through a guanyl nucleotide-dependent mechanism.

Growth hormone-releasing factor stimulates adenylate cyclase activity in the anterior pituitary gland

Synthetic human pancreatic growth hormone-releasing factor (hpGRF)(1-40)-NH2 stimulates adenylate cyclase activity in rat anterior pituitary particulate fraction at an ED50 value of approximately 150 nM. GTP more than doubles the stimulatory effect of hpGRF and PGE2 on [32P] cyclic AMP formation. The present data show that hpGRF as well as PGE2, another potent stimulus of GH secretion, act at least partly, through GTP-dependent mechanisms in their coupling with adenylate cyclase.

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.

Characteristics of the β-adrenergic receptor in the rat ventral prostate using [125I]cyanopindolol

The binding characteristics of the beta-adrenergic receptor in the rat ventral prostate homogenate have been studied using the highly potent beta-adrenergic antagonist [125I]cyanopindolol (CYP) as ligand. The bound ligand was separated from the free moiety by precipitation with polyethylene glycol (PEG-6000). This technique is simple, accurate, fast and more advantageous than filtration of the hormone-receptor complex on glass fiber filters or direct centrifugation. [125I]CYP binds to a single class of high affinity sites at an apparent KD value of 23 pM. Using 0.1 microM (-)propranolol to determine non-specific binding, a number of sites of 600 fmol/mg protein were measured. The observed order of potency of adrenergic agonists (KD values) in competing for [125I]CYP binding was: (-)isoproterenol (25 nM) greater than (-)epinephrine (74 nM) much greater than (-)norepinephrine (1900 nM). Detailed study of the binding potency of a large series of beta 1- and beta 2-adrenergic agonists and antagonists showed the presence of a typical beta 2-subtype adrenergic receptor in the rat ventral prostate. The best estimate indicates that the proportion of beta 2-adrenergic receptors in rat ventral prostate is more than 95% of the total population of beta-adrenergic receptors in this tissue. The high selectivity and density of beta 2-adrenergic receptors in rat ventral prostate suggest a physiological role of circulating and/or locally secreted catecholamines in the control of prostatic growth and function.

Chronic estradiol treatment increases anterior pituitary but not striatal D2 dopamine receptor mRNA levels in rats.

The effect of chronic 17 beta-estradiol treatment (10 micrograms, twice each day, for 2 weeks) of ovariectomized rats on D2 dopamine (DA) receptor mRNA levels was investigated in striatum and anterior pituitary gland tissues. We used 32P-labeled probes specific for D2 receptor and beta-actin mRNAs in Northern blot analysis. The ratio of D2 DA receptor mRNA/beta-actin mRNA level was significantly increased in the anterior pituitary of estradiol-treated rats compared to vehicle-treated animals. The D2 DA receptor mRNA/beta-actin mRNA ratio in the striatum was not affected by estradiol treatment. However, the medial portion of the striatum showed a significantly lower ratio compared to the lateral portion of the striatum in both vehicle- and estradiol-treated rats. Thus, the estradiol effect on anterior pituitary D2 receptors may implicate transcriptional regulation, whereas our results do not support this hypothesis for the estradiol action on striatal D2 receptors.

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.

CRF stimulates adenylate cyclase activity in the intermediate lobe of the pituitary gland

Ovine corticotropin-releasing factor (CRF) stimulates adenylate cyclase activity in homogenate of the intermediate lobe of the bovine pituitary gland at an ED50 value of 150 nM. GTP increases the stimulatory effect induced by CRF as well as by the beta-adrenergic agonist isoproterenol on [32P]cyclic AMP formation in rat pars intermedia homogenate. In addition, GTP is required for inhibition by dopamine of the stimulatory action of both CRF and isoproterenol. The present data show that CRF stimulates adenylate cyclase activity in the intermediate lobe of the pituitary gland at least partly through a GTP-dependent mechanism. Moreover, dopamine can interfere with the action of CRF as well as that of isoproterenol, thus indicating that the neurohormone could be involved, in addition to beta-adrenergic agents, as stimulator of pars intermedia cell activity.