Karen L. Gentile

Gene expression analysis of peripheral blood leukocytes from discordant sib-pairs with schizophrenia and bipolar disorder reveals points of convergence between genetic and functional genomic approaches†

We performed global RNA transcript analysis and comprehensive gene group analysis of peripheral blood leukocyte (PBL) RNA from two groups of matched sib‐pairs that were discordant for either schizophrenia (n = 33 sib‐pairs) or bipolar disorder (n = 5 sib‐pairs). The pairs chosen for these analyses were selected from families with known patterns of genetic linkage (5q for schizophrenia and 6q for bipolar disorder). At the single gene level, we obtained lists of the transcripts with the most significant changes in expression and from these lists determined those with the highest degree of predictive power for classifying subjects according to diagnosis in these samples. At the gene group level, we comprehensively analyzed pairwise expression changes of more than 4,000 functional groups and cytogenetic locations, and present a novel method of displaying these data that we term “cytogenomic” mapping. Verification of selected changes in expression was performed using quantitative real‐time RT‐PCR. Our results provide compelling evidence for the utility of analyzing PBL RNA for changes in expression in neuropsychiatric disorders.

Deletion at the SLC1A1 glutamate transporter gene co-segregates with schizophrenia and bipolar schizoaffective disorder in a 5-generation family

Growing evidence for genetic overlap between schizophrenia (SCZ) and bipolar disorder (BPD) suggests that causal variants of large effect on disease risk may cross traditional diagnostic boundaries. Extended multigenerational families with both SCZ and BPD cases can be a valuable resource for discovery of shared biological pathways because they can reveal the natural evolution of the underlying genetic disruptions and their phenotypic expression. We investigated a deletion at the SLC1A1 glutamate transporter gene originally identified as a copy number variant exclusively carried by members of a 5‐generation Palauan family. Using an expanded sample of 21 family members, quantitative PCR confirmed the deletion in all seven individuals with psychosis, three “obligate‐carrier” parents and one unaffected sibling, while four marry‐in parents were non‐carriers. Linkage analysis under an autosomal dominant model generated a LOD‐score of 3.64, confirming co‐segregation of the deletion with psychosis. For more precise localization, we determined the approximate deletion end points using alignment of next‐generation sequencing data for one affected deletion‐carrier and then designed PCR amplicons to span the entire deletion locus. These probes established that the deletion spans 84,298 bp, thus eliminating the entire promoter, the transcription start site, and the first 59 amino acids of the protein, including the first transmembrane Na2+/dicarboxylate symporter domain, one of the domains that perform the glutamate transport action. Discovery of this functionally relevant SLC1A1 mutation and its co‐segregation with psychosis in an extended multigenerational pedigree provides further support for the important role played by glutamatergic transmission in the pathophysiology of psychotic disorders.

Complete maternal uniparental isodisomy of chromosome 4 in a subject with major depressive disorder detected by high density SNP genotyping arrays

Uniparental isodisomy (iUPD) is a rare genetic condition caused by non‐disjunction during meiosis that ultimately leads to a duplication of either the maternal or paternal chromosome in the affected individual. Two types of disorders can result, those due to imprinted genes and those due to homozygosity of recessive disease‐causing mutations. Here, we describe the third known case of complete chromosome 4 iUPD of maternal origin. This condition became apparent during whole genome linkage studies of psychiatric disorders in the Portuguese population. The proband is an adult female with normal fertility and no major medical complaints, but a history of major depressive disorder and multiple suicide attempts. The probands siblings and parents had normal chromosome 4 genotypes and no history of mood disturbance. A brief review of other studies lends support for the possibility that genes on chromosome 4 might confer risk for mood disorders. We conclude that chromosome 4 maternal uniparental disomy (UPD) is a rare disorder that may present with a major depressive phenotype. The lack of a common disease phenotype between this and two other cases of chromosome 4 iUPD [Lindenbaum et al. [1991] Am J Med Genet 49(Suppl 285):1582; Spena et al. [2004] Eur J Hum Genet 12:891–898) would suggest that there is no vital maternal gene imprinting on chromosome 4. However, since there is no reported case of paternal chromosome 4 UPD, paternal gene imprinting on chromosome 4 cannot be excluded.

Association between autism spectrum disorder in individuals with velocardiofacial (22q11.2 deletion) syndrome and PRODH and COMT genotypes.

Velocardiofacial (VCFS; 22q11.2 deletion) syndrome is a genetic disorder that results from a hemizygous deletion of the q11.2 region on chromosome 22, and is associated with greatly increased risk for psychiatric disorders, including autism spectrum disorder (ASD) and schizophrenia. There is emerging evidence for the involvement of catechol-O-methyltransferase (COMT) and proline dehydrogenase (oxidase) 1 (PRODH) in the psychiatric phenotype of individuals with VCFS. Here, we tested the hypothesis that PRODH and COMT are associated with ASD in youths with VCFS. We found that individuals with VCFS and the low-activity alleles of both PRODH and COMT (rs4819756A and rs4680A) were more likely to present with ASD as compared with individuals with VCFS and the high-activity alleles of these genes [P<0.05; odds ratio=6.0 (95% confidence interval=1.27–28.26; N=87)]. Our results suggest that PRODH and COMT may interact to contribute to the ASD phenotype in individuals with VCFS.

Evaluation of cell proliferation, apoptosis, and dna-repair genes as potential biomarkers for ethanol-induced cns alterations

BackgroundAlcohol use disorders (AUDs) lead to alterations in central nervous system (CNS) architecture along with impaired learning and memory. Previous work from our group and that of others suggests that one mechanism underlying these changes is alteration of cell proliferation, apoptosis, and DNA-repair in neural stem cells (NSCs) produced as a consequence of ethanol-induced effects on the expression of genes related to p53-signaling. This study tests the hypothesis that changes in the expression of p53-signaling genes represent biomarkers of ethanol abuse which can be identified in the peripheral blood of rat drinking models and human AUD subjects and posits that specific changes may be correlated with differences in neuropsychological measures and CNS structure.ResultsRemarkably, microarray analysis of 350 genes related to p53-signaling in peripheral blood leukocytes (PBLs) of binge-drinking rats revealed 190 genes that were significantly altered after correcting for multiple testing. Moreover, 40 of these genes overlapped with those that we had previously observed to be changed in ethanol-exposed mouse NSCs. Expression changes in nine of these genes were tested for independent confirmation by a custom QuantiGene Plex (QGP) assay for a subset of p53-signaling genes, where a consistent trend for decreased expression of mitosis-related genes was observed. One mitosis-related gene (Pttg1) was also changed in human lymphoblasts cultured with ethanol. In PBLs of human AUD subjects seven p53-signaling genes were changed compared with non-drinking controls. Correlation and principal components analysis were then used to identify significant relationships between the expression of these seven genes and a set of medical, demographic, neuropsychological and neuroimaging measures that distinguished AUD and control subjects. Two genes (Ercc1 and Mcm5) showed a highly significant correlation with AUD-induced decreases in the volume of the left parietal supramarginal gyrus and neuropsychological measures.ConclusionsThese results demonstrate that alcohol-induced changes in genes related to proliferation, apoptosis, and DNA-repair are observable in the peripheral blood and may serve as a useful biomarker for CNS structural damage and functional performance deficits in human AUD subjects.

Cyclosporine Inhibition of Angiogenesis Involves the Transcription Factor HESR1

PURPOSE Angiogenesis is critical in normal development and in tumor growth. Experimentally, cyclosporine A (CyA) inhibits angiogenesis in an in vivo mouse model and an in vitro capillary tube model. The mechanisms behind its antiangiogenic effects are not well characterized. To determine which nuclear factor, if any, may be involved in the antiangiogenic effects of CyA, we performed a microarray analysis of human aortic endothelial cells (HAEC) subjected to CyA and another calcineurin inhibitor, FK 506. METHODS HAEC were divided into four groups: (1) HAEC incubated with CyA 2 microg/mL; (2) HAEC incubated with CyA 10 microg/mL; (3) HAEC incubated with FK 506 1 microg/mLl for 24 h; and (4) HAEC as control. We used Affymetrix GeneChip U133-A for gene expression analysis and validated our results with quantitative reverse transcription-polymerase chain reaction. RESULTS At a 2 microg/mL dose, CyA treated HAEC revealed a 44-fold increase in the expression of hairy enhancer of split-related protein 1 (HESR1) and 1.73-fold down-regulation of transcripts encoding for the vascular endothelial growth factor (VEGF) receptor (VEGFR2). At 10 microg/mL, the expression of the HESR1 transcript was 57-fold higher than control, and VEGFR2 exhibited a 1.93-fold down-regulation. Quantitative reverse transcription-polymerase chain reaction confirmed a significant (P < 0.0001) increase in expression of HESR1 in CyA treated cells. In contrast, the expression level of HESR1 was not affected by the FK 506 treatment. CONCLUSION CyA demonstrate antiangiogenic activities linked to an overexpression of HESR1 transcription factor, and down-regulation of VEGFR2. Thus, use of high-dose CyA may provide a novel treatment in angiogenesis dependent disease.

Genetic overlap of schizophrenia and bipolar disorder in a high‐density linkage survey in the Portuguese Island population

Recent family and genome‐wide association studies strongly suggest shared genetic risk factors for schizophrenia (SZ) and bipolar disorder (BP). However, linkage studies have not been used to test for statistically significant genome‐wide overlap between them. Forty‐seven Portuguese families with sibpairs concordant for SZ, BP, or psychosis (PSY, which includes either SZ or psychotic BP) were genotyped for over 57,000 markers using the Affymetrix 50K Xba SNP array. NPL and Kong and Cox LOD scores were calculated in Merlin for all three phenotypes. Empirical significance was determined using 1,000 gene‐dropping simulations. Significance of genome‐wide genetic overlap between SZ and BP was determined by the number of simulated BP scans having the same number of loci jointly linked with the real SZ scan, and vice versa. For all three phenotypes, a number of regions previously linked in this sample remained so. For BP, chromosome 1p36 achieved significance (11.54–15.71 MB, LOD = 3.51), whereas it was not even suggestively linked at lower marker densities, as did chromosome 11q14.1 (89.32–90.15 MB, NPL = 4.15). Four chromosomes had loci at which both SZ and BP had NPL ≥ 1.98, which was more than would be expected by chance (empirical P = 0.01 using simulated SZ scans; 0.07 using simulated BP scans), although they did not necessarily meet criteria for suggestive linkage individually. These results suggest that high‐density marker maps may provide greater power and precision in linkage studies than lower density maps. They also further support the hypothesis that SZ and BP share at least some risk alleles.

Associations between neurodevelopmental genes, neuroanatomy, and ultra high risk symptoms of psychosis in 22q11.2 deletion syndrome

22q11.2 deletion syndrome is a neurogenetic disorder resulting in the deletion of over 40 genes. Up to 40% of individuals with 22q11.2DS develop schizophrenia, though little is known about the underlying mechanisms. We hypothesized that allelic variation in functional polymorphisms in seven genes unique to the deleted region would affect lobar brain volumes, which would predict risk for psychosis in youth with 22q11.2DS. Participants included 56 individuals (30 males) with 22q11.2DS. Anatomic MR images were collected and processed using Freesurfer. Participants were genotyped for 10 SNPs in the COMT, DGCR8, GNB1L, PIK4CA, PRODH, RTN4R, and ZDHHC8 genes. All subjects were assessed for ultra high risk symptoms of psychosis. Allelic variation of the rs701428 SNP of RTN4R was significantly associated with volumetric differences in gray matter of the lingual gyrus and cuneus of the occipital lobe. Moreover, occipital gray matter volumes were robustly associated with ultra high risk symptoms of psychosis in the presence of the G allele of rs701428. Our results suggest that RTN4R, a relatively under‐studied gene at the 22q11 locus, constitutes a susceptibility gene for psychosis in individuals with this syndrome through its alteration of the architecture of the brain.