Genetic and phenotypic overlap of specific obsessive-compulsive and attention-deficit/hyperactive subtypes with Tourette syndrome.

BACKGROUND: The unique phenotypic and genetic aspects of obsessive-compulsive (OCD) and attention-deficit/hyperactivity disorder (ADHD) among individuals with Tourette syndrome (TS) are not well characterized. Here, we examine symptom patterns and heritability of OCD and ADHD in TS families. METHOD: OCD and ADHD symptom patterns were examined in TS patients and their family members (N = 3494) using exploratory factor analyses (EFA) for OCD and ADHD symptoms separately, followed by latent class analyses (LCA) of the resulting OCD and ADHD factor sum scores jointly; heritability and clinical relevance of the resulting factors and classes were assessed. RESULTS: EFA yielded a 2-factor model for ADHD and an 8-factor model for OCD. Both ADHD factors (inattentive and hyperactive/impulsive symptoms) were genetically related to TS, ADHD, and OCD. The doubts, contamination, need for sameness, and superstitions factors were genetically related to OCD, but not ADHD or TS; symmetry/exactness and fear-of-harm were associated with TS and OCD while hoarding was associated with ADHD and OCD. In contrast, aggressive urges were genetically associated with TS, OCD, and ADHD. LCA revealed a three-class solution: few OCD/ADHD symptoms (LC1), OCD & ADHD symptoms (LC2), and symmetry/exactness, hoarding, and ADHD symptoms (LC3). LC2 had the highest psychiatric comorbidity rates (⩾50% for all disorders). CONCLUSIONS: Symmetry/exactness, aggressive urges, fear-of-harm, and hoarding show complex genetic relationships with TS, OCD, and ADHD, and, rather than being specific subtypes of OCD, transcend traditional diagnostic boundaries, perhaps representing an underlying vulnerability (e.g. failure of top-down cognitive control) common to all three disorders.

Parental mood during pregnancy and post-natally is associated with offspring risk of Tourette syndrome or chronic tics: prospective data from the Avon Longitudinal Study of Parents and Children (ALSPAC).

Little is known about risk factors for Tourette syndrome (TS) and chronic tic disorders (CT) but maternal psychological morbidity in pregnancy may be associated with TS/CT. We examined whether pre- and post-natal parental anxiety and/or depression are associated with risk of TS/CT in the Avon Longitudinal Study of Parents and Children. We compared self-reported anxiety and depression measures collected prospectively at four time points (18 and 32 weeks prenatally, and 8 weeks and 8 months post-natally) among parents of children who subsequently met criteria for TS/CT at 13 years of age as compared to other children from the cohort. We adjusted for various socioeconomic measures and tested both for time period-specific exposure and chronic exposure using multivariable logistic regression models. 122 children had TS/CT (50 TS, 72 CT) and 5968 children had no tics. In crude analyses, both pre- and post-natal maternal anxiety and depression, but only post-natal paternal depression at 8 months, showed associations with TS/CT. In the final, adjusted multivariable models, chronic maternal anxiety (odds ratio 2.17, 95% CI 1.23, 3.84, p = 0.007) and pre-natal maternal depression (odds ratio 1.86, 95% CI 1.02, 3.39, p = 0.04) showed associations with TS/CT though the latter was consistent with chance (p = 0.07) after adjustment for past maternal depression. We find associations between maternal psychological morbidity pre- and post-natally and risk of future TS/CT in offspring. These associations may reflect either shared genetic susceptibility or a pre-natal exposure. Further work is required to see if these findings can be replicated in larger datasets.

Meta-analysis of association between obsessive-compulsive disorder and the 3' region of neuronal glutamate transporter gene SLC1A1.

The neuronal glutamate transporter gene SLC1A1 is a candidate gene for obsessive-compulsive disorder (OCD) based on linkage studies and convergent evidence implicating glutamate in OCD etiology. The 3' end of SLC1A1 is the only genomic region with consistently demonstrated OCD association, especially when analyzing male-only probands. However, specific allele associations have not been consistently replicated, and recent OCD genome-wide association and meta-analysis studies have not incorporated all previously associated SLC1A1 SNPs. To clarify the nature of association between SLC1A1 and OCD, pooled analysis was performed on all available relevant raw study data, comprising a final sample of 815 trios, 306 cases and 634 controls. This revealed weak association between OCD and one of nine tested SLC1A1 polymorphisms (rs301443; uncorrected P = 0.046; non-significant corrected P). Secondary analyses of male-affecteds only (N = 358 trios and 133 cases) demonstrated modest association between OCD and a different SNP (rs12682807; uncorrected P = 0.012; non-significant corrected P). Findings of this meta-analysis are consistent with the trend of previous candidate gene studies in psychiatry and do not clarify the putative role of SLC1A1 in OCD pathophysiology. Nonetheless, it may be important to further examine the potential associations demonstrated in this amalgamated sample, especially since the SNPs with modest associations were not included in the more highly powered recent GWAS or in a past meta-analysis including five SLC1A1 polymorphisms. This study underscores the need for much larger sample sizes in future genetic association studies and suggests that next-generation sequencing may be beneficial in examining the potential role of rare variants in OCD.

Genome-wide association study of obsessive-compulsive disorder.

Obsessive-compulsive disorder (OCD) is a common, debilitating neuropsychiatric illness with complex genetic etiology. The International OCD Foundation Genetics Collaborative (IOCDF-GC) is a multi-national collaboration established to discover the genetic variation predisposing to OCD. A set of individuals affected with DSM-IV OCD, a subset of their parents, and unselected controls, were genotyped with several different Illumina SNP microarrays. After extensive data cleaning, 1465 cases, 5557 ancestry-matched controls and 400 complete trios remained, with a common set of 469,410 autosomal and 9657 X-chromosome single nucleotide polymorphisms (SNPs). Ancestry-stratified case-control association analyses were conducted for three genetically-defined subpopulations and combined in two meta-analyses, with and without the trio-based analysis. In the case-control analysis, the lowest two P-values were located within DLGAP1 (P=2.49 × 10(-6) and P=3.44 × 10(-6)), a member of the neuronal postsynaptic density complex. In the trio analysis, rs6131295, near BTBD3, exceeded the genome-wide significance threshold with a P-value=3.84 × 10(-8). However, when trios were meta-analyzed with the case-control samples, the P-value for this variant was 3.62 × 10(-5), losing genome-wide significance. Although no SNPs were identified to be associated with OCD at a genome-wide significant level in the combined trio-case-control sample, a significant enrichment of methylation QTLs (P<0.001) and frontal lobe expression quantitative trait loci (eQTLs) (P=0.001) was observed within the top-ranked SNPs (P<0.01) from the trio-case-control analysis, suggesting these top signals may have a broad role in gene expression in the brain, and possibly in the etiology of OCD.

Genome-wide association study of Tourette's syndrome.

Tourette's syndrome (TS) is a developmental disorder that has one of the highest familial recurrence rates among neuropsychiatric diseases with complex inheritance. However, the identification of definitive TS susceptibility genes remains elusive. Here, we report the first genome-wide association study (GWAS) of TS in 1285 cases and 4964 ancestry-matched controls of European ancestry, including two European-derived population isolates, Ashkenazi Jews from North America and Israel and French Canadians from Quebec, Canada. In a primary meta-analysis of GWAS data from these European ancestry samples, no markers achieved a genome-wide threshold of significance (P<5 × 10(-8)); the top signal was found in rs7868992 on chromosome 9q32 within COL27A1 (P=1.85 × 10(-6)). A secondary analysis including an additional 211 cases and 285 controls from two closely related Latin American population isolates from the Central Valley of Costa Rica and Antioquia, Colombia also identified rs7868992 as the top signal (P=3.6 × 10(-7) for the combined sample of 1496 cases and 5249 controls following imputation with 1000 Genomes data). This study lays the groundwork for the eventual identification of common TS susceptibility variants in larger cohorts and helps to provide a more complete understanding of the full genetic architecture of this disorder.

Evolutionary divergence of the mouse and human Lgn1/SMA repeat structures.

The orthologous genomic segments on mouse chromosome 13D1-D3 and human chromosome 5q11.2-q13.3 have been extensively studied because of their involvement in two distinct disease phenotypes, spinal muscular atrophy (SMA) in human and susceptibility to Legionella pneumophila (determined by Lgn1) in mice. The overlapping intervals in both species contain genomic amplifications of distinct structure, indicating an independent origin. We have endeavored to construct a comprehensive comparative gene map of the mouse and human Lgn1/SMA intervals in the hopes that the origins and maintenance of the genomic amplifications may become clear. Our comparative gene map demonstrates that the only regional gene in common between the amplified segments in mouse and human is the Lgn1 candidate Naip/NAIP. We have also determined that mice of the 129 haplotype harbor seven intact and three partial Naip transcription units arranged in a closely linked direct repeat on chromosome 13. Several, but not all, of these Naip loci are contained within the Lgn1 critical interval. We present a model for the origins of the mouse and human repetitive arrays from a common ancestral haplotype.

Comparative sequence analysis of the mouse and human Lgn1/SMA interval.

Human chromosome 5q11.2-q13.3 and its ortholog on mouse chromosome 13 contain candidate genes for an inherited human neurodegenerative disorder called spinal muscular atrophy (SMA) and for an inherited mouse susceptibility to infection with Legionella pneumophila (Lgn1). These homologous genomic regions also have unusual repetitive organizations that create practical difficulties in mapping and raise interesting issues about the evolutionary origin of the repeats. In an attempt to analyze this region in detail, and as a way to identify additional candidate genes for these diseases, we have determined the sequence of 179 kb of the mouse Lgn1/SMA interval. We have analyzed this sequence using BLAST searches and various exon prediction programs to identify potential genes. Since these methods can generate false-positive exon declarations, our alignments of the mouse sequence with available human orthologous sequence allowed us to discriminate rapidly among this collection of potential coding regions by indicating which regions were well conserved and were more likely to represent actual coding sequence. As a result of our analysis, we accurately mapped two additional genes in the SMA interval that can be tested for involvement in the pathogenesis of SMA. While no new Lgn1 candidates emerged, we have identified new genetic markers that exclude Smn as an Lgn1 candidate. In addition to providing important resources for studying SMA and Lgn1, our data provide further evidence of the value of sequencing the mouse genome as a means to help with the annotation of the human genomic sequence and vice versa.

Human and mouse RAD17 genes: identification, localization, genomic structure and histological expression pattern in normal testis and seminoma.

Recently, the human orthologue to the cell cycle checkpoint genes rad17 (Schizosaccharomyces pombe) and RAD24 (Saccharomyces cerevisiae), called HRAD17, has been isolated and localized to chromosome 4. Independently, we have isolated the HRAD17 transcript and mapped it to chromosome 5q13 between the CCNB1 and BTF2p44cen genes. Furthermore, we have identified the complete exon-intron structure of HRAD17. The gene is organized into 14 exons, the translation initiation site lies within exon 2, and the stop codon within exon 14. Two further HRAD17 pseudogenes, HRAD17P1 and HRAD17P2, were identified on chromosomes 7p21 and 13q14.3, respectively, encompassing exons 3-14 and bearing 84% and 93% homology, respectively. Additionally, we have isolated the coding region of the mouse orthologue, Mrad17, and mapped it on chromosome 13 between Ccnb1 and Btf2p44, the same two genes between which it maps in human. The predicted Mrad17 polypeptide encompasses 687 amino acids and shows 89% similarity to HRAD17. Both genes are most highly expressed in testis compared to all other tissues, as shown by Northern blot hybridization. Histological studies, based on in situ hybridization with radioactively labeled antisense HRAD17 riboprobes, showed a strong expression within the germinal epithelium of the seminiferous tubuli in normal testis whereas in testicular tumors (seminomas) only weak, diffuse signals were seen. In light of the known function of the yeast orthologue at meiotic and mitotic checkpoints, as well as the strong expression in testis and weak expression in seminomas, we suggest a putative involvement of HRAD 17 in testicular tumorigenesis.

Identification of a candidate modifying gene for spinal muscular atrophy by comparative genomics.

Spinal muscular atrophy (SMA) is a common recessive disorder characterized by the loss of lower motor neurons in the spinal cord. The disease has been classified into three types based on age of onset and severity. SMA I-III all map to chromosome 5q13 (refs 2,3), and nearly all patients display deletions or gene conversions of the survival motor neuron (SMN1) gene. Some correlation has been established between SMN protein levels and disease course; nevertheless, the genetic basis for SMA phenotypic variability remains unclear, and it has been postulated that the loss of an additional modifying factor contributes to the severity of type I SMA. Using comparative genomics to screen for such a factor among evolutionarily conserved sequences between mouse and human, we have identified a novel transcript, H4F5, which lies closer to SMN1 than any previously identified gene in the region. A multi-copy microsatellite marker that is deleted in more than 90% of type I SMA chromosomes is embedded in an intron of this gene, indicating that H4F5 is also highly deleted in type I SMA chromosomes, and thus is a candidate phenotypic modifier for SMA.

The mouse region syntenic for human spinal muscular atrophy lies within the Lgn1 critical interval and contains multiple copies of Naip exon 5.

Spinal muscular atrophy (SMA) is a relatively common, autosomal recessively inherited neurodegenerative disorder that maps to human chromosome 5q13. This region of the human genome has an intricate genomic structure that has complicated the evaluation of SMA candidate genes. We have chosen to study the mouse region syntenic for human SMA in the hope that the homologous mouse interval would contain the same genes as human 5q13 on a simpler genomic background. Here, we report the mapping of such a region to mouse chromosome 13 and to the critical interval for Lgn1, a mouse locus responsible for modulating the intracellular replication and pathogenicity of the bacterium Legionella pneumophila. We have generated a mouse YAC contig across the Lgn1/Sma interval and have mapped the two flanking gene markers for the human SMA locus, MAP1B and CCNB1, onto this contig. In addition, we have localized the two SMA candidate genes, SMN and NAIP, to the Lgn1 critical region, making these two genes candidates for the Lgn1 phenotype. Upon subcloning of the YAC contig into P1s and BACs, we have detected a large, low copy number repeat that contains at least one copy of Naip exon 5. Identification of the Lgn1 gene will either provide a novel function for SMN or NAIP or reveal the existence of another, yet uncharacterized gene in the SMA critical region. Mutations in such a gene might help to explain some of the phenotypic variability among the human SMAs.

Expressed cadherin pseudogenes are localized to the critical region of the spinal muscular atrophy gene.

Low-copy repeats have been associated with genomic rearrangements and have been implicated in the generation of mutations in several diseases. Here we characterize a subset of low-copy repeats in the spinal muscular atrophy (SMA) region in human chromosome 5q13. We show that this repeated sequence, named c41-cad, is a highly expressed pseudogene derived from an intact neuronal cadherin gene, Br-cadherin, situated on 5p13-14. Br-cadherin is expressed specifically in the brain, whereas the c41-cad transcripts are 10-15 times more abundant and are present in all tissues examined. We speculate that the c41-cad repeats, separately or in concert with other repeats in the SMA region, are involved in the pathogenesis of SMA by promoting rearrangements and deletions.

Concerted evolution of the tandem array encoding primate U2 snRNA occurs in situ, without changing the cytological context of the RNU2 locus.

In primates, the tandemly repeated genes encoding U2 small nuclear RNA evolve concertedly, i.e. the sequence of the U2 repeat unit is essentially homogeneous within each species but differs somewhat between species. Using chromosome painting and the NGFR gene as an outside marker, we show that the U2 tandem array (RNU2) has remained at the same chromosomal locus (equivalent to human 17q21) through multiple speciation events over > 35 million years leading to the Old World monkey and hominoid lineages. The data suggest that the U2 tandem repeat, once established in the primate lineage, contained sequence elements favoring perpetuation and concerted evolution of the array in situ, despite a pericentric inversion in chimpanzee, a reciprocal translocation in gorilla and a paracentric inversion in orang utan. Comparison of the 11 kb U2 repeat unit found in baboon and other Old World monkeys with the 6 kb U2 repeat unit in humans and other hominids revealed that an ancestral U2 repeat unit was expanded by insertion of a 5 kb retrovirus bearing 1 kb long terminal repeats (LTRs). Subsequent excision of the provirus by homologous recombination between the LTRs generated a 6 kb U2 repeat unit containing a solo LTR. Remarkably, both junctions between the human U2 tandem array and flanking chromosomal DNA at 17q21 fall within the solo LTR sequence, suggesting a role for the LTR in the origin or maintenance of the primate U2 array.

Antitumor activity and reporter gene transfer into rat brain neoplasms inoculated with herpes simplex virus vectors defective in thymidine kinase or ribonucleotide reductase.

Herpes simplex virus (HSV) mutants or recombinant vectors might be useful oncolytic agents. Three general types of HSV vectors can be potentially used for this purpose: (1) mutants in viral transcription factors, such as ICP0 and ICP4; (2) mutants in enzymes involved in nucleic acid metabolism, such as thymidine kinase (TK) and ribonucleotide reductase (RR); and (3) mutants in neurovirulence factors, such as gamma 34.5. We tested the destructive ability of each type against rat 9L gliosarcoma cells in culture. We found that the HSV vectors defective in TK or RR were more efficient at tumor cell lysis in culture than the other types of HSV vectors. This increased efficiency provided the rationale for evaluating the TK and RR mutants in vivo following their stereotactic inoculation into 9L gliosarcomas implanted in rat brains. We employed the X-gal enzymatic histochemical assay to show that HSV-mediated lacZ gene expression was present in cells within the tumor mass in a relatively selective fashion. Immunoreactive HSV capsid and core antigens were present both in cells within the tumor, as well as in cells such as neurons and astrocytes, directly adjacent to the tumor mass. Long-term survival studies revealed that rats treated with either the TK or RR mutant lived significantly longer than control rats (p = 0.014, Kruskal-Wallis one-way analysis of variance). These results indicate that HSV vectors, defective in enzymes needed in nucleic acid metabolism, can preferentially mediate lacZ gene expression in cells within the tumor. (ABSTRACT TRUNCATED AT 250 WORDS)

Effects of immunosuppressive drugs on the morphology of the microvilli in Sjögren's syndrome.

Electron microscopic study of conjunctiva in two cases of Sjögren's syndrome showed decrease in height and number of microvilli and lack of branching. Following immunosuppressive treatment, an increase in height, number and branching of conjunctival microvilli was observed. Notwithstanding the lack of influence on tear secretion, immunosuppressive drugs are of benefit in the treatment of ocular manifestations of Sjögren's syndrome. The increase in number, height and branching of microvilli enlarge the surface of the conjunctiva and thus improve the efficacy of artificial tears.