The RD-Connect Genome-Phenome Analysis Platform: Accelerating diagnosis, research, and gene discovery for rare diseases.

Rare disease patients are more likely to receive a rapid molecular diagnosis nowadays thanks to the wide adoption of next-generation sequencing. However, many cases remain undiagnosed even after exome or genome analysis, because the methods used missed the molecular cause in a known gene, or a novel causative gene could not be identified and/or confirmed. To address these challenges, the RD-Connect Genome-Phenome Analysis Platform (GPAP) facilitates the collation, discovery, sharing, and analysis of standardized genome-phenome data within a collaborative environment. Authorized clinicians and researchers submit pseudonymised phenotypic profiles encoded using the Human Phenotype Ontology, and raw genomic data which is processed through a standardized pipeline. After an optional embargo period, the data are shared with other platform users, with the objective that similar cases in the system and queries from peers may help diagnose the case. Additionally, the platform enables bidirectional discovery of similar cases in other databases from the Matchmaker Exchange network. To facilitate genome-phenome analysis and interpretation by clinical researchers, the RD-Connect GPAP provides a powerful user-friendly interface and leverages tens of information sources. As a result, the resource has already helped diagnose hundreds of rare disease patients and discover new disease causing genes.

Truncating variant burden in high-functioning autism and pleiotropic effects of LRP1 across psychiatric phenotypes

Background: Previous research has implicated de novo and inherited truncating mutations in autism-spectrum disorder. We aim to investigate whether the load of inherited truncating mutations contributes similarly to high-functioning autism, and to characterize genes that harbour de novo variants in high-functioning autism. Methods: We performed whole-exome sequencing in 20 high-functioning autism families (average IQ = 100). Results: We observed no difference in the number of transmitted versus nontransmitted truncating alleles for high-functioning autism (117 v. 130, p = 0.78). Transmitted truncating and de novo variants in high-functioning autism were not enriched in gene ontology (GO) or Kyoto Encyclopedia of Genes and Genomes (KEGG) categories, or in autism-related gene sets. However, in a patient with high-functioning autism we identified a de novo variant in a canonical splice site of LRP1, a postsynaptic density gene that is a target for fragile X mental retardation protein (FRMP). This de novo variant leads to in-frame skipping of exon 29, removing 2 of 6 blades of the ß-propeller domain 4 of LRP1, with putative functional consequences. Large data sets implicate LRP1 across a number of psychiatric disorders: de novo variants are associated with autism-spectrum disorder (p = 0.039) and schizophrenia (p = 0.008) from combined sequencing projects; common variants using genome-wide association study data sets from the Psychiatric Genomics Consortium show gene-based association in schizophrenia (p = 6.6 × E−07) and in a meta-analysis across 7 psychiatric disorders (p = 2.3 × E−03); and the burden of ultra-rare pathogenic variants has been shown to be higher in autism-spectrum disorder (p = 1.2 × E−05), using whole-exome sequencing from 6135 patients with schizophrenia, 1778 patients with autism-spectrum disorder and 7875 controls. Limitations: We had a limited sample of patients with high-functioning autism, related to difficulty in recruiting probands with high cognitive performance and no family history of psychiatric disorders. Conclusion: Previous studies and ours suggest an effect of truncating mutations restricted to severe autism-spectrum disorder phenotypes that are associated with intellectual disability. We provide evidence for pleiotropic effects of common and rare variants in the LRP1 gene across psychiatric phenotypes.

Adaptive Mistranslation Accelerates the Evolution of Fluconazole Resistance and Induces Major Genomic and Gene Expression Alterations in Candida albicans.

Regulated erroneous protein translation (adaptive mistranslation) increases proteome diversity and produces advantageous phenotypic variability in the human pathogen Candida albicans. It also increases fitness in the presence of fluconazole, but the underlying molecular mechanism is not understood. To address this question, we evolved hypermistranslating and wild-type strains in the absence and presence of fluconazole and compared their fluconazole tolerance and resistance trajectories during evolution. The data show that mistranslation increases tolerance and accelerates the acquisition of resistance to fluconazole. Genome sequencing, array-based comparative genome analysis, and gene expression profiling revealed that during the course of evolution in fluconazole, the range of mutational and gene deregulation differences was distinctively different and broader in the hypermistranslating strain, including multiple chromosome duplications, partial chromosome deletions, and polyploidy. Especially, the increased accumulation of loss-of-heterozygosity events, aneuploidy, translational and cell surface modifications, and differences in drug efflux seem to mediate more rapid drug resistance acquisition under mistranslation. Our observations support a pivotal role for adaptive mistranslation in the evolution of drug resistance in C. albicans. IMPORTANCE Infectious diseases caused by drug-resistant fungi are an increasing threat to public health because of the high mortality rates and high costs associated with treatment. Thus, understanding of the molecular mechanisms of drug resistance is of crucial interest for the medical community. Here we investigated the role of regulated protein mistranslation, a characteristic mechanism used by C. albicans to diversify its proteome, in the evolution of fluconazole resistance. Such codon ambiguity is usually considered highly deleterious, yet recent studies found that mistranslation can boost adaptation in stressful environments. Our data reveal that CUG ambiguity diversifies the genome in multiple ways and that the full spectrum of drug resistance mechanisms in C. albicans goes beyond the traditional pathways that either regulate drug efflux or alter the interactions of drugs with their targets. The present work opens new avenues to understand the molecular and genetic basis of microbial drug resistance.

The Fungus Candida albicans Tolerates Ambiguity at Multiple Codons.

The ascomycete Candida albicans is a normal resident of the gastrointestinal tract of humans and other warm-blooded animals. It occurs in a broad range of body sites and has high capacity to survive and proliferate in adverse environments with drastic changes in oxygen, carbon dioxide, pH, osmolarity, nutrients, and temperature. Its biology is unique due to flexible reassignment of the leucine CUG codon to serine and synthesis of statistical proteins. Under standard growth conditions, CUG sites incorporate leucine (3% of the times) and serine (97% of the times) on a proteome wide scale, but leucine incorporation fluctuates in response to environmental stressors and can be artificially increased up to 98%. In order to determine whether such flexibility also exists at other codons, we have constructed several serine tRNAs that decode various non-cognate codons. Expression of these tRNAs had minor effects on fitness, but growth of the mistranslating strains at different temperatures, in medium with different pH and nutrients composition was often enhanced relatively to the wild type (WT) strain, supporting our previous data on adaptive roles of CUG ambiguity in variable growth conditions. Parallel evolution of the recombinant strains (100 generations) followed by full genome resequencing identified various strain specific single nucleotide polymorphisms (SNP) and one SNP in the deneddylase (JAB1) gene in all strains. Since JAB1 is a subunit of the COP9 signalosome complex, which interacts with cullin (Cdc53p) to mediate degradation of a variety of cellular proteins, our data suggest that neddylation plays a key role in tolerance and adaptation to codon ambiguity in C. albicans.

Evolution of Robustness to Protein Mistranslation by Accelerated Protein Turnover.

Translational errors occur at high rates, and they influence organism viability and the onset of genetic diseases. To investigate how organisms mitigate the deleterious effects of protein synthesis errors during evolution, a mutant yeast strain was engineered to translate a codon ambiguously (mistranslation). It thereby overloads the protein quality-control pathways and disrupts cellular protein homeostasis. This strain was used to study the capacity of the yeast genome to compensate the deleterious effects of protein mistranslation. Laboratory evolutionary experiments revealed that fitness loss due to mistranslation can rapidly be mitigated. Genomic analysis demonstrated that adaptation was primarily mediated by large-scale chromosomal duplication and deletion events, suggesting that errors during protein synthesis promote the evolution of genome architecture. By altering the dosages of numerous, functionally related proteins simultaneously, these genetic changes introduced large phenotypic leaps that enabled rapid adaptation to mistranslation. Evolution increased the level of tolerance to mistranslation through acceleration of ubiquitin-proteasome-mediated protein degradation and protein synthesis. As a consequence of rapid elimination of erroneous protein products, evolution reduced the extent of toxic protein aggregation in mistranslating cells. However, there was a strong evolutionary trade-off between adaptation to mistranslation and survival upon starvation: the evolved lines showed fitness defects and impaired capacity to degrade mature ribosomes upon nutrient limitation. Moreover, as a response to an enhanced energy demand of accelerated protein turnover, the evolved lines exhibited increased glucose uptake by selective duplication of hexose transporter genes. We conclude that adjustment of proteome homeostasis to mistranslation evolves rapidly, but this adaptation has several side effects on cellular physiology. Our work also indicates that translational fidelity and the ubiquitin-proteasome system are functionally linked to each other and may, therefore, co-evolve in nature.

Colorectal adenomas contain multiple somatic mutations that do not coincide with synchronous adenocarcinoma specimens.

We have performed a comparative ultrasequencing study of multiple colorectal lesions obtained simultaneously from four patients. Our data show that benign lesions (adenomatous or hyperplastic polyps) contain a high mutational load. Additionally multiple synchronous colorectal lesions show non overlapping mutational signatures highlighting the degree of heterogeneity between multiple specimens in the same patient. Observations in these cases imply that considering not only the number of mutations but an effective oncogenic combination of mutations can determine the malignant progression of colorectal lesions.

Case-control genome-wide association study of persistent attention-deficit hyperactivity disorder identifies FBXO33 as a novel susceptibility gene for the disorder.

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder with high heritability. At least 30% of patients diagnosed in childhood continue to suffer from ADHD during adulthood and genetic risk factors may play an essential role in the persistence of the disorder throughout lifespan. To date, genome-wide association studies (GWAS) of ADHD have been completed in seven independent datasets, six of which were pediatric samples and one on persistent ADHD using a DNA-pooling strategy, but none of them reported genome-wide significant associations. In an attempt to unravel novel genes for the persistence of ADHD into adulthood, we conducted the first two-stage GWAS in adults with ADHD. The discovery sample included 607 ADHD cases and 584 controls. Top signals were subsequently tested for replication in three independent follow-up samples of 2104 ADHD patients and 1901 controls. None of the findings exceeded the genome-wide threshold for significance (PGC<5e-08), but we found evidence for the involvement of the FBXO33 (F-box only protein 33) gene in combined ADHD in the discovery sample (P=9.02e-07) and in the joint analysis of both stages (P=9.7e-03). Additional evidence for a FBXO33 role in ADHD was found through gene-wise and pathway enrichment analyses in our genomic study. Risk alleles were associated with lower FBXO33 expression in lymphoblastoid cell lines and with reduced frontal gray matter volume in a sample of 1300 adult subjects. Our findings point for the first time at the ubiquitination machinery as a new disease mechanism for adult ADHD and establish a rationale for searching for additional risk variants in ubiquitination-related genes.

The involvement of serotonin polymorphisms in autistic spectrum symptomatology.

BACKGROUND: Autism spectrum disorders (ASD) are highly inherited developmental syndromes, resulting from a complex interaction between environmental and genetic factors. To date, only a limited number of genetic variants have been discovered with respect to autism, and their contribution to the development of the disorder has not been clearly determined. Investigation of specific autistic symptomatology may improve the chances of identifying related genes and may help to better understand these disorders. MATERIALS AND METHODS: We investigated the contribution of 80 genetic variants in 15 serotonin genes to ASD phenotypes [intelligence quotation (IQ), intellectual disability (ID) and language onset delay (LD)] in a cohort of 141 children and young adults (121 male patients and 20 female patients, average age 14.5±5.1 years). RESULTS: Two polymorphisms in the HTR2B gene, rs10194776 and rs16827801, were associated with IQ (P=0.0004 and 0.003, respectively), ID (P=0.02 and 0.03) and LD (P=0.04 and 0.004). Nominal associations were also detected between the ASD phenotypes investigated and 5-HT2A, 5-HT4 and 5-HT6 genetic variants. CONCLUSION: Our study provides evidence of the contribution of serotonergic variants to IQ, ID and LD in ASD patients.

Genome-wide copy number variation analysis in adult attention-deficit and hyperactivity disorder.

Attention-deficit and hyperactivity disorder (ADHD) is a common psychiatric disorder with a worldwide prevalence of 5-6% in children and 4.4% in adults. Recently, copy number variations (CNVs) have been implicated in different neurodevelopmental disorders such as ADHD. Based on these previous reports that focused on pediatric cohorts, we hypothesize that structural variants may also contribute to adult ADHD and that such genomic variation may be enriched for CNVs previously identified in children with ADHD. To address this issue, we performed for the first time a whole-genome CNV study on 400 adults with ADHD and 526 screened controls. In agreement with recent reports in children with ADHD or in other psychiatric disorders, we identified a significant excess of insertions in ADHD patients compared to controls. The overall rate of CNVs >100 kb was 1.33 times higher in ADHD subjects than in controls (p = 2.4e-03), an observation mainly driven by a higher proportion of small events (from 100 kb to 500 kb; 1.35-fold; p = 1.3e-03). These differences remained significant when we considered CNVs that overlap genes or when structural variants spanning candidate genes for psychiatric disorders were evaluated, with duplications showing the greatest difference (1.41-fold, p = 0.024 and 2.85-fold, p = 8.5e-03, respectively). However, no significant enrichment was detected in our ADHD cohort for childhood ADHD-associated CNVs, CNVs previously identified in at least one ADHD patient or CNVs previously implicated in autism or schizophrenia. In conclusion, our study provides tentative evidence for a higher rate of CNVs in adults with ADHD compared to controls and contributes to the growing list of structural variants potentially involved in the etiology of the disease.

Recurrent inactivation of STAG2 in bladder cancer is not associated with aneuploidy.

Urothelial bladder cancer (UBC) is heterogeneous at the clinical, pathological and genetic levels. Tumor invasiveness (T) and grade (G) are the main factors associated with outcome and determine patient management. A discovery exome sequencing screen (n = 17), followed by a prevalence screen (n = 60), identified new genes mutated in this tumor coding for proteins involved in chromatin modification (MLL2, ASXL2 and BPTF), cell division (STAG2, SMC1A and SMC1B) and DNA repair (ATM, ERCC2 and FANCA). STAG2, a subunit of cohesin, was significantly and commonly mutated or lost in UBC, mainly in tumors of low stage or grade, and its loss was associated with improved outcome. Loss of expression was often observed in chromosomally stable tumors, and STAG2 knockdown in bladder cancer cells did not increase aneuploidy. STAG2 reintroduction in non-expressing cells led to reduced colony formation. Our findings indicate that STAG2 is a new UBC tumor suppressor acting through mechanisms that are different from its role in preventing aneuploidy.

Genetic relationship between five psychiatric disorders estimated from genome-wide SNPs.

Most psychiatric disorders are moderately to highly heritable. The degree to which genetic variation is unique to individual disorders or shared across disorders is unclear. To examine shared genetic etiology, we use genome-wide genotype data from the Psychiatric Genomics Consortium (PGC) for cases and controls in schizophrenia, bipolar disorder, major depressive disorder, autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD). We apply univariate and bivariate methods for the estimation of genetic variation within and covariation between disorders. SNPs explained 17-29% of the variance in liability. The genetic correlation calculated using common SNPs was high between schizophrenia and bipolar disorder (0.68 ± 0.04 s.e.), moderate between schizophrenia and major depressive disorder (0.43 ± 0.06 s.e.), bipolar disorder and major depressive disorder (0.47 ± 0.06 s.e.), and ADHD and major depressive disorder (0.32 ± 0.07 s.e.), low between schizophrenia and ASD (0.16 ± 0.06 s.e.) and non-significant for other pairs of disorders as well as between psychiatric disorders and the negative control of Crohn's disease. This empirical evidence of shared genetic etiology for psychiatric disorders can inform nosology and encourages the investigation of common pathophysiologies for related disorders.

Microarray and deep sequencing cross-platform analysis of the mirRNome and isomiR variation in response to epidermal growth factor.

BACKGROUND: Epidermal Growth Factor (EGF) plays an important function in the regulation of cell growth, proliferation, and differentiation by binding to its receptor (EGFR) and providing cancer cells with increased survival responsiveness. Signal transduction carried out by EGF has been extensively studied at both transcriptional and post-transcriptional levels. Little is known about the involvement of microRNAs (miRNAs) in the EGF signaling pathway. miRNAs have emerged as major players in the complex networks of gene regulation, and cancer miRNA expression studies have evidenced a direct involvement of miRNAs in cancer progression. RESULTS: In this study, we have used an integrative high content analysis approach to identify the specific miRNAs implicated in EGF signaling in HeLa cells as potential mediators of cancer mediated functions. We have used microarray and deep-sequencing technologies in order to obtain a global view of the EGF miRNA transcriptome with a robust experimental cross-validation. By applying a procedure based on Rankprod tests, we have delimited a solid set of EGF-regulated miRNAs. After validating regulated miRNAs by reverse transcription quantitative PCR, we have derived protein networks and biological functions from the predicted targets of the regulated miRNAs to gain insight into the potential role of miRNAs in EGF-treated cells. In addition, we have analyzed sequence heterogeneity due to editing relative to the reference sequence (isomiRs) among regulated miRNAs. CONCLUSIONS: We propose that the use of global genomic miRNA cross-validation derived from high throughput technologies can be used to generate more reliable datasets inferring more robust networks of co-regulated predicted miRNA target genes.

Reversion of a fungal genetic code alteration links proteome instability with genomic and phenotypic diversification.

Many fungi restructured their proteomes through incorporation of serine (Ser) at thousands of protein sites coded by the leucine (Leu) CUG codon. How these fungi survived this potentially lethal genetic code alteration and its relevance for their biology are not understood. Interestingly, the human pathogen Candida albicans maintains variable Ser and Leu incorporation levels at CUG sites, suggesting that this atypical codon assignment flexibility provided an effective mechanism to alter the genetic code. To test this hypothesis, we have engineered C. albicans strains to misincorporate increasing levels of Leu at protein CUG sites. Tolerance to the misincorporations was very high, and one strain accommodated the complete reversion of CUG identity from Ser back to Leu. Increasing levels of Leu misincorporation decreased growth rate, but production of phenotypic diversity on a phenotypic array probing various metabolic networks, drug resistance, and host immune cell responses was impressive. Genome resequencing revealed an increasing number of genotype changes at polymorphic sites compared with the control strain, and 80% of Leu misincorporation resulted in complete loss of heterozygosity in a large region of chromosome V. The data unveil unanticipated links between gene translational fidelity, proteome instability and variability, genome diversification, and adaptive phenotypic diversity. They also explain the high heterozygosity of the C. albicans genome and open the door to produce microorganisms with genetic code alterations for basic and applied research.

Analysis of two language-related genes in autism: a case-control association study of FOXP2 and CNTNAP2.

Impairment of language abilities is a common feature in autistic individuals. Heterozygous mutations in the Forkhead Box P2 (FOXP2) gene lead to a severe spoken language disorder. Recently, several studies have pinpointed the involvement of common variants of the Contactin-Associated Protein-Like 2 (CNTNAP2) gene, whose transcription is regulated by the product of FOXP2, in several disorders characterized by language impairments such as autism, specific language impairment (SLI), and selective mutism (SM). In the present study, common variants of the FOXP2 and the CNTNAP2 genes were analyzed through a case-control association study in 322 Spanish autistic patients and 524 controls. The results of this study suggest that common variants of FOXP2 are unlikely to contribute to autism susceptibility, in agreement with previous findings. Furthermore, we failed to replicate in our sample a previous association finding of two single nucleotide polymorphisms (rs2710102 and rs7794745) in the CNTNAP2 gene with autism. No evidence for the association of these genes with language traits was observed in our analysis.

Evaluation of common variants in 16 genes involved in the regulation of neurotransmitter release in ADHD.

Attention-deficit hyperactivity disorder (ADHD) is a neurobehavioral disorder characterized by inappropriate difficulties to sustain attention, control impulses and modulate activity level. Although ADHD is one of the most prevalent childhood psychiatric disorders, it also persists into adulthood in around 30-50% of the cases. Based on the effect of psychostimulants used in the pharmacological treatment of ADHD, dysfunctions in neuroplasticity mechanisms and synapses have been postulated to be involved in the pathophysiology of ADHD. With this background, we evaluated, both in childhood and adulthood ADHD, the role of several genes involved in the control of neurotransmitter release through synaptic vesicle docking, fusion and recycling processes by means of a population-based association study. We analyzed single nucleotide polymorphisms across 16 genes in a clinical sample of 950 ADHD patients (506 adults and 444 children) and 905 controls. Single and multiple-marker analyses identified several significant associations after correcting for multiple testing with a false discovery rate (FDR) of 15%: (i) the SYT2 gene was strongly associated with both adulthood and childhood ADHD (p=0.001, OR=1.49 (1.18-1.89) and p=0.007, OR=1.37 (1.09-1.72), respectively) and (ii) STX1A was found associated with ADHD only in adults (p=0.0041; OR=1.28 (1.08-1.51)). These data provide preliminary evidence for the involvement of genes that participate in the control of neurotransmitter release in the genetic predisposition to ADHD through a gene-system association study. Further follow-up studies in larger cohorts and deep-sequencing of the associated genomic regions are required to identify sequence variants directly involved in ADHD.

Neurotransmitter systems and neurotrophic factors in autism: association study of 37 genes suggests involvement of DDC.

OBJECTIVES: Neurotransmitter systems and neurotrophic factors can be considered strong candidates for autism spectrum disorder (ASD). The serotoninergic and dopaminergic systems are involved in neurotransmission, brain maturation and cortical organization, while neurotrophic factors (NTFs) participate in neurodevelopment, neuronal survival and synapses formation. We aimed to test the contribution of these candidate pathways to autism through a case-control association study of genes selected both for their role in central nervous system functions and for pathophysiological evidences. METHODS: The study sample consisted of 326 unrelated autistic patients and 350 gender-matched controls from Spain. We genotyped 369 tagSNPs to perform a case-control association study of 37 candidate genes. RESULTS: A significant association was obtained between the DDC gene and autism in the single-marker analysis (rs6592961, P = 0.00047). Haplotype-based analysis pinpointed a four-marker combination in this gene associated with the disorder (rs2329340C-rs2044859T-rs6592961A-rs11761683T, P = 4.988e-05). No significant results were obtained for the remaining genes after applying multiple testing corrections. However, the rs167771 marker in DRD3, associated with ASD in a previous study, displayed a nominal association in our analysis (P = 0.023). CONCLUSIONS: Our data suggest that common allelic variants in the DDC gene may be involved in autism susceptibility.

Epigenomic analysis detects widespread gene-body DNA hypomethylation in chronic lymphocytic leukemia.

We have extensively characterized the DNA methylomes of 139 patients with chronic lymphocytic leukemia (CLL) with mutated or unmutated IGHV and of several mature B-cell subpopulations through the use of whole-genome bisulfite sequencing and high-density microarrays. The two molecular subtypes of CLL have differing DNA methylomes that seem to represent epigenetic imprints from distinct normal B-cell subpopulations. DNA hypomethylation in the gene body, targeting mostly enhancer sites, was the most frequent difference between naive and memory B cells and between the two molecular subtypes of CLL and normal B cells. Although DNA methylation and gene expression were poorly correlated, we identified gene-body CpG dinucleotides whose methylation was positively or negatively associated with expression. We have also recognized a DNA methylation signature that distinguishes new clinico-biological subtypes of CLL. We propose an epigenomic scenario in which differential methylation in the gene body may have functional and clinical implications in leukemogenesis.

Spinal muscular atrophy associated with progressive myoclonic epilepsy is caused by mutations in ASAH1.

Spinal muscular atrophy (SMA) is a clinically and genetically heterogeneous disease characterized by the degeneration of lower motor neurons. The most frequent form is linked to mutations in SMN1. Childhood SMA associated with progressive myoclonic epilepsy (SMA-PME) has been reported as a rare autosomal-recessive condition unlinked to mutations in SMN1. Through linkage analysis, homozygosity mapping, and exome sequencing in three unrelated SMA-PME-affected families, we identified a homozygous missense mutation (c.125C>T [p.Thr42Met]) in exon 2 of ASAH1 in the affected children of two families and the same mutation associated with a deletion of the whole gene in the third family. Expression studies of the c.125C>T mutant cDNA in Farber fibroblasts showed that acid-ceramidase activity was only 32% of that generated by normal cDNA. This reduced activity was able to normalize the ceramide level in Farber cells, raising the question of the pathogenic mechanism underlying the CNS involvement in deficient cells. Morpholino knockdown of the ASAH1 ortholog in zebrafish led to a marked loss of motor-neuron axonal branching, a loss that is associated with increased apoptosis in the spinal cord. Our results reveal a wide phenotypic spectrum associated with ASAH1 mutations. An acid-ceramidase activity below 10% results in Farber disease, an early-onset disease starting with subcutaneous lipogranulomata, joint pain, and hoarseness of the voice, whereas a higher residual activity might be responsible for SMA-PME, a later-onset phenotype restricted to the CNS and starting with lower-motor-neuron disease.

An association study of sequence variants in the forkhead box P2 (FOXP2) gene and adulthood attention-deficit/hyperactivity disorder in two European samples.

OBJECTIVES: Attention-deficit/hyperactivity disorder (ADHD) is a common psychiatric disorder manifesting as symptoms of inattention, hyperactivity, and/or impulsivity. Learning disabilities co-occur with ADHD in 20-30% of cases and this high co-occurrence raises the possibility of a common etiological background. Forkhead box P2 (FOXP2) encodes a transcription factor involved in speech and language impairment and in the control of the corticobasal ganglia circuits known to be relevant in ADHD, suggesting a possible role of FOXP2 in ADHD. Our aim was to carry out an association study between FOXP2 and adulthood ADHD. METHODS: We carried out a case-control association study in 643 adult ADHD patients and 619 controls from Germany and in 361 adult ADHD patients and 442 controls from Spain with 12 tagging single nucleotide polymorphisms covering the FOXP2 gene. RESULTS: The single-marker and multiple-marker analyses showed an association between FOXP2 and combined ADHD in the German cohort [rs12533005: P=0.0033; odds ratio=1.30 (1.09-1.56); rs12533005/rs1229761: P=4.1e-04; odds ratio=1.38 (1.15-1.66)]. These positive results, however, were not confirmed in the Spanish sample. CONCLUSION: Although these preliminary findings provide a tentative evidence for the contribution of FOXP2 to ADHD and suggest common genetic factors for this psychiatric disorder and learning disabilities, they should be interpreted with caution. Further studies in larger samples are needed to clarify the role of this transcription factor in ADHD.