New insights into the pharmacogenomics of antidepressant response from the GENDEP and STAR*D studies: rare variant analysis and high-density imputation.

Genome-wide association studies have generally failed to identify polymorphisms associated with antidepressant response. Possible reasons include limited coverage of genetic variants that this study tried to address by exome genotyping and dense imputation. A meta-analysis of Genome-Based Therapeutic Drugs for Depression (GENDEP) and Sequenced Treatment Alternatives to Relieve Depression (STAR*D) studies was performed at the single-nucleotide polymorphism (SNP), gene and pathway levels. Coverage of genetic variants was increased compared with previous studies by adding exome genotypes to previously available genome-wide data and using the Haplotype Reference Consortium panel for imputation. Standard quality control was applied. Phenotypes were symptom improvement and remission after 12 weeks of antidepressant treatment. Significant findings were investigated in NEWMEDS consortium samples and Pharmacogenomic Research Network Antidepressant Medication Pharmacogenomic Study (PGRN-AMPS) for replication. A total of 7062 950 SNPs were analyzed in GENDEP (n=738) and STAR*D (n=1409). rs116692768 (P=1.80e-08, ITGA9 (integrin α9)) and rs76191705 (P=2.59e-08, NRXN3 (neurexin 3)) were significantly associated with symptom improvement during citalopram/escitalopram treatment. At the gene level, no consistent effect was found. At the pathway level, the Gene Ontology (GO) terms GO: 0005694 (chromosome) and GO: 0044427 (chromosomal part) were associated with improvement (corrected P=0.007 and 0.045, respectively). The association between rs116692768 and symptom improvement was replicated in PGRN-AMPS (P=0.047), whereas rs76191705 was not. The two SNPs did not replicate in NEWMEDS. ITGA9 codes for a membrane receptor for neurotrophins and NRXN3 is a transmembrane neuronal adhesion receptor involved in synaptic differentiation. Despite their meaningful biological rationale for being involved in antidepressant effect, replication was partial. Further studies may help in clarifying their role.

Congenital Neuronal Ceroid Lipofuscinosis with a Novel CTSD Gene Mutation: A Rare Cause of Neonatal-Onset Neurodegenerative Disorder.

Neuronal ceroid lipofuscinoses represent a heterogeneous group of early onset neurodegenerative disorders that are characterized by progressive cognitive and motor function decline, visual loss, and epilepsy. The age of onset has been historically used for the phenotypic classification of this group of disorders, but their molecular genetic delineation has now enabled a better characterization, demonstrating significant genetic heterogeneity even among individuals with a similar phenotype. The rare Congenital Neuronal Ceroid Lipofuscinosis (CLN10) caused by mutations in the CTSD gene encoding for cathepsin D is associated with a dramatic presentation with onset before or around birth. We report on a female born to consanguineous parents who presented at birth with severe neonatal encephalopathy with massive cerebral and cerebellar shrinking on magnetic resonance imaging. Whole exome sequencing with targeted bioinformatic analysis of a panel of genes associated with prenatal/perinatal onset of neurodegenerative disease was performed and revealed the presence of a novel homozygous in-frame deletion in CTSD. Additional functional studies further confirmed the pathogenic character of this variant and established the diagnosis of CLN10 in the patient.

Experience of a multidisciplinary task force with exome sequencing for Mendelian disorders.

BACKGROUND: In order to optimally integrate the use of high-throughput sequencing (HTS) as a tool in clinical diagnostics of likely monogenic disorders, we have created a multidisciplinary "Genome Clinic Task Force" at the University Hospitals of Geneva, which is composed of clinical and molecular geneticists, bioinformaticians, technicians, bioethicists, and a coordinator. METHODS AND RESULTS: We have implemented whole exome sequencing (WES) with subsequent targeted bioinformatics analysis of gene lists for specific disorders. Clinical cases of heterogeneous Mendelian disorders that could potentially benefit from HTS are presented and discussed during the sessions of the task force. Debate concerning the interpretation of identified variants and the content of the final report constitutes a major part of the task force's work. Furthermore, issues related to bioethics, genetic counseling, quality control, and reimbursement are also addressed. CONCLUSIONS: This multidisciplinary task force has enabled us to create a platform for regular exchanges between all involved experts in order to deal with the multiple complex issues related to HTS in clinical practice and to continuously improve the diagnostic use of HTS. In addition, this task force was instrumental to formally approve the reimbursement of HTS for molecular diagnosis of Mendelian disorders in Switzerland.

Copy number variants and therapeutic response to antidepressant medication in major depressive disorder.

It would be beneficial to find genetic predictors of antidepressant response to help personalise treatment of major depressive disorder (MDD). Rare copy number variants (CNVs) have been implicated in several psychiatric disorders, including MDD, but their role in antidepressant response has yet to be investigated. CNV data were available for 1565 individuals with MDD from the NEWMEDS (Novel Methods leading to New Medications in Depression and Schizophrenia) consortium with prospective data on treatment outcome with either a serotonergic or noradrenergic antidepressant. No association was seen between the presence of CNV (rare or common), the overall number of CNVs or genomic CNV 'burden' and antidepressant response. Specific CNVs were nominally associated with antidepressant response, including 15q13.3 duplications and exonic NRXN1 deletions. These were associated with poor response to antidepressants. Overall burden of CNVs is unlikely to contribute to personalising antidepressant treatment. Specific CNVs associated with antidepressant treatment require replication and further study to confirm their role in the therapeutic action of antidepressant.

Insertion of beta-satellite repeats identifies a transmembrane protease causing both congenital and childhood onset autosomal recessive deafness.

Approximately 50% of childhood deafness is caused by mutations in specific genes. Autosomal recessive loci account for approximately 80% of nonsyndromic genetic deafness. Here we report the identification of a new transmembrane serine protease (TMPRSS3; also known as ECHOS1) expressed in many tissues, including fetal cochlea, which is mutated in the families used to describe both the DFNB10 and DFNB8 loci. An 8-bp deletion and insertion of 18 monomeric (approximately 68-bp) beta-satellite repeat units, normally present in tandem arrays of up to several hundred kilobases on the short arms of acrocentric chromosomes, causes congenital deafness (DFNB10). A mutation in a splice-acceptor site, resulting in a 4-bp insertion in the mRNA and a frameshift, was detected in childhood onset deafness (DFNB8). This is the first description of beta-satellite insertion into an active gene resulting in a pathogenic state, and the first description of a protease involved in hearing loss.

Genome-wide association study of increasing suicidal ideation during antidepressant treatment in the GENDEP project.

Suicidal thoughts during antidepressant treatment have been the focus of several candidate gene association studies. The aim of the present genome-wide association study was to identify additional genetic variants involved in increasing suicidal ideation during escitalopram and nortriptyline treatment. A total of 706 adult participants of European ancestry, treated for major depression with escitalopram or nortriptyline over 12 weeks in the Genome-Based Therapeutic Drugs for Depression (GENDEP) study were genotyped with Illumina Human 610-Quad Beadchips (Illumina, San Diego, CA, USA). A total of 244 subjects experienced an increase in suicidal ideation during follow-up. The genetic marker most significantly associated with increasing suicidality (8.28 × 10(-7)) was a single-nucleotide polymorphism (SNP; rs11143230) located 30 kb downstream of a gene encoding guanine deaminase (GDA) on chromosome 9q21.13. Two suggestive drug-specific associations within KCNIP4 (Kv channel-interacting protein 4; chromosome 4p15.31) and near ELP3 (elongation protein 3 homolog; chromosome 8p21.1) were found in subjects treated with escitalopram. Suggestive drug by gene interactions for two SNPs near structural variants on chromosome 4q12, one SNP in the apolipoprotein O (APOO) gene on chromosome Xp22.11 and one on chromosome 11q24.3 were found. The most significant association within a set of 33 candidate genes was in the neurotrophic tyrosine kinase receptor type 2 (NTRK2) gene. Finally, we also found trend for an association within genes previously associated with psychiatric phenotypes indirectly linked to suicidal behavior, that is, GRIP1, NXPH1 and ANK3. The results suggest novel pathways involved in increasing suicidal ideation during antidepressant treatment and should help to target treatment to reduce the risk of this dramatic adverse event. Limited power precludes definitive conclusions and replication in larger sample is warranted.

Endocytic protein intersectin-l regulates actin assembly via Cdc42 and N-WASP.

Intersectin-s is a modular scaffolding protein regulating the formation of clathrin-coated vesicles. In addition to the Eps15 homology (EH) and Src homology 3 (SH3) domains of intersectin-s, the neuronal variant (intersectin-l) also has Dbl homology (DH), pleckstrin homology (PH) and C2 domains. We now show that intersectin-l functions through its DH domain as a guanine nucleotide exchange factor (GEF) for Cdc42. In cultured cells, expression of DH-domain-containing constructs cause actin rearrangements specific for Cdc42 activation. Moreover, in vivo studies reveal that stimulation of Cdc42 by intersectin-l accelerates actin assembly via N-WASP and the Arp2/3 complex. N-WASP binds directly to intersectin-l and upregulates its GEF activity, thereby generating GTP-bound Cdc42, a critical activator of N-WASP. These studies reveal a role for intersectin-l in a novel mechanism of N-WASP activation and in regulation of the actin cytoskeleton.

No evidence for the presence of genetic variants predisposing to psychotic disorders on the non-deleted 22q11.2 allele of VCFS patients.

The velo-cardio-facial syndrome (VCFS) is caused by hemizygous deletions on chromosome 22q11.2. The VCFS phenotype is complex and characterized by frequent occurrence of neuropsychiatric symptoms with up to 25-30% of cases suffering from psychotic disorders compared with only ~1% in the general population (odds ratio≈20-25). This makes the 22q11.2 deletion one of the most prominent risk factors for schizophrenia. However, its penetrance for neuropsychiatric phenotypes is incomplete suggesting that additional risk factors are required for disease development. These additional risk factors could lie anywhere on the genome, but by reducing the normal diploid to a haploid state, the 22q11.2 deletion could result in the unmasking of otherwise recessive alleles or functional variants on the non-deleted 22q11.2 allele. To test this hypothesis, we captured and sequenced the whole 22q11.2 non-deleted region in 88 VCFS patients with (n=40) and without (n=48) psychotic disorders to identify genetic variation that could increase the risk for schizophrenia. Single nucleotide variants (SNVs), small insertions/deletions (indels) and copy number variants were called and their distributions were compared between the two diagnostic groups using variant-, gene- and region-based association tests. None of these tests resulted in statistical evidence for the existence of a genetic variation in the non-deleted allele that would increase schizophrenia risk in VCFS patients. Power analysis showed that our study was able to achieve >80% statistical power to detect association of a risk variant with an odd ratio of ⩾22. However, it is certainly under-powered to detect risk variant of smaller effect sizes. Our study did not provide evidence that genetic variants of very large effect size located on the non-deleted 22q1.2 allele in VCFS patients increase the risk for developing psychotic disorders. Variants with smaller effects may be located in the remaining 22q11.2 allele and elsewhere in the genome. Therefore, whole exome or even genome sequencing for larger sample size would appear to be the next logical steps in the search for the genetic modifiers of the 22q11.2-deletion neuropsychiatric phenotype.

Novel missense mutations of TMPRSS3 in two consanguineous Tunisian families with non-syndromic autosomal recessive deafness.

Recently the TMPRSS3 gene, which encodes a transmembrane serine protease, was found to be responsible for two non-syndromic recessive deafness loci located on human chromosome 21q22.3, DFNB8 and DFNB10. We found evidence for linkage to the DFNB8/10 locus in two unrelated consanguineous Tunisian families segregating congenital autosomal recessive sensorineural deafness. The audiometric tests showed a loss of hearing greater than 70 dB, in all affected individuals of both families. Mutation screening of TMPRSS3 revealed two novel missense mutations, W251C and P404L, altering highly conserved amino acids of the serine protease domain. Both mutations were not found in 200 control Tunisian chromosomes. The detection of naturally-occurring TMPRSS3 missense mutations in deafness families identifies functionally important amino acids. Comparative protein modeling of the TMPRSS3 protease domain predicted that W251C might lead to a structural rearrangement affecting the active site H257 and that P404L might alter the geometry of the active site loop and therefore affect the serine protease activity.

Lack of association between juvenile myoclonic epilepsy and GABRA5 and GABRB3 genes.

Alpha 5 and beta 3 GABAA receptor genes are major candidates for epilepsy, as they code for subunits of the most important human inhibitory neurotransmitter. Moreover, they are located within a region of the human genome previously implicated in disorders including epilepsy. We carried out an association study between dinucleotide repeat polymorphisms in these two genes and juvenile myoclonic epilepsy (JME). JME is the most common idiopathic epilepsy and is characterized by a complex mode of inheritance. We did not find significant differences between controls and patients for allele or genotype frequencies.

Dihydropyridine-like effects of amiodarone and desethylamiodarone on thyrotropin secretion and intracellular calcium concentration in rat pituitary.

Amiodarone (AM) and its major metabolite desethylamiodarone (DEA) are structurally similar to biologically active thyroid hormones. Amiodarone therapy is frequently associated with impairment of thyrotropic function, whose mechanisms are still controversial. Besides its effect on nuclear thyroid hormone binding. AM is able to displace dihydropyridine (DH) binding on membrane preparations from several tissues. By perifusing rat pituitary fragments and measuring thyrotropin (TSH) release we examined: the effect of AM on Ca(2+)-dependent and DHP-sensitive potentiation of the TSH response to thyrotropin-releasing hormone (TRH) induced by either triiodothyronine (T3, perifused for only 30 min before a TRH pulse) or by the prepro-TRH peptide 160-169 (PS4); and the effect of DEA on TRH-induced TSH response in the presence or absence of the DHP nifedipine. We show that AM reverses T3 or PS4 potentiation of the TSH response to TRH; this effect is specific because AM does not modify ionomycin potentiation of that response. In contrast, DEA significantly potentiates the TSH response to TRH and the DHP nifedipine reverses that potentiation. We also tested whether AM would change the acute T3-induced increase in intracellular Ca2+ concentration by measuring intracellular Ca2+ ([Ca2+])i with fura-2 imaging on primary cultures of pituitary cells. We show that AM reverses the effect of T3 on [Ca2+]i as well as the PS4-induced increase in [Ca2+]i. In contrast, DEA increases [Ca2+]i and nifedipine reverses this effect. Our results suggest that AM and DEA display DHP-like effects on TRH-induced TSH release, behaving either as a Ca2+ channel blocker (AM) or as a Ca2+ channel agonist (DEA).

Identification of a new locus for generalized epilepsy with febrile seizures plus (GEFS+) on chromosome 2q24-q33.

We report the identification of a new locus for generalized epilepsy with febrile seizures plus (GEFS+). Six family members manifested isolated typical febrile seizures (FS), and five had typical FS associated with generalized epilepsy (FS+, generalized tonic/clonic seizures). Afebrile seizures occurred from childhood until the teenage years. The maximum two-point LOD score was 3.99 for markers D2S294 and D2S2314. Flanking markers place the GEFS+ locus between D2S141 and D2S116, with multipoint analysis favoring the 13-cM interval spanned by D2S294 and D2S364. This locus is the second GEFS+ locus to be reported, which suggests that this syndrome is genetically heterogeneous.

Two isoforms of a human intersectin (ITSN) protein are produced by brain-specific alternative splicing in a stop codon.

Using selected trapped exons with homology to specific protein domains, we identified a new full-length cDNA encoding a protein containing many motifs for protein-protein interactions. There are two major mRNA transcripts, a ubiquitously expressed mRNA of 5.3 kb and a brain-specific transcript of approximately 15 kb, encoding proteins of 1220 and 1721 amino acids, respectively. The stop codon of the ORF of the shorter transcript is split between adjacent exons. In brain tissues the last exon of the short transcript is skipped, and an alternative downstream exon, the first of several additional, is used to produce the 15-kb mRNA. The putative human protein is highly homologous to Xenopus intersectin (81% identical) and to Drosophila dynamin-associated protein, Dap160 (31% identical) and was termed intersectin (ITSN). Both human proteins contain five SH3 (Src homology 3) domains, two EH (Eps15 homology) domains, and an alpha-helix-forming region. The brain-specific long transcript encodes for three additional domains: a GEF (guanine-nucleotide exchange factors), a PH (pleckstrin homology), and a C2 domain. The Drosophila homologue is associated with dynamin, a protein family involved in the endocytic pathway and/or synaptic vesicle recycling. The structure of the human ITSN protein is consistent with its involvement in membrane-associated molecular trafficking and signal transduction pathways. The human ITSN gene has been mapped to 21q22. 1-q22.2 between markers D21S319 and D21S65, and its importance in Down syndrome and monogenic disorders is currently unknown.

Genomic structure, sequence, and refined mapping of the human intersectin gene (ITSN), which encompasses 250 kb on chromosome 21q22.1-->q22.2.

The ubiquitously expressed and brain-specific human intersectin (ITSN) isoforms are scaffold proteins probably involved in general endocytosis and synaptic vesicle recycling, respectively. Here, analysis of 21q22.1-->q22.2 genomic sequence revealed that ITSN consists of 41 exons spanning approximately 250 kb and maps between GART and D21S325. The probable function of the ITSN isoforms and mapping position of ITSN suggest that disproportionate expression of this gene may be implicated in the phenotypic characteristics of Down syndrome.

Genomic structure of a copy of the human TPTE gene which encompasses 87 kb on the short arm of chromosome 21.

The testis-expressed human TPTE is a putative transmembrane tyrosine phosphatase, probably involved in signal transduction pathways of the endocrine and/or the spermatogenetic function of the testis. TPTE was mapped to the pericentromeric region of human chromosomes 21 and 13, and to chromosomes 15, 22, and Y. It is unknown which of the TPTE copies are transcribed, contain intronic sequences, and/or have open reading frames. Here, in silico analysis of the genomic sequence of human chromosome 21 allowed the determination of the genomic structure of a copy of the TPTE gene. This copy consists of 24 exons and spans approximately 87 kb. The mapping position of this copy of TPTE on the short arm of chromosome 21 was confirmed by FISH using the BAC 15L0C0 clone as a probe that contains almost the entire TPTE gene. This is the first description of the genomic sequence of a non-RNR gene on the short arm of human acrocentric chromosomes.

Isolation of the human BACH1 transcription regulator gene, which maps to chromosome 21q22.1.

In order to contribute to the development of the transcriptional map of chromosome 21, we performed exon trapping using cosmid clones mapped in the region 21q22.1-22.2 and identified a number of potential exons. One of the trapped exons (Genbank No. AF026200) showed a strong homology with the mouse Bach1 gene (Genbank No. D86603), a transcription factor regulating gene expression. We then isolated the full-length coding region of the human BACH1 gene using expressed sequence tags, reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends. The predicted BACH1 protein contains 736 amino acids and is 88% identical to its mouse homolog. It contains basic leucine zipper and BTB-zinc finger domains (which are directly involved in DNA binding for transcription regulation). The BACH1 gene maps in a relatively gene-poor region on 21q22.1 in yeast artificial chromosome 814c1 of the collection of Chumakov et al. Northern blot analysis revealed that it is expressed as an mRNA species of approximately 5.8 kb in all 16 adult and 4 fetal tissues examined; an additional mRNA species of 2.8 kb was observed in adult testis. The contribution of the BACH1 gene to the pathophysiology of trisomy or monosomy 21 is unknown. In addition, no monogenic disorders associated with mutations in the BACH1 gene have yet been identified.

A nonsense mutation in the alpha4 subunit of the nicotinic acetylcholine receptor (CHRNA4) cosegregates with 20q-linked benign neonatal familial convulsions (EBNI)

Benign Familial Neonatal Convulsions (BFNC) is an epileptic disorder with an autosomal dominant mode of transmission. It has been shown that about 80% of BFNC pedigrees are linked to a genetic defect on chromosome 20q13.3. A candidate gene for the epilepsies, the gene coding for the alpha4 subunit of the nicotinic cholinergic receptor (CHRNA4), has previously been localized on chromosome 20. Here we report a single point mutation converting a serine codon to a stop codon in the exon 5 of CHRNA4, in one BFNC family. Identification of CHRNA4 as the defective gene in 20q-BFNC represents the first example of a human idiopathic epilepsy caused by a mutation directly affecting a neurotransmitter receptor in the central nervous system.

Linkage mapping of benign familial infantile convulsions (BFIC) to chromosome 19q.

Benign familial infantile convulsions (BFIC) are an autosomal-dominant epileptic syndrome characterized by an age of onset within the first year of life. Although they were first reported in families of Italian descent, BFIC have also been described in non-Italian families. We have mapped the BFIC gene to chromosome 19 by linkage analysis in five Italian families with a maximum two-point lod score of 6.36 at D19S114; maximum multipoint lod scores > 8 were obtained for the interval D19S250-D19S245. BFIC are therefore the third idiopathic partial epileptic syndrome to be mapped on the human genome.

Structure of the human Lanosterol synthase gene and its analysis as a candidate for holoprosencephaly (HPE1).

Holoprosencephaly (HPE) is the most common birth defect of the brain in humans. It involves various degrees of incomplete separation of the cerebrum into distinct left and right halves, and it is frequently accompanied by craniofacial anomalies. The HPE1 locus in human chromosome 21q22.3 is one of a dozen putative genetic loci implicated in causing HPE. Here, we report the complete gene structure of the human lanosterol synthase (LS) gene, which is located in this interval, and present its mutational analysis in HPE patients. We considered LS an excellent candidate HPE gene because of the requirement for cholesterol modification of the Sonic Hedgehog protein for the correct patterning activity of this HPE-associated protein. Despite extensive pedigree analysis of numerous polymorphisms, as well as complementation studies in yeast on one of the missense mutations, we find no evidence that the LS gene is in fact HPE1, implicating another gene located in this chromosomal region in HPE pathogenesis.