A role for TENM1 mutations in congenital general anosmia.

Congenital general anosmia (CGA) is a neurological disorder entailing a complete innate inability to sense odors. While the mechanisms underlying vertebrate olfaction have been studied in detail, there are still gaps in our understanding of the molecular genetic basis of innate olfactory disorders. Applying whole-exome sequencing to a family multiply affected with CGA, we identified three members with a rare X-linked missense mutation in the TENM1 (teneurin 1) gene (ENST00000422452:c.C4829T). In Drosophila melanogaster, TENM1 functions in synaptic-partner-matching between axons of olfactory sensory neurons and target projection neurons and is involved in synapse organization in the olfactory system. We used CRISPR-Cas9 system to generate a Tenm1 disrupted mouse model. Tenm1(-/-) and point-mutated Tenm1(A) (/A) adult mice were shown to have an altered ability to locate a buried food pellet. Tenm1(A) (/A) mice also displayed an altered ability to sense aversive odors. Results of our study, that describes a new Tenm1 mouse, agree with the hypothesis that TENM1 has a role in olfaction. However, additional studies should be done in larger CGA cohorts, to provide statistical evidence that loss-of-function mutations in TENM1 can solely cause the disease in our and other CGA cases.

Convergent lines of evidence support CAMKK2 as a schizophrenia susceptibility gene.

Genes that are differentially expressed between schizophrenia patients and healthy controls may have key roles in the pathogenesis of schizophrenia. We analyzed two large-scale genome-wide expression studies, which examined changes in gene expression in schizophrenia patients and their matched controls. We found calcium/calmodulin (CAM)-dependent protein kinase kinase 2 (CAMKK2) is significantly downregulated in individuals with schizophrenia in both studies. To seek the potential genetic variants that may regulate the expression of CAMKK2, we investigated the association between single-nucleotide polymorphisms (SNPs) within CAMKK2 and the expression level of CAMKK2. We found one SNP, rs1063843, which is located in intron 17 of CAMKK2, is strongly associated with the expression level of CAMKK2 in human brains (P=1.1 × 10(-6)) and lymphoblastoid cell lines (the lowest P=8.4 × 10(-6)). We further investigated the association between rs1063843 and schizophrenia in multiple independent populations (a total of 130 623 subjects) and found rs1063843 is significantly associated with schizophrenia (P=5.17 × 10(-5)). Interestingly, we found the T allele of rs1063843, which is associated with lower expression level of CAMKK2, has a higher frequency in individuals with schizophrenia in all of the tested samples, suggesting rs1063843 may be a causal variant. We also found that rs1063843 is associated with cognitive function and personality in humans. In addition, protein-protein interaction (PPI) analysis revealed that CAMKK2 participates in a highly interconnected PPI network formed by top schizophrenia genes, which further supports the potential role of CAMKK2 in the pathogenesis of schizophrenia. Taken together, these converging lines of evidence strongly suggest that CAMKK2 may have pivotal roles in schizophrenia susceptibility.

Support for association of HSPG2 with tardive dyskinesia in Caucasian populations.

Tardive dyskinesia (TD) is a severe adverse effect of chronic antipsychotic drug treatment. In addition to clinical risk factors, TD susceptibility is influenced by genetic predisposition. Recently, Syu et al. (2010) reported a genome-wide association screening of TD in Japanese schizophrenia patients. The best result was association of single-nucleotide polymorphism (SNP) rs2445142 in the HSPG2 (heparan sulfate proteoglycan 2) gene with TD. In the present study, we report a replication study of the five top Japanese TD-associated SNPs in two Caucasian TD samples. Applying logistic regression and controlling for relevant clinical risk factors, we were able to replicate the association of HSPG2 SNP rs2445142 with TD in a prospective study sample of 179 Americans of European origin by performing a secondary analysis of the CATIE (Clinical Antipsychotic Trials of Intervention Effectiveness) genome-wide association study data set, and using a perfect proxy surrogate marker (rs878949; P = 0.039). An association of the 'G' risk allele of HSPG2 SNP rs2445142 with TD was also shown in a sample of Jewish Israeli schizophrenia patients (retrospective, cross-sectional design; P = 0.03). Although the associations were only nominally significant, the findings provide further support for the possible involvement of HSPG2 in susceptibility to TD.

Evidence for an interaction of schizophrenia susceptibility loci on chromosome 6q23.3 and 10q24.33-q26.13 in Arab Israeli families.

A genome scan for schizophrenia related loci in Arab Israeli families by Lerer et al. [Lerer et al. (2003); Mol Psychiatry 8:488-498] detected significant evidence for linkage at chromosome 6q23. Subsequent fine mapping [Levi et al. (2005); Eur J Hum Genet 13:763-771], association [Amann-Zalcenstein et al. (2006); Eur J Hum Genet 14:1111-1119] and replication studies [Ingason et al. (2007); Eur J Hum Genet 15:988-991] identified AHI1 as a putative susceptibility gene. The same genome scan revealed suggestive evidence for a schizophrenia susceptibility locus in the 10q23-26 region. Genes at these two loci may act independently in the pathogenesis of the disease in our homogeneous sample of Arab Israeli families or may interact with each other and with other factors in a common biological pathway. The purpose of our current study was to test the hypothesis of genetic interaction between these two loci and to identify the type of interaction between them. The initial stage of our study focused on the 10q23-q26 region which has not been explored further in our sample. The second stage of the study included a test for possible genetic interaction between the 6q23.3 locus and the refined 10q24.33-q26.13 locus. A final candidate region of 19.9 Mb between markers D10S222 (105.3 Mb) and D10S587 (125.2 Mb) was found on chromosome 10 by non-parametric and parametric linkage analyses. These linkage findings are consistent with previous reports in the same chromosomal region. Two-locus multipoint linkage analysis under three complex disease inheritance models (heterogeneity, multiplicative, and additive models) yielded a best maximum LOD score of 7.45 under the multiplicative model suggesting overlapping function of the 6q23.3 and 10q24.33-q26.13 loci.

The CC2D1A, a member of a new gene family with C2 domains, is involved in autosomal recessive non-syndromic mental retardation.

BACKGROUND: The molecular basis of autosomal recessive non-syndromic mental retardation (NSMR) is poorly understood, mostly owing to heterogeneity and absence of clinical criteria for grouping families for linkage analysis. Only two autosomal genes, the PRSS12 gene on chromosome 4q26 and the CRBN on chromosome 3p26, have been shown to cause autosomal recessive NSMR, each gene in only one family. OBJECTIVE: To identify the gene causing autosomal recessive NSMR on chromosome 19p13.12. RESULTS: The candidate region established by homozygosity mapping was narrowed down from 2.4 Mb to 0.9 Mb on chromosome 19p13.12. A protein truncating mutation was identified in the gene CC2D1A in nine consanguineous families with severe autosomal recessive NSMR. The absence of the wild type protein in the lymphoblastoid cells of the patients was confirmed. CC2D1A is a member of a previously uncharacterised gene family that carries two conserved motifs, a C2 domain and a DM14 domain. The C2 domain is found in proteins which function in calcium dependent phospholipid binding; the DM14 domain is unique to the CC2D1A protein family and its role is unknown. CC2D1A is a putative signal transducer participating in positive regulation of I-kappaB kinase/NFkappaB cascade. Expression of CC2D1A mRNA was shown in the embryonic ventricular zone and developing cortical plate in staged mouse embryos, persisting into adulthood, with highest expression in the cerebral cortex and hippocampus. CONCLUSIONS: A previously unknown signal transduction pathway is important in human cognitive development.

Mapping of a new locus for autosomal recessive non-syndromic mental retardation in the chromosomal region 19p13.12-p13.2: further genetic heterogeneity.

OBJECTIVE: To identify and clinically evaluate four consanguineous families of Israeli Arab origin with non-syndromic mental retardation (NSMR), comprising a total of 10 affected and 24 unaffected individuals. PARTICIPANTS AND METHODS: All the families originated from the same small village and had the same family name. Association of the condition in these families with the two known autosomal recessive NSMR loci on chromosomes 3p25-pter and 4q24 (neurotrypsin gene) was excluded. RESULTS: Linkage of the disease gene to chromosome 19p13.12-p13.2(Zmax = 7.06 at theta = 0.00) for the marker D19S840 was established. All the affected individuals were found to be homozygous for a common haplotype for the markers cen-RFX1-D19S840-D19S558-D19S221-tel. CONCLUSIONS: The results suggest that the disease is caused by a single mutation derived from a single ancestral founder in all the families. Recombination events and a common disease bearing haplotype defined a critical region of 2.4 Mb, between the loci D19S547 proximally and D19S1165 distally.