Stefan Herms

Direct Conversion of Fibroblasts into Stably Expandable Neural Stem Cells

Recent advances have suggested that direct induction of neural stem cells (NSCs) could provide an alternative to derivation from somatic tissues or pluripotent cells. Here we show direct derivation of stably expandable NSCs from mouse fibroblasts through a curtailed version of reprogramming to pluripotency. By constitutively inducing Sox2, Klf4, and c-Myc while strictly limiting Oct4 activity to the initial phase of reprogramming, we generated neurosphere-like colonies that could be expanded for more than 50 passages and do not depend on sustained expression of the reprogramming factors. These induced neural stem cells (iNSCs) uniformly display morphological and molecular features of NSCs, such as the expression of Nestin, Pax6, and Olig2, and have a genome-wide transcriptional profile similar to that of brain-derived NSCs. Moreover, iNSCs can differentiate into neurons, astrocytes, and oligodendrocytes. Our results demonstrate that functional NSCs can be generated from somatic cells by factor-driven induction.

Key susceptibility locus for nonsyndromic cleft lip with or without cleft palate on chromosome 8q24.

We conducted a genome-wide association study involving 224 cases and 383 controls of Central European origin to identify susceptibility loci for nonsyndromic cleft lip with or without cleft palate (NSCL/P). A 640-kb region at chromosome 8q24.21 was found to contain multiple markers with highly significant evidence for association with the cleft phenotype, including three markers that reached genome-wide significance. The 640-kb cleft-associated region was saturated with 146 SNP markers and then analyzed in our entire NSCL/P sample of 462 unrelated cases and 954 controls. In the entire sample, the most significant SNP (rs987525) had a P value of 3.34 × 10−24. The odds ratio was 2.57 (95% CI = 2.02–3.26) for the heterozygous genotype and 6.05 (95% CI = 3.88–9.43) for the homozygous genotype. The calculated population attributable risk for this marker is 0.41, suggesting that this study has identified a major susceptibility locus for NSCL/P.

Genome-wide association study identifies two susceptibility loci for nonsyndromic cleft lip with or without cleft palate

We conducted a genome-wide association study for nonsyndromic cleft lip with or without cleft palate (NSCL/P) in 401 affected individuals and 1,323 controls, with replication in an independent sample of 793 NSCL/P triads. We report two new loci associated with NSCL/P at 17q22 (rs227731, combined P = 1.07 × 10−8, relative risk in homozygotes = 1.84, 95% CI 1.34–2.53) and 10q25.3 (rs7078160, combined P = 1.92 × 10−8, relative risk in homozygotes = 2.17, 95% CI 1.32–3.56).

Mutations in GRIN2A cause idiopathic focal epilepsy with rolandic spikes

Idiopathic focal epilepsy (IFE) with rolandic spikes is the most common childhood epilepsy, comprising a phenotypic spectrum from rolandic epilepsy (also benign epilepsy with centrotemporal spikes, BECTS) to atypical benign partial epilepsy (ABPE), Landau-Kleffner syndrome (LKS) and epileptic encephalopathy with continuous spike and waves during slow-wave sleep (CSWS). The genetic basis is largely unknown. We detected new heterozygous mutations in GRIN2A in 27 of 359 affected individuals from 2 independent cohorts with IFE (7.5%; P = 4.83 × 10−18, Fishers exact test). Mutations occurred significantly more frequently in the more severe phenotypes, with mutation detection rates ranging from 12/245 (4.9%) in individuals with BECTS to 9/51 (17.6%) in individuals with CSWS (P = 0.009, Cochran-Armitage test for trend). In addition, exon-disrupting microdeletions were found in 3 of 286 individuals (1.0%; P = 0.004, Fishers exact test). These results establish alterations of the gene encoding the NMDA receptor NR2A subunit as a major genetic risk factor for IFE.

Small molecules enable highly efficient neuronal conversion of human fibroblasts

Forced expression of proneural transcription factors has been shown to direct neuronal conversion of fibroblasts. Because neurons are postmitotic, conversion efficiencies are an important parameter for this process. We present a minimalist approach combining two-factor neuronal programming with small molecule–based inhibition of glycogen synthase kinase-3β and SMAD signaling, which converts postnatal human fibroblasts into functional neuron-like cells with yields up to >200% and neuronal purities up to >80%.

Genome-wide meta-analyses of nonsyndromic cleft lip with or without cleft palate identify six new risk loci

We have conducted the first meta-analyses for nonsyndromic cleft lip with or without cleft palate (NSCL/P) using data from the two largest genome-wide association studies published to date. We confirmed associations with all previously identified loci and identified six additional susceptibility regions (1p36, 2p21, 3p11.1, 8q21.3, 13q31.1 and 15q22). Analysis of phenotypic variability identified the first specific genetic risk factor for NSCLP (nonsyndromic cleft lip plus palate) (rs8001641; PNSCLP = 6.51 × 10−11; homozygote relative risk = 2.41, 95% confidence interval (CI) 1.84–3.16).

Genome-wide association study reveals two new risk loci for bipolar disorder

Bipolar disorder (BD) is a common and highly heritable mental illness and genome-wide association studies (GWAS) have robustly identified the first common genetic variants involved in disease aetiology. The data also provide strong evidence for the presence of multiple additional risk loci, each contributing a relatively small effect to BD susceptibility. Large samples are necessary to detect these risk loci. Here we present results from the largest BD GWAS to date by investigating 2.3 million single-nucleotide polymorphisms (SNPs) in a sample of 24,025 patients and controls. We detect 56 genome-wide significant SNPs in five chromosomal regions including previously reported risk loci ANK3, ODZ4 and TRANK1, as well as the risk locus ADCY2 (5p15.31) and a region between MIR2113 and POU3F2 (6q16.1). ADCY2 is a key enzyme in cAMP signalling and our finding provides new insights into the biological mechanisms involved in the development of BD.

Genome-Wide Association-, Replication-, and Neuroimaging Study Implicates HOMER1 in the Etiology of Major Depression

BACKGROUND Genome-wide association studies are a powerful tool for unravelling the genetic background of complex disorders such as major depression. METHODS We conducted a genome-wide association study of 604 patients with major depression and 1364 population based control subjects. The top hundred findings were followed up in a replication sample of 409 patients and 541 control subjects. RESULTS Two SNPs showed nominally significant association in both the genome-wide association study and the replication samples: 1) rs9943849 (p(combined) = 3.24E-6) located upstream of the carboxypeptidase M (CPM) gene and 2) rs7713917 (p(combined) = 1.48E-6), located in a putative regulatory region of HOMER1. Further evidence for HOMER1 was obtained through gene-wide analysis while conditioning on the genotypes of rs7713917 (p(combined) = 4.12E-3). Homer1 knockout mice display behavioral traits that are paradigmatic of depression, and transcriptional variants of Homer1 result in the dysregulation of cortical-limbic circuitry. This is consistent with the findings of our subsequent human imaging genetics study, which revealed that variation in single nucleotide polymorphism rs7713917 had a significant influence on prefrontal activity during executive cognition and anticipation of reward. CONCLUSION Our findings, combined with evidence from preclinical and animal studies, suggest that HOMER1 plays a role in the etiology of major depression and that the genetic variation affects depression via the dysregulation of cognitive and motivational processes.

A strobilurin fungicide enhances the resistance of tobacco against tobacco mosaic virus and Pseudomonas syringae pv tabaci.

The strobilurin class of fungicides comprises a variety of synthetic plant-protecting compounds with broad-spectrum antifungal activity. In the present study, we demonstrate that a strobilurin fungicide, F 500 (Pyraclostrobin), enhances the resistance of tobacco (Nicotiana tabacum cv Xanthi nc) against infection by either tobacco mosaic virus (TMV) or the wildfire pathogenPseudomonas syringae pv tabaci. F 500 was also active at enhancing TMV resistance in NahGtransgenic tobacco plants unable to accumulate significant amounts of the endogenous inducer of enhanced disease resistance, salicylic acid (SA). This finding suggests that F 500 enhances TMV resistance in tobacco either by acting downstream of SA in the SA signaling mechanism or by functioning independently of SA. The latter assumption is the more likely because in infiltrated leaves, F 500 did not cause the accumulation of SA-inducible pathogenesis-related (PR)-1 proteins that often are used as conventional molecular markers for SA-induced disease resistance. However, accumulation of PR-1 proteins and the associated activation of the PR-1 genes were elicited upon TMV infection of tobacco leaves and both these responses were induced more rapidly in F 500-pretreated plants than in the water-pretreated controls. Taken together, our results suggest that F 500, in addition to exerting direct antifungal activity, may also protect plants by priming them for potentiated activation of subsequently pathogen-induced cellular defense responses.

The DISC locus and schizophrenia: evidence from an association study in a central European sample and from a meta-analysis across different European populations

Association studies, as well as the initial translocation family study, identified the gene Disrupted-In-Schizophrenia-1 (DISC1) as a risk factor for schizophrenia. DISC1 encodes a multifunctional scaffold protein involved in neurodevelopmental processes implicated in the etiology of schizophrenia. The present study explores the contribution of the DISC locus to schizophrenia using three different approaches: (i) systematic association mapping aimed at detecting DISC risk variants in a schizophrenia sample from a central European population (556 SNPs, n = 1621 individuals). In this homogenous sample, a circumscribed DISC1 interval in intron 9 was significantly associated with schizophrenia in females (P = 4 x 10(-5)) and contributed most strongly to early-onset cases (P = 9 x 10(-5)). The odds ratios (ORs) were in the range of 1.46-1.88. (ii) The same sample was used to test for the locus-specific SNP-SNP interaction most recently associated with schizophrenia. Our results confirm the SNP interplay effect between rs1538979 and rs821633 that significantly conferred disease risk in male patients with schizophrenia (P = 0.016, OR 1.57). (iii) In order to detect additional schizophrenia variants, a meta-analysis was performed using nine schizophrenia samples from different European populations (50 SNPs, n = 10 064 individuals maximum, n = 3694 minimum). We found evidence for a common schizophrenia risk interval within DISC1 intron 4-6 (P = 0.002, OR 1.27). The findings point to a complex association between schizophrenia and DISC, including the presence of different risk loci and SNP interplay effects. Furthermore, our phenotype-genotype results--including the consideration of sex-specific effects--highlight the value of homogenous samples in mapping risk genes for schizophrenia in general, and at the DISC locus in particular.