Genome-wide scan demonstrates significant linkage for male sexual orientation.

BACKGROUND: Findings from family and twin studies support a genetic contribution to the development of sexual orientation in men. However, previous studies have yielded conflicting evidence for linkage to chromosome Xq28. METHOD: We conducted a genome-wide linkage scan on 409 independent pairs of homosexual brothers (908 analyzed individuals in 384 families), by far the largest study of its kind to date. RESULTS: We identified two regions of linkage: the pericentromeric region on chromosome 8 (maximum two-point LOD = 4.08, maximum multipoint LOD = 2.59), which overlaps with the second strongest region from a previous separate linkage scan of 155 brother pairs; and Xq28 (maximum two-point LOD = 2.99, maximum multipoint LOD = 2.76), which was also implicated in prior research. CONCLUSIONS: Results, especially in the context of past studies, support the existence of genes on pericentromeric chromosome 8 and chromosome Xq28 influencing development of male sexual orientation.

Evidence that duplications of 22q11.2 protect against schizophrenia.

A number of large, rare copy number variants (CNVs) are deleterious for neurodevelopmental disorders, but large, rare, protective CNVs have not been reported for such phenotypes. Here we show in a CNV analysis of 47 005 individuals, the largest CNV analysis of schizophrenia to date, that large duplications (1.5-3.0 Mb) at 22q11.2--the reciprocal of the well-known, risk-inducing deletion of this locus--are substantially less common in schizophrenia cases than in the general population (0.014% vs 0.085%, OR=0.17, P=0.00086). 22q11.2 duplications represent the first putative protective mutation for schizophrenia.

Schizophrenia susceptibility alleles are enriched for alleles that affect gene expression in adult human brain.

It is widely thought that alleles that influence susceptibility to common diseases, including schizophrenia, will frequently do so through effects on gene expression. As only a small proportion of the genetic variance for schizophrenia has been attributed to specific loci, this remains an unproven hypothesis. The International Schizophrenia Consortium (ISC) recently reported a substantial polygenic contribution to that disorder, and that schizophrenia risk alleles are enriched among single-nucleotide polymorphisms (SNPs) selected for marginal evidence for association (P<0.5) from genome-wide association studies (GWAS). It follows that if schizophrenia susceptibility alleles are enriched for those that affect gene expression, those marginally associated SNPs, which are also expression quantitative trait loci (eQTLs), should carry more true association signals compared with SNPs that are not marginally associated. To test this, we identified marginally associated (P<0.5) SNPs from two of the largest available schizophrenia GWAS data sets. We assigned eQTL status to those SNPs based upon an eQTL data set derived from adult human brain. Using the polygenic score method of analysis reported by the ISC, we observed and replicated the observation that higher probability cis-eQTLs predicted schizophrenia better than those with a lower probability for being a cis-eQTL. Our data support the hypothesis that alleles conferring risk of schizophrenia are enriched among those that affect gene expression. Moreover, our data show that notwithstanding the likely developmental origin of schizophrenia, studies of adult brain tissue can, in principle, allow relevant susceptibility eQTLs to be identified.

Nonsense mutations in the C-terminal SH2 region of the GTPase activating protein (GAP) gene in human tumours.

GTPase Activating Protein (GAP) is involved in down-regulating normal ras proteins and in the signal transduction pathway of some growth factors. We have screened 188 human tumours for mutations in the catalytic domain and at the C terminal SH2 region GAP. Three nonsense mutations in basal cell carcinomas were detected in the SH2 region and no mutations could be demonstrated in the catalytic domain. We conclude that mutations in the SH2 region of GAP may play a role in tumorigenesis and that inactivating mutations of the GAP catalytic domain do not contribute to tumour development.

Genome-wide association study of recurrent early-onset major depressive disorder.

A genome-wide association study was carried out in 1020 case subjects with recurrent early-onset major depressive disorder (MDD) (onset before age 31) and 1636 control subjects screened to exclude lifetime MDD. Subjects were genotyped with the Affymetrix 6.0 platform. After extensive quality control procedures, 671 424 autosomal single nucleotide polymorphisms (SNPs) and 25 068 X chromosome SNPs with minor allele frequency greater than 1% were available for analysis. An additional 1 892 186 HapMap II SNPs were analyzed based on imputed genotypic data. Single-SNP logistic regression trend tests were computed, with correction for ancestry-informative principal component scores. No genome-wide significant evidence for association was observed, assuming that nominal P<5 × 10(-8) approximates a 5% genome-wide significance threshold. The strongest evidence for association was observed on chromosome 18q22.1 (rs17077540, P=1.83 × 10(-7)) in a region that has produced some evidence for linkage to bipolar-I or -II disorder in several studies, within an mRNA detected in human brain tissue (BC053410) and approximately 75 kb upstream of DSEL. Comparing these results with those of a meta-analysis of three MDD GWAS data sets reported in a companion article, we note that among the strongest signals observed in the GenRED sample, the meta-analysis provided the greatest support (although not at a genome-wide significant level) for association of MDD to SNPs within SP4, a brain-specific transcription factor. Larger samples will be required to confirm the hypothesis of association between MDD (and particularly the recurrent early-onset subtype) and common SNPs.

Novel loci for major depression identified by genome-wide association study of Sequenced Treatment Alternatives to Relieve Depression and meta-analysis of three studies.

We report a genome-wide association study (GWAS) of major depressive disorder (MDD) in 1221 cases from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study and 1636 screened controls. No genome-wide evidence for association was detected. We also carried out a meta-analysis of three European-ancestry MDD GWAS data sets: STAR*D, Genetics of Recurrent Early-onset Depression and the publicly available Genetic Association Information Network-MDD data set. These data sets, totaling 3957 cases and 3428 controls, were genotyped using four different platforms (Affymetrix 6.0, 5.0 and 500 K, and Perlegen). For each of 2.4 million HapMap II single-nucleotide polymorphisms (SNPs), using genotyped data where available and imputed data otherwise, single-SNP association tests were carried out in each sample with correction for ancestry-informative principal components. The strongest evidence for association in the meta-analysis was observed for intronic SNPs in ATP6V1B2 (P=6.78 x 10⁻7), SP4 (P=7.68 x 10⁻7) and GRM7 (P=1.11 x 10⁻6). Additional exploratory analyses were carried out for a narrower phenotype (recurrent MDD with onset before age 31, N=2191 cases), and separately for males and females. Several of the best findings were supported primarily by evidence from narrow cases or from either males or females. On the basis of previous biological evidence, we consider GRM7 a strong MDD candidate gene. Larger samples will be required to determine whether any common SNPs are significantly associated with MDD.

GWA study data mining and independent replication identify cardiomyopathy-associated 5 (CMYA5) as a risk gene for schizophrenia.

We conducted data-mining analyses using the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) and molecular genetics of schizophrenia genome-wide association study supported by the genetic association information network (MGS-GAIN) schizophrenia data sets and performed bioinformatic prioritization for all the markers with P-values ≤0.05 in both data sets. In this process, we found that in the CMYA5 gene, there were two non-synonymous markers, rs3828611 and rs10043986, showing nominal significance in both the CATIE and MGS-GAIN samples. In a combined analysis of both the CATIE and MGS-GAIN samples, rs4704591 was identified as the most significant marker in the gene. Linkage disequilibrium analyses indicated that these markers were in low LD (3 828 611-rs10043986, r(2)=0.008; rs10043986-rs4704591, r(2)=0.204). In addition, CMYA5 was reported to be physically interacting with the DTNBP1 gene, a promising candidate for schizophrenia, suggesting that CMYA5 may be involved in the same biological pathway and process. On the basis of this information, we performed replication studies for these three single-nucleotide polymorphisms. The rs3828611 was found to have conflicting results in our Irish samples and was dropped out without further investigation. The other two markers were verified in 23 other independent data sets. In a meta-analysis of all 23 replication samples (family samples, 912 families with 4160 subjects; case-control samples, 11 380 cases and 15 021 controls), we found that both markers are significantly associated with schizophrenia (rs10043986, odds ratio (OR)=1.11, 95% confidence interval (CI)=1.04-1.18, P=8.2 × 10(-4) and rs4704591, OR=1.07, 95% CI=1.03-1.11, P=3.0 × 10(-4)). The results were also significant for the 22 Caucasian replication samples (rs10043986, OR=1.11, 95% CI=1.03-1.17, P=0.0026 and rs4704591, OR=1.07, 95% CI=1.02-1.11, P=0.0015). Furthermore, haplotype conditioned analyses indicated that the association signals observed at these two markers are independent. On the basis of these results, we concluded that CMYA5 is associated with schizophrenia and further investigation of the gene is warranted.

Analysis of 10 independent samples provides evidence for association between schizophrenia and a SNP flanking fibroblast growth factor receptor 2.

We and others have previously reported linkage to schizophrenia on chromosome 10q25-q26 but, to date, a susceptibility gene in the region has not been identified. We examined data from 3606 single-nucleotide polymorphisms (SNPs) mapping to 10q25-q26 that had been typed in a genome-wide association study (GWAS) of schizophrenia (479 UK cases/2937 controls). SNPs with P<0.01 (n=40) were genotyped in an additional 163 UK cases and those markers that remained nominally significant at P<0.01 (n=22) were genotyped in replication samples from Ireland, Germany and Bulgaria consisting of a total of 1664 cases with schizophrenia and 3541 controls. Only one SNP, rs17101921, was nominally significant after meta-analyses across the replication samples and this was genotyped in an additional six samples from the United States/Australia, Germany, China, Japan, Israel and Sweden (n=5142 cases/6561 controls). Across all replication samples, the allele at rs17101921 that was associated in the GWAS showed evidence for association independent of the original data (OR 1.17 (95% CI 1.06-1.29), P=0.0009). The SNP maps 85 kb from the nearest gene encoding fibroblast growth factor receptor 2 (FGFR2) making this a potential susceptibility gene for schizophrenia.

Genomewide linkage scan of schizophrenia in a large multicenter pedigree sample using single nucleotide polymorphisms.

A genomewide linkage scan was carried out in eight clinical samples of informative schizophrenia families. After all quality control checks, the analysis of 707 European-ancestry families included 1615 affected and 1602 unaffected genotyped individuals, and the analysis of all 807 families included 1900 affected and 1839 unaffected individuals. Multipoint linkage analysis with correction for marker-marker linkage disequilibrium was carried out with 5861 single nucleotide polymorphisms (SNPs; Illumina version 4.0 linkage map). Suggestive evidence for linkage (European families) was observed on chromosomes 8p21, 8q24.1, 9q34 and 12q24.1 in nonparametric and/or parametric analyses. In a logistic regression allele-sharing analysis of linkage allowing for intersite heterogeneity, genomewide significant evidence for linkage was observed on chromosome 10p12. Significant heterogeneity was also observed on chromosome 22q11.1. Evidence for linkage across family sets and analyses was most consistent on chromosome 8p21, with a one-LOD support interval that does not include the candidate gene NRG1, suggesting that one or more other susceptibility loci might exist in the region. In this era of genomewide association and deep resequencing studies, consensus linkage regions deserve continued attention, given that linkage signals can be produced by many types of genomic variation, including any combination of multiple common or rare SNPs or copy number variants in a region.

Meta-analysis of 32 genome-wide linkage studies of schizophrenia.

A genome scan meta-analysis (GSMA) was carried out on 32 independent genome-wide linkage scan analyses that included 3255 pedigrees with 7413 genotyped cases affected with schizophrenia (SCZ) or related disorders. The primary GSMA divided the autosomes into 120 bins, rank-ordered the bins within each study according to the most positive linkage result in each bin, summed these ranks (weighted for study size) for each bin across studies and determined the empirical probability of a given summed rank (P(SR)) by simulation. Suggestive evidence for linkage was observed in two single bins, on chromosomes 5q (142-168 Mb) and 2q (103-134 Mb). Genome-wide evidence for linkage was detected on chromosome 2q (119-152 Mb) when bin boundaries were shifted to the middle of the previous bins. The primary analysis met empirical criteria for 'aggregate' genome-wide significance, indicating that some or all of 10 bins are likely to contain loci linked to SCZ, including regions of chromosomes 1, 2q, 3q, 4q, 5q, 8p and 10q. In a secondary analysis of 22 studies of European-ancestry samples, suggestive evidence for linkage was observed on chromosome 8p (16-33 Mb). Although the newer genome-wide association methodology has greater power to detect weak associations to single common DNA sequence variants, linkage analysis can detect diverse genetic effects that segregate in families, including multiple rare variants within one locus or several weakly associated loci in the same region. Therefore, the regions supported by this meta-analysis deserve close attention in future studies.

Genetic mapping of common diseases: the challenges of manic-depressive illness and schizophrenia.

Advances in genetic mapping of human diseases have led to the identification of single locus susceptibility for several common disorders. There have been a number of reports of linkage for the psychiatric disorders manic-depressive illness and schizophrenia, but none of these linkage reports is uncontested. Nonetheless, it appears promising to continue attempts to map these psychiatric disorders, since linkage can now be detected even when the inheritance is complex and includes genetic heterogeneity and variable penetrance.

Transcriptome sequencing study implicates immune-related genes differentially expressed in schizophrenia: new data and a meta-analysis.

We undertook an RNA sequencing (RNAseq)-based transcriptomic profiling study on lymphoblastoid cell lines of a European ancestry sample of 529 schizophrenia cases and 660 controls, and found 1058 genes to be differentially expressed by affection status. These differentially expressed genes were enriched for involvement in immunity, especially the 697 genes with higher expression in cases. Comparing the current RNAseq transcriptomic profiling to our previous findings in an array-based study of 268 schizophrenia cases and 446 controls showed a highly significant positive correlation over all genes. Fifteen (18%) of the 84 genes with significant (false discovery rate<0.05) expression differences between cases and controls in the previous study and analyzed here again were differentially expressed by affection status here at a genome-wide significance level (Bonferroni P<0.05 adjusted for 8141 analyzed genes in total, or P<~6.1 × 10-6), all with the same direction of effect, thus providing corroborative evidence despite each sample of fully independent subjects being studied by different technological approaches. Meta-analysis of the RNAseq and array data sets (797 cases and 1106 controls) showed 169 additional genes (besides those found in the primary RNAseq-based analysis) to be differentially expressed, and provided further evidence of immune gene enrichment. In addition to strengthening our previous array-based gene expression differences in schizophrenia cases versus controls and providing transcriptomic support for some genes implicated by other approaches for schizophrenia, our study detected new genes differentially expressed in schizophrenia. We highlight RNAseq-based differential expression of various genes involved in neurodevelopment and/or neuronal function, and discuss caveats of the approach.

Allelic loss from chromosome 11 in parathyroid tumors.

Parathyroid tumors may occur in a sporadic fashion or, more rarely, as part of a familial syndrome (such as familial multiple endocrine neoplasia type I). The MENI gene has been mapped by linkage analysis to chromosome 11 at band q11-q13, and presumably acts as a tumor suppressor gene. In the present study, which is an extension of our previous studies, we examined 41 parathyroid tumors from patients with familial multiple endocrine neoplasia type I and 61 sporadic parathyroid tumors with markers on chromosome 11, to assess the extent of allelic loss in those tumors. Twenty-four of the MENI-associated tumors (58%) and 16 of the sporadic parathyroid tumors (26%) displayed allelic loss from chromosome 11. The region of overlap of the allelic losses in the MENI-associated tumors enables us to place the MENI gene between PGA centromerically and INT2 telomerically, a region spanning about 7.5 cM. Taken together with locus ordering by linkage analysis, this clearly localizes the MENI gene telomeric to the PGA locus. Our inability to detect allelic loss on chromosome 11 in some parathyroid tumors suggests the existence of other genes involved in the development and/or progression of this subgroup of presumably monoclonal tumors; or that localized events involving the 11q tumor suppressor gene have occurred in some parathyroid tumors whose detection is beyond the sensitivity of our analysis; or that at least some of the specimens analyzed were in fact primarily hyperplastic parathyroid tissue.

Detection of mutations in insulin receptor gene by denaturing gradient gel electrophoresis.

Denaturing gradient gel electrophoresis (DGGE) has been used to screen for mutations in the insulin receptor gene. Each of the 22 exons was amplified by the polymerase chain reaction (PCR). For each exon, one of the two PCR primers contained a guanine-cytosine (GC) clamp at its 5' end. The DNA was analyzed by electrophoresis through a polyacrylamide gel containing a gradient of denaturants. Two geometries for the gels were compared; the gradient of denaturants was oriented either parallel or perpendicular to the electric field. The sensitivity of the technique was evaluated by determining whether DGGE succeeded in detecting known mutations and polymorphisms in the insulin receptor gene. With parallel gels, 12 of 16 sequence variants were detected. The use of perpendicular gels increased the sensitivity of detection so that all 16 sequence variants were successfully detected when DNA was analyzed by a combination of perpendicular and parallel gels. Furthermore, DGGE was used to investigate a patient with leprechaunism whose insulin receptor genes had not previously been studied. Two mutant alleles were identified in this patient. The allele inherited from the father had a mutation substituting alanine for Val-28; in the allele inherited from the mother, arginine was substituted for Gly-366.

X-chromosome markers and manic-depressive illness. Rejection of linkage to Xq28 in nine bipolar pedigrees.

Numerous reports have been published concerning linkage of X-chromosome markers of the q28 region (including protan and deutan color blindness [CB] and glucose-6-phosphate dehydrogenase deficiency) to manic-depressive illness. We studied nine bipolar pedigrees (in which there was no male-to-male transmission) in an attempt to detect linkage, using three tightly linked polymorphic DNA loci, DXS15, DXS52 and F8C (factor 8 gene), all of which are closely linked to the CB and glucose 6-phosphate dehydrogenase classic Xq28 markers. Linkage to this region of Xq28 could be excluded unequivocally in these nine families. When these data were combined with our earlier series of bipolar pedigrees, informative for either protan or deutan CB, a total of 14 bipolar pedigrees have been studied, with no evidence of linkage or heterogeneity. At a recombination fraction (theta) of 1%, this series had greater than 95% power to detect linkage if only 50% of the pedigrees studied were linked to the CB region. Our failure to confirm the previously reported linkage of manic-depressive illness to the CB region of the X chromosome indicates that this linkage is not as common as previously suggested.

Allelic variation in the D4 dopamine receptor (DRD4) gene does not predict response to clozapine.

OBJECTIVE: To test the hypothesis that interindividual differences in response to clozapine therapy might be attributable to the D4 dopamine receptor (DRD4) alleles they carry. Different alleles of the D4 dopamine receptor, coded by the DRD4 gene, differ in the affinity with which they bind the atypical antipsychotic drug clozapine in vitro. This may have physiologic implications. Clinical response to clozapine therapy varies among patients. The observation that, in vitro, clozapine binds the protein products of different DRD4 alleles with differing affinity characteristics suggested this hypothesis. METHOD: The region of the DRD4 gene that encodes the putative third cytoplasmic loop of the D4 receptor contains a 48-base pair sequence repeated a variable number of times. With use of polymerase chain reaction amplification, we assessed this variable number of tandem repeats polymorphism in a series of schizophrenic and schizoaffective subjects who had been treated with clozapine, and related genotype with treatment response, to test the hypothesis that DRD4 alleles lead to varying response to clozapine. RESULTS: Allelic variation at the DRD4 locus does not predict clinical response to clozapine relative to either fluphenazine hydrochloride or placebo in subjects with treatment-refractory schizophrenia or schizoaffective disorder. CONCLUSIONS: DRD4 alleles do not predict therapeutic response to clozapine in schizophrenic and schizoaffective patients. There are implications from these data for the pathophysiology of schizophrenia and the mechanism of clozapine's therapeutic effect are discussed.

No abnormality in the gene for the G protein stimulatory alpha subunit in patients with bipolar disorder.

BACKGROUND: The available evidence for an involvement of the heterotrimeric guanine-nucleotide-binding proteins (G proteins) in bipolar disorder relies primarily on the effects of lithium salts on G protein function and on alterations in the concentration or function of G proteins (most notably Gs-alpha) in peripheral leukocytes and in postmortem tissues of patients with bipolar disorder. METHODS: The hypothesis that a mutation in Gs-alpha gene confers an increased susceptibility to bipolar disorder was tested by the following strategies: (1) mutational screening of the Gs-alpha subunit gene coding sequences and promoter sequences by denaturing gradient gel electrophoresis in unrelated individuals with bipolar disorder and (2) association and linkage analyses with a common silent exonic polymorphism, using genetic allelic information from American families with at least 1 affected child. For association analysis, the transmission test for linkage disequilibrium was used; for linkage analysis, nonparametric methods were used. RESULTS: No structural or regulatory mutations in this gene were found in bipolar disorder; the results of association and genetic linkage were negative. CONCLUSION: Our results do not support the speculation that the Gs-alpha protein gene has a role in the genetic predisposition to bipolar disorder.

A novel mutation adjacent to the switch III domain of G(S alpha) in a patient with pseudohypoparathyroidism.

A novel G(S alpha) mutation encoding the substitution of arginine for serine 250 (G[S alpha] S250R) was identified in a patient with pseudohypoparathyroidism type Ia. Both G(S) activity and G(S alpha) expression were decreased by about 50% in erythrocyte membranes from the affected patient. The cDNA of this G(S alpha) mutant, as well as one in which the S250 residue is deleted (G[S alpha]-deltaS250), was generated, and the biochemical properties of the products of in vitro transcription/translation were examined. Both mutants had a sedimentation coefficient similar to that of wild type G(S alpha) (approximately 3.7S) when kept at 0 C after synthesis. However when maintained for 1-2 h at 30-37 C, both mutants aggregated to a material sedimenting at approximately 6.3S or greater (G[S alpha]-S250R to a greater extent than G(S alpha]-deltaS250), while wild type G(S alpha) sedimented at approximately 3.7S, suggesting that the mutants were thermolabile. Incubation in the presence of high doses of guanine nucleotide partially prevented heat denaturation of G(S alpha) deltaS250 but had no protective effect on G(S alpha-S250R. Sucrose density gradient centrifugation at 0 C in the presence and absence of beta gamma-dimers demonstrated that, in contrast to wild type G(S alpha) neither mutant could interact with beta gamma. Trypsin protection assays revealed no protection of G(S alpha)-S250R by GTPgammaS or AIF4- at any temperature. GTPgammaS conferred modest protection of G(S alpha)-deltaS250 (approximately 50% of wild-type G[S alpha]) at 30 C but none at 37 C, while AIF4- conferred slight protection at 20 C but none at 30 C or above. Consistent with this result, G(S alpha)-deltaS250 was able to stimulate adenylyl cyclase at 30 C when reconstituted with cyc- membranes in the presence of GTPgammaS but not in the presence of AIF4-. G(S alpha)-S250R showed no ability to stimulate adenylyl cyclase in the presence of either agent. Stable transfection of mutant and wild-type G(S alpha) into cyc- S49 lymphoma cells revealed that the majority of wild type G(S alpha) localized to membranes, while little or no membrane localization occurred for either mutant. Modeling of G(S alpha) based upon the crystal structure of G(t alpha) or G(i alpha) suggests that Ser250 interacts with several residues within and around the conserved NKXD motif, which directly interacts with the guanine ring of bound GDP or GTP. It is therefore possible that substitution or deletion of this residue may alter guanine nucleotide binding, which could lead to thermolability and impaired function.

The thyrotropin receptor (TSH-R) is not an oncogene for thyroid tumors: structural studies of the TSH-R and the alpha-subunit of Gs in human thyroid neoplasms.

The development and progression of thyroid tumors are associated with phenotype-specific mutations of genes involved in growth control. Thyroid cell growth is controlled in part by the interaction of TSH with its receptor, with subsequent activation of the GTP-binding protein and its effector, adenylyl cyclase. The resulting increase in intracellular cAMP stimulates growth in thyrocytes. The TSH receptor (TSH-R) is a seven-transmembrane domain receptor. Intracellular domains of the TSH-R important for signal transduction and which may serve as targets for mutational activation have been defined. In addition, mutations at specific loci of the alpha-subunit of G-protein in human thyroid tumors have been described. We examined 92 benign and malignant neoplastic thyroid tissues for possible mutations of the intracytoplasmic domains of the TSH-R known to be involved in signal transduction and for mutations within the hot spots of Gs alpha. Screening was carried out by single strand conformation polymorphism (TSH-R) or denaturing gradient gel electrophoresis (Gs alpha) of polymerase chain reaction-amplified tumor DNA. No mutations were observed in the cytoplasmic domains of the TSH-R, except for a neutral base substitution in codon 460 (GCG [Ala]-->GCA [Ala]) in 3 tumors, which was also present in constitutional DNA from the affected individuals. A heterozygous mutation of codon 201 of Gs alpha (GGT [Arg]-CAT [His]) was observed in a nodule from an adenomatous goiter. In addition, a codon 227 mutation (CAG [Glu]-CAT [His]) was identified in a follicular adenoma. We conclude that mutational activation of the intracytoplasmatic domains of the TSH-R is not a significant mechanism of thyroid tumorigenesis, whereas putative activating mutations within exons 8 and 9 of Gs alpha occur infrequently in some benign follicular tumors.