The GRM7 gene, early response to risperidone, and schizophrenia: a genome-wide association study and a confirmatory pharmacogenetic analysis.

The search for biomarkers of response to antipsychotic medications is hindered by difficulties inherent in the topic or related to persistent methodological difficulties, such as high rates of anticipated discontinuation and consequent distortions in the imputation of missing data. Because early response to antipsychotics represents a sufficiently reliable index of the subsequent treatment response in patients with schizophrenia, we undertook a real-world, genome-wide association study (GWAS) with the aim of identifying genetic predictors of response to risperidone after 2 weeks in 86 patients with schizophrenia. Limited to the associations reaching significance in the GWAS, confirmatory analysis relative to risperidone response over 9 months was also designed involving 97 patients (European only) enroled in the CATIE (Clinical Antipsychotic Trials of Intervention Effectiveness) genetic substudy. The GWAS revealed a significant association (false discovery rate 0.02) of the single-nucleotide polymorphism rs2133450 inside the GRM7 gene with Emsley's positive domain derived from the positive and negative syndrome scale (PANSS). Patients with the rs2133450 CC genotype presented poorer improvement in the positive domain over 2 weeks, with odds ratios of 12.68 (95% CI, 3.51-45.76) and 6.95 (95% confidence interval (CI), 2.37-20.37) compared with patients with the AA and AC genotypes, respectively. Compared with A homozygotes, rs2133450 C homozygotes enroled in the CATIE-derived confirmatory analysis showed less improvement in Emsley's positive, excited and depression domains, positive and general PANSS subtypes, and total PANSS after 9 months of treatment with risperidone. The original GWAS and the CATIE-derived confirmatory analysis support the proposal that the rs2133450 may have translational relevance as a predictor of response to risperidone.

Proteasome system dysregulation and treatment resistance mechanisms in major depressive disorder.

Several studies have demonstrated that allelic variants related to inflammation and the immune system may increase the risk for major depressive disorder (MDD) and reduce patient responsiveness to antidepressant treatment. Proteasomes are fundamental complexes that contribute to the regulation of T-cell function. Only one study has shown a putative role of proteasomal PSMA7, PSMD9 and PSMD13 genes in the susceptibility to an antidepressant response, and sparse data are available regarding the potential alterations in proteasome expression in psychiatric disorders such as MDD. The aim of this study was to clarify the role of these genes in the mechanisms underlying the response/resistance to MDD treatment. We performed a case-control association study on 621 MDD patients, of whom 390 were classified as treatment-resistant depression (TRD), and we collected peripheral blood cells and fibroblasts for mRNA expression analyses. The analyses showed that subjects carrying the homozygous GG genotype of PSMD13 rs3817629 had a twofold greater risk of developing TRD and exhibited a lower PSMD13 mRNA level in fibroblasts than subjects carrying the A allele. In addition, we found a positive association between PSMD9 rs1043307 and the presence of anxiety disorders in comorbidity with MDD, although this result was not significant following correction for multiple comparisons. In conclusion, by confirming the involvement of PSMD13 in the MDD treatment response, our data corroborate the hypothesis that the dysregulation of the complex responsible for the degradation of intracellular proteins and potentially controlling autoimmunity- and immune tolerance-related processes may be involved in several phenotypes, including the TRD.

Association between baseline serum vascular endothelial growth factor levels and response to electroconvulsive therapy.

OBJECTIVE: Several studies have shown that vascular endothelial growth factor (VEGF) is implicated in different neuronal processes involved in major depressive disorder (MDD) and in the mechanisms of action of antidepressants. The aim of this study was to investigate whether VEGF serum levels before treatment might be associated with the antidepressant response. METHOD: Two groups of patients were enrolled. One was composed of 50 MDD patients receiving an antidepressant drug treatment. Illness severity was measured before the treatment (T0) and after 12 weeks (T1). The second group was composed of 67 treatment-resistant depressed (TRD) patients undergoing electroconvulsive therapy (ECT). Illness severity was assessed before the treatment (T0) and 1 month after the end of ECT (T1). Blood samples for VEGF measurements were collected for both groups at the baseline (T0). RESULTS: A significant correlation was observed between baseline VEGF serum levels and the percentage reduction in depressive symptomatology after ECT (P = 0.003). In particular, VEGF levels at baseline were significantly lower in patients showing no response to ECT at follow-up (P = 0.008). No correlation between T0 VEGF concentrations and drug treatment outcome was found. CONCLUSION: Our results suggest that VEGF plays a role in the mechanism of response to ECT.

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.

Genetic background predicts poor prognosis in frontotemporal lobar degeneration.

BACKGROUND: Ruling out predictors of survival in frontotemporal lobar degeneration (FTLD) is a clinical challenge for defining disease outcomes and monitoring therapeutic interventions. Little is known about determinants of survival in FTLD. OBJECTIVE: The aim of the present study was to identify whether genetic determinants are key, not only as risk factors but as predictors of survival in FTLD. METHODS: Ninety-seven FTLD patients were considered in the present study. A clinical evaluation and a standardized assessment were carried out. Each patient underwent blood sampling for genetic testing, and mutations within the progranulin (PGRN) gene, microtubule-associated protein tau (MAPT) haplotype, apolipoprotein E (APOE) genotype and 4 vascular endothelial growth factor (VEGF) polymorphisms were evaluated. Discrete-time survival models were applied. RESULTS: Monogenic FTLD due to PGRN mutations [odds ratio (OR) = 3.62, 95% confidence interval (CI) = 1.12-11.7; p = 0.032], and MAPT *H2 haplotype (OR = 3.23, 95% CI = 1.08-9.69; p = 0.036) were associated with an increased hazard risk of poor outcome. Conversely, APOE genotype, and VEGF polymorphisms were not associated with survival risk in the FTLD sample. CONCLUSIONS: Genetic background is not only crucial in disease pathogenesis, but it also modulates disease course. Genetic factors influencing prognosis should be taken into account to include homogeneous groups in future clinical trials and to monitor efficacy of future interventions.

The new Alzheimer's criteria in a naturalistic series of patients with mild cognitive impairment.

To test the validity of the new diagnostic criteria for Alzheimer's disease (AD) in a naturalistic series of patients with mild cognitive impairment (MCI). Ninety consecutive MCI patients were enrolled in a longitudinal study on the natural history of cognitive impairment. Medial temporal (MT) atrophy on MRI was defined as hippocampal volume below the fifth percentile of the distribution in healthy elders, abnormal CSF was based on Sjogren's cutoffs for Abeta42 and tau, and temporoparietal hypometabolism on 18F-FDG PET based on Herholz's t sum score. Patients were followed clinically to detect conversion to AD (MCI-AD), non-AD dementia (MCI-nAD), or no conversion (MCI-NC). The 24 MCI-AD and 15 MCI-nAD patients had sociodemographic, clinical, and neuropsychological baseline features similar to the 51 MCI-NC patients. All MCI patients with MT atrophy converted to AD, as did all those with abnormal CSF, but only 48 and 35% of those without MT atrophy or abnormal CSF converted (p on logrank test = 0.0007 and 0.001). Prediction of AD conversion was enhanced when positivity to either MT atrophy or abnormal CSF was considered, with only 15% of those MCI patients negative on both converting to AD (p < 0.0005). Markers were not predictive of non-AD dementia conversion. The accuracy of either MT atrophy or abnormal CSF in discriminating MCI-AD from MCI-NC was good (AUC 0.82, 95% CI 0.70-0.95). MT atrophy and abnormal CSF are the single most robust predictors of conversion to AD in MCI patients, and their combination enhances prediction. AD markers are not predictive of conversion to non-AD dementia.

TARDBP mutations in frontotemporal lobar degeneration: frequency, clinical features, and disease course.

The 43-kD transactive response (TAR)-DNA-binding protein (TARDBP) mutations have been demonstrated to be causative of sporadic and familial forms of amyotrophic lateral sclerosis. More recently, these mutations have been reported in cases of frontotemporal lobar degeneration (FTLD). The aim of this study was to evaluate the role of TARDBP genetic variations in a large sample of consecutive patients with FTLD. A total of 252 FTLD patients were investigated. Each subject had a clinical and neuropsychological evaluation and a brain imaging study. The clinical diagnosis was confirmed by at least 1 year of follow up. The entire TARDBP gene, the intronic flaking regions, and the 5'-untranslated region (5'-UTR) were screened. Six genetic variations were identified in patients with behavioral variant frontotemporal dementia (FTD) and FTD with motor neuron disease phenotypes. Two of these mutations, namely N267S and M359V, lead to amino acid changes within exon 6. We further identified three genetic variations, i.e., Y214Y, IVS-IV + 45C/T, and 5'-UTR G/A, that could potentially affect the normal splicing process as predicted by in silico analyses. None of these genetic variations was found in healthy age-matched controls. Moreover, we identified a previously described benign variant, A66A, in 5 patients. Our study has confirmed and extended the list of pathogenetic mutations in the TARDBP gene in both apparently sporadic and familial FTLD patients. This work further supports the need for TARDBP screening in FTLD. Also intronic splicing that affects mutations should be considered as well.

Mutation within TARDBP leads to frontotemporal dementia without motor neuron disease.

It has been recently demonstrated that the 43-kDa transactive response (TAR)-DNA-binding protein (TARDBP) is the neuropathological hallmark of Frontotemporal Dementia (FTD) with ubiquitin-positive and tau-negative inclusions. Large series of FTD patients without motor neuron disease have been previously analysed, but no TARDBP mutation was identified. The aim of the present study was to evaluate whether TARDBP gene mutations may be associated with FTD. We report that a pathogenetic TARDBP mutation is causative of behavioural variant FTD (bvFTD). An aged woman in her seventies initially started to present apathy and depression associated with impairment in executive functions. The diagnosis of bvFTD (apathetic syndrome) was accomplished by three-year follow-up, and structural and functional neuroimaging. By five-years after onset, extensive electrophysiological investigations excluded subclinical motor neuron disease. In this patient, a single base substitution c.800A>G of TARDBP gene was identified. This mutation, already described as causative of ALS, predicted the amino acidic change arginine to serine at position 267 (N267S). In silico analysis demonstrated that this substitution generates a new phosphorylation site, and western blot analysis on lymphoblastoid cells reported a decrease of protein expression in N267S mutation carrier. Our study suggests that TARDBP mutations can be pathogenetic of bvFTD without motor neuron disease. TARDBP screening needs to be considered in FTD cases.

Serum leptin levels are higher in females affected by frontotemporal lobar degeneration than Alzheimer's disease.

Frontotemporal lobar degeneration (FTLD) includes different heterogeneous conditions, mainly characterised by personality changes, along with cognitive deficits in language and executive functions. Movement disorders are variably represented. Behavioural disturbances constitute the core feature of FTLD, and eating disorders represent one of the most distinguishing symptoms between FTLD and Alzheimer's disease (AD). The biochemical correlates of such dysfunctions remain to be defined. The adipocyte derived hormone leptin is known to play a foundamental role in food intake and energy balance. To understand whether leptin could be involved in FTLD eating abnormalities, we measured serum leptin levels in 59 patients with FTLD compared with 25 with AD. Serum leptin levels in patients with FTLD were comparable with those in patients with AD. Nevertheless, females with FTLD showed significantly higher leptin levels compared with females with AD. No difference was found between FTDL and AD males or within the spectrum of patients with FTLD. Hyperphagic FTLD females showed higher circulating leptin levels in comparison with those without eating abnormalities; no differences were found between males with FTLD with respect to serum leptin and food intake disturbances. The present study showed a selective gender difference in leptin levels between females with FTLD and AD, which may suggest specific cognitive and behavioural networks need to be investigated.

Dementia, delusions and seizures: storage disease or genetic AD?

We describe a case of a young patient suffering from a rapidly progressive cognitive decline, associated with delusions, myoclonus and seizures and with no family history for dementia. Clinical features, along with skin biopsy findings were overlapping storage disease; the genetic analysis, however, demonstrated a de novo presenilin 1 mutation. The present report suggests the usefulness of genetic determinations in early-onset cases of dementia, even without an autosomal dominant trait of inheritance; for these cases and their relatives an extensive genetic counselling should be recommended.

No evidence for allelic association of serotonin 2A receptor and transporter gene polymorphisms with depression in Alzheimer disease.

Patients with Alzheimer disease (AD) often exhibit psychiatric symptoms associated with cognitive impairment. The serotoninergic system may be involved in the development of depressive symptoms in AD patients, as suggested by the evidence that antidepressant drugs having the serotonin transporter as their target are effectively used to treat depressive AD patients. The aim of this study was to investigate the role of serotonin in depression, searching for association of two serotoninergic polymorphisms (T102C of serotonin receptor 5-HT2A and serotonin transporter linked polymorphic region -5-HTTLPR- of SLC6A4 gene) with depressive symptoms and considering their possible interactions with Apolipoprotein E (ApoE) and between themselves, in a sample of 208 sporadic AD patients and 116 normal controls from Italy. 5-HTTLPR and T102C are not associated with AD when separately analysed. However, we found out an interaction between the two polymorphisms in L/L and C/C genotype carriers increasing the risk for the disease (p=0.015, OR=8.048; 95% CI: 1.497-43.262). No association of the polymorphisms was detected with depression linked to AD. No interaction between 5-HTTLPR and T102C was detected in depressive AD subjects, even after stratification according to the presence of ApoE4 allele. These results suggest that the serotoninergic system may be not involved in the pathogenesis of depressive symptoms in AD patients, and it may be involved in other aspects of disease pathophysiology like cognitive symptoms and psychosis.

Italian guidelines for molecular analysis in myotonic dystrophies.

Myotonic dystrophies, the most common form of adult muscular dystrophy, comprise at least two forms, clinically and genetically heterogeneous. Myotonic dystrophy type 1 and type 2 are both caused by unstable repetitions in untranslated gene regions: a [CTG]n expansion in the 3' region of the DMPK gene on chromosome 19q13 (DM1) and [CCTG]n tetranucleotide repeat located in the first intron of the ZNF9 gene on chromosome 3q21 (DM2). DM clinical features are caused by a gain of functions RNA mechanism in which the CUG and CCUG repeats alter nuclear functions, including alternative splicing of shared genes. Southern blot and/or polymerase chain reaction PCR-based approaches allow the detection of DM mutations in almost 100% of cases, however, the expansion size and the elevated grade of somatic instability make molecular testing for DM a diagnostic challenge. The increased use of DNA testing for DM generates many questions regarding the indications and interpretations of the test which require standardized methods, routinely available in molecular genetic laboratories. Here, we propose Guidelines for the molecular diagnosis of DM1 and DM2 approved by the Italian Ministry of Health in 2005 (Piano Nazionale Linee Guida, PNLG). Best practice for DM molecular analysis in diagnostic application, presymptomatic and prenatal testing, using direct and indirect approaches are described, with particular attention focused on ethical, legal and social issues. Overviews of materials used in the molecular diagnosis, as well as internet resources, are also included.

Cytokine gene polymorphisms in gastric cancer patients from two Italian areas at high and low cancer prevalence.

Polymorphisms of interleukin-1beta (IL-1beta), IL-1 receptor antagonist (IL1-RN), and tumor necrosis factor-alpha (TNF-alpha) genes are supposed to be key determinants of gastric cancer risk. Our aim was to study the association between these polymorphisms and gastric cancer in two areas characterized by high (Pavia/Bologna, North Italy) and low (San Giovanni Rotondo, South Italy) gastric cancer prevalence. Genomic DNA was obtained from 216 healthy donors and 98 gastric cancer patients from Pavia and Bologna, and 146 healthy donors and 86 gastric cancer patients from San Giovanni Rotondo. Two SNP in IL-1beta (-511 C/T) and TNF-alpha (-308 G/A) as well as the VNTR polymorphism of IL-1RN locus were studied. A significant linkage disequilibrium was found between IL-1beta -511 and IL-1RN. Genotype and allele frequencies at the IL-1beta, IL-1RN, and TNF-alpha loci in gastric cancer cases were not significantly different from controls. An epistatic effect between IL-1beta -511 and IL-1RN was found with the IL-1beta -511C/IL-1RN*2 haplotype conferring a significant protection against the intestinal-type of gastric cancer in the Southern population. In conclusion, IL-1beta, IL1-RN, and TNF-alpha genotypes are not associated with gastric cancer in Italian patients. An epistatic interrelationship between IL-1beta -511 and IL-1RN confers protection against gastric cancer in low-risk Italian population.

Repetitive transcranial magnetic stimulation (rTMS) at high and low frequency: an efficacious therapy for major drug-resistant depression?

OBJECTIVE: Repetitive transcranial magnetic stimulation (rTMS) is proposed for the treatment of drug-resistant depression. Studies performed in accordance with evidence-based medicine (EBM) are scarce, particularly in seeking optimal treatment and evaluation parameters. We aimed to test various types of rTMS in a large sample of depressed patients following EBM rules and to investigate treatment-related changes in plasma levels of neurotransmitters involved in depression. METHODS: Seventy-one drug-resistant depressed patients were randomly assigned to low (1 Hz) or high (17 Hz) rate TMS, applied for 5 days over the left dorsolateral prefrontal cortex (L-DLPFC). Patients were separated into two study designs. One group (20 patients) received only active treatment, while the other entered a double-blind, placebo-controlled, crossover design. Pre- and post-treatment blood samples were taken for evaluation of plasma levels of dopamine and serotonin. RESULTS: After a week of treatment patients had a measurable benefit. However, overall the placebo stimulation did not differ significantly from real stimulation, nor were differences observed between the two rates of rTMS. The only difference emerged when the real stimulation was applied at 17 Hz following placebo treatment. Plasma levels of neurotransmitters between active and placebo rTMS were similar. CONCLUSIONS: Using the treatment schedule of 1 week, although a clinical improvement after active treatment was indeed observed, this was both clinically and biochemically indistinguishable from that seen in the placebo arm. SIGNIFICANCE: This suggests that most of the previous emphasis, for short period of treatment, should be tempered down and that further work is required in order to verify whether optimal stimulation and evaluation parameters for TMS-treatment of depression beyond the placebo effect may be found following EBM rules.

Allelic variation in the human prodynorphin gene promoter and schizophrenia.

Experimental and clinical studies suggest an involvement of the opioid neuropeptide system in schizophrenia. In particular, the prodynorphin (PDYN), the precursor of the dynorphin opioid peptides, has been shown to play an important role in several aspects of human mental diseases. Recently, a functional polymorphism in the promoter of PDYN gene has been described. We studied the possible relationship between this polymorphism and schizophrenia and we found no significant difference in allelic and genotype distributions between schizophrenic patients and control subjects. However, we observed a significant interactive effect with the receptor 3 of dopamine gene (DRD3); in particular, the frequency of subjects carrying PDYN allele 3 being also homozygotes for DRD3 Gly allele (of Ser9Gly polymorphism) was significantly greater in patients than controls. We conclude that PDYN gene polymorphism alone does not alter the risk for schizophrenia but, by an epistatic interaction with the Gly allele of DRD3 gene, may contribute to the susceptibility to this disorder.

Association between the ionotropic glutamate receptor kainate 3 (GRIK3) ser310ala polymorphism and schizophrenia.

Schizophrenia is a severe psychiatric illness characterised by disturbance of thought, hallucination and delusions.(1) Several studies have suggested that dysfunctions in the glutamatergic transmission are linked to the pathogenesis of schizophrenia, and in particular an excessive activation of glutamate receptors seems to be related to the disruption of neuronal ionic gradients leading to excitotoxicity.(2-7) Numerous findings suggested that the kainate ionotropic glutamate receptors are primarily involved in this mechanism. Recently it has been demonstrated that the GRIK3 gene encoding for the ionotropic glutamate receptor kainate 3 contains a functional polymorphism (T928G) leading to the substitution of a serine with an alanine in position 310 of the protein sequence.(8-11) We performed an association study between the ser310ala GRIK3polymorphism and schizophrenia in a sample of 99 schizophrenic patients and 116 controls. We found a significant difference in the genotype distribution and in particular considering the ala allele as dominant (P = 0.0105, odds ratio (OR) 2.031, 95% confidence interval (CI) 1.177-3.504). This finding suggests a potential role for GRIK3 for susceptibility to schizophrenia.

Modulation of fibroblast growth factor-2 by stress and corticosteroids: from developmental events to adult brain plasticity.

Neurotrophic factors are a heterogeneous group of peptides that play important roles on brain function at different development stages. Basic fibroblast growth factor (FGF-2), one of these molecules, is highly expressed in developing and adult brain. Its expression can be regulated under different experimental situations and this may be relevant for cellular vulnerability and brain plasticity. Stress and glucocorticoid hormones produce short- and long-term effects on brain function, which can involve the regulation of specific neurotrophic factors within selected brain structures. Treatments with corticosterone or dexamethasone up-regulate FGF-2 expression in different rat brain regions as well as in cultured astroglial cells. A similar elevation of FGF-2 biosynthesis is also observed in several brain regions following an acute restraint stress. This response is rapid and transient and, as FGF-2 is neuroprotective, may represent a defense mechanism through which the brain may limit the deleterious effect of stress over time. Moreover exposure to corticosterone during late stage of embryonic life (E18-E20) produces a significant reduction of FGF-2 mRNA levels in the adult hippocampus of male rats as well as changes in its acute modulation in response to stress or corticosterone. These data suggest that stress-related events taking place during brain maturation can modulate the expression of FGF-2 within selected brain regions thus contributing to permanent structural and functional alterations leading to an increased vulnerability to challenging life events.

Long-term treatment with S-adenosylmethionine induces changes in presynaptic CaM kinase II and synapsin I.

BACKGROUND: According to current hypotheses, antidepressant drug action is the result of adaptive changes in neuronal signaling mechanisms rather than a primary effect on neurotransmitter transporters, receptors, or metabolic enzymes. Among the signaling mechanisms involved, protein kinases and phosphorylation have been shown to be modified by drug treatment. Presynaptic signaling (calcium/calmodulin-dependent protein kinase II [CaMKII]) and the protein machinery regulating transmitter release have been implicated in the action of these drugs. METHODS: We investigated the effect of S-adenosylmethionine (SAM), a compound with putative antidepressant activity, on presynaptic CaMKII and its synaptic vesicle substrate synapsin I. The activity of CaMKII was assayed in synaptic subcellular fractions prepared from hippocampus (HI), frontal cortex (FCX), striatum (STR), and parieto-temporal cortex. RESULTS: The kinase activity was increased after SAM treatment in the synaptic vesicle fraction of HI (31.7%), FCX (35.9%), and STR (18.4%). The protein level of CaMKII was also increased in synaptic vesicles of HI (40.4%). The synapsin I level was unchanged in synaptic vesicles but markedly increased in synaptic cytosol of HI (75.8%) and FCX (163.0%). No changes for both CaMKII and synapsin I level were found in homogenates, suggesting that synaptic protein changes are not explained by an increase in total level of proteins, but rather by translocation to nerve terminals. CONCLUSIONS: Similar to typical antidepressant drugs, SAM induces changes in CaMKII activity and increases synapsin I level in HI and FCX nerve terminals, suggesting a modulatory action on transmitter release.

Human Y-chromosome variation in the western Mediterranean area: implications for the peopling of the region.

Y-chromosome variation was analyzed in a sample of 1127 males from the Western Mediterranean area by surveying 16 biallelic and 4 multiallelic sites. Some populations from Northeastern Europe and the Middle East were also studied for comparison. All Y-chromosome haplotypes were included in a parsimonious genealogic tree consisting of 17 haplogroups, several of which displayed distinct geographic specificities. One of the haplogroups, HG9.2, has some features that are compatible with a spread into Europe from the Near East during the Neolithic period. However, the current distribution of this haplogroup would suggest that the Neolithic gene pool had a major impact in the eastern and central part of the Mediterranean basin, but very limited consequences in Iberia and Northwestern Europe. Two other haplogroups, HG25.2 and HG2.2, were found to have much more restricted geographic distributions. The first most likely originated in the Berbers within the last few thousand years, and allows the detection of gene flow to Iberia and Southern Europe. The latter haplogroup is common only in Sardinia, which confirms the genetic peculiarity and isolation of the Sardinians. Overall, this study demonstrates that the dissection of Y-chromosome variation into haplogroups with a more restricted geographic distribution can reveal important differences even between populations that live at short distances, and provides new clues to their past interactions.