Zissis Mamuris

Mitochondrial DNA variation in Northeast Atlantic and Mediterranean populations of Norway lobster, Nephrops norvegicus

Analysis of the genetic structure of the Norway lobster (Nephrops norvegicus), a marine crustacean with high commercial value, was undertaken to gain information regarding the differentiation of Atlantic from Mediterranean populations of marine invertebrates. Restriction fragment length polymorphism analysis of two mitochondrial DNA segments, 3.6 kilobases in total, was performed. Twelve populations from the North Sea, Irish Sea, Portuguese coast and Aegean Sea were analysed. Low levels of differentiation were found among them (FST = 0.018, P < 0.001) and there were no signs of an Atlantic–Mediterranean divide or of an isolation‐by‐distance scheme of differentiation. Possible reasons for these low levels of differentiation can be found in the recent expansion of N. norvegicus populations. This is supported by the mismatch distribution of pairwise haplotype differences, as well as by the high mean haplotype diversity (h = 0.93) combined with medium nucleotide diversity (π = 0.0057) (in comparison to values for marine crustaceans or teleosts) found in this study. This combination of high levels of haplotype diversity with moderate to low levels of nucleotide diversity has also been frequently attributed to a recent time of divergence for various marine species. No evidence was found for a Mediterranean refugium during glaciation periods, separate from the Atlantic, as has been reported for some marine species. The Irish Sea population was the most differentiated as a result of reduced levels of diversity. Results are also discussed in the light of future management of N. norvegicus stocks.

Pharmacogenetic analysis of TNF, TNFRSF1A, and TNFRSF1B gene polymorphisms and prediction of response to anti-TNF therapy in psoriasis patients in the Greek population.

AbstractBackground: Although biologic therapies have revolutionized the treatment of psoriasis, patients exhibit a substantial heterogeneous response that could be due to complex genetic heterogeneity. Objective: The aim of this study was to investigate the possible influence of tumor necrosis factor-α (TNF), TNF receptor I (TNFRSF1A), and TNF receptor II (TNFRSF1B) gene polymorphisms on anti-TNF treatment responsiveness in psoriasis patients. Methods: A Greek multicenter collaboration was established to recruit a cohort of patients (n = 80) with psoriasis treated with anti-TNF drugs. Single nucleotide polymorphisms (SNPs) in TNF -238G>A, -308G>A, -857C>T), TNFRSF1A (36A>G), and TNFRSF1B (676T>G) were genotyped by PCR-restriction fragment length polymorphism assays. SNPs and haplotypes, including stratification by comorbidity status, were analyzed for association with treatment response after 6 months of therapy, defined as a reduction in the Psoriasis Area and Severity Index (PASI) score by >75% (responders) or ≤50% (nonresponders). Results: Sixty-three patients (78.8%) were defined as responders (PASI score reduction >75%) and 17 patients (21.2%) were defined as nonresponders (PASI score reduction ≤50%). Carriage of TNF -857C or TNFRSF1B 676T alleles was associated with positive response to drug treatment in patients treated with etanercept (p = 0.002 and p = 0.001, respectively). None of the genotyped SNPs were associated with responsiveness to treatment with infliximab or adalimumab. Additionally, when patients were stratified by comorbidity status, none of the genotyped SNPs were alone associated with responsiveness to drug treatment. Conclusion: This study is the first in the field of psoriasis demonstrating a strong association between genetic markers and positive response to drug treatment. Validation of this result in larger studies, as well as analysis of other drug treatments, could provide the basis for individually tailored treatment, along with increased cost effectiveness and reduced unnecessary exposure to toxicity.

Microsatellite analysis of olive fly populations in the Mediterranean indicates a westward expansion of the species.

Bactrocera oleae is the major insect pest of the olive fruit. Twelve microsatellite loci isolated from the genome of this insect were used in a Mediterranean-wide population analysis. These loci were highly polymorphic with a mean number of alleles per locus of 10.42 and a mean effective number of alleles of 2.76. The analysis was performed on a sample of 671 flies collected from nineteen locations around the European part of the Mediterranean basin. Despite the high level of gene flow across the Mediterranean, results support the notion of a differentiation of three subpopulations: one of the Iberian Peninsula, one of Greece and Italy and one of Cyprus. In addition, the gradual decrease of heterozygosity from the Eastern to the Western part of the Mediterranean indicates a westward expansion of the species.

Genetic structure of Greek brown hare (Lepus europaeus) populations as revealed by mtDBNA RFLP-PCR analysis : implications for conserving genetic diversity

The genetic differentiation and the phylogenetic status of brown hare (Lepus europaeus) populations from central Greece as well as the impact of the releases of reared individuals on the native populations genetic structure was assessed, using mtDNA RFLP-RCR analysis. Data analysis revealed extensive haplotype diversity (42 out of 56 haplotypes were unique) within and among wild populations. Haplotype diversity was equally distributed within and between geographical regions, while significant genetic structuring was evident from heterogeneity of haplotype frequencies among sampling sites. Specific mtDNA profiles clearly differentiated reared from wild individuals and proved highly indicative for reared hares from past releases caught within wild populations. MtDNA analysis suggests the introgression of allochthonous gene pools into the native populations. To conserve indigenous genotypes and to prevent loss of genetic diversity, restocking operations should be stopped and an appropriate management adjusted to the local population dynamics should be developed.

Mitochondrial tRNA Mutations: Clinical and Functional Perturbations

During the last decade, there has been a progressive accumulation of reports that connect the identification of specific mitochondrial tRNA gene mutations to severe disorders in human. As a result, mitochondrial tRNA genes and their products have emerged as novel and essential molecular markers for wide biochemical and genetic screenings among different human populations. So far, 139 pathogenic and 243 polymorphic mt tRNA mutations have been described and they have become the foreground of numerous case reports. Given the complexity of mitochondrial genetics and biochemistry, the clinical manifestations of mitochondrial disorders are extremely heterogeneous. They range from lesions of single tissues or structures to more severe impairements including myopathies, encephalomyopathies, cardiomyopathies, or complex multisystem syndromes. Moreover, the exact mechanisms by which biochemical cascades can be dramatically affected by mitochondrial tRNA mutations still remain uncharacterized. However and regardless of the vast amount of information that daily emerges, only few efforts have been carried out to systematically record all the mitochondrial tRNA-associated pathogenic mutations or polymorphisms. In this report, we summarize all the clinical phenotypes associated with mitochondrial tRNA pathogenic mutations that have been reported so far. In a next step we describe in detail all the pathogenic and polymorphic mutations that have been recorded so far and we categorize them per tRNA species and per associated disease. Finally, we discuss the impact of the frequency of mitochondrial tRNA mutations in general population surveys and we preview any relevant implications on the essential functional integrity of mitochondrial biochemical pathways.

The chemotherapeutic drug melphalan induces breakage of chromosomes regions rearranged in secondary leukemia

A cytogenetic study is reported on the lesions induced in vitro by melphalan, a currently used anticancer drug. The distribution of 2166 breakpoints shows that they do not occur at random. There is a large excess of breaks in region q1 of chromosome 9 and R bands are significantly more affected than G-band-rich segments. Furthermore, some regions of chromosomes 5, 7, 11, and 17, which are the chromosomes usually rearranged and deleted in secondary leukemias, presumably induced by such treatments, are frequently affected. It is presumed that the frequent involvement of 9q1 largely reflects preexisting monostrand breaks. The frequent breakage of chromosomes 5, 7, 11, and 17 and of R bands in general, which are known to be G-C rich, may result from the preferential methylation of the O6 of guanine by melphalan.

Major histocompatibility complex variation at class II DQA locus in the brown hare (Lepus europaeus)

The major histocompatability complex (MHC) is a multigene family of receptors that bind and present antigenic peptides to T‐cells. Genes of the MHC are characterized by an outstanding genetic polymorphism, which is considered to be maintained by positive selection. Sites involved in peptide binding form binding pockets (P) that are collectively termed the peptide‐binding region (PBR). In this study, we examined the level of MHC genetic diversity within and among natural populations of brown hare (Lepus europaeus) from Europe and Anatolia choosing for analysis of the second exon of the DQA locus, one of the most polymorphic class II loci. We aimed at an integrated population genetic analysis of L. europeaus by (i) correlating MHC polymorphism to genetic variability and phylogenetic status estimated previously from maternally (mtDNA) and biparentally (allozymes, microsatellites) inherited loci; and (ii) comparing full‐length exon amino acid polymorphism with functional polymorphism in the PBR and the binding pockets P1, P6 and P9. A substantial level of DQA exon 2 polymorphism was detected with two completely different set of alleles between the Anatolian and European populations. However, the phylogeny of full‐length exon 2 Leeu‐DQA alleles did not show a strong phylogeographic signal. The presence of balancing selection was supported by a statistically significant excess of nonsynonymous substitutions over synonymous in the PBR and a trans‐species pattern of evolution detected after phylogenetic reconstruction. The differentiating patterns detected between genetic and functional polymorphism, i.e. the number and the distribution of pocket variants within and among populations, indicated a hierarchical action of selection pressures.

Discrimination of the closely related biocontrol agents Macrolophus melanotoma (Hemiptera: Miridae) and M. pygmaeus using mitochondrial DNA analysis

The separation of the closely related predatory species Macrolophus melanotoma Costa (= M. caliginosus Wagner) and Macrolophus pygmaeus (Rambur) based exclusively on the different colour pattern of the first antennal segment (white central band in M. melanotoma and entirely black in M. pygmaeus) is rather precarious and their taxonomic status is still in doubt. In the present study their taxonomic status was evaluated by DNA confirmatory analysis and hybridization experiments between M. pygmaeus and a Macrolophus taxon, resembling M. melanotoma, with a first antennal segment entirely black or with a white central band collected from Dittrichia viscosa (L.) W. Greuter (Asteraceae) in southern Greece. Adult females from Dittrichia plants hybridized with males of M. pygmaeus and vice versa did not produce viable eggs. The Macrolophus species from Dittrichia irrespective of the first antennal segment coloration differed from M. pygmaeusin digestive patterns generated by AseI, XbaI, and MseI on 16S rRNA and in RAPD profiles produced by the primers OPA-18 and OPA-20. These results demonstrate that on Dittrichia plants there is a distinct dimorphic taxon, M. melanotoma, as it is the only species of the genus Macrolophus bearing a first antennal segment with a central white band. Given the limitation of the coloration pattern, the mtDNA genetic markers are the appropriate method for the identification of M. melanotomaand M. pygmaeus.

Biochemical Genetic Variability in Brown Hares (Lepus europaeus) From Greece

Allozyme variability of 91 brown hares (Lepus europaeus) from seven regions in Greece was compared to existing data of Bulgarian populations to test the hypothesis of the occurrence of specific alleles in Greece, likely stemming from an isolated Late Pleistocene refugial population in the southern Balkans. This hypothesis is particularly suggested by some subfossil Late Pleistocene hare remains in Greece and the reported high mtDNA diversity in Greek hares. Allozymic diversity could be higher in Greek hares than in hares from neighboring regions as a result of the accumulation of variants in a long-lasting Pleistocene refugium. Conversely, Greek hares could exhibit reduced genetic diversity because of long-lasting low effective population sizes during the Late Glacial Maximum and a lower chance of postglacial gene flow from other populations into this rather marginal part in the southern Balkans. Horizontal starch gel electrophoresis of proteins from 35~loci revealed three alleles (Es-1−162, Pep-2114, Mpi88) at low frequencies, which were not found in Bulgarian or any other brown hare population. In contrast, some alleles from the populations from Bulgaria and other regions of Europe were absent in the Greek samples. Population genetic statistics indicated only a slight tendency of increased gene pool diversity in Greek hares, little substructuring in Greek and Bulgarian populations, respectively, as well as an only slightly lower level of gene flow between the two neighboring regions, as compared to the gene flow within each region. The results conform to the hypothesis of a Late Pleistocene refugial population in the southern Balkans, with some few specific nuclear gene pool characteristics, but little effect on the overall genetic differentiation between Greek and Bulgarian hares.

Phylogenetic relationships among four species of Mullidae (Perciformes) inferred from DNA sequences of mitochondrial cytochrome b and 16S rRNA genes

DNA sequence comparisons of two mitochondrial DNA genes were used to infer phylogenetic relationships among four species of mullids. Approximately 238bp of the mitochondrial 16S ribosomal RNA (rRNA) and 261bp of the cytochrome b (cytb) genes were sequenced from representatives of three mullid genera (Mullus, Upeneus, Pseudopeneus), present in the Mediterranean Sea. Trees were constructed using three methods: maximum likelihood (ML), neighbor joining (NJ) and parsimony (MP). The results of the analyses of these data together with published data of the same mtDNA segments of two other perciform species (Sparus aurata, Perca fluviatilis), support the previous taxonomic classification of the three genera examined, as well as the classification of the two red mullet species in the same genus.