BACKGROUND: The dispersed occurrence of holocentric chromosomes across eukaryotes implies they are adaptive, but the conditions under which they confer an advantage over monocentric chromosomes remain unclear. Due to their extended kinetochore and the attachment of spindle microtubules along their entire length, holocentric chromosomes tolerate fragmentation; hence, they may be advantageous in times of exposure to factors that cause chromosomal fragmentation (clastogens). SCOPE: It is shown that holocentric organisms may, indeed, thrive better than monocentric organisms under clastogenic conditions and that such conditions of various duration and intensity have occurred many times throughout the history of Earth's biota. One of the most important clastogenic events in eukaryotic history, in which holocentric chromosomes may have played the key role, was the colonization of land by plants and animals half a billion years ago. In addition to arguments supporting the anticlastogenic hypothesis of holocentric chromosomes and a discussion of its evolutionary consequences, experiments and analyses are proposed to explore this hypothesis in more depth. CONCLUSIONS: It is argued that the tolerance to clastogens explains the origin of holocentric lineages and may also have far-reaching consequences for eukaryotic evolution in general as exemplified by the potential role of holocentric chromosomes in terrestrialization.
- Keywords
- Clastogens, Zygnematophyceae, chromosomal fragmentation, cosmic radiation, desiccation, gamma radiation, herbivory, holokinetic chromosomes, land plants, monocentric chromosomes, terrestrialization, ultraviolet radiation,
- MeSH
- Biological Evolution * MeSH
- Centromere physiology MeSH
- Chromosomes, Plant MeSH
- Chromosomes * physiology MeSH
- Eukaryota genetics MeSH
- Mutation MeSH
- Selection, Genetic genetics MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The nuclear architecture of selected chromosomes in apoptotic nuclei of human leukemic cells K-562 and HL-60 was investigated. Etoposide and prolonged confluence were used for the induction of apoptosis. DAPI as well as TUNEL labeling of apoptotic nuclear bodies was combined with visualization of chromosomal territories by the FISH technique. Simultaneous vital staining by annexin V, propidium iodide, and Hoechst 33342 was applied to distinguish apoptotic, necrotic, and intact cell fraction of tested populations. Our FISH analyses revealed that the three-dimensional (3D) structure of apoptotic nuclei as well as the 3D structure of apoptotic bodies is preserved in formaldehyde-fixed cells. High-molecular-weight DNA fragmentation was determined in apoptotic K-562 cells in contrast to oligonucleosomal cleavage observed in apoptotic HL-60 cells. In K-562 populations, chromosomal territories were located separately either in one apoptotic body or underwent disassembly into chromosomal segments dispersed into single and/or several apoptotic bodies. The apoptotic disorganization of chromosomal territories was irregular, leading mainly to chromosomal segments of different sizes and, consequently, chromosomal disassembly was not observed at specific sites. In comparison with the control, an increased number of centromeric FISH signals were observed in prolonged confluence-treated K-562 cells induced to apoptosis. This finding can be explained either as a consequence of apoptosis or by polyploidization. Sequential staining of the same apoptotic nuclei by the FISH and TUNEL techniques revealed that chromosomal territory segmentation precedes the formation of nuclear apoptotic bodies.
Chromosomal rearrangements act as barriers to gene flow and can thus promote speciation. In moths and butterflies (Lepidoptera), which possess holocentric chromosomes facilitating karyotype changes, chromosome fusions are more common than fissions. Yet, limited evidence suggests that when speciation involves chromosomal rearrangements, it is most often linked to fissions. Notable karyotypic variation is observed in three clades of the subfamily Polyommatinae (Lycaenidae), with chromosome numbers ranging from n = 10 to n = 225. We investigated genome sizes and karyotypes in several species of the genera Polyommatus and Lysandra with modal and derived high chromosome numbers. Our findings showed no support for polyploidy, confirming previous conclusions about karyotypic diversification via chromosome fragmentation in this butterfly family. Species with high chromosome numbers have slightly larger genomes, which indicate a potential role of repetitive sequences but contradicts the hypothesis of holocentric drive. Ends of fragmented chromosomes were healed with telomeres synthesized de novo, which were significantly larger than those of species with modal karyotype. No interstitial telomeric sequences were detected on autosomes. Internal telomeric signals on sex chromosomes, however, revealed multiple sex chromosome systems in Polyommatus (Plebicula) dorylas and Polyommatus icarus, with two karyotype races differing in sex chromosome constitution in the latter. Notably, the W chromosome resisted fragmentation, presumably due to its epigenetic silencing.
- Keywords
- Polyommatus, butterfly, fission, fusion, sex chromosomes, telomere,
- Publication type
- Journal Article MeSH
Role of male factor in recurrent abortion and in vitro fertilization failure has not been fully defined yet and there is much controversy about evaluating male patients with normal semen analysis. One of the factors that might help establish the male role is DNA fragmentation index. However, strong correlation between this factor and quality of semen, has caused many clinicians to believe that it does not help in abortion and implantation failure. We aim to assess this factor in our patients. In a prospective observational study, we assessed age, duration of infertility, undesired fertility related events (assisted reproductive techniques attempts and abortions), semen parameters and DNA fragmentation index in patients with multiple abortions or in vitro fertilization failures and analysed the results by statistical software SPSS version 24. DNA fragmentation index was remarkably correlated with age, duration of infertility and semen parameters. Among all groups in our study, patients with abnormal semen analysis had statistically significant higher level of DNA fragmentation. Ten percent of patients with normal or slightly abnormal semen analysis had abnormally high SDFI (sperm DNA fragmentation index). Checking DNA fragmentation index is recommended in all couples with fertilization problems even in the presence of normal semen analysis. It might be more reasonable to assess it in aged men, long duration of infertility or candidates with remarkable semen abnormality.
- Keywords
- Abortion, DNA fragmentation index, In vitro fertilization, Intracytoplasmic sperm injection, Male, Sperm,
- MeSH
- Semen Analysis MeSH
- Fertilization in Vitro methods MeSH
- DNA Fragmentation MeSH
- Abortion, Habitual * MeSH
- Humans MeSH
- Infertility, Male * diagnosis genetics MeSH
- Aged MeSH
- Semen MeSH
- Spermatozoa MeSH
- Pregnancy MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Aged MeSH
- Pregnancy MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Observational Study MeSH
The capital city of Prague is one of the most polluted areas of the Czech Republic. The impact of air pollution on the level of chromosomal aberrations was systematically studied: analyses were performed using fluorescence in situ hybridization (FISH) with whole-chromosome painting for chromosomes #1 and #4. In the present study, we analyzed the levels of stable (one-way and two-way translocations) and unstable (acentric fragments) chromosomal aberrations in 42 mothers living in Prague and in their newborns. The average age of the mothers was 29 years (range, 20-40 years). Blood samples were collected from October 2007 to February 2008. The average levels of carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) and benzo[a]pyrene (B[a]P) in respirable particles (PM2.5), as determined by stationary monitoring, were 21.0+/-12.3 ng/m(3) and 2.9+/-1.8 ng/m(3), respectively. We did not observe any effect of either c-PAH or B[a]P exposure on the genomic frequency of translocations (per 100 cells, F(G)/100) in either group due to their similar exposure during the winter months. The mean values of F(G)/100 representing stable aberrations were 0.09+/-0.13 vs 0.80+/-0.79 (p<0.001) for newborns vs mothers, indicating a significant increase of F(G)/100 with age. On the other hand, the frequency of unstable aberrations did not differ between the two groups. Our results demonstrate how the patterns of different types of aberration differed between newborns and mothers: we observed 64.3% unstable aberrations and 35.7% stable aberrations in newborns vs 19.7% and 80.3% in mothers, respectively. Our results indicate that after birth the frequencies of aberrations are very low and that the aberrations are represented mainly by acentric fragments. The changes observed in mothers show a shift to stable aberrations represented mainly by two-way translocations. The mother's age affected the level of aberrations in newborns: the group of children born to older mothers (31-40 years) had significantly increased F(G)/100 levels.
- MeSH
- Chromosome Aberrations * MeSH
- Adult MeSH
- Fetal Blood MeSH
- In Situ Hybridization, Fluorescence MeSH
- Air Pollutants toxicity MeSH
- Humans MeSH
- Chromosome Painting MeSH
- Maternal Exposure adverse effects MeSH
- Mutagens toxicity MeSH
- Infant, Newborn * MeSH
- Polycyclic Aromatic Hydrocarbons toxicity MeSH
- Pregnancy MeSH
- Translocation, Genetic MeSH
- Maternal Age MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Infant, Newborn * MeSH
- Pregnancy MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Czech Republic MeSH
- Names of Substances
- Air Pollutants MeSH
- Mutagens MeSH
- Polycyclic Aromatic Hydrocarbons MeSH
A dose-response analysis of chromosomal aberrations was performed in male progeny of gamma-irradiated males in the flour moth, Ephestia kuehniella. For comparison, several female progeny from each dose level were examined. Aberrations were detected on microspread preparations of pachytene nuclei in the electron microscope and classified according to pairing configurations of synaptonemal complexes (SCs). Fragmentation and various translocations were the most numerous aberrations, whereas interstitial deletion and inversion were rare. At 100 Gy, relatively simple multiple translocations were found. Multiple translocations showing complicated configurations occurred at 150 and 200 Gy, and their number increased with the dose. In males, the mean number of chromosomal breaks resulting in aberrations linearly increased with the dose from 8.4 to 16.2 per nucleus. In females, this value achieved a maximum of 11.2 breaks/nucleus at 200 Gy. Three factors were suggested to contribute to the reported higher level of F1 sterility in males than females: (i) survival of males with high numbers of breaks, (ii) crossing-over in spermatogenesis but not in the achiasmatic oogenesis, and (iii) a higher impact of induced changes on the fertility of males than females. It was concluded that translocations are most responsible for the production of unbalanced gametes resulting in sterility of F1 moths. However, F1 sterility predicted according to the observed frequency of aberrations was much higher than the actual sterility reported earlier. This suggests a regulation factor which corrects the predicted unbalanced state towards balanced segregation of translocated chromosomes.
- MeSH
- Chromosome Aberrations MeSH
- Chromosomes radiation effects ultrastructure MeSH
- Microscopy, Electron MeSH
- Infertility genetics MeSH
- Crosses, Genetic MeSH
- Moths genetics radiation effects MeSH
- Sex Characteristics MeSH
- Radiation Tolerance genetics MeSH
- Translocation, Genetic MeSH
- Dose-Response Relationship, Radiation MeSH
- Gamma Rays MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Female MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Comparative Study MeSH
While mitochondrial genome content and organization is quite diverse across all Eukaryotes, most bilaterian animal mitochondrial genomes (mitogenomes) exhibit highly conserved gene content and organisation, with genes typically encoded on a single circular chromosome. However, many species of parasitic lice (Insecta: Phthiraptera) are among the notable exceptions, having mitogenomes fragmented into multiple circular chromosomes. To better understand the process of mitogenome fragmentation, we conducted a large-scale genomic study of a major group of lice, Amblycera, with extensive taxon sampling. Analyses of the evolution of mitogenome structure across a phylogenomic tree of 90 samples from 53 genera revealed evidence for multiple independent origins of mitogenome fragmentation, some inferred to have occurred less than five million years ago. We leveraged these many independent origins of fragmentation to compare the rates of DNA substitution and gene rearrangement, specifically contrasting branches with fragmented and non-fragmented mitogenomes. We found that lineages with fragmented mitochondrial genomes had significantly higher rates of mitochondrial sequence evolution. In addition, lineages with fragmented mitochondrial genomes were more likely to have mitogenome gene rearrangements than those with single-chromosome mitochondrial genomes. By combining phylogenomics and mitochondrial genomics we provide a detailed portrait of mitogenome evolution across this group of insects with a remarkably unstable mitogenome structure, identifying processes of molecular evolution that are correlated with mitogenome fragmentation.
BACKGROUND: A single circular mitochondrial (mt) genome is a common feature across most metazoans. The mt-genome includes protein-coding genes involved in oxidative phosphorylation, as well as RNAs necessary for translation of mt-RNAs, whose order and number are highly conserved across animal clades, with few known exceptions of alternative mt-gene order or mt-genome architectures. One such exception consists of the fragmented mitochondrial genome, a type of genome architecture where mt-genes are split across two or more mt-chromosomes. However, the origins of mt-genome fragmentation and its effects on mt-genome evolution are unknown. Here, we investigate these origin and potential mechanisms underlying mt-genome fragmentation, focusing on a genus of booklice, Liposcelis, which exhibits elevated sequence divergence, frequent rearrangement of mt-gene order, and fragmentation of the mt genome, and compare them to other Metazoan clades. RESULTS: We found this genus Liposcelis exhibits very low conservation of mt-gene order across species, relative to other metazoans. Levels of gene order rearrangement were, however, unrelated to whether or not mt-genomes were fragmented or intact, suggesting mitochondrial genome fragmentation is not affecting mt-gene order directly. We further investigated possible mechanisms underpinning these patterns and revealed very high conservation of non-coding sequences at the edges of multiple recombination regions across populations of one particular Liposcelis species, supportive of a hypothesis that mt-fragmentation arises from recombination errors between mt-genome copies. We propose these errors may arise as a consequence of a heightened mutation rate in clades exhibiting mt-fragmentation. Consistent with this, we observed a striking pattern across three Metazoan phyla (Arthropoda, Nematoda, Cnidaria) characterised by members exhibiting high levels of mt-gene order rearrangement and cases of mt-fragmentation, whereby the mt-genomes of species more closely related to species with fragmented mt-genomes diverge more rapidly despite experiencing strong purifying selection. CONCLUSIONS: We showed that contrary to expectations, mt-genome fragmentation is not correlated with the increase in mt-genome rearrangements. Furthermore, we present evidence that fragmentation of the mt-genome may be part of a general relaxation of a natural selection on the mt-genome, thus providing new insights into the origins of mt-genome fragmentation and evolution.
- Keywords
- Booklice, Evolution, Fragmentation, Mitochondrial genome, Rearrangement, Recombination,
- MeSH
- Phylogeny MeSH
- Genome, Mitochondrial * genetics MeSH
- Gene Rearrangement MeSH
- Genes, Mitochondrial MeSH
- Evolution, Molecular MeSH
- Gene Order MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Using cryopreservation techniques can increase the effectiveness of reproducing cultured fish species by ensuring a dependable supply of sperm, although the quality of the sperm could be impacted by the procedures involved. The goal of this study was to investigate the effect of purified seminal plasma transferrin (Tf), bovine serum albumin (BSA), and antifreeze protein (AFP) types I and III at 1 µg mL-1 on relevant characteristics of cryopreserved sperm from common carp Cyprinus carpio. We compared oxidative stress indices, antioxidant activity, and DNA fragmentation of fresh sperm to that frozen with extender only or with Tf, BSA, or AFP types I and III. Fresh sperm had significantly lower levels of thiobarbituric acid reactive substances (TBARS) compared to samples that underwent cryopreservation without protein treatment, which resulted in 0.54 ± 0.06 nmol/108 cells of TBARS. Carbonyl derivatives of proteins (CP) decreased significantly (ANOVA; P > 0.05) in carp sperm with addition of Tf, AFPI, and AFPIII. Significant differences in superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx) activity were seen in sperm supplemented with Tf, BSA, AFPI, and AFPIII from those without. Significantly less DNA damage, expressed as percent tail DNA (11.56 ± 1.34) and olive tail moment (0.59 ± 0.13), was recorded in samples cryopreserved with Tf. The findings indicated that addition of Tf, BSA, AFPI, or AFPIII to cryopreservation medium is beneficial to sperm preservation. The mechanisms through which these proteins act positively on sperm need to be further investigated.
- Keywords
- Cyprinidae, Freeze/thaw, Proteins, Reactive oxygen species, Sperm DNA fragmentation,
- MeSH
- alpha-Fetoproteins MeSH
- Antioxidants MeSH
- DNA Fragmentation MeSH
- Carps * MeSH
- Cryopreservation veterinary methods MeSH
- Cryoprotective Agents MeSH
- Antifreeze Proteins MeSH
- Thiobarbituric Acid Reactive Substances MeSH
- Sperm Motility MeSH
- Oxidative Stress MeSH
- Semen MeSH
- Spermatozoa MeSH
- Semen Preservation * veterinary methods MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- alpha-Fetoproteins MeSH
- Antioxidants MeSH
- Cryoprotective Agents MeSH
- Antifreeze Proteins MeSH
- Thiobarbituric Acid Reactive Substances MeSH
The pattern of chromosomal aberrations (CA) was studied by fluorescence in situ hybridization (FISH) technique (whole chromosomes #1 and #4 painting) in workers occupationally exposed to any of the four following conditions: acrylonitrile (ACN), ethyl benzene (EB), carcinogenic polycyclic aromatic hydrocarbons (c-PAHs), and irradiation in nuclear power plants (NPP), respectively. Decrease in the relative frequency of translocations was observed in EB group, and an increase in reciprocal translocations in ACN and NPP-exposed groups. An increase in a relative number of insertions was registered under all four conditions (significant at ACN, EB, c-PAHs, quasisignificant at NPP-exposed groups). Significant differences in the percentage of lymphocytes with aberrations on chromosome #1 (58.8+/-32.7%, versus 73.8+/-33.6% in the controls, P < 0.05), and chromosome #4 (47.0+/-34.1%, versus 29.4+/-32.2%, P < 0.01) were found in workers exposed to ACN. Similarly, a decrease in the proportion of cells with aberration on chromosome #1 (61.0+/-24.0%, versus 73.8+/-33.6%, P < 0.05) and an increase on chromosome #4 (45.6+/-24.6%, versus 29.4+/-32.2%, P < 0.05) were observed in workers exposed to EB. Frequency of aberrant cells (%AB.C.) as well as genomic frequency of translocations (F(G)/100) increased with age (P < 0.001). Aging also increased the percentage of translocations and reciprocal translocations (P < 0.05), but decreased the relative number of acentric fragments (P < 0.01). Smoking led to significantly increased F(G)/100 (P < 0.05), but did not affect the pattern of chromosomal aberrations. Our results seem to indicate that different carcinogens may induce a different pattern of chromosomal aberrations.
- MeSH
- Acrylonitrile toxicity MeSH
- Benzene Derivatives toxicity MeSH
- Chromosome Aberrations chemically induced MeSH
- Adult MeSH
- Radiation, Ionizing MeSH
- Smoking adverse effects MeSH
- Cells, Cultured MeSH
- Humans MeSH
- Lymphocytes drug effects radiation effects MeSH
- Chromosome Painting * MeSH
- Mutagens toxicity MeSH
- Polycyclic Aromatic Hydrocarbons toxicity MeSH
- Occupational Exposure adverse effects MeSH
- Regression Analysis MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Male MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Comparative Study MeSH
- Names of Substances
- Acrylonitrile MeSH
- Benzene Derivatives MeSH
- ethylbenzene MeSH Browser
- Mutagens MeSH
- Polycyclic Aromatic Hydrocarbons MeSH
