Reproductivity and life span of mouse populations from 25 generations of irradiated sires.
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Animals↗
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Molecular signatures for sex in the Placozoa.
Placozoans, the simplest free-living animals, have never been observed to reproduce sexually. Here, we describe molecular evidence for sexual reproduction within one clade of the Placozoa. In a population sample of 10 individuals, within-individual and overall nucleotide diversity were similar to each other and consistent with levels observed in sexually reproducing species. Intergenic recombination as well as the sharing of alleles between heterozygous and homozygous individuals was also observed. These hallmarks of sexual reproduction establish that sex is indeed present in this phylum.
Animals↗
A theoretical study of random segregation of minicircles in trypanosomatids.
The kinetoplast (k) DNA network of trypanosomatids is made up of approximately 50 maxicircles and the order of 10(4) minicircles. It has been proposed, based on various observations and experiments, that the minicircles are randomly segregated between daughter cells when the parent cell divides. In this paper, this random segregation hypothesis is theoretically tested in a population dynamics model to see if it can account for the observed phenomena. The hypothesis is shown to successfully explain, in Leishmania tarentolae, the observation that there are a few major and many minor minicircle classes, the fluctuations of minicircle class copy numbers over time, the loss of non-essential minicircle classes, the long survival times of a few of these classes and that these classes are likely to be the major classes within the population. Implications of the model are examined for trypanosomatids in general, leading to several predictions. The model predicts variation in network size within a population, variation in the average network size and large-scale changes in class copy number over long time-scales, an evolutionary pressure towards larger network sizes, the selective advantage of non-random over random segregation, very strong selection for the amplified class in Crithidia fasciculata if its minicircles undergo random segregation and that Trypanosoma brucei may use sexual reproduction to maintain its viability.
Animals↗
[Cooperation between genetic counseling centers, cytogenetic laboratories and in vitro fertilization centers in the treatment of reproductive disorders].
The techniques of assisted reproduction have recently become the most effective methods of treatment of infertility; namely ICSI (intra-cytoplasmic sperm injection), MESA (microepididymal sperm aspiration), TESA (testicular sperm aspiration) and TESE (testicular sperm extraction). The techniques have been increasingly successful, even above the average efficiency of classical IVF (in vitro fertilization). It can be demonstrated by the percentage of ICSI-aided births percentage per 100% of embryotransfers in ISCARE; 1996 = 21.3%, 1997 = 26.15%, 1998 = 29.7%. The successful use of these techniques is associated with the rise of risks which result from the selection of couples for assisted reproduction with genetic-based infertility and with the rise of risks involving the introduction of genetic-based defects in to the next generation. Presently, a list of indications is being developed, which, while still not accepted officially, identifies patients for genetic counselling. Only the counselling center has the competence to estimate genetic risks over generations. Subsequently, after selection by the center, during 1997 and 1998 the chromosomes of 731 patients were cytogenetically examined, representing 429 infertile couples from the centres ISCARE, PRONATAL, FERTIMED, and CAR 1. LF UK. Within these 429 couples, belonging to four groups of indications, the cytogenetic examination was informative in 8.15%. This finding of a relatively high percentage (10 times more than in the general population) confirms the validity of the list of indications and the necessity of cooperation among the genetic counselling center, cytogenetic laboratory and the IVF centre.
Chromosome Aberrations↗
Differences in hypothalamic 2-[125I]iodomelatonin binding in photoresponsive and non-photoresponsive white-footed mice, Peromyscus leucopus.
Photoperiod is an environmental cue used by many temperate-zone species to regulate their reproductive timing. Within species, the degree of reproductive photoresponsiveness can vary widely both among and within populations. The neuroendocrine mechanisms causing this individual variation in photoresponsiveness are unknown. Using selected lines from a population of white-footed mice known to vary genetically in reproductive photoresponsiveness, we tested the hypothesis that variation in the number and/or location of melatonin receptors is the basis for individual differences in reproductive photoresponsiveness. The brains and pars tuberalis of the pituitary from sixteen mice, (eight mice from each of two lines selected for two generations to respond strongly or weakly to photoperiod), were processed for autoradiography using the radioligand 2-[125I]-iodomelatonin (IMEL). We found significantly higher specific IMEL binding in the medial preoptic area and the bed nucleus of the stria terminalis of non-responsive mice than responsive mice. There were no differences between groups in specific IMEL binding in the suprachiasmatic and dorsomedial nuclei of the hypothalamus, pars tuberalis, or paraventricular nucleus of the thalamus. These results provide support for the hypothesis that individual variation in photoresponsiveness is due in part to differences in the density or affinity of melatonin receptors.
Animals↗
Genetically heterogeneous and selected lines of rats: behavioral and reproductive comparison.
Avoidance learning, open-field, and reproductive behaviors of a genetically heterogeneous stock (derived from a four-way cross of selected lines) were compared with the corresponding behaviors of the parental lines. The heterogeneous stock showed heterosis on the body development, fertility rate, litter size at birth and at weaning, and directional dominance on the avoidance learning and open-field measures.
Animals↗
Evidence for a global Wolbachia replacement in Drosophila melanogaster.
Wolbachia are maternally inherited intracellular alpha-Proteobacteria found in numerous arthropod and filarial nematode species. They influence the biology of their hosts in many ways. In some cases, they act as obligate mutualists and are required for the normal development and reproduction of the host. They are best known, however, for the various reproductive parasitism traits that they can generate in infected hosts. These include cytoplasmic incompatibility (CI) between individuals of different infection status, the parthenogenetic production of females, the selective killing of male embryos, and the feminization of genetic males. Wolbachia infections of Drosophila melanogaster are extremely common in both wild populations and long-term laboratory stocks. Utilizing the newly completed genome sequence of Wolbachia pipientis wMel, we have identified a number of polymorphic markers that can be used to discriminate among five different Wolbachia variants within what was previously thought to be the single clonal infection of D. melanogaster. Analysis of long-term lab stocks together with wild-caught flies indicates that one of these variants has replaced the others globally within the last century. This is the first report of a global replacement of a Wolbachia strain in an insect host species. The sweep is at odds with current theory that cannot explain how Wolbachia can invade this host species given the observed cytoplasmic incompatibility characteristics of Wolbachia infections in D. melanogaster in the field.
Animals↗
Preimplantation genetic diagnosis for Marfan syndrome.
OBJECTIVE: To develop and apply efficient and reliable protocols for preimplantation genetic diagnosis (PGD) for Marfan syndrome. DESIGN: Two mutation-specific protocols were developed, and the markers D15S1028, D15S992, D15S196, D15S576, D15S123, and D15S143 were used to set up four multiplex polymerase chain reactions (PCRs). SETTING: Research Center Reproduction and Genetics. PATIENT(S): Ten couples carrying mutations in the FBN1 gene. INTERVENTION(S): Six PGD protocols were developed for 10 couples, and 7 of them underwent a total of 16 clinical cycles. MAIN OUTCOME MEASURE(S): Amplification, allele drop-out (ADO), and contamination rates during the preclinical assays. DNA analyses of blastomeres from embryos biopsied during PGD cycles. RESULT(S): Six different protocols were set up, with the main objective being to to use one protocol for several couples. A total of 16 PGD cycles were performed, which resulted in the delivery of an unaffected boy and three ongoing pregnancies. CONCLUSION(S): The development of single-cell multiplex PCRs for linked markers and its use in PGD reduce the workload of the genetic diagnostic laboratory as well as the average waiting time for patients. This approach also allows for the simultaneous and accurate detection of recombination, contamination, and ADO, thereby increasing the reliability of the diagnosis.
Adult↗
High male:female ratio of germ-line mutations: an alternative explanation for postulated gestational lethality in males in X-linked dominant disorders.
In this paper I suggest that a vastly higher rate of de novo mutations in males than in females would explain some, if not most, X-linked dominant disorders associated with a low incidence of affected males. It is the inclusion of the impact of a high ratio of male:female de novo germ-line mutations that makes this model new and unique. Specifically, it is concluded that, if an X-linked disorder results in a dominant phenotype with a significant reproductive disadvantage (genetic lethality), affected females will, in virtually all cases, arise from de novo germ-line mutations inherited from their fathers rather than from their mothers. Under this hypothesis, the absence of affected males is explained by the simple fact that sons do not inherit their X chromosome (normal or abnormal) from their fathers. Because females who are heterozygous for a dominant disorder will be clinically affected and will, in most cases, either be infertile or lack reproductive opportunities, the mutant gene will not be transmitted by them to the next generation (i.e., it will be a genetic lethal). This, not gestational lethality in males, may explain the absence of affected males in most, if not all, of the 13 known X-linked dominant diseases characterized by high ratios of affected female to male individuals. Evidence suggesting that this mechanism could explain the findings in the Rett syndrome is reviewed in detail.
Fathers↗
Sex ratio equilibrium under partial sib mating.
A general equation for equilibrium sex allocation is provided which models asymmetries between son and daughter in the costs of offspring production, the genetic relatedness to the controlling genotype and the amount of competition for mating opportunities and reproductive resources. A genetic proof is given which is valid for diploid and haplodiploid systems with a variety of modes of sex allocation control, provided sib mating is the only source of inbreeding. By way of example, some variations of Hamilton's (1967) model are discussed.
Animals↗
The genic nature of gamete eliminator in rice.
The two cultivated rice species, Oryza sativa and Oryza glaberrima, are morphologically alike but are reproductively isolated from each other by hybrid sterility. The hybrid is male sterile but partially female fertile. Backcross experiments were conducted to introduce an alien factor controlling hybrid sterility from O. glaberrima (W025) into O. sativa (T65wx) and examine the genetic basis. An extracted sterility factor, closely linked to the wx locus, induced gametic abortion due to allelic interaction and was tentatively designated as S(t). The segregation patterns for infertility was explained by assuming that W025 and T65wx carried S(t) and S(t)a, respectively, and gametes with S(t)a aborted only in the heterozygote (S(t)/S(t)a) although the elimination of female gametes was incomplete. Thus, S(t) seemed to be intermediate between a gamete eliminator and pollen killer. However, S(t) was proven to be likely the same as S1 which was formerly reported as gamete eliminator in a different genetic background of O. sativa. In addition, a chromosomal segment containing S1 (or S(t] caused a marked suppression of crossing over around it, suggesting the presence of an inversion. Further, female transmission of S1a increased as the segment containing S1 became small by recombination. After S1 was further purified by successive backcrosses up to the BC15 generation, it became pollen killer. The present results give evidence that a profound sterility gene such as gamete eliminator can be made from accumulation of pollen killer and its modifier(s) when pollen killer and modifier(s) are linked, they behave as a gene complex in the hybrid.
Alleles↗
Effect of crossbreeding on genetic improvement of growth and reproduction in pigs.
Nine-year data from 3426 pigs were analyzed to present a retrospective evaluation of purebred, 2-breed crossing, and 3-breed rotational crossbreeding in the sixties and seventies. No significant heterosis effect was observed for litter size and the average number of pigs per litter (10) remained constant as crossbreeding intensified and the management system improved. Parental crossing did not influence sex ratios and no significant deviation from the 50:50 sex ratio occurred throughout the study. Among purebreds, Hampshire pigs were heavier (P less than .05) at birth and weaning than Duroc pigs. Crossbred dams sired by Duroc or Yorkshire boars produced offspring which were comparable in birth and weaning weights, but weighed less (P less than .05) than those sired by Landrace boars. Effect of birth weight on weaning weight of crossbred and purebred pigs was consistently positive whereas litter size influenced weaning weight negatively. Survival of the pigs was not dependent on parental crossing and did not change over the years when crossbreeding intensified. Yearly environmental variation influenced birth weight and weaning weight, but not litter traits. Male pigs were heavier (P less than .01) at birth than females, but the two groups were comparable at weaning.
Animals↗
[Comparative characteristics of reproduction of the wheat striped mosaic virus in winter and spring Triticum aestivum L. in natural agrocoenosis and during clinostatting].
Microgravity (a transformed environment) was produced with the use of a multi-purpose clinostat. Object of the investigation was wheat striped mosaic virus (WSMV) affecting a great variety of wheat species in natural agrocoenosis, and super-dwarf cultivar Apogee in the transformed environment. Enzyme immunodetection (das-ELISA) as well as electron microscopy were employed for virus identification. Viral reproduction was found high (titre 1/2560) in winter and spring wheat species in agrocoenosis (natural transmissible background). Clinostatting in the horizontal and vertical planes (R = 400 mm and R = 250 mm) inhibited virus reproduction by day 21, 25 and 18 post inoculation, respectively. Clinostatting improved health of WSMV-infected plants and resulted in harvesting the first Apogee crop. Productivity of WSMV-infected plants after clinostatting was increased owing to a large seed content of the heads as compared with stationary and clinostatted healthy crops. This experience of inhibiting virus reproduction should be taken into consideration in virus-free seed production biotechnology development.
Animals↗
The epigenetic basis of gender in flowering plants and mammals.
What makes a sperm male or an egg female, and how can we tell? A gamete's gender could be defined in many ways, such as the sex of the individual or organ that produced it, its cellular morphology, or its behaviour at fertilization. In flowering plants and mammals, however, there is an extra dimension to the gender of a gamete--due to parental imprinting, some of the genes it contributes to the next generation will have different expression patterns depending on whether they were maternally or paternally transmitted. The non-equivalence of gamete genomes, along with natural and experimental modification of imprinting, reveal a level of sexual identity that we describe as 'epigender'. In this paper, we explore epigender in the life history of plants and animals, and its significance for reproduction and development.
Animals↗
Estimates of genetic parameters for Canadian Holstein female reproduction traits.
Age at first insemination, days from calving to first insemination, number of services, first-service nonreturn rate to 56 d, days from first service to conception, calving ease, stillbirth, gestation length, and calf size of Canadian Holstein cows were jointly analyzed in a linear multiple-trait model. Traits covered a wide spectrum of aspects related to reproductive performance of dairy cows. Other frequently used fertility characteristics, like days open or calving intervals, could easily be derived from the analyzed traits. Data included 94,250 records in parities 1 to 6 on 53,158 cows from Ontario and Quebec, born in the years 1997 to 2002. Reproductive characteristics of heifers and cows were treated as different but genetically correlated traits that gave 16 total traits in the analysis. Repeated records for later parities were modeled with permanent environmental effects. Direct and maternal genetic effects were included in linear models for traits related to calving performance. Bayesian methods with Gibbs sampling were used to estimate covariance components of the model and respective genetic parameters. Estimates of heritabilities for fertility traits were low, from 3% for nonreturn rate in heifers to 13% for age at first service. Interval traits had higher heritabilities than binary or categorical traits. Service sire, sire of calf, and artificial insemination technician were important (relative to additive genetic) sources of variation for nonreturn rate and traits related to calving performance. Fertility traits in heifers and older cows were not the same genetically (genetic correlations in general were smaller than 0.9). Genetic correlations (both direct and maternal) among traits indicated that different traits measured different aspects of reproductive performance of a dairy cow. These traits could be used jointly in a fertility index to allow for selection for better fertility of dairy cattle.
Animals↗
Advances in physiology of growth, reproduction and lactation.
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Animal Population Groups↗
Preimplantation genetic diagnosis.
Preimplantation genetic diagnosis (PGD) is an early form of prenatal diagnosis whereby embryos obtained in vitro are tested for the presence of a certain genetic disease. Patients who are at risk to have a child with a genetic disease can thus avoid a prenatal diagnosis and a possible termination of pregnancy. At the Centres for Medical Genetics and Reproductive Medicine, we have applied PGD for monogenic diseases since 1993 and are now one of the largest in the world. In this paper, the theoretical and technical side of PGD will first be explained. Thereafter, our activity since 1993 will be described. At the end of 2004, we had carried out 713 cycles for 319 patients for 54 different indications, leading to 159 (22 %) clinical pregnancies. The ESHRE PGD Consortium, of which I am chairperson, has been collating data on PGD from PGD centres from the whole world. This has led to the publication of four reports that are considered widely as important documents, as well as a comprehensive set of guidelines. Finally, there is the aspect of the scientific research ensuing from the PGD programme. The research into the causes of instability of triplet repeats in genetic diseases such as DM1 and Huntington's disease has made significant progress. The embryonic stem cell lab was started up in 2002, and has already succeeded in deriving five new lines, as well as progressing significantly into the research in differentiation to muscle cells and the behaviour of triplet repeats in totipotent stem cells.
Chromosome Aberrations↗
Is there a possible correlation between chromosomal variants and spermatogenesis?
AIM: Heterochromatin polymorphism is considered a variant of a normal karyotype but is more frequent in infertile men. The aim of this study was to evaluate the correlation between heterochromatic variants and male infertility and to discuss the possible mechanisms of how heterochromatic polymorphism might affect spermatogenesis. METHODS: Cytogenetic analysis was undertaken in 210 infertile males who had been taken into assisted reproductive techniques and in 183 men with proven fertility. Additionally, C-banding was performed in men with heterochromatin polymorphism. Sperm fluorescence in situ hybridization (FISH) was applied in 54 men with normal karyotype presenting either normal or abnormal sperm parameters as well as in 8 men with heterochromatin polymorphism. The outcomes of assisted reproductive techniques were compared between infertile men with normal karyotype and men with heterochromatin polymorphism. RESULTS: The incidence of heterochromatin polymorphism was higher in infertile men. The most frequent chromosome involved in heterochromatin polymorphism was chromosome 9. Sperm FISH analysis revealed an increased rate of aneuploidy in men with heterochromatin polymorphism. Laboratory and clinical outcomes in assisted reproductive techniques were compromised in men with heterochromatin polymorphism. CONCLUSIONS: An increased rate of heterochromatin polymorphism in infertile males seems to be more than an incidental finding, and must not be considered as a normal variant. Polymorphic heterochromatin may have deleterious effects on the genetic constitution of spermatozoa. More attention must be directed to infertile men with heterochromatin polymorphism.
Adult↗