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PubMed2006

Gene transposition as a cause of hybrid sterility in Drosophila.

We describe reproductive isolation caused by a gene transposition. In certain Drosophila melanogaster-D. simulans hybrids, hybrid male sterility is caused by the lack of a single-copy gene essential for male fertility, JYAlpha. This gene is located on the fourth chromosome of D. melanogaster but on the third chromosome of D. simulans. Genomic and molecular analyses show that JYAlpha transposed to the third chromosome during the evolutionary history of the D. simulans lineage. Because of this transposition, a fraction of hybrids completely lack JYAlpha and are sterile, representing reproductive isolation without sequence evolution.

Animals↗

PubMed2002

Intensive genetic assessment of the mating system and reproductive success in a semi-closed population of the mottled sculpin, Cottus bairdi.

Most genetic surveys of parentage in nature sample only a small fraction of the breeding population. Here we apply microsatellite markers to deduce the genetic mating system and assess the reproductive success of females and males in an extensively collected, semi-closed stream population of the mottled sculpin fish, Cottus bairdi. In this species, males guard nest rocks where females deposit the eggs for fertilization. The potential exists for both males and females to mate with multiple partners and for males to provide parental care to genetically unrelated offspring. Four hundred and fifty-five adults and subadults, as well as 1,259 offspring from 23 nests, were genotyped at five polymorphic microsatellite loci. Multilocus maternal genotypes, deduced via genetic analyses of embryos, were reconstructed for more than 90% of the analysed nests, thus allowing both male and female reproductive success to be estimated accurately. There was no genetic evidence for cuckoldry, but one nest probably represents a takeover event. Successful males spawned with a mean of 2.8 partners, whereas each female apparently deposited her entire clutch of eggs in a single nest (mean fecundity = 66 eggs/female). On average, genetically deduced sires and dams were captured 1.6 and 9.3 metres from their respective nests, indicating little movement by breeders during the spawning season. Based on a 'genetic mark-recapture' estimate, the total number of potentially breeding adults (c. 570) was an order-of-magnitude larger than genetically based estimates of the effective number of breeders (c. 54). In addition, significantly fewer eggs per female were deposited in single than in multidam nests. Not only were perceived high-quality males spawning with multiple partners, but they were receiving more eggs from each female.

Animals↗

PubMed1992

The C.E.B.A.S.-Aquarack project: the laboratory prototype and first results of the scientific frame program.

The paper explains the basic conception of a "Closed Equilibrated Biological Aquatic System" (C.E.B.A.S.) incorporated in a Aquarack as a research tool for zoological, botanical and interdisciplinary research in space biology and describes the construction principle of laboratory prototype consisting of a modular habitat for aquatic animals a semi-biological/physical water recycling system and a computerized control unit. Further on the running scientific frame program in which as well five german and two U.S.-universities as the DLR Institute of Aerospace Medicine are involved is presented which includes the subtopics reproductive biology, genetics, embryology/teratology, neurobiology, vestibularis research, stress research general endocrinology, ethology, gerontology and skeleton research. Within this the choice of the experimental animals, the teleost Xiphophorus helleri (vertebrate model) and the pulmonate snail Biomphalaria glabrata (invertebrate model) is explained. Examples of results of the scientific program mainly derive from the hardware-related research and from the reproductive biology subproject with X. helleri.

Animals↗

PubMed1987

The reduction of gene exchange due to a prezygotic isolating mechanism with monogenic inheritance.

The efficiency of an incomplete prezygotic reproductive isolating mechanism in one- and two-population models is studied. The isolating mechanism studied has a monogenic hereditary basis, and depends on the fact that the various genotypes "choose" different periods or sites to perform their reproductive activity. In the one-population models, the "neutral" gene exchange between the two morphs characterized by the alternative forms of the isolating mechanism decreases drastically only when there is an extremely low frequency of individuals with different genotypes reproducing in the same sites and during the same periods. Furthermore, the reduction in gene exchange caused by the prezygotic isolation is smaller with tight linkage between the gene-determining partial reproductive isolation and the neutral gene. In the two-population models the prezygotic isolation causes a reduction in gene exchange which is smaller with low migration rates, and is negligible for very low rates.

Gene Frequency↗

PubMed1992

Effects of genetic strain and light management on the reproductive performance of turkeys.

The laying performance of six genetic strains of turkeys, which have been bred and maintained at the Ohio Agricultural Research and Development Center, Wooster, OH, was compared under three laying house lighting regimens over a period of 3 yr. Light Treatment 1 (L1) consisted of 14 h of continuous light (L) and 10 h of dark (D; 14L:10D) throughout the laying period. Treatment 2 (L2) consisted of 14 h of intermittent light (IL, 15 min L and 45 min D/h) followed by 10 h of continuous dark. The IL treatment was started following a period (6 wk) in which the hens were trained to use the trapnests. Thus, during the first 6 wk of their laying period, L2 hens were also provided 14L:10D. Treatment 3 (L3) hens were provided the same program as L1 for the first 14 wk of the laying period. They were then moved to a continuous period of 19L:5D for the remainder of the laying period. All eggs produced were recorded through 180 days after the first egg was laid. Traits studied included: the number of days to first egg after light stimulation; the number of eggs produced through 84, 120, and 180 days after the first egg was laid; the average clutch length; the maximum clutch length; the total days lost to broodiness; the rate of lay; and the effective length of the laying period. Highly significant differences (P less than or equal to .01) were observed among the strains used for all traits measured. Light treatments showed no significant effects on any trait measured. Thus, from the present studies, the delayed IL program provides an economically attractive management program for environmentally controlled turkey breeder houses.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1996

Are there genetic risks associated with microassisted reproduction?

Of all the techniques available for microassisted reproduction, the direct injection of individual sperm cells or spermatids into the cytoplasm of the oocyte (ICSI) is the most invasive, through which any possible selection against sperm cells with genomic defects would be excluded. It has, however, been shown that such a possible selection is present neither in the female genital tract nor at the zona pellucida. Selection against genetic-based defects occurs after the fertilization of the oocyte, during both embryonic and fetal development. Based on the data to date, it can be assumed that ICSI would not result in either a significant increase in genetic-based diseases, or in an increase in the number of infertile males. If, however, mutations of X-chromosomal or Y-chromosomal genes should play a major role in male fertility disorders, one could expect, over generations, an increase, though probably very slight, in the number of males with such disorders.

Animals↗

PubMed2004

Loss of complementation and the logic of two-step meiosis.

Meiosis is usually a two-step process: two divisions preceded by a duplication. One-step meiosis, a single division without prior replication, is a more logical way to produce haploid gametes; moreover, one-step meiosis leads to higher variabilty in the progeny than two-step meiosis. Yet one-step meiosis is very rare in nature, and may not even exist at all. I suggest that this is because one-step meiosis, in contrast to two-step meiosis, can be easily invaded and replaced by asexual reproduction. I discuss why other existing peculiar forms of division leading to the production of haploid gametes, but not one-step meiosis, have the same effect as two-step meiosis.

Animals↗

PubMed2003

Shared ITS DNA substitutions in isolates of opposite mating type reveal a recombining history for three presumed asexual species in the filamentous ascomycete genus Alternaria.

About 15,000 species of ascomycete fungi lack a known sexual state. For fungi with asexual states in the anamorph genera Embellisia, Ulocladium, and Alternaria, six species have known sexual states but more than 50 species do not. In sexual filamentous ascomycetes, opposite mating type information at the MAT1 locus regulates mating and the opposite mating type genes each have a clonal, non-recombining phylogenetic history. We used PCR to amplify and sequence fragments of the opposite mating type genes from three supposedly asexual species, A. brassicae, A. brassicicola and A. tenuissima. Each haploid fungal isolate had just one mating type, but both mating types were present in all the three species. We sequenced the ribosomal ITS regions for isolates of opposite mating type, for the three asexual species and four known related sexual species. In a phylogenetic analysis including other ITS sequences from GenBank, the three asexual species were not closely related to any of the known sexual species. Isolates of opposite mating type but the same species had identical ITS sequences. During any period of asexual evolutionary history, lineages of each mating type would have had a separate evolutionary history and any ITS substitutions shared between isolates of opposite mating type would have had to accumulate by convergence. Allowing for varying substitution rates and assuming a Poisson distribution of substitutions, the probability that isolates of opposite mating type shared an ITS substitution through convergence was low. This suggests that isolates of opposite mating type of A. brassicae, A. brassicicola and A. tenuissima were exchanging substitutions through sexual or parasexual reproduction while the ITS was evolving. If sexuality was lost, it was lost after the period of evolutionary history represented by the shared substitutions.

Alternaria↗

PubMed1992

Genetic and environmental variation in reproductive and lactational performance of Jersey cattle in the coastal lowland semi-humid tropics.

Reproductive and lactational performances, including length of productive life, were evaluated from records for 1960 to 1988 for a Jersey herd in coastal lowland semi-humid Kenya. The herd grazed natural pastures and until the mid 1970s received supplementary feeding. Mean performance included 31 months age at first calving, lactation milk yield (MY) of 1,788 kg in 3.3 lactations and a calving interval (CI) of 408 days. Mean milk yields declined from over 2,200 kg in the 1960s to about 1,500 kg in the 1980s with concomitant changes in calving interval, length of productive life and infertility. While annual genetic components of change in MY and CI were not significantly different from zero, the environmental components were large and significant (P < 0.01) showing that the declines in performance probably resulted from decreased feed availability and less efficient disease control. Estimates of genetic parameters were consistent with those in the literature. With good management purebred Jersey cows in coastal lowland semi-humid Kenya were productive, but animal and herd productivity were highly dependent on management level which had a major effect on both milk yield and reproductive wastage.

Age Factors↗

PubMed2002

Outcrossing increases infection success and competitive ability: experimental evidence from a hermaphrodite parasite.

The maintenance of two genetically distinct reproductive modes such as outcrossing and selfing within a population of animals or plants is still a matter of considerable debate. Hermaphroditic parasites often reproduce either alone by selfing or in pairs by outcrossing. They can be used as a model to study potential benefits of outcrossing. Any advantage from outcrossing may be important, especially in host-parasite coevolution, but has not, to our knowledge, been studied yet in any parasite species. We studied the potential effect of outcrossing in a tapeworm, Schistocephalus solidus, on both infection success and growth in its first intermediate host, the copepod Macrocyclops albidus. Tapeworms that had been obtained from natural populations of three-spined sticklebacks (Gasterosteus aculeatus) were allowed to reproduce either alone or in pairs, in an in vitro system that replaced the final host's gut. This resulted in either selfed or outcrossed offspring, respectively. In one part of the experiment, copepods were exposed to either selfed or outcrossed parasites, in a second part to both types simultaneously, in order to study the effect of competition between them. To discriminate parasites of either origin within the same host, a novel method for fluorescent vital labeling was used. We show here for the first time that outcrossed parasites had a higher infection success and faster development in the host. This advantage of outcrossing became apparent only in the competitive situation, in which superior abilities of parasites to extract limiting resources from the host become crucial.

Animals↗

PubMed1999

Paraoxonase polymorphism and its effect on male reproductive outcomes among Chinese pesticide factory workers.

BACKGROUND: Serum paraoxonase has been associated with the metabolism of organophosphate pesticides in humans. Molecular analysis of the human paraoxonase gene (PON1) has revealed that Arg192 homozygotes have a greater detoxifying capability than Gln192 homozygotes. We examined the effects of PON1 genotypes on male reproductive outcomes and its interaction with exposure to organophosphate pesticides. METHODS: We studied 60 Chinese pesticide-factory workers and 89 textile-factory workers who were unexposed to pesticides. The respective allele frequencies of Arg192 and Gln192 were 0.62 and 0.38. Pesticide exposure among 36 exposed subjects and 12 unexposed subjects, regardless of gender, was assessed by personal measurement of pesticide residues over an entire 8-hr shift and measurement of urinary p-nitrophenol level over a 24-hr period. We analyzed semen and hormone data collected from male subjects. RESULTS: When the three PON1 genotypes were analyzed separately, a gene dose effect was not detected. We used the unexposed Arg192 homo/heterozygotes as the reference group, and re-analyzed the data. Exposed Arg192 homo/heterozygotes had significantly lower sperm count (chi 2 = 9.01, P < 0.01) and lower percentage of sperm with normal morphology (chi 2 = 4.18, P < 0.05) than the reference group. Both unexposed Gln192 homozygotes (chi 2 = 4.90, P < 0.05) and exposed Arg192 homo/heterozygotes (chi 2 = 10.00, P < 0.01) showed significantly lower sperm concentrations than the reference group. In addition, exposed Arg192 homo/heterozygotes had significantly higher serum LH levels (chi 2 = 7.94, P < 0.01) than the reference group. CONCLUSIONS: Because of a small sample size, our findings are highly preliminary. Nevertheless, it calls for further investigation of the interaction between the PON1 genotype and organophosphate pesticide exposure on male reproductive outcomes.

Adult↗

PubMed2003

Phenotype characteristics of transgenic male mice expressing human aromatase under ubiquitin C promoter.

To study the significance of the increased ratio of the estrogen/androgen concentration for the male reproductive functions, we have generated transgenic mice expressing human P450 aromatase under a promoter providing ubiquitous and permanent transgene expression (AROM+ mice). AROM+ male mice are characterized by elevated serum estradiol and prolactin (Prl) concentrations, combined with markedly reduced testosterone levels. The mice are present with a multitude of structural and functional alterations in the reproductive organs such as cryptorchidism, Leydig cell hyperplasia, disrupted spermatogenesis and infertility. Furthermore, the mice develop infravesical obstruction associated with the rhabdosphincter atrophy and rudimentary accessory sex glands. Interestingly, the mammary gland in AROM+ males undergo a ductal and alveolar development morphologically resembling terminally differentiated female mammary glands, and express several signaling proteins typical for female mammary glands. Some of the abnormalities seen in AROM+ mice are similar to those described in both mice and humans exposed to diethylstilbestrol (DES) in utero. The importance of the AROM+ model may lie in its predictability, i.e. the model suggests which abnormalities of the human reproductive functions may be associated with the increased ratio of estrogen/androgen concentrations in early life and at adult age as well.

Animals↗

PubMed2026

A Comprehensive Survey and Evaluation of Preimplantation Genetic Testing Practices in Canadian Assisted Reproductive Technology Clinics.

OBJECTIVES: In Canada, access to provincial funding for fertility treatments, such as in vitro fertilization (IVF) and preimplantation genetic testing (PGT), vary significantly. Despite rising demands, the lack of data on current practices across Canadian assisted reproductive technology (ART) clinics has contributed to the absence of standardized guidelines to support clinics offering these services. This pilot study surveys fertility clinics to examine current demands and practices related to PGT, while also exploring providers' perspectives on its implementation and future applications. METHODS: A 40-question survey was distributed to Canadian ART clinics offering IVF and PGT services. RESULTS: The responses confirm that there is a high demand for IVF and PGT services. Although clinical criteria for PGT for aneuploidy (PGT-A) were generally consistent across clinics, views on its effectiveness and eligibility for public funding varied. PGT for monogenic disorders (PGT-M) appears to be widely available, and respondents showed strong support for public funding in cases involving serious heritable conditions. CONCLUSIONS: This study outlines current practice and highlights variations across clinics, while also presenting the perspectives of providers of ART clinics throughout Canada. It also provides a degree of foresight as to the direction the PGT practice may take in the coming years.

assisted reproductive technology↗

PubMed2002

Overexpression of human stanniocalcin affects growth and reproduction in transgenic mice.

In mammals stanniocalcin (STC) is widely expressed, and in the kidney and gut it regulates serum calcium levels by promoting phosphate reabsorption. To shed further light on its functional significance in mammals we have created several lines of mice that express a human STC (hSTC) transgene. Three lines expressed the hSTC transgene, but only two lines exhibited high expression and contained circulating hSTC, and in these animals there was a reduction in postnatal growth (30-50%) that persisted after weaning. Moreover, even wild-type pups exhibited a growth retardation phenotype when nursed by a transgenic foster mother, and this implies that hSTC overexpression deleteriously affects maternal behavior and/or lactation. The reproductive potential of female transgenic mice was also compromised, as evidenced by significantly smaller litter sizes, but transgenic male fertility was unchanged even though the transgene was most highly expressed in testes. Interestingly, transgene-derived serum hSTC increased significantly after puberty and was severalfold higher in females than in males, suggesting a gender-specific mechanism for maintaining elevated circulating levels of STC. Blood analysis revealed that both transgenic lines had elevated phosphate and decreased alkaline phosphatase levels, indicative of altered kidney and bone metabolism. These studies provide the first evidence that STC is involved in growth and reproduction and reaffirm its role in mineral homeostasis.

Alkaline Phosphatase↗

PubMed2002

Reproductive health in individuals with homozygous beta-thalassemia: knowledge, attitudes, and behavior.

OBJECTIVE: To review the reproductive health knowledge, attitudes, and behaviors of persons with homozygous beta-thalassemia. DESIGN: Case-control study. SETTING: Patients treated at a tertiary hospital and community-based healthy controls. PARTICIPANT(S): One hundred and thirty persons, 16 years of age or older, who had homozygous beta-thalassemia and were attending hospital for regular blood transfusion, and 99 demographically matched persons without thalassemia. ASSESSMENT TOOL: Reproductive health questionnaire. RESULT(S): 104 (80%) persons with homozygous beta-thalassemia completed the questionnaire and were compared with 99 controls. Persons with homozygous beta-thalassemia were as likely as healthy peers to be in a relationship, employed full-time, sexually active, and using contraception and to have had children. Hypogonadotrophic hypogonadism was present in 55 (52.8%) patients, 46 (83.6%) of whom were compliant with hormone replacement therapy. Understanding of genetics and reproductive potential was suboptimal among persons with homozygous beta-thalassemia, and this group had a higher rate of unplanned pregnancy. CONCLUSION(S): This study suggests that with optimal therapy, most young adults with homozygous beta-thalassemia can achieve reproductive, sexual, and social experiences similar to those of their healthy peers.

Adolescent↗

PubMed2003

Ecological and morphological differentiation among cryptic evolutionary lineages in freshwater limpets of the nominal form-group Ancylus fluviatilis (O.F. Müller, 1774).

The phylogeny and potential mode of speciation of the river limpet Ancylus fluviatilis (Basommatophora) was examined using mitochondrial DNA sequences from 16S ribosomal RNA, cytochrome c oxidase subunit I (COI) and nuclear DNA from internal transcribed spacer (ITS-1) regions from 103 populations across Europe. Four highly divergent lineages were observed within Ancylus. Clade 1, representing the nominal taxon Ancylus fluviatilis (O.F. Müller, 1774), is mainly found in central and northern Europe, Clade 2 is present in a single Portuguese population, Clade 3 is distributed on the Canary islands, North Africa and the eastern Mediterranean region, whereas Clade 4 inhabits the Northern Mediterranean coasts. Phylogenetic analyses revealed an overall consistent topology of nuclear and mitochondrial gene trees. Based on a molecular clock, we estimated that the basic radiation occurred in the late Pliocene. Although clades differ significantly in size independent shell shape, morphological differentiation of lineages is not feasible without genetic data. Environmental data related to climate (precipitation, temperature, etc.) showed a significant differentiation of clades. Clade 1 dwells in relatively colder and more stable habitats than Clades 3 and 4, whose habitats in turn differ in a low or high amount of precipitation during spring and autumn, respectively. Based on the combined data sets on mitochondrial DNA, nuclear DNA, morphological and ecological differentiation, we conclude that Ancylus represents a cryptic species complex of reproductively and genetically isolated lineages. In addition, the joint analysis suggests that ecological speciation is probable to explain current patterns.

Analysis of Variance↗

PubMed2026

Shared genetic architecture and cellular convergence between female reproductive disorders and pulmonary function: a genome-wide cross-trait analysis.

Female reproductive disorders (FRDs), including polycystic ovary syndrome, endometriosis, uterine leiomyomata, and infertility, have been epidemiologically associated with impaired pulmonary function. However, it remains unclear whether this cross-organ link reflects shared genetic etiology and, if so, which cellular mechanisms mediate it. We performed a systematic genome-wide cross-trait analysis of three FRDs and lung function traits (FEV₁, FVC, FEV₁/FVC) using GWAS summary statistics from individuals of European ancestry, integrating genetic correlation, bidirectional causal inference, pleiotropy mapping, and single-cell enrichment analyses. We identified significant negative genetic correlations between FRDs and lung volume traits, most prominently for FVC (rg range: - 0.077 to - 0.178). Bidirectional causal analyses indicated that FRDs have a detrimental effect on lung volume, with higher FRD genetic liability associated with reduced lung volume. Cross-trait meta-analysis identified 17 pleiotropic variants across 11 loci, with the 19q13.2 (LTBP4) and 12q13.13 (HOXC6/HOXC9) loci showing strong evidence of shared causal variants. Critically, single-cell analyses revealed that shared genetic risk converged on mesenchymal lineages across organs, specifically alveolar adventitial fibroblasts in the lung and stromal/smooth muscle cells in the endometrium. Transcriptome-wide analyses further nominated the estrogen-responsive gene RERG as a convergent gene linking these conditions with lung function. Our study revealed a shared genetic architecture between female reproductive disorders and lung function traits, providing a basis for further mechanistic investigations and potential clinical evaluation. Furthermore, our findings suggest that shared fibroproliferative and hormone-responsive pathways may offer insights into the biological mechanisms underlying these conditions.

Female↗

PubMed1996

Genomic individuality and its biological implications.

It is a widely accepted fundamental concept that all somatic genomes of a human individual are identical to each other. The theoretical basis of this concept is that all of these somatic genomes are the descendants of the genome of a single fertilized cell as well as the simple replicated products of asexual reproduction, thus not forming any new recombined genomes. The question here is whether such a concept might only represent one side of somatic genome biology and, even worse, whether it has perhaps already led to a very prevalent misconception that within the organism body, there exists no variability among individual somatic genomes. A hypothesis, called genomic individuality, is proposed, simply saying that every individual somatic genome, perhaps with rare exceptions, has its own unique or individual 'genetic identity' or 'fingerprint', which is characterized by its distinctive sequences or patterns of deoxyribonucleic acid molecules, or both. Thus, no two somatic genomes can be identical to each other in every or all aspects, and consequently, there must be a great deal of genomic variation present within the body of any multicellular organism. The concept or hypothesis of genomic individuality would not only provide a more complete understanding of genome biology, but also suggest a new insight into the studies of the biology of cells and organisms.

Adult↗