Hybrid Embryos Research Articles

Embryonic development and inviability phenotype of chicken-Japanese quail F1 hybrids.

Interspecific hybrid incompatibility, including inviability and sterility, is important in speciation; however, its genetic basis remains largely unknown in vertebrates. Crosses between male chickens and female Japanese quails using artificial insemination can generate intergeneric hybrids; however, the hatching rate is low, and hatched hybrids are only sterile males. Hybrid development is arrested frequently during the early embryonic stages, and the sex ratio of living embryos is male-biased. However, the development and sex ratio of hybrid embryos have not been comprehensively analyzed. In the present study, we observed delayed embryonic development of chicken-quail hybrids during the early stage, compared with that of chickens and quails. The survival rate of hybrids decreased markedly during the blastoderm-to-pre-circulation stage and then decreased gradually through the subsequent stages. Hybrid females were observed at more than 10 d of incubation; however, the sex ratio of hybrids became male-biased from 10 d of incubation. Severely malformed embryos were observed frequently in hybrids. These results suggest that developmental arrest occurs at various stages in hybrid embryos, including a sexually non-biased arrest during the early stage and a female-biased arrest during the late stage. We discuss the genetic basis for hybrid inviability and its sex bias.

Early embryo and larval development of inviable intergeneric hybrids derived from Crassostrea angulata and Saccostrea cucullata

To detect the intergeneric hybridization between the oyster Crassostrea angulata and Saccostrea cucullata coexisting along the southern coast of China, reciprocal crosses were conducted between the two species. Barriers for sperm recognizing, binding, penetrating the egg, and forming the pronucleus were detected by fluorescence staining. From the results, although fertilization success was observed in hybrid crosses, the overall fertilization rate was lower than that of intraspecific crosses. A large number of hybrid larvae died at 6–8 d after hatching, and those survived could not complete metamorphosis. C. angulata ♀× S. cucullata ♂ larvae had a growth rate similar to that of the maternal species, whereas S. cucullata ♀ × C. angulata ♂ larvae grew the slowest among all crosses. Molecular genetics analysis revealed that hybrid progeny were amphimixis hybrids. This study demonstrated that hybrid embryos generated by crossing C. angulata and S. cucullata could develop normally to the larval state, but could not complete metamorphosis and then develop to the spat stage. Thus, there is a post-reproductive isolation between C. angulata and S. cucullata.

Diploid-tetraploid crosses as the instrument for obtaining apomictic maize plants

In this paper, the opportunity to reveal pseudogamous apomixis in maize inbred lines when tetraploids are used as pollinators is demonstrated for the first time. Kernels with hybrid endosperm, from which plants of maternal type developed, were obtained in five of ten studied lines. Hybrid nature of these kernels was proven using SDS electrophoresis of endosperm proteins. In addition to apomictic kernels, the normally developed kernels with di-, three- and tetraploid hybrid embryos were obtained.

Up-regulating the abscisic acid inactivation gene ZmABA8ox1b contributes to seed germination heterosis by promoting cell expansion.

Heterosis has been widely used in agriculture, but the underlying molecular principles are still largely unknown. During seed germination, we observed that maize (Zea mays) hybrid B73/Mo17 was less sensitive than its parental inbred lines to exogenous abscisic acid (ABA), and endogenous ABA content in hybrid embryos decreased more rapidly than in the parental inbred lines. ZmABA8ox1b, an ABA inactivation gene, was consistently more highly up-regulated in hybrid B73/Mo17 than in its parental inbred lines at early stages of seed germination. Moreover, ectopic expression of ZmABA8ox1b obviously promoted seed germination in Arabidopsis Remarkably, microscopic observation revealed that cell expansion played a major role in the ABA-mediated maize seed germination heterosis, which could be attributed to the altered expression of cell wall-related genes.

Development of monosomic alien addition lines from the wild rice (Oryza brachyantha A. Chev. et Roehr.) for introgression of yellow stem borer (Scirpophaga incertulas Walker.) resistance into cultivated rice (Oryza sativa L.)

Oryza brachyantha, the African wild rice which is resistant to yellow stem borer (YSB), was exploited as a source for introgression of YSB resistance trait into cultivated rice (O. sativa), through development of monosomic alien addition lines (MAALs). BC2F1 backcross hybrids (O. sativa cv Savitri/O. brachyantha//O. sativa cv Savitri///O. sativa cv Savitri) were produced employing embryo rescue, with a crossability of 0.12 %. Hybrid embryos that were collected at 10 and 12 days after pollination showed highest percentage of survival in culture with a germination percentage of 35.8 %. Cytological analysis of pollen mother cells (PMCs) of the BC2F1 hybrids revealed 15 hybrids with 2n + 1(2n = 25) chromosome number that exhibited typical trisomic chromosomal configurations. These aneuploids were putatively designated as MAALs and characterized morphologically and cytologically. Based on their morphological similarity to primary trisomics of the cultivated rice (O. sativa), 8 MAALs viz., MAALs-4 (Sterile), 5 (Twisted leaf), 7 (Narrow leaf), 8 (Rolled leaf), 9 (Stout), 10 (Short grain), 11 (Pseudonormal) and 12 (Tall) were isolated, each of which exhibited several distinct morphological features. Among the 505 PMCs analysed, 79.80 % had 12II, 5.45 % had 11II and 1.78 % PMCs had 1III configurations. The size of the extra chromosome was found to be smaller than those of O. sativa chromosomes and in 97.25 % of PMCs it remained unpaired and at a distance from the rest of the chromosomes. Of the 8 MAALs screened for YSB resistance, MAAL 11 was found to be moderately resistant. Undesirable morphological traits of O. brachyantha were found to be eliminated in the MAALs.

Embryo development and corresponding factors affecting in vitro germination of Cymbidium faberi × C. sinense hybrid seeds

A better understanding of embryo development would provide insights into seed quality and subsequent germination events in the interspecific hybridization of Cymbidium faberi ?Jiepeimei? ? C. sinense ?Qijianheimo?. At the mature stage, 26.1% of the ovules were abnormal. Most of the hybrid embryos could develop normally. Abortions mainly occurred at the zygote (9.5%) and 2-4-celled embryo (15.1%) stages. No germination was observed at 90 and 105 days after pollination (DAP), when the embryo was at the early globular stage, with abundant organelles but no storage materials. During 110-130 DAP, the globular embryo was formed and the starch grains began to accumulate in plastids. The hybrid seeds collected at 120 DAP showed initiation of germination. Germination significantly increased at 135 DAP and was maximal at 150 DAP, during which period the hybrid embryos developed into the late globular stage. The storage materials, i.e. lipid and protein bodies, began to accumulate and the filamentary structures derived from suspensor cells still persisted. After the seeds matured (160 DAP), the germination percentage declined sharply. Safranin staining revealed that the outer seed coat was totally cuticularized and the inner seed coat appeared as a cuticle layer enclosing the embryo proper tightly, which may be the main factor inhibiting the subsequent germination of hybrid seeds. In conclusion, 150 DAP should be the opportune time for the in vitro germination of C. faberi ?Jiepeimei? ? C. sinense ?Qijianheimo? hybrid seeds.

Spermatozoa telomeres determine telomere length in early embryos and offspring.

Offspring telomere length (TL) has been correlated with paternal TL, but the mechanism for this parent of origin-specific inheritance remains unclear. The objective of this study has been to determine the role of spermatozoa TL in embryonic telomere lengthening by using two mouse models showing dimorphism in their spermatozoa TL: Mus musculus vs Mus spretus and old vs young Mus musculus. Mus spretus spermatozoa displayed a shorter TL than Mus musculus. Hybrid offspring exhibited lower TL compared with Mus musculus starting at the two-cell stage, before the onset of telomerase expression. To analyze the role of spermatozoa telomeres in early telomere lengthening, we compared the TL in oocytes, zygotes, two-cell embryos and blastocysts produced by parthenogenesis or by fertilization with Mus musculus or Mus spretus spermatozoa. TL was significantly higher in spermatozoa compared with oocytes, and it increased significantly from the oocyte to the zygote stage in those embryos fertilized with Mus musculus spermatozoa, but not in those fertilized with Mus spretus spermatozoa or produced by parthenogenesis. A further increase was noted from the zygote to the two-cell stage in fertilized Mus musculus embryos, whereas hybrid embryos maintained the oocyte TL. Spermatozoa TL shortened with age in Mus musculus and the offspring from young males showed a significantly higher TL compared with that fathered by old males. These significant differences were already noticeable at the two-cell stage. These results suggest that spermatozoa telomeres act as a guide for telomerase-independent telomere lengthening resulting in differences in TL that persist after birth.

INTERSPECIFIC HYBRIDIZATION BETWEEN ACTINIDIA ARGUTA AND A. DELICIOSA AND EMBRYO CULTURE IN VITRO OF ITS F1 HYBRIDS

Interspecific hybidization was achieved beween Actinidia argute (4x) females and A. deliciosa (6x) males, and hybrid embryos were cultured on a solidified Murashige and Skoog (MS) basal medium, supplemented with 16 different combinations of 3-indoleacetic acid (IAA), 6-benzylaminopurine (BAP) and gibberellins (GA). Best results were obtained when the F1 embryos were cultured with supplementation with 1-naphthaleneacetic acid NAA (0.3 mg L-1), BAP (2 mg L-1) and GA (0.2 mg L-1). When the plantlets were cultured in medium with BAP (4 mg L-1) and NAA (0.01 mg L-1) significant improvement in proliferation was achieved within one month. Plantlets were rooted on 1/2 MS medium in combination with different concentrations of indole-3-butyric acid (IBA) or NAA, and high rooting and survival was achieved using 1/2 MS media with NAA (0.2 mg L-1). This study offered a new path for Actinidia breeding.

Competitive Expression of Endogenous Wheat CENH3 May Lead to Suppression of Alien ZmCENH3 in Transgenic Wheat × Maize Hybrids

Uniparental chromosome elimination in wheat × maize hybrid embryos is widely used in double haploid production of wheat. Several explanations have been proposed for this phenomenon, one of which is that the lack of cross-species CENH3 incorporation may act as a barrier to interspecies hybridization. However, it is unknown if this mechanism applies universally. To study the role of CENH3 in maize chromosome elimination of wheat × maize hybrid embryos, maize ZmCENH3 and wheat αTaCENH3-B driven by the constitutive CaMV35S promoter were transformed into wheat variety Yangmai 158. Five transgenic lines for ZmCENH3 and six transgenic lines for αTaCENH3-B were identified. RT-PCR analysis showed that the transgene could be transcribed at a low level in all ZmCENH3 transgenic lines, whereas transcription of endogenous wheat CENH3 was significantly up-regulated. Interestingly, the expression levels of both wheat CENH3 and ZmCENH3 in the ZmCENH3 transgenic wheat × maize hybrid embryos were higher than those in the non-transformed Yangmai 158 × maize hybrid embryos. This indicates that the alien ZmCENH3 in wheat may induce competitive expression of endogenous wheat CENH3, leading to suppression of ZmCENH3 over-expression. Eliminations of maize chromosomes in hybrid embryos of ZmCENH3 transgenic wheat × maize and Yangmai 158 × maize were compared by observations on micronuclei presence, by marker analysis using maize SSRs (simple sequence repeats), and by FISH (fluorescence in situ hybridization) using 45S rDNA as a probe. The results indicate that maize chromosome elimination events in the two crosses are not significantly different. Fusion protein ZmCENH3-YFP could not be detected in ZmCENH3 transgenic wheat by either Western blotting or immnunostaining, whereas accumulation and loading of the αTaCENH3-B-GFP fusion protein was normal in αTaCENH3-B transgenic lines. As ZmCENH3-YFP did not accumulate after AM114 treatment, we speculate that low levels of ZmCENH3 protein in transgenic wheat may be one of the factors that lead to failure of suppression of maize chromatin elimination in ZmCENH3 transgenic wheat × maize hybrids.

Preferential recruitment of the maternal centromere-specific histone H3 (CENH3) in oat (Avena sativa L.) × pearl millet (Pennisetum glaucum L.) hybrid embryos.

Chromosome elimination occurs frequently in interspecific hybrids between distantly related species in Poaceae. However, chromosomes from both parents behave stably in a hybrid of female oat (Avena sativa L.) pollinated by pearl millet (Pennisetum glaucum L.). To analyze the chromosome behavior in this hybrid, we cloned the centromere-specific histone H3 (CENH3) genes of oat and pearl millet and produced a pearl millet-specific anti-CENH3 antibody. Application of this antibody together with a grass species common anti-CENH3 antibody revealed the dynamic CENH3 composition of the hybrid cells before and after fertilization. Despite co-expression of CENH3 genes encoded by oat and pearl millet, only an oat-type CENH3 was incorporated into the centromeres of both species in the hybrid embryo. Oat CENH3 enables a functional centromere in pearl millet chromosomes in an oat genetic background. Comparison of CENH3 genes among Poaceae species that show chromosome elimination in interspecific hybrids revealed that the loop 1 regions of oat and pearl millet CENH3 exhibit exceptionally high similarity.

Heterologous murine and bovine IVF using bottlenose dolphin (Tursiops truncatus) spermatozoa

Assisted reproductive technologies are of great importance for increasing the genetic diversity in captive animals. The use of bovine or murine oocytes in heterologous IVF provides advantages compared to homologous IVF in nondomestic animals, such as the accessibility to oocytes and the availability of well-developed in vitro maturation systems. The aim of this study was to determine the heterologous IVF parameters using cryopreserved dolphin spermatozoa and zona-intact bovine or murine oocytes and to examine the nuclear chromatin status of the dolphin spermatozoa. All the processes involved in the fertilization including embryo cleavage were observed by confocal microscopy and hybrid embryo formation was confirmed by polymerase chain reaction. Heterologous bovine IVF showed no polyspermy, lower percentages of pronuclear formation, and a lower cleavage rate compared to homologous IVF group (34.8% vs. 89.3%). Heterologous murine IVF showed a lower cleavage rate than homologous IVF (9.6% vs. 77.1%). With respect to dolphin sperm chromatin, it was more stable, i.e. more resistant to EDTA-SDS decondensation than the bovine sperm chromatin. This study revealed the stability of the dolphin sperm chromatin and the ability of the dolphin spermatozoa to penetrate zona-intact bovine and murine oocytes, leading to hybrid embryo formation.

A New Synthetic Amphiploid (AADDAA) between Gossypium hirsutum and G. arboreum Lays the Foundation for Transferring Resistances to Verticillium and Drought.

Gossypium arboreum, a cultivated cotton species (2n = 26, AA) native to Asia, possesses invaluable characteristics unavailable in the tetraploid cultivated cotton gene pool, such as resistance to pests and diseases and tolerance to abiotic stresses. However, it is quite difficult to transfer favorable traits into Upland cotton through conventional methods due to the cross-incompatibility of G. hirsutum (2n = 52, AADD) and G. arboreum. Here, we improved an embryo rescue technique to overcome the cross-incompatibility between these two parents for transferring favorable genes from G. arboreum into G. hirsutum. Our results indicate that MSB2K supplemented with 0.5 mgl-1 kinetin and 250 mg-1 casein hydrolysate is an efficient initial medium for rescuing early (3 d after pollination) hybrid embryos. Eight putative hybrids were successfully obtained, which were further verified and characterized by cytology, molecular markers and morphological analysis. The putative hybrids were subsequently treated with different concentrations of colchicine solution to double their chromosomes. The results demonstrate that four putative hybrid plants were successfully chromosome-doubled by treatment with 0.1% colchicine for 24 h and become amphiploid, which were confirmed by cytological observation, self-fertilization and backcrossing. Preliminary assessments of resistance at seedling stage indicate that the synthetic amphiploid showed highly resistant to Verticillium and drought. The synthetic amphiploid between G. hirsutum × G. arboreum would lay the foundation for developing G. arboreum-introgressed lines with the uniform genetic background of G. hirsutum acc TM-1, which would greatly enhance and simplify the mining, isolation, characterization, cloning and use of G. arboreum-specific desirable genes in future cotton breeding programs.

Hybridization Processes in Putative Hybrid Swarms of Scots Pine and Mountain Dwarf Pine as Revealed by Chloroplast DNA

Abstract Gene flow among individual trees of Pinus sylvestris and P. mugo putative hybrid swarms in Slovakia was fol-lowed at four localities using the species-diagnostic cpDNA trnV-trnH/Hinf I restriction profile. Variable proportions of P. sylvestris and P. mugo haplotypes were revealed among the sampled localities. Low between-habitus consistency of the trees and their cpDNA haplotypes indicates the hybrid nature of the swarms. Molecular analy-sis based on mutual comparison of the haplotypes of a given tree and its embryos suggests direct and recipro-cal hybridization between trees of the P. sylvestris and P. mugo haplotypes. Besides conspecific embryos resulting from hybridization of trees with the same haplotype (P. sylvestris × P. sylvestris and P. mugo × P. mugo), hybrid embryos of P. sylvestris × P. mugo (8.03%) and P. mugo × P. sylvestris (11.50%) were also detected in open-pollinated offspring. The results are discussed from the standpoint of primary and introgressive hybridization between the parental species.

Effective accumulated temperature is associated with the efficiency of hybrid ovary culture between Brassica napus and B. oleracea

Ovary culture has been widely used to overcome the fertilization barrier of interspecific hybridizations. In order to understand the relation between ovary culture and the growth temperature of hybrid siliques, three sets of interspecific hybridization were carried out in the field. Hybrid siliques in each set of hybridizations were excised at 10, 15, and 20 days after pollination and temperature from pollination to excision was recorded. No significant correlation was found between hybrid embryo yield in ovary culture and the average temperature. However, a significant quadratic correlation between the efficiency of ovary culture and the effective accumulated temperature (EAT) was observed. It indicated a rise-and-fall relation between the optimal excision time and the growth temperature of hybrid siliques. Our data suggested that EAT is a more reliable indicator than silique age to determine the optimal time for excising hybrid B. napus × B. oleracea siliques for ovary culture.

Interspecific hybridization between Brassica napus and Brassica rapa ssp. chinensis genotypes through embryo rescue and their evaluation for crossability

The genus Brassica contains several important crop species that are used for a variety of purposes. Brassica napus and Brassica rapa are the most important ones for their use as oilseed crops. In Brassica , interspecific hybridization is a potential and useful method for transferring valuable traits between species of commercial interest. For breeding Brassicas resistant to some diseases, i.e. clubroot, attempts of transferring resistant genes (CR) through interspecific hybridization have also been reported. The main step in the introgression process is the production of interspecific hybrids between the two species. However, the cross-incompatibility occurring in wide hybridization might hamper the possibility of obtaining hybrid progenies. For that reason, the crossability study is essential and may give an insight into the cross-compatibility relationship among the species, the direction of success of crossing, and the crossability barriers of some combinations, if any. In the present study, interspecific reciprocal crosses between B. napus and B. rapa ssp. chinensis genotypes were carried out in order to determine their crossability and to produce their F1 hybrids. Crossability was analyzed based on the pollen germination index (PGI) and the development of hybrid embryos in in vitro cultures. It was observed that the unilateral interspecific incompatibility occurred in crosses between B. napus × B. rapa ssp. chinensis. When B. napus cultivars were used as a maternal parent, pollen grains of B. rapa germinated well on the stigmas, while only a small number of pollen tubes could elongate near the ovules, resulting in a low development of hybrid embryos. Using the B. rapa ssp. chinensis as the pistillate parent in the crosses, it was found that the crossability was relatively higher than that in the case of the reciprocal cross. This resulted in a greater number of embryos obtained. Generally, it was concluded that the selection of parental components for hybridization is an important step for obtaining breeding success.

258 THE PRELIMINARY RESULTS OF IN VITRO PRODUCTION OF THE WISENT HYBRID EMBRYOS

Wisent (Bison bonasus), also called the European bison, is listed as vulnerable on the International Union for the Conservation of Nature Red List of Threatened Species. In Poland, a program for protection in situ and ex situ is being implemented. One new approach is the use of the in vitro embryo production (IVP) procedures to obtain wisent offspring. In contrast to previous successes with cattle IVP, use of IVP with wisent is limited by the small size of the population (only ~5000 individuals in more than 200 herds in Europe) and seasonal reproduction. The aim of this preliminary study was to obtain hybrid embryos (Bison bonasus × Bos taurus) in vitro. Ovaries were isolated from wisent females outside the reproductive season and eliminated from breeding for reasons other than infertility. Cumulus-oocytes complexes (COC) were isolated from all follicles above 2 mm in diameter. All COC were matured in TCM 199 supplemented with 10% fetal bovine serum, 0.02 IU mL–1 of porcine FSH, 17 β-oestradiol, 0.2 mM Na pyruvate, and antibiotics. The COC were cultured for 24 h at 38.5°C and 5% CO2 in humidified air. The matured COC (Bison bonasus) were fertilized in vitro with sperm from Jersey bulls (Bos taurus) in TALP supplemented with 6 mg mL–1 of fatty acid free BSA (BSA FAF), 0.2 mM Na pyruvate, 20 µM penicillamine,10 µM hypotaurine, 1 µM epinephrine, 2 µg mL–1 heparin, and antibiotics. Spermatozoa were used at a final concentration of 1 × 105 per oocyte and were co-cultured for 18 h at 38.5°C and 5% CO2 in humidified air. The hybrid zygotes were cultured in KSOM supplemented with 5 µg mL–1 of MEM Nonessential Amino Acid Solution (100×), 3 mg mL–1 of BSA FAF, and antibiotic for 192 h at 38.5°C and 5% CO2 in humidified air. The medium was partly replaced by fresh medium after 48 and 144 h of culture. Development was evaluated every day. From 25 COC isolated from wisent ovaries, only 18 COC were qualified for in vitro maturation (60%). Of these, 15 COC (83.3%) matured. The percentage of hybrid embryos that cleaved was 80% after 48 h of culture, and the percentage of embryos that developed up to the 8-cell stage was 33% after 96 h of culture. The morula/blastocyst rate was 26.6% after 192 h of culture, as represented by 1 early blastocyst, 2 compact morulae, and 1 morula. The use of the cattle IVP procedure allowed to receive hybrid embryos (Bison bonasus × Bos taurus), but they developed slower than cattle embryos under the same conditions, based on our previous studies. This research will be continued and may make a contribution to the protection of this threatened species.

Reproductive barriers in interspecific hybridizations among Chimonanthus praecox (L.) Link, C. salicifolius S. Y. Hu, and C. nitens Oliver from pollen–pistil interaction and hybrid embryo development

To investigate interspecific cross-compatibility among Chimonanthus praecox (L.) Link, C. salicifolius S. Y. Hu, and C. nitens Oliver, pollen–pistil interaction by fluorescence microscopy and hybrid embryo development by whole mount clearing technique were observed. The results indicated that for all reciprocal crosses among the three species, pollen grains of the male parents could adhere to and germinate in the stigmas of female parents. For any cross combination, pollen tube growth could reach the embryo sac, and double fertilization could be completed. These findings indicated that no obvious barriers to interspecific hybridization existed at the stages of pollen germination and pollen tube elongation until double fertilization. Although certain proportion (29.6% at 9d and 36.3% at 15d after pollination) of abortions (e.g., non-fertilization and retarded or non-existent endosperm development) in normally pollinated embryos of C. praecox at different stages were also observed, a greatly increased proportion (66.1% at 8d and 76.7% at 15d after pollination in C. praecox×C. nitens, and 60.0% at 8d and 75.0% at 15d after pollination in C. praecox×C. salicifolius) of hybrid embryos did not complete double fertilization or completed double fertilization but underwent abortion due to the retardation of endosperm development. Comparing to normally pollinated embryos of C. praecox, the retardation of endosperm development in hybridizations occurred earlier. Moreover, the occurrence of abortions among different cross combinations was basically consistent. Thus, the retardation of the endosperm development of hybrid embryos after double fertilization (after the globular embryo stage) is an important factor leading to the failure of distant hybridization between Chimonanthus species.

Allele-specific genome editing and correction of disease-associated phenotypes in rats using the CRISPR-Cas platform.

The bacterial CRISPR/Cas system has proven to be an efficient gene-targeting tool in various organisms. Here we employ CRISPR/Cas for accurate and efficient genome editing in rats. The synthetic chimeric guide RNAs (gRNAs) discriminate a single-nucleotide polymorphism (SNP) difference in rat embryonic fibroblasts, allowing allele-specific genome editing of the dominant phenotype in (F344 × DA)F1 hybrid embryos. Interestingly, the targeted allele, initially assessed by the allele-specific gRNA, is repaired by an interallelic gene conversion between homologous chromosomes. Using single-stranded oligodeoxynucleotides, we recover three recessive phenotypes: the albino phenotype by SNP exchange; the non-agouti phenotype by integration of a 19-bp DNA fragment; and the hooded phenotype by eliminating a 7,098-bp insertional DNA fragment, evolutionary-derived from an endogenous retrovirus. Successful in vivo application of the CRISPR/Cas system confirms its importance as a genetic engineering tool for creating animal models of human diseases and its potential use in gene therapy.

Paternal RNA contributions in the Caenorhabditis elegans zygote.

Development of the early embryo is thought to be mainly driven by maternal gene products and post-transcriptional gene regulation. Here, we used metabolic labeling to show that RNA can be transferred by sperm into the oocyte upon fertilization. To identify genes with paternal expression in the embryo, we performed crosses of males and females from divergent Caenorhabditis elegans strains. RNA sequencing of mRNAs and small RNAs in the 1-cell hybrid embryo revealed that about one hundred sixty paternal mRNAs are reproducibly expressed in the embryo and that about half of all assayed endogenous siRNAs and piRNAs are also of paternal origin. Together, our results suggest an unexplored paternal contribution to early development.

Devolved Regulation as a Two-Stage Rocket to Public Acceptance of Experiments with Human Gametes and Embryos

Kazancigil endorses governance to the extent that it has a greater capacity to cope with policy making on complex issues in our differentiated societies. At the same time, he is skeptical of how governance excludes ‘politics’ from the process of policy-making. Policy fields that are highly dependent on scientific knowledge are considered by him to be especially vulnerable for ‘policy making without politics’. In this article, the case of UK policy making concerning the creation of human animal hybrid embryos will be analyzed to provide insights into the problems that can be connected to governance as form of managing public decision making. In this case, it is not so much the exclusion of ‘politics’ in the sense of ‘the representative democratic institutions and processes’ that appears to be the problem of governance but rather the downplaying of differences in societal views concerning the issue and the lack of real reconciliation of such views.