Abstract P303: Development Of Casper/myl7/annexin-5 Transparent Transgenic In-vivo Zebrafish Model To Study The Cardiomyocyte Function

The Zebrafish provided an excellent platform to study the genetic and molecular approach ofcardiac research. Zebrafish heart cells similar to human heart cells at the molecular level anddetermine gene functions that control cardiac function and dysfunction. In zebrafish heart, myl7is myosin 7 gene and identified as a regulatory gene orthologs to human MYL7. In the heart,Annexin5 activities contribute to cardiomyocyte dedifferentiation, proliferation and epicardial injuryresponses which leads to cardiac cell death by apoptosis and narcosis pathways. We aredeveloping annexin-5 activity in the cardiovascular function under normal and in metabolicaberration by generating homozygous Casper/ myl7:RFP; annexin-5:YFP transgenic zebrafish.By developing Casper/myl7/Annexin-5 transparent transgenic zebrafish model, we establish time-lapse in-vivo confocal microscopy to study of cellular phenotype/pathologies of thecardiomyocytes over time in newly developed strain to quantify changes in cardiomyocytemorphology and function overtime, comparing control and cardiac injury and cardio-oncologymodels. Transgenic zebrafish has normal type skin pigmentation background. In zebrafish,tracking of transgenic reporter activity in in-vivo is only possible in transparent stage. To maintaintransparency throughout the life, these strains crossbred with the skin transparent mutant Casper.Casper contributes to the study by integrating a transparent characteristic in adult zebrafish thatallows for simpler transparent visualization and observation. We develop casper transgenicprogenies through cross breeding with the transgenic strain of myl7:RFP;annexin-5:YFP .Confocal and fluorescent microscopy used to get accurate, precise imaging and to determinefluorescent protein being activated. 1.1: Generation of homozygous casper / myl7:RFP;annexin-5:YFP zebrafish (Generation F01-F05). 1.2: Screening and sorting the transgenic progeny andIn vivo imaging to validate cardiac morphology through in-vivo confocal imaging. Generation ofhomozygous casper / myl7:RFP;annexin-5:YFP zebrafish: Casper-Annexin5 homozygous stain:Cross breed casper and myl7/Annexin5 fish; F01: Generate the eggs from breeder and grow theembryo to attenuate larvae to screen for transgenic expression. F01 generation, larvae showtransgenic expression (47%). F02: transgenic expression larvae (39%). F02 heterozygous shownormal skin pattern; F03, larval show transgenic expression (43%). F04, transgenic larvae(90%).F04; 100% fishes are phenotypically casper; F05: heterozygous transgenic progeny togrow and continue to generate until achieve 100% homozygous casper-myl7-Annexin5 strain.These novel results provide in-vivo whole organism-based platform to design high throughputscreening and establish new horizon for drug discovery in the Cardiac Disease and Cardio-oncology.

DNA Methylation Silences Exogenous Gene Expression in Transgenic Birch Progeny

The genetic stability of exogenous genes in the progeny of transgenic trees is extremely important in forest breeding; however, it remains largely unclear. We selected transgenic birch (Betula platyphylla) and its hybrid F1 progeny to investigate the expression stability and silencing mechanism of exogenous genes. We found that the exogenous genes of transgenic birch could be transmitted to their offspring through sexual reproduction. The exogenous genes were segregated during genetic transmission. The hybrid progeny of transgenic birch WT1×TP22 (184) and WT1×TP23 (212) showed higher Bgt expression and greater insect resistance than their parents. However, the hybrid progeny of transgenic birch TP23×TP49 (196) showed much lower Bgt expression, which was only 13.5% of the expression in its parents. To elucidate the mechanism underlying the variation in gene expression between the parents and progeny, we analyzed the methylation rates of Bgt in its promoter and coding regions. The hybrid progeny with normally expressed exogenous genes showed much lower methylation rates (0–29%) than the hybrid progeny with silenced exogenous genes (32.35–45.95%). These results suggest that transgene silencing in the progeny is mainly due to DNA methylation at cytosine residues. We further demonstrated that methylation in the promoter region, rather than in the coding region, leads to gene silencing. We also investigated the relative expression levels of three methyltransferase genes: BpCMT, BpDRM, and BpMET. The transgenic birch line 196 with a silenced Gus gene showed, respectively, 2.54, 9.92, and 4.54 times higher expression levels of BpCMT, BpDRM, and BpMET than its parents. These trends are consistent with and corroborate the high methylation levels of exogenous genes in the transgenic birch line 196. Therefore, our study suggests that DNA methylation in the promoter region leads to silencing of exogenous genes in transgenic progeny of birch.

Homozygous Transgenic Barley (Hordeum vulgare L.) Plants by Anther Culture

Production of homozygous lines derived from transgenic plants is one of the important steps for phenotyping and genotyping transgenic progeny. The selection of homozygous plants is a tedious process that can be significantly shortened by androgenesis, cultivation of anthers, or isolated microspores. Doubled haploid (DH) production achieves complete homozygosity in one generation. We obtained transgenic homozygous DH lines from six different transgenic events by using anther culture. Anthers were isolated from T0 transgenic primary regenerants and cultivated in vitro. The ploidy level was determined in green regenerants. At least half of the 2n green plants were transgenic, and their progeny were shown to carry the transgene. The process of dihaploidization did not affect the expression of the transgene. Embryo cultures were used to reduce the time to seed of the next generation. The application of these methods enables rapid evaluation of transgenic lines for gene function studies and trait evaluation.

Aseptic Rearing and Infection with Gut Bacteria Improve the Fitness of Transgenic Diamondback Moth, Plutella xylostella

Mass insect rearing can have a range of applications, for example in biological control of pests. The competitive fitness of released insects is extremely important in a number of applications. Here, we investigated how to improve the fitness of a transgenic diamondback moth, which has shown variation in mating ability when reared in different insectaries. Specifically we tested whether infection with a gut bacteria, Enterobacter cloacae, and aseptic rearing of larvae could improve insect growth and male performance. All larvae were readily infected with E. cloacae. Under aseptic rearing, pupal weights were reduced and there was a marginal reduction in larval survival. However, aseptic rearing substantially improved the fitness of transgenic males. In addition, under aseptic rearing, inoculation with E. cloacae increased pupal weights and male fitness, increasing the proportion of transgenic progeny from 20% to 30% relative to uninfected insects. Aseptic conditions may improve the fitness of transgenic males by excluding microbial contaminants, while symbiont inoculation could further improve fitness by providing additional protection against infection, or by normalizing insect physiology. The simple innovation of incorporating antibiotic into diet, and inoculating insects with symbiotic bacteria that are resistant to that antibiotic, could provide a readily transferable tool for other insect rearing systems.

Gnotobiotic Rearing and Controlled Infection with Gut Symbionts Improve Adult Fitness in Transgenic Diamondback Moth, Plutella xylostella

Mass insect rearing can have a range of applications, for example in biological control of insects. Since the performance of released biological control agents determines efficacy, the competitive fitness of insects post release is a key variable. Here, we tested whether inoculation with a gut symbiont, Enterobacter cloacae, and gnotobiotic rearing of larvae could improve insect growth and male competitive fitness of a transgenic diamondback moth, which has shown variation in fitness when reared in different insectaries. All larvae were readily infected with the focal symbiont. Under gnotobiotic rearing pupal weights were reduced and there was a marginal reduction in larval survival. However, gnotobiotic rearing substantially improved the fitness of transgenic males. In addition, in gnotobiotic conditions, inoculation with the gut symbiont increased pupal weights and male fitness, increasing the proportion of transgenic progeny from 20 to 30% relative to symbiont-free insects. Gnotobiotic conditions may improve the fitness of transgenic males by excluding microbial contaminants, while symbiont inoculation could further improve fitness by providing additional protection against infections, or by normalizing insect physiology. The simple innovation of incorporating antibiotic into diet, and inoculating insects with symbiotic bacteria that are resistant to that antibiotic, could provide a readily transferable tool for other insect rearing systems.

Different genetic mechanisms mediate spontaneous versus UVR-induced malignant melanoma

Genetic variation conferring resistance and susceptibility to carcinogen-induced tumorigenesis is frequently studied in mice. We have now turned this idea to melanoma using the collaborative cross (CC), a resource of mouse strains designed to discover genes for complex diseases. We studied melanoma-prone transgenic progeny across seventy CC genetic backgrounds. We mapped a strong quantitative trait locus for rapid onset spontaneous melanoma onset to Prkdc, a gene involved in detection and repair of DNA damage. In contrast, rapid onset UVR-induced melanoma was linked to the ribosomal subunit gene Rrp15. Ribosome biogenesis was upregulated in skin shortly after UVR exposure. Mechanistically, variation in the ‘usual suspects’ by which UVR may exacerbate melanoma, defective DNA repair, melanocyte proliferation, or inflammatory cell infiltration, did not explain melanoma susceptibility or resistance across the CC. Instead, events occurring soon after exposure, such as dysregulation of ribosome function, which alters many aspects of cellular metabolism, may be important.

Different genetic mechanisms mediate spontaneous versus UVR-induced malignant melanoma

Genetic variation conferring resistance and susceptibility to carcinogen-induced tumorigenesis is frequently studied in mice. We have now turned this to melanoma using the collaborative cross (CC), a resource of mouse strains designed to discover genes for complex diseases. We studied melanoma-prone transgenic progeny across seventy CC genetic backgrounds. We mapped a strong quantitative trait locus for rapid onset spontaneous melanoma onset toPrkdc, a gene involved in detection and repair of DNA damage. In contrast, rapid onset UVR-induced melanoma was linked to the ribosomal subunit geneRrp15. Ribosome biogenesis was upregulated in skin shortly after UVR exposure, Mechanistically, variation in the “usual suspects” by which UVR may exacerbate melanoma, defective DNA repair, melanocyte proliferation, or inflammatory cell infiltration, did not explain melanoma susceptibility or resistance across the CC. Instead, events occurring soon after exposure, such as dysregulation of ribosome function, which alters many aspects of cellular metabolism, may be important.

Robust Generation of Transgenic Mice by Hypotonic Shock Mediated Transgene Delivery in Testicular Germ Cells

Our ability to decipher gene sequences has increased enormously with the advent of modern sequencing tools but the ability to divulge functions of new genes have not increased correspondingly. This has caused a remarkable delay in functional interpretation of several newly found genes in tissue and age specific manner, limiting the pace of biological research. This is mainly due to lack of advancements in methodological tools for transgenesis. Predominantly practiced method of transgenesis by pronuclear DNA-microinjection is time consuming, tedious and requires highly skilled persons for embryo-manipulation. Testicular electroporation mediated transgenesis requires use of electric current to testis. To this end, we have now developed an innovative technique for making transgenic mice by giving hypotonic shock to male germ cells for the gene delivery. Desired transgene was suspended in hypotonic Tris-HCl solution (pH 7.0) and simply injected in testis. This resulted in internalization of the transgene in dividing germ-cells residing at basal compartment of tubules leading to its integration in native genome of mice. Such males generated transgenic progeny by natural mating. Several transgenic animals can be generated with minimum skill within short span of time by this easily adaptable novel technique.