Effective silencing of Sry gene with RNA interference in developing mouse embryos resulted in feminization of XY gonad

Recent Genome-Editing Approaches toward Post-Implanted Fetuses in Mice

Genome editing, as exemplified by the CRISPR/Cas9 system, has recently been employed to effectively generate genetically modified animals and cells for the purpose of gene function analysis and disease model creation. There are at least four ways to induce genome editing in individuals: the first is to perform genome editing at the early preimplantation stage, such as fertilized eggs (zygotes), for the creation of whole genetically modified animals; the second is at post-implanted stages, as exemplified by the mid-gestational stages (E9 to E15), for targeting specific cell populations through in utero injection of viral vectors carrying genome-editing components or that of nonviral vectors carrying genome-editing components and subsequent in utero electroporation; the third is at the mid-gestational stages, as exemplified by tail-vein injection of genome-editing components into the pregnant females through which the genome-editing components can be transmitted to fetal cells via a placenta-blood barrier; and the last is at the newborn or adult stage, as exemplified by facial or tail-vein injection of genome-editing components. Here, we focus on the second and third approaches and will review the latest techniques for various methods concerning gene editing in developing fetuses.

Advancements in mammalian X and Y sperm differences and sex control technology

Mammal sex determination depends on whether the X sperm or Y sperm binds to the oocyte during fertilization. If the X sperm joins in oocyte, the offspring will be female, if the Y sperm fertilizes, the offspring will be male. Livestock sex control technology has tremendous value for livestock breeding as it can increase the proportion of female offspring and improve the efficiency of livestock production. This review discusses the detailed differences between mammalian X and Y sperm with respect to their morphology, size, and motility in the reproductive tract and in in vitro conditions, as well as ’omics analysis results. Moreover, research progress in mammalian sex control technology has been summarized.

Environmental epigenetics of sex differences in the brain

Experiences throughout the life course lead to unique phenotypes even among those with the same genotype. Genotype sets the substrate on which physiologic processes, which communicate with the brain, mediate the effects of life experiences via epigenetics. Epigenetics modify the expression of genes in the brain and body in response to circulating hormones and other mediators, which are activated to facilitate survival responses through a process called allostasis. Epigenetic signatures can even be inherited, resulting in transgenerational effects. This chapter addresses epigenetics in the context of sex differences, discussing the intersection between genetics and gonadal hormones and their effect in the brain at discrete developmental periods.

Sex Manipulation Technologies Progress in Livestock: A Review

Sex manipulation technologies allow predetermination of the sex of animal offspring by altering the normal reproductive process. In livestock production, the difference in type and gender can translate into significant economic benefits, including alleviation of severe food shortages. In livestock, however, the commercial application of sex manipulation technologies is currently available for cattle only. In this review, we described the brief history of sex manipulation, and the research progresses of common methods used in sex manipulation thus far. Information presented in this review can inform future studies on expanding the scope and use of sex manipulation technologies in livestock.

Hydrodynamics-Based Transplacental Delivery as a Useful Noninvasive Tool for Manipulating Fetal Genome

We previously demonstrated that the injection of pregnant wild-type female mice (carrying enhanced green fluorescent protein (EGFP)-expressing transgenic fetuses) at embryonic day (E) 12.5 with an all-in-one plasmid conferring the expression of both Cas9 and guide RNA (targeted to the EGFP cDNA) complexed with the gene delivery reagent, resulted in some fetuses exhibiting reduced fluorescence in their hearts and gene insertion/deletion (indel) mutations. In this study, we examined whether the endogenous myosin heavy-chain α (MHCα) gene can be successfully genome-edited by this method in the absence of a gene delivery reagent with potential fetal toxicity. For this, we employed a hydrodynamics-based gene delivery (HGD) system with the aim of ensuring fetal gene delivery rates and biosafety. We also investigated which embryonic stages are suitable for the induction of genome editing in fetuses. Of the three pregnant females injected at E9.5, one had mutated fetuses: all examined fetuses carried exogenous plasmid DNA, and four of 10 (40%) exhibited mosaic indel mutations in MHCα. Gene delivery to fetuses at E12.5 and E15.5 did not cause mutations. Thus, the HGD-based transplacental delivery of a genome editing vector may be able to manipulate the fetal genomes of E9.5 fetuses.

Transplacental Gene Delivery (TPGD) as a Noninvasive Tool for Fetal Gene Manipulation in Mice

Transplacental gene delivery (TPGD) is a technique for delivering nucleic acids to fetal tissues via tail-vein injections in pregnant mice. After transplacental transport, administered nucleic acids enter fetal circulation and are distributed among fetal tissues. TPGD was established in 1995 by Tsukamoto et al., and its mechanisms, and potential applications have been further characterized since. Recently, discoveries of sequence specific nucleases, such as zinc-finger nuclease (ZFN), transcription activator-like effector nucleases (TALEN), and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) (CRISPR/Cas9), have revolutionized genome editing. In 2019, we demonstrated that intravenous injection of plasmid DNA containing CRISPR/Cas9 produced indels in fetal myocardial cells, which are comparatively amenable to transfection with exogenous DNA. In the future, this unique technique will allow manipulation of fetal cell functions in basic studies of fetal gene therapy. In this review, we describe developments of TPGD and discuss their applications to the manipulation of fetal cells.

RNAi as a tool to control the sex ratio of mouse offspring by interrupting Zfx/Zfy genes in the testis

The objective of this study was to explore a novel method to alter the sex-ratio balance of mouse offspring by silencing the paralogous genes Zfx/Zfy (Zinc finger X/Y-chromosomal transcription factor gene) during spermatogenesis. Four recombined vectors PRZ1, PRZ2, PRZ3, and PRZ4 (RNAi-Ready-pSIREN-RetroQ-ZsGreen) were constructed for interrupting the Zfx gene. Additionally, a recombined vector Psilencer/Zfy-shRNA was constructed for interrupting the Zfy gene. Male mice were randomly divided into 8 groups, with 20 animals per group. Five groups of mice were injected with PRZ1, PRZ2, PRZ3, PRZ4, and Psilencer/Zfy-shRNA vectors, respectively. The three control groups were injected with an equal volume of physiological saline, empty RNAi-Ready-pSIREN-RetroQ-ZsGreen vector, and empty Psilencer/Zfy-shRNA vector, respectively. All groups were injected every 7 days for a total of four injections. Fourteen days after the fourth injection, 10 male mice from each group were mated individually with 10 females. Testicular tissue of 10 male mice in each group was collected, and the expression level of Zfx/Zfy mRNA was determined by qRT-PCR. Results showed that, compared with the empty RNAi-Ready-pSIREN-RetroQ-ZsGreen vector and the physiological saline group, expression of Zfx mRNA decreased significantly after injection of PRZ1 (p < 0.01), PRZ3 (p < 0.01), and PRZ4 (p < 0.01), and 78.75 ± 7.50% of the offspring were male in PRZ4 group, significantly higher than the offspring derived from the empty RNAi-Ready-pSIREN-RetroQ-ZsGreen vector and physiological saline group (p < 0.01). In the PRZ1 group, the expression of Zfx mRNA was also significantly lower (p < 0.01), but the male rate of offspring was not different (p > 0.05). Conversely, the expression of Zfy mRNA decreased significantly after injection of Psilencer/Zfy-shRNA (p < 0.01) and 31.00 ± 11.00% of the offspring were male, significantly lower than in the physiological saline group (p < 0.01). In conclusion, our findings show that RNAi-mediated disruption of Zfx/Zfy in mouse testis affected X/Y spermatogenesis. Additionally, results suggest that the paralogous genes Zfx/Zfy play an important role in the process of X and Y sperm development. The individual interference of Zfx/Zfy may predict the outcome of X and Y haploid sperms. Presented herein is an advanced method developed to control mouse X/Y spermatogenesis and sex ratio of offspring.

Dmy initiates masculinity by altering Gsdf/Sox9a2/Rspo1 expression in medaka (Oryzias latipes)

Despite identification of several sex-determining genes in non-mammalian vertebrates, their detailed molecular cascades of sex determination/differentiation are not known. Here, we used a novel RNAi to characterise the molecular mechanism of Dmy (the sex-determining gene of medaka)-mediated masculinity in XY fish. Dmy knockdown (Dmy-KD) suppressed male pathway (Gsdf, Sox9a2, etc.) and favoured female cascade (Rspo1, etc.) in embryonic XY gonads, resulting in a fertile male-to-female sex-reversal. Gsdf, Sox9a2, and Rspo1 directly interacted with Dmy, and co-injection of Gsdf and Sox9a2 re-established masculinity in XY-Dmy-KD transgenics, insinuating that Dmy initiates masculinity by stimulating and suppressing Gsdf/Sox9a2 and Rspo1 expression, respectively. Gonadal expression of Wt1a starts prior to Dmy and didn’t change upon Dmy-KD. Furthermore, Wt1a stimulated the promoter activity of Dmy, suggesting Wt1a as a regulator of Dmy. These findings provide new insights into the role of vertebrate sex-determining genes associated with the molecular interplay between the male and female pathways.

Production of Sry knockout mouse using TALEN via oocyte injection

Recently developed transcription activator-like effector nuclease (TALEN) technology has enabled the creation of knockout mice, even for genes on the Y chromosome. In this study, we generated a knockout mouse for Sry, a sex-determining gene on the Y chromosome, using microinjection of TALEN RNA into pronuclear stage oocytes. As expected, the knockout mouse had female external and internal genitalia, a female level of blood testosterone and a female sexually dimorphic nucleus in the brain. The knockout mouse exhibited an estrous cycle and performed copulatory behavior as females, although it was infertile or had reduced fertility. A histological analysis showed that the ovary of the knockout mouse displayed a reduced number of oocytes and luteinized unruptured follicles, implying that a reduced number of ovulated oocytes is a possible reason for infertility and/or reduced fertility in the KO mouse.

Genetic manipulation of the mouse developing hypothalamus through in utero electroporation

Genetic modification of specific regions of the developing mammalian brain is a very powerful experimental approach. However, generating novel mouse mutants is often frustratingly slow. It has been shown that access to the mouse brain developing in utero with reasonable post-operatory survival is possible. Still, results with this procedure have been reported almost exclusively for the most superficial and easily accessible part of the developing brain, i.e. the cortex. The thalamus, a narrower and more medial region, has proven more difficult to target. Transfection into deeper nuclei, especially those of the hypothalamus, is perhaps the most challenging and therefore very few results have been reported. Here we demonstrate a procedure to target the entire hypothalamic neuroepithelium or part of it (hypothalamic regions) for transfection through electroporation. The keys to our approach are longer narcosis times, injection in the third ventricle, and appropriate kind and positioning of the electrodes. Additionally, we show results of targeting and subsequent histological analysis of the most recessed hypothalamic nucleus, the mammillary body.

Gene silencing of 4-1BB by RNA interference inhibits acute rejection in rats with liver transplantation

The 4-1BB signal pathway plays a key role in organ transplantation tolerance. In this study, we have investigated the effect of gene silencing of 4-1BB by RNA interference (RNAi) on the acute rejection in rats with liver transplantation. The recombination vector of lentivirus that contains shRNA targeting the 4-1BB gene (LV-sh4-1BB) was constructed. The liver transplantation was performed using the two-cuff technique. Brown-Norway (BN) recipient rats were infected by the recombinant LVs. The results showed that gene silencing of 4-1BB by RNAi downregulated the 4-1BB gene expression of the splenic lymphocytes in vitro, and the splenic lymphocytes isolated from the rats with liver transplantation. LV-sh4-1BB decreased the plasma levels of liver injury markers including AST, ALT, and BIL and also decreased the level of plasma IL-2 and IFN-γ in recipient rats with liver transplantation. Lentivirus-mediated delivery of shRNA targeting 4-1BB gene prolonged the survival time of recipient and alleviated the injury of liver morphology in recipient rats with liver transplantation. In conclusion, our results demonstrate that gene silencing of 4-1BB by RNA interference inhibits the acute rejection in rats with liver transplantation.