Role of hepcidin upregulation and proteolytic cleavage of ferroportin 1 in hepatitis C virus-induced iron accumulation.

Hepatitis C virus (HCV) is a pathogen characterized not only by its persistent infection leading to the development of cirrhosis and hepatocellular carcinoma (HCC), but also by metabolic disorders such as lipid and iron dysregulation. Elevated iron load is commonly observed in the livers of patients with chronic hepatitis C, and hepatic iron overload is a highly profibrogenic and carcinogenic factor that increases the risk of HCC. However, the underlying mechanisms of elevated iron accumulation in HCV-infected livers remain to be fully elucidated. Here, we observed iron accumulation in cells and liver tissues under HCV infection and in mice expressing viral proteins from recombinant adenoviruses. We established two molecular mechanisms that contribute to increased iron load in cells caused by HCV infection. One is the transcriptional induction of hepcidin, the key hormone for modulating iron homeostasis. The transcription factor cAMP-responsive element-binding protein hepatocyte specific (CREBH), which was activated by HCV infection, not only directly recognizes the hepcidin promoter but also induces bone morphogenetic protein 6 (BMP6) expression, resulting in an activated BMP-SMAD pathway that enhances hepcidin promoter activity. The other is post-translational regulation of the iron-exporting membrane protein ferroportin 1 (FPN1), which is cleaved between residues Cys284 and Ala285 in the intracytoplasmic loop region of the central portion mediated by HCV NS3-4A serine protease. We propose that host transcriptional activation triggered by endoplasmic reticulum stress and FPN1 cleavage by viral protease work in concert to impair iron efflux, leading to iron accumulation in HCV-infected cells.

Recent Advances in the Production of Genome-Edited Rats.

The rat is an important animal model for understanding gene function and developing human disease models. Knocking out a gene function in rats was difficult until recently, when a series of genome editing (GE) technologies, including zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and the type II bacterial clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated Cas9 (CRISPR/Cas9) systems were successfully applied for gene modification (as exemplified by gene-specific knockout and knock-in) in the endogenous target genes of various organisms including rats. Owing to its simple application for gene modification and its ease of use, the CRISPR/Cas9 system is now commonly used worldwide. The most important aspect of this process is the selection of the method used to deliver GE components to rat embryos. In earlier stages, the microinjection (MI) of GE components into the cytoplasm and/or nuclei of a zygote was frequently employed. However, this method is associated with the use of an expensive manipulator system, the skills required to operate it, and the egg transfer (ET) of MI-treated embryos to recipient females for further development. In vitro electroporation (EP) of zygotes is next recognized as a simple and rapid method to introduce GE components to produce GE animals. Furthermore, in vitro transduction of rat embryos with adeno-associated viruses is potentially effective for obtaining GE rats. However, these two approaches also require ET. The use of gene-engineered embryonic stem cells or spermatogonial stem cells appears to be of interest to obtain GE rats; however, the procedure itself is difficult and laborious. Genome-editing via oviductal nucleic acids delivery (GONAD) (or improved GONAD (i-GONAD)) is a novel method allowing for the in situ production of GE zygotes existing within the oviductal lumen. This can be performed by the simple intraoviductal injection of GE components and subsequent in vivo EP toward the injected oviducts and does not require ET. In this review, we describe the development of various approaches for producing GE rats together with an assessment of their technical advantages and limitations, and present new GE-related technologies and current achievements using those rats in relation to human diseases.

Generation of Flag/DYKDDDDK Epitope Tag Knock-In Mice Using i-GONAD Enables Detection of Endogenous CaMKIIα and ß Proteins.

Specific antibodies are necessary for cellular and tissue expression, biochemical, and functional analyses of protein complexes. However, generating a specific antibody is often time-consuming and effort-intensive. The epitope tagging of an endogenous protein at an appropriate position can overcome this problem. Here, we investigated epitope tag position using AlphaFold2 protein structure prediction and developed Flag/DYKDDDDK tag knock-in CaMKIIα and CaMKIIß mice by combining CRISPR-Cas9 genome editing with electroporation (i-GONAD). With i-GONAD, it is possible to insert a small fragment of up to 200 bp into the genome of the target gene, enabling efficient and convenient tagging of a small epitope. Experiments with commercially available anti-Flag antibodies could readily detect endogenous CaMKIIα and ß proteins by Western blotting, immunoprecipitation, and immunohistochemistry. Our data demonstrated that the generation of Flag/DYKDDDDK tag knock-in mice by i-GONAD is a useful and convenient choice, especially if specific antibodies are unavailable.

Successful i-GONAD in Mice at Early Zygote Stage through In Vivo Electroporation Three Min after Intraoviductal Instillation of CRISPR-Ribonucleoprotein.

Improved genome editing via oviductal nucleic acids delivery (i-GONAD) is a new technology enabling in situ genome editing of mammalian zygotes exiting the oviductal lumen, which is now available in mice, rats, and hamsters. In this method, CRISPR/Cas9 genome-editing reagents are delivered directly to the oviducts of pregnant animals (corresponding to late zygote stage). After intraoviductal instillation, electric shock to the entire oviduct was provided with a specialized electroporation (EP) device to drive the genome editing reagents into the zygotes present in the oviductal lumen. i-GONAD toward early zygotes has been recognized as difficult, because they are tightly surrounded by a cumulus cell layer, which often hampers effective transfer of nucleic acids to zygotes. However, in vivo EP three min after intraoviductal instillation of the genome-editing reagents enabled genome editing of early zygotes with an efficiency of 70%, which was in contrast with the rate of 18% when in vivo EP was performed immediately after intraoviductal instillation at Day 0.5 of pregnancy (corresponding to 13:00-13:30 p.m. on the day when vaginal plug was recognized after natural mating). We also found that addition of hyaluronidase, an enzyme capable of removing cumulus cells from a zygote, slightly enhanced the efficiency of genome editing in early zygotes. These findings suggest that cumulus cells surrounding a zygote can be a barrier for efficient generation of genome-edited mouse embryos and indicate that a three-minute interval before in vivo EP is effective for achieving i-GONAD-mediated genome editing at the early zygote stage. These results are particularly beneficial for researchers who want to perform genome editing experiments targeting early zygotes.

Modification of improved-genome editing via oviductal nucleic acids delivery (i-GONAD)-mediated knock-in in rats.

BACKGROUND: Improved genome-editing via oviductal nucleic acids delivery (i-GONAD) is a new technology that facilitates in situ genome-editing of mammalian zygotes exiting the oviductal lumen. The i-GONAD technology has been developed for use in mice, rats, and hamsters; however, oligonucleotide (ODN)-based knock-in (KI) is more inefficient in rats than mice. To improve the efficiency of i-GONAD in rats we examined KI efficiency using three guide RNAs (gRNA), crRNA1, crRNA2 and crRNA3. These gRNAs recognize different portions of the target locus, but also overlap each other in the target locus. We also examined the effects of commercially available KI -enhancing drugs (including SCR7, L755,507, RS-1, and HDR enhancer) on i-GONAD-mediated KI efficiency. RESULTS: The KI efficiency in rat fetuses generated after i-GONAD with crRNA2 and single-stranded ODN was significantly higher (24%) than crRNA1 (5%; p < 0.05) or crRNA3 (0%; p < 0.01). The KI efficiency of i-GONAD with triple gRNAs was 11%. These findings suggest that KI efficiency largely depends on the type of gRNA used. Furthermore, the KI efficiency drugs, SCR7, L755,507 and HDR enhancer, all of which are known to enhance KI efficiency, increased KI efficiency using the i-GONAD with crRNA1 protocol. In contrast, only L755,507 (15 µM) increased KI efficiency using the i-GONAD with crRNA2 protocol. None of them were significantly different. CONCLUSIONS: We attempted to improve the KI efficiency of i-GONAD in rats. We demonstrated that the choice of gRNA is important for determining KI efficiency and insertion and deletion rates. Some drugs (e.g. SCR7, L755,507 and HDR enhancer) that are known to increase KI efficiency in culture cells were found to be effective in i-GONAD in rats, but their effects were limited.

Critical role of CREBH-mediated induction of transforming growth factor ß2 by hepatitis C virus infection in fibrogenic responses in hepatic stellate cells.

Mechanisms of hepatic fibrogenesis induced by hepatitis C virus (HCV), one of the leading causes of liver fibrosis, are not fully understood. We studied transcriptional up-regulation of transforming growth factor ß (TGF-ß), especially TGF-ß2, which is mediated by activation of liver-enriched transcription factor cAMP-responsive element-binding protein, hepatocyte specific (CREBH) triggered by HCV infection and its functional significance for induction of profibrogenic phenotypes by interaction of HCV-infected cells with hepatic stellate cells (HSCs). Compared to TGF-ß1, expression of TGF-ß2 mRNA was induced faster and to a higher level upon HCV infection. Serum TGF-ß2 levels in hepatitis C patients were higher compared to those in healthy individuals and were positively correlated with hepatic fibrosis stages F0-F2. TGF-ß2 promoter activity was decreased and increased, respectively, by silencing and overexpression of CREBH. CREBH recognition sites were identified in the TGF-ß2 promoter. CREBH binding to the promoter and its increase in cells expressing HCV Core-NS2 were shown by gel mobility shift and chromatin immunoprecipitation, respectively. The active form of CREBH was detectable in HCV-infected chimeric mice with human livers and cells expressing HCV proteins. Involvement of CREBH in HCV-induced fibrogenic response was further demonstrated in the CREBH null-mutant mouse model. Fibrogenic phenotypes were assessed using co-cultures of HCV-infected cells and HSCs. Expressions of fibrogenic factors and TGF-ß1 increasing in the co-cultures was prevented by TGF-ß2- or CREBH silencing. CONCLUSION: CREBH was identified as a key positive regulator of TGF-ß2 transcription in HCV-infected cells. TGF-ß2 released from infected cells potentially contributes to cross-induction of TGF-ß in an autocrine manner through its own signaling pathway, leading to an increase in fibrogenic responses in adjacent HSCs. (Hepatology 2017;66:1430-1443).

Identification of Two Additional Genomic Loci Responsible for experimentally induced testicular teratoma 2 and 3 (ett2 and ett3).

Experimental testicular teratomas (ETTs) can be induced in 129/Sv mouse by E12.5 fetal testes transplant into adult testes. Previously, we conducted linkage analysis to explore candidate genes possibly involved in ETT development using F2 intercross fetuses derived from F1[LTXBJ × 129/Sv- + /Ter (+ /+)] hybrids. By linkage analysis on Chr 18 and Chr 19, we identified the genomic locus for experimental testicular teratoma 1 (ett1) on Chr 18. In the present study, we conducted additional mapping and linkage analysis on teratoma susceptibility and genome composition on Chr 1-17. The results revealed two new candidate loci, experimental testicular teratoma 2 (ett2) and experimental testicular teratoma 3 (ett3), on Chr 3 and 7. Interestingly, the rates of ETT generation were increased in the case of ett2 and ett3 regions replaced with LTXBJ strain. To determine whether a polymorphic gene was present, we performed exome analysis of 129/Sv- + /Ter (+ /+) and LTXBJ. This revealed the presence of SNPs in all three loci, ett1 to ett3. ett1 contains polymorphic Mc4r; ett2 contains polymorphic Polr3c, Cd160, and Pdzk1; and ett3 contains polymorphic Prmt3. We found additional loci responsible for ETT formation, namely, ett2 and ett3, and identified candidate genes in these regions by exome analysis.

Common marmoset CD117+ hematopoietic cells possess multipotency.

Analysis of the hematopoiesis of non-human primates is important to clarify the evolution of primate-specific hematopoiesis and immune regulation. However, the engraftment and development of the primate hematopoietic system are well-documented only in humans and are not clear in non-human primates. Callithrix jacchus (common marmoset, CM) is a New World monkey with a high rate of pregnancy and small size that lives in closed colonies. As stem cell factor (SCF) is an essential molecule for hematopoietic stem cell development in mice and humans, we focused on CD117, the SCF receptor, and examined whether CD117-expressing cells possess the hematopoietic stem/progenitor cell characteristics of newborn marmoset-derived hematopoietic cells that can develop into T cells and B cells. When CD117(+) cell fractions of the bone marrow were transplanted into immunodeficient NOD (non-obese diabetic)/Shi-scid, common γc-null (NOG) mice, these cells engrafted efficiently in the bone marrow and spleens of the NOG mice. The CD117(+) cells developed into myeloid lineage cells, CD20(+) B cells and CD3(+) T cells, which could express CM cytokines in vivo. The development of B cells did not precede that of T cells. The development of CD8(+) T cells was dominant in NOG mice. The engraftment was comparable for both CD117(+)CD34(+) cells and CD117(+)CD34(-) cells. These results suggest that the CD117(+) cell fraction can differentiate into all three cell lineages, and the development of marmoset immunity in the xenogeneic environment follows diverse developmental pathways compared with human immunity.

Identification of genomic locus responsible for experimentally induced testicular teratoma 1 (ett1) on mouse Chr 18.

Spontaneous testicular teratomas (STTs) composed by various kinds of tissues are derived from primordial germ cells (PGCs) in the fetal testes of the mouse. In contrast, intra-testicular grafts of the mouse strain (129/Sv-Ter (+/+)) fetal testes possessed the ability to develop the experimental testicular teratomas (ETTs), indistinguishable from the STTs at a morphological level. In this study, linkage analysis was performed for exploration of possible candidate genes involving in ETT development using F2 intercross fetuses derived from [LTXBJ × 129/Sv-Ter (+/+)] F1 hybrids. Linkage analysis with selected simple sequence length polymorphisms along chromosomes 18 and 19, which have been expected to contain ETT-susceptibility loci, demonstrated that a novel recessive candidate gene responsible for ETT development is located in 1.1 Mb region between the SSLP markers D18Mit81 and D18Mit184 on chromosome 18 in the 129/Sv-Ter (+/+) genetic background. Since this locus is different from the previously known loci (including Ter, pgct1, and Tgct1) for STT development, we named this novel gene "experimental testicular teratoma 1 (ett1)". To resolve the location of ett1 independently from other susceptibility loci, ett1 loci was introduced in a congenic strain in which the distal segment of chromosome 18 in LTXBJ strain mice had been replaced by a 1.99 Mbp genomic segment of the 129/Sv-Ter (+/+) mice. Congenic males homozygous for the ett1 loci were confirmed to have the ability to form ETTs, indicating that this locus contain the gene responsible for ETTs. We listed candidate genes included in this region, and discussed about their possible involvement in induction of ETTs.

The Mc4r gene is responsible for the development of experimentally induced testicular teratomas.

Teratomas in mice, composed of different tissue types, are derived from primordial germ cells in the fetal gonads. Previously, we identified a locus responsible for experimental testicular teratoma (ETT) formation on chromosome 18, referred to as ett1. The strongest candidate sequence in the ett1 locus was found to be a missense mutation in the melanocortin 4 receptor (Mc4r), Mc4rG25S. We established a strain with a point mutation in the Mc4r gene in the ETT-nonsusceptible LT strain, called LT- Mc4rG25S, by genome editing. Surprisingly, highly developed ovarian teratomas (OTs), rather than testicular teratomas, appeared in the LT-Mc4rG25S strain. The results demonstrated that Mc4r is also one of the genes responsible for OT formation and suggested that missense mutations in Mc4r promote teratoma formation in both sexes. In this study, we performed ETT experiments in different host-graft combinations of the LT-Mc4rG25S and LT strains. Furthermore, the expression of MC4R in germ cells in the testis was demonstrated. Expression of Mc4r in testis was also confirmed by RT-PCR. The results demonstrated that MC4R is expressed in germ cells in the testis and that a point mutation in the Mc4r gene is responsible for ETT formation.

MC4R mutant mice develop ovarian teratomas.

Teratomas in mice, composed of different tissue types, are derived from primordial germ cells (PGCs) in the foetal gonads. The strongest candidate gene in the testicular teratoma locus (Ter) responsible for testicular teratoma formation was identified as mutation in Dnd1, Dnd1R178*. However, the phenotype of mice with a mutated Dnd1 gene was germ cell loss. This suggests that other genes are involved in teratoma formation. Testicular teratomas can also be induced experimentally (experimentally testicular teratomas: ETTs) in 129/Sv mice by transplanting E12.5 foetal testes into adult testes. Previously, we mapped the ett1 locus, which is the locus responsible for ETT formation on chromosome 18. By exome sequence analysis of the 129 and LTXBJ (LT) strains, we identified a missense mutation in the melanocortin 4 receptor (MC4R) gene among 8 genes in the ett1 region. The missense mutation causes a substitution of glycine 25 by serine. Thus, this gene is a candidate for ETT formation. We established the LT-ett1 congenic strain, which introduced the locus responsible for ETT formation genetically into the genomes of a testicular teratoma non-susceptible strain. In this study, we crossed LT-ett1 and a previously established LT-Ter strain to establish the double congenic strain LT-Ter-ett1. Also, we established a strain with a point mutation in the MC4R gene of the LT strain by genome editing, LT-MC4RG25S. Furthermore, double genetically modified strain LT-Ter-MC4RG25S was established to address the relation between Ter and MC4R. Surprisingly, highly developed ovarian teratomas (OTs), instead of testicular teratomas, appeared not only in the LT-Ter-MC4RG25S and LT-MC4RG25S strains but also in the LT-ett1 and LT-Ter-ett1 strains. The incidence of OT formation was high in double genetically modified strains. The results demonstrated that MC4R is one of the genes responsible for OT formation. It was suggested that the effect of the missense mutation in MC4R on teratoma formation was promoted by abnormal germ cell formation by the mutation in DND1.

ATP6V0A1 encoding the a1-subunit of the V0 domain of vacuolar H+-ATPases is essential for brain development in humans and mice.

Vacuolar H+-ATPases (V-ATPases) transport protons across cellular membranes to acidify various organelles. ATP6V0A1 encodes the a1-subunit of the V0 domain of V-ATPases, which is strongly expressed in neurons. However, its role in brain development is unknown. Here we report four individuals with developmental and epileptic encephalopathy with ATP6V0A1 variants: two individuals with a de novo missense variant (R741Q) and the other two individuals with biallelic variants comprising one almost complete loss-of-function variant and one missense variant (A512P and N534D). Lysosomal acidification is significantly impaired in cell lines expressing three missense ATP6V0A1 mutants. Homozygous mutant mice harboring human R741Q (Atp6v0a1R741Q) and A512P (Atp6v0a1A512P) variants show embryonic lethality and early postnatal mortality, respectively, suggesting that R741Q affects V-ATPase function more severely. Lysosomal dysfunction resulting in cell death, accumulated autophagosomes and lysosomes, reduced mTORC1 signaling and synaptic connectivity, and lowered neurotransmitter contents of synaptic vesicles are observed in the brains of Atp6v0a1A512P/A512P mice. These findings demonstrate the essential roles of ATP6V0A1/Atp6v0a1 in neuronal development in terms of integrity and connectivity of neurons in both humans and mice.

Recent Advances and Future Perspectives of In Vivo Targeted Delivery of Genome-Editing Reagents to Germ Cells, Embryos, and Fetuses in Mice.

The recently discovered clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) systems that occur in nature as microbial adaptive immune systems are considered an important tool in assessing the function of genes of interest in various biological systems. Thus, development of efficient and simple methods to produce genome-edited (GE) animals would accelerate research in this field. The CRISPR/Cas9 system was initially employed in early embryos, utilizing classical gene delivery methods such as microinjection or electroporation, which required ex vivo handling of zygotes before transfer to recipients. Recently, novel in vivo methods such as genome editing via oviductal nucleic acid delivery (GONAD), improved GONAD (i-GONAD), or transplacental gene delivery for acquiring genome-edited fetuses (TPGD-GEF), which facilitate easy embryo manipulation, have been established. Studies utilizing these techniques employed pregnant female mice for direct introduction of the genome-editing components into the oviduct or were dependent on delivery via tail-vein injection. In mice, embryogenesis occurs within the oviducts and the uterus, which often hampers the genetic manipulation of embryos, especially those at early postimplantation stages (days 6 to 8), owing to a thick surrounding layer of tissue called decidua. In this review, we have surveyed the recent achievements in the production of GE mice and have outlined the advantages and disadvantages of the process. We have also referred to the past achievements in gene delivery to early postimplantation stage embryos and germ cells such as primordial germ cells and spermatogonial stem cells, which will benefit relevant research.

Nanopore sequencing reveals a structural alteration of mirror-image duplicated genes in a genome-editing mouse line.

CRISPR-Cas9 technology has been used in various studies; however, it has also been found to introduce unexpected structural alternations. In this study, we used nanopore sequencing to characterize an unexpected structural alteration of mirror-image duplicated genes in a mouse line, in which we aimed to delete a part of the duplicated genes using genome editing. We removed low-molecular-weight DNA fragments and increased the input, which led to improved sequence performance. With 14.9 Gb input for whole-genome analysis, we detected a complex structural alteration involving inversion and deletion, which appears to be difficult to characterize with short-read sequencers. Therefore, our study clearly showed the utility of nanopore sequencing for characterizing unexpected complex structural alterations caused by genome editing.

Sequential i-GONAD: An Improved In Vivo Technique for CRISPR/Cas9-Based Genetic Manipulations in Mice.

Improved genome-editing via oviductal nucleic acid delivery (i-GONAD) is a technique capable of inducing genomic changes in preimplantation embryos (zygotes) present within the oviduct of a pregnant female. i-GONAD involves intraoviductal injection of a solution containing genome-editing components via a glass micropipette under a dissecting microscope, followed by in vivo electroporation using tweezer-type electrodes. i-GONAD does not involve ex vivo handling of embryos (isolation of zygotes, microinjection or electroporation of zygotes, and egg transfer of the treated embryos to the oviducts of a recipient female), which is required for in vitro genome-editing of zygotes. i-GONAD enables the generation of indels, knock-in (KI) of ~ 1 kb sequence of interest, and large deletion at a target locus. i-GONAD is usually performed on Day 0.7 of pregnancy, which corresponds to the late zygote stage. During the initial development of this technique, we performed i-GONAD on Days 1.4-1.5 (corresponding to the 2-cell stage). Theoretically, this means that at least two GONAD steps (on Day 0.7 and Day 1.4-1.5) must be performed. If this is practically demonstrated, it provides additional options for various clustered regularly interspaced palindrome repeats (CRISPR)/Caspase 9 (Cas9)-based genetic manipulations. For example, it is usually difficult to induce two independent indels at the target sites, which are located very close to each other, by simultaneous transfection of two guide RNAs and Cas9 protein. However, the sequential induction of indels at a target site may be possible when repeated i-GONAD is performed on different days. Furthermore, simultaneous introduction of two mutated lox sites (to which Cre recombinase bind) for making a floxed allele is reported to be difficult, as it often causes deletion of a sequence between the two gRNA target sites. However, differential KI of lox sites may be possible when repeated i-GONAD is performed on different days. In this study, we performed proof-of-principle experiments to demonstrate the feasibility of the proposed approach called "sequential i-GONAD (si-GONAD)."

Modification of i-GONAD Suitable for Production of Genome-Edited C57BL/6 Inbred Mouse Strain.

Improved genome editing via oviductal nucleic acid delivery (i-GONAD) is a novel method for producing genome-edited mice in the absence of ex vivo handling of zygotes. i-GONAD involves the intraoviductal injection of clustered regularly interspaced short palindromic repeats (CRISPR) ribonucleoproteins via the oviductal wall of pregnant females at 0.7 days post-coitum, followed by in vivo electroporation (EP). Unlike outbred Institute of Cancer Research (ICR) and hybrid mouse strains, genome editing of the most widely used C57BL/6J (B6) strain with i-GONAD has been considered difficult but, recently, setting a constant current of 100 mA upon EP enabled successful i-GONAD in this strain. Unfortunately, the most widely used electroporators employ a constant voltage, and thus we explored conditions allowing the generation of a 100 mA current using two electroporators: NEPA21 (Nepa Gene Co., Ltd.) and GEB15 (BEX Co., Ltd.). When the current and resistance were set to 40 V and 350-400 Ω, respectively, the current was fixed to 100 mA. Another problem in using B6 mice for i-GONAD is the difficulty in obtaining pregnant B6 females consistently because estrous females often fail to be found. A single intraperitoneal injection of low-dose pregnant mare's serum gonadotrophin (PMSG) led to synchronization of the estrous cycle of these mice. Consequently, approximately 51% of B6 females had plugs upon mating with males 2 days after PMSG administration, which contrasts with the case (≈26%) when B6 females were subjected to natural mating. i-GONAD performed on PMSG-treated pregnant B6 females under conditions of average resistance of 367 Ω and average voltage of 116 mA resulted in the production of pregnant females at a rate of 56% (5/9 mice), from which 23 fetuses were successfully delivered. Nine (39%) of these fetuses exhibited successful genome editing at the target locus.

A spontaneous smc1b mutation causes cohesin protein dysfunction and sterility in mice.

In this paper, we describe a novel spontaneous mutation of the Smc1b gene coding a cohesin component, which causes female and male sterility. We have discovered an ICR male mouse with a novel autosomal recessive gene that causes small gonads and sterility in both sexes. Mutant female and male mice homozygous for the novel sterility gene had normal body weights and showed normal mating behavior, but did not produce any offspring. Histological examination showed that Sertoli cells and spermatogonia were present in the testicular seminiferous tubules in 8-week-old mutant male mice, but no spermatids or spermatozoa were observed. Mutant females showed a markedly reduced number of oocytes with age. The novel sterility gene mapped between D15Mit105 (47.9 cM) and D15Mit171 (54.5 cM) on chromosome 15. Sequences of three candidate sterility genes, Dmc1, Mei1 and Smc1b, which are closely linked to these microsatellite markers, were compared between normal and mutant mice. The Dmc1 and Mei1 genes showed the same sequences in both normal and mutant mice, but the Smc1b gene had a deletion of 16 nucleotides in exon 5, in the mutant mice. We concluded that this deletion led to a frame-shift, which generated a stop codon at position 761 (amino acid 247) of the Smc1b cDNA in mutant mice.

Development of microsatellite DNA markers and their chromosome assignment in the common marmoset.

This study was performed to develop microsatellite DNA markers, which are useful for linkage analyses, gene mapping and blood chimera analyses in the common marmoset (Callithrix jacchus). We searched 153 of 295 bacterial artificial clone DNA sequences of the common marmoset that were archived in the NCBI database in 2004. On the basis of the search, we designed 186 PCR primer sets. When tested using 5 unrelated individuals, we successfully detected 154 markers with PCR products, of which 80 (52%) were polymorphic and 74 (48%) were monomorphic. We assigned each of the 154 markers to a human chromosome based on BLAST searches, which was achieved by searching the entire human genome sequences using an approximately 3 kb section of each forward primer sequence, including approximately 1.5 kb of the upstream and approximately 1.5 kb of the downstream sequences. Combining our assignment data and the chromosome painting-assisted karyotype of the common marmoset [Sherlock et al., Genomics 33:214-219, 1996], we prepared a list of 154 microsatellite DNA markers that were assigned to human chromosomes, except for the Y chromosome, which is equivalent to a chromosome map. Using five microsatellite DNA markers, we have established a fragment analysis method with a sequencer, which can be routinely used for blood chimera analysis, parentage diagnosis and individual identification.

Creation of CRISPR-based germline-genome-engineered mice without ex vivo handling of zygotes by i-GONAD.

Methods to create genetically engineered mice involve three major steps: harvesting embryos from one set of females, microinjection of reagents into embryos ex vivo and their surgical transfer to another set of females. Although tedious, these methods have been used for more than three decades to create mouse models. We recently developed a method named GONAD (genome editing via oviductal nucleic acids delivery), which bypasses these steps. GONAD involves injection of CRISPR components (Cas9 mRNA and guide RNA (gRNA)) into the oviducts of pregnant females 1.5 d post conception, followed by in vivo electroporation to deliver the components into the zygotes in situ. Using GONAD, we demonstrated that target genes can be disrupted and analyzed at different stages of mouse embryonic development. Subsequently, we developed improved GONAD (i-GONAD) by delivering CRISPR ribonucleoproteins (RNPs; Cas9 protein or Cpf1 protein and gRNA) into day-0.7 pregnant mice, which made it suitable for routine generation of knockout and large-deletion mouse models. i-GONAD can also generate knock-in models containing up to 1-kb inserts when single-stranded DNA (ssDNA) repair templates are supplied. i-GONAD offers other advantages: it does not require vasectomized males and pseudo-pregnant females, the females used for i-GONAD are not sacrificed and can be used for other experiments, it can be easily adopted in laboratories lacking sophisticated microinjection equipment, and can be implemented by researchers skilled in small-animal surgery but lacking embryo-handling skills. Here, we provide a step-by-step protocol for establishing the i-GONAD method. The protocol takes ∼6 weeks to generate the founder mice.

i-GONAD (improved genome-editing via oviductal nucleic acids delivery), a convenient in vivo tool to produce genome-edited rats.

Zygote-microinjection or in vitro electroporation of isolated zygotes are now widely used methods to produce genome-edited mice. However, these technologies require laborious and time-consuming ex vivo handling of fertilized eggs, including zygote isolation, gene delivery into zygotes and embryo transfer into recipients. We recently developed an alternative method called improved genome-editing via oviductal nucleic acids delivery (i-GONAD), which does not require the above-mentioned ex vivo handing of zygotes, but instead involves intraoviductal instillation of genome-editing components, Cas9 protein and synthetic gRNAs, into the oviducts of pregnant females at the late 1-cell embryo stage under a dissecting microscope and subsequent electroporation. With this method, we succeeded in generating genome-edited mice at relatively high efficiencies (for example, knockout alleles were produced at ~97% efficiency). Here, we extended this improved technology to rats, and found that i-GONAD can create genome-edited rats in various strains, including Sprague Dawley and Lewis, and F1 hybrids (between Sprague Dawley and Brown Norway), with efficiencies of ~62% for indel mutations and ~9% for knock-ins. Thus, i-GONAD will be especially useful for the production of genome-edited rats in small laboratories where expensive micromanipulator systems and highly skilled personnel for embryo manipulation are unavailable.