Engineered miniature CRISPR-Cas system for mammalian genome regulation and editing.

Compact and versatile CRISPR-Cas systems will enable genome engineering applications through high-efficiency delivery in a wide variety of contexts. Here, we create an efficient miniature Cas system (CasMINI) engineered from the type V-F Cas12f (Cas14) system by guide RNA and protein engineering, which is less than half the size of currently used CRISPR systems (Cas9 or Cas12a). We demonstrate that CasMINI can drive high levels of gene activation (up to thousands-fold increases), while the natural Cas12f system fails to function in mammalian cells. We show that the CasMINI system has comparable activities to Cas12a for gene activation, is highly specific, and allows robust base editing and gene editing. We expect that CasMINI can be broadly useful for cell engineering and gene therapy applications ex vivo and in vivo.

Refining computational inference of gene regulatory networks: integrating knockout data within a multi-task framework.

Constructing accurate gene regulatory network s (GRNs), which reflect the dynamic governing process between genes, is critical to understanding the diverse cellular process and unveiling the complexities in biological systems. With the development of computer sciences, computational-based approaches have been applied to the GRNs inference task. However, current methodologies face challenges in effectively utilizing existing topological information and prior knowledge of gene regulatory relationships, hindering the comprehensive understanding and accurate reconstruction of GRNs. In response, we propose a novel graph neural network (GNN)-based Multi-Task Learning framework for GRN reconstruction, namely MTLGRN. Specifically, we first encode the gene promoter sequences and the gene biological features and concatenate the corresponding feature representations. Then, we construct a multi-task learning framework including GRN reconstruction, Gene knockout predict, and Gene expression matrix reconstruction. With joint training, MTLGRN can optimize the gene latent representations by integrating gene knockout information, promoter characteristics, and other biological attributes. Extensive experimental results demonstrate superior performance compared with state-of-the-art baselines on the GRN reconstruction task, efficiently leveraging biological knowledge and comprehensively understanding the gene regulatory relationships. MTLGRN also pioneered attempts to simulate gene knockouts on bulk data by incorporating gene knockout information.

Characterization of the cystargolide biosynthetic gene cluster and functional analysis of the methyltransferase CysG.

Cystargolides are natural products originally isolated from Kitasatospora cystarginea NRRL B16505 as inhibitors of the proteasome. They are composed of a dipeptide backbone linked to a ß-lactone warhead. Recently, we identified the cystargolide biosynthetic gene cluster, but systematic genetic analyses had not been carried out because of the lack of a heterologous expression system. Here, we report the discovery of a homologous cystargolide biosynthetic pathway in Streptomyces durhamensis NRRL-B3309 by genome mining. The gene cluster was cloned via transformation-associated recombination and heterologously expressed in Streptomyces coelicolor M512. We demonstrate that it contains all genes necessary for the production of cystargolide A and B. Single gene deletion experiments reveal that only five of the eight genes from the initially proposed gene cluster are essential for cystargolide synthesis. Additional insights into the cystargolide pathway could be obtained from in vitro assays with CysG and chemical complementation of the respective gene knockout. This could be further supported by the in vitro investigation of the CysG homolog BelI from the belactosin biosynthetic gene cluster. Thereby, we confirm that CysG and BelI catalyze a cryptic SAM-dependent transfer of a methyl group that is critical for the construction of the cystargolide and belactosin ß-lactone warheads.

Differential responses to UCP1 ablation in classical brown versus beige fat, despite a parallel increase in sympathetic innervation.

In the cold, the absence of the mitochondrial uncoupling protein 1 (UCP1) results in hyper-recruitment of beige fat, but classical brown fat becomes atrophied. Here we examine possible mechanisms underlying this phenomenon. We confirm that in brown fat from UCP1-knockout (UCP1-KO) mice acclimated to the cold, the levels of mitochondrial respiratory chain proteins were diminished; however, in beige fat, the mitochondria seemed to be unaffected. The macrophages that accumulated massively not only in brown fat but also in beige fat of the UCP1-KO mice acclimated to cold did not express tyrosine hydroxylase, the norepinephrine transporter (NET) and monoamine oxidase-A (MAO-A). Consequently, they could not influence the tissues through the synthesis or degradation of norepinephrine. Unexpectedly, in the cold, both brown and beige adipocytes from UCP1-KO mice acquired an ability to express MAO-A. Adipose tissue norepinephrine was exclusively of sympathetic origin, and sympathetic innervation significantly increased in both tissues of UCP1-KO mice. Importantly, the magnitude of sympathetic innervation and the expression levels of genes induced by adrenergic stimulation were much higher in brown fat. Therefore, we conclude that no qualitative differences in innervation or macrophage character could explain the contrasting reactions of brown versus beige adipose tissues to UCP1-ablation. Instead, these contrasting responses may be explained by quantitative differences in sympathetic innervation: the beige adipose depot from the UCP1-KO mice responded to cold acclimation in a canonical manner and displayed enhanced recruitment, while the atrophy of brown fat lacking UCP1 may be seen as a consequence of supraphysiological adrenergic stimulation in this tissue.

Splice variants of CK1α and CK1α-like: Comparative analysis of subcellular localization, kinase activity, and function in the Wnt signaling pathway.

Members of the casein kinase 1 (CK1) family are important regulators of multiple signaling pathways. CK1α is a well-known negative regulator of the Wnt/ß-catenin pathway, which promotes the degradation of ß-catenin via its phosphorylation of Ser45. In contrast, the closest paralog of CK1α, CK1α-like, is a poorly characterized kinase of unknown function. In this study, we show that the deletion of CK1α, but not CK1α-like, resulted in a strong activation of the Wnt/ß-catenin pathway. Wnt-3a treatment further enhanced the activation, which suggests there are at least two modes, a CK1α-dependent and Wnt-dependent, of ß-catenin regulation. Rescue experiments showed that only two out of ten naturally occurring splice CK1α/α-like variants were able to rescue the augmented Wnt/ß-catenin signaling caused by CK1α deficiency in cells. Importantly, the ability to phosphorylate ß-catenin on Ser45 in the in vitro kinase assay was required but not sufficient for such rescue. Our compound CK1α and GSK3α/ß KO models suggest that the additional nonredundant function of CK1α in the Wnt pathway beyond Ser45-ß-catenin phosphorylation includes Axin phosphorylation. Finally, we established NanoBRET assays for the three most common CK1α splice variants as well as CK1α-like. Target engagement data revealed comparable potency of known CK1α inhibitors for all CK1α variants but not for CK1α-like. In summary, our work brings important novel insights into the biology of CK1α, including evidence for the lack of redundancy with other CK1 kinases in the negative regulation of the Wnt/ß-catenin pathway at the level of ß-catenin and Axin.

FDX2, an iron-sulfur cluster assembly factor, is essential to prevent cellular senescence, apoptosis or ferroptosis of ovarian cancer cells.

Recent studies reveal that biosynthesis of iron-sulfur clusters (Fe-Ss) is essential for cell proliferation, including that of cancer cells. Nonetheless, it remains unclear how Fe-S biosynthesis functions in cell proliferation/survival. Here, we report that proper Fe-S biosynthesis is essential to prevent cellular senescence, apoptosis or ferroptosis, depending on cell context. To assess these outcomes in cancer, we developed an ovarian cancer line with conditional KO of FDX2, a component of the core Fe-S assembly complex. FDX2 loss induced global down-regulation of Fe-S-containing proteins and Fe2+ overload, resulting in DNA damage and p53 pathway activation, and driving the senescence program. p53-deficiency augmented DNA damage responses upon FDX2 loss, resulting in apoptosis rather than senescence. FDX2 loss also sensitized cells to ferroptosis, as evidenced by compromised redox homeostasis of membrane phospholipids (PLs). Our results suggest that p53 status and PL homeostatic activity are critical determinants of diverse biological outcomes of Fe-S deficiency in cancer cells.

A CRISPR-del-based pipeline for complete gene knockout in human diploid cells.

The advance of CRISPR/Cas9 technology has enabled us easily to generate gene knockout cell lines by introducing insertion-deletion mutations (indels) at the target site via the error-prone non-homologous end joining repair system. Frameshift-promoting indels can disrupt gene functions by generation of a premature stop codon. However, there is growing evidence that targeted genes are not always knocked out by the indel-based gene disruption. Here, we established a pipeline of CRISPR-del, which induces a large chromosomal deletion by cutting two different target sites, to perform 'complete' gene knockout efficiently in human diploid cells. Quantitative analyses show that the frequency of gene deletion with this approach is much higher than that of conventional CRISPR-del methods. The lengths of the deleted genomic regions demonstrated in this study are longer than those of 95% of the human protein-coding genes. Furthermore, the pipeline enabled the generation of a model cell line having a bi-allelic cancer-associated chromosomal deletion. Overall, these data lead us to propose that the CRISPR-del pipeline is an efficient and practical approach for producing 'complete' gene knockout cell lines in human diploid cells.

An aptamer-mediated base editing platform for simultaneous knockin and multiple gene knockout for allogeneic CAR-T cells generation.

Gene editing technologies hold promise for enabling the next generation of adoptive cellular therapies. In conventional gene editing platforms that rely on nuclease activity, such as clustered regularly interspaced short palindromic repeats CRISPR-associated protein 9 (CRISPR-Cas9), allow efficient introduction of genetic modifications; however, these modifications occur via the generation of DNA double-strand breaks (DSBs) and can lead to unwanted genomic alterations and genotoxicity. Here, we apply a novel modular RNA aptamer-mediated Pin-point base editing platform to simultaneously introduce multiple gene knockouts and site-specific integration of a transgene in human primary T cells. We demonstrate high editing efficiency and purity at all target sites and significantly reduced frequency of chromosomal translocations compared with the conventional CRISPR-Cas9 system. Site-specific knockin of a chimeric antigen receptor and multiplex gene knockout are achieved within a single intervention and without the requirement for additional sequence-targeting components. The ability to perform complex genome editing efficiently and precisely highlights the potential of the Pin-point platform for application in a range of advanced cell therapies.

Spem2, a novel testis-enriched gene, is required for spermiogenesis and fertilization in mice.

Spermiogenesis is considered to be crucial for the production of haploid spermatozoa with normal morphology, structure and function, but the mechanisms underlying this process remain largely unclear. Here, we demonstrate that SPEM family member 2 (Spem2), as a novel testis-enriched gene, is essential for spermiogenesis and male fertility. Spem2 is predominantly expressed in the haploid male germ cells and is highly conserved across mammals. Mice deficient for Spem2 develop male infertility associated with spermiogenesis impairment. Specifically, the insufficient sperm individualization, failure of excess cytoplasm shedding, and defects in acrosome formation are evident in Spem2-null sperm. Sperm counts and motility are also significantly reduced compared to controls. In vivo fertilization assays have shown that Spem2-null sperm are unable to fertilize oocytes, possibly due to their impaired ability to migrate from the uterus into the oviduct. However, the infertility of Spem2-/- males cannot be rescued by in vitro fertilization, suggesting that defective sperm-egg interaction may also be a contributing factor. Furthermore, SPEM2 is detected to interact with ZPBP, PRSS21, PRSS54, PRSS55, ADAM2 and ADAM3 and is also required for their processing and maturation in epididymal sperm. Our findings establish SPEM2 as an essential regulator of spermiogenesis and fertilization in mice, possibly in mammals including humans. Understanding the molecular role of SPEM2 could provide new insights into future therapeutic treatment of human male infertility and development of non-hormonal male contraceptives.

zMADM (zebrafish mosaic analysis with double markers) for single-cell gene knockout and dual-lineage tracing.

As a vertebrate model organism, zebrafish has many unique advantages in developmental studies, regenerative biology, and disease modeling. However, tissue-specific gene knockout in zebrafish is challenging due to technical difficulties in making floxed alleles. Even when successful, tissue-level knockout can affect too many cells, making it difficult to distinguish cell autonomous from noncell autonomous gene function. Here, we present a genetic system termed zebrafish mosaic analysis with double markers (zMADM). Through Cre/loxP-mediated interchromosomal mitotic recombination of two reciprocally chimeric fluorescent genes, zMADM generates sporadic (<0.5%), GFP+ mutant cells along with RFP+ sibling wild-type cells, enabling phenotypic analysis at single-cell resolution. Using wild-type zMADM, we traced two sibling cells (GFP+ and RFP+) in real time during a dynamic developmental process. Using nf1 mutant zMADM, we demonstrated an overproliferation phenotype of nf1 mutant cells in comparison to wild-type sibling cells in the same zebrafish. The readiness of zMADM to produce sporadic mutant cells without the need to generate floxed alleles should fundamentally improve the throughput of genetic analysis in zebrafish; the lineage-tracing capability combined with phenotypic analysis at the single-cell level should lead to deep insights into developmental and disease mechanisms. Therefore, we are confident that zMADM will enable groundbreaking discoveries once broadly distributed in the field.

5-methylcytosine modification by Plasmodium NSUN2 stabilizes mRNA and mediates the development of gametocytes.

5-methylcytosine (m5C) is an important epitranscriptomic modification involved in messenger RNA (mRNA) stability and translation efficiency in various biological processes. However, it remains unclear if m5C modification contributes to the dynamic regulation of the transcriptome during the developmental cycles of Plasmodium parasites. Here, we characterize the landscape of m5C mRNA modifications at single nucleotide resolution in the asexual replication stages and gametocyte sexual stages of rodent (Plasmodium yoelii) and human (Plasmodium falciparum) malaria parasites. While different representations of m5C-modified mRNAs are associated with the different stages, the abundance of the m5C marker is strikingly enhanced in the transcriptomes of gametocytes. Our results show that m5C modifications confer stability to the Plasmodium transcripts and that a Plasmodium ortholog of NSUN2 is a major mRNA m5C methyltransferase in malaria parasites. Upon knockout of P. yoelii nsun2 (pynsun2), marked reductions of m5C modification were observed in a panel of gametocytogenesis-associated transcripts. These reductions correlated with impaired gametocyte production in the knockout rodent malaria parasites. Restoration of the nsun2 gene in the knockout parasites rescued the gametocyte production phenotype as well as m5C modification of the gametocytogenesis-associated transcripts. Together with the mRNA m5C profiles for two species of Plasmodium, our findings demonstrate a major role for NSUN2-mediated m5C modifications in mRNA transcript stability and sexual differentiation in malaria parasites.

The Role of Retinal Dopamine D1 Receptors in Ocular Growth and Myopia Development in Mice.

Dopamine is a key neurotransmitter in the signaling cascade controlling ocular refractive development, but the exact role and site of action of dopamine D1 receptors (D1Rs) involved in myopia remains unclear. Here, we determine whether retinal D1Rs exclusively mediate the effects of endogenous dopamine and systemically delivered D1R agonist or antagonist in the mouse form deprivation myopia (FDM) model. Male C57BL/6 mice subjected to unilateral FDM or unobstructed vision were divided into the following four groups: one noninjected and three groups that received intraperitoneal injections of a vehicle, D1R agonist SKF38393 (18 and 59 nmol/g), or D1R antagonist SCH39166 (0.1 and 1 nmol/g). The effects of these drugs on FDM were further assessed in Drd1-knock-out (Drd1-KO), retina-specific conditional Drd1-KO (Drd1-CKO) mice, and corresponding wild-type littermates. In the visually unobstructed group, neither SKF38393 nor SCH39166 affected normal refractive development, whereas myopia development was attenuated by SKF38393 and enhanced by SCH39166 injections. In Drd1-KO or Drd1-CKO mice, however, these drugs had no effect on FDM development, suggesting that activation of retinal D1Rs is pertinent to myopia suppression by the D1R agonist. Interestingly, the development of myopia was unchanged by either Drd1-KO or Drd1-CKO, and neither SKF38393 nor SCH39166 injections, nor Drd1-KO, affected the retinal or vitreal dopamine and the dopamine metabolite DOPAC levels. Effects on axial length were less marked than effects on refraction. Therefore, activation of D1Rs, specifically retinal D1Rs, inhibits myopia development in mice. These results also suggest that multiple dopamine D1R mechanisms play roles in emmetropization and myopia development.SIGNIFICANCE STATEMENT While dopamine is recognized as a "stop" signal that inhibits myopia development (myopization), the location of the dopamine D1 receptors (D1Rs) that mediate this action remains to be addressed. Answers to this key question are critical for understanding how dopaminergic systems regulate ocular growth and refraction. We report here the results of our study showing that D1Rs are essential for controlling ocular growth and myopia development in mice, and for identifying the retina as the site of action for dopaminergic control via D1Rs. These findings highlight the importance of intrinsic retinal dopaminergic mechanisms for the regulation of ocular growth and suggest specific avenues for exploring the retinal mechanisms involved in the dopaminergic control of emmetropization and myopization.

Sdr16c5 and Sdr16c6 control a dormant pathway at a bifurcation point between meibogenesis and sebogenesis.

Genes Sdr16c5 and Sdr16c6 encode proteins that belong to a superfamily of short-chain dehydrogenases/reductases (SDR16C5 and SDR16C6). Simultaneous inactivation of these genes in double-KO (DKO) mice was previously shown to result in a marked enlargement of the mouse Meibomian glands (MGs) and sebaceous glands, respectively. However, the exact roles of SDRs in physiology and biochemistry of MGs and sebaceous glands have not been established yet. Therefore, we characterized, for the first time, meibum and sebum of Sdr16c5/Sdr16c6-null (DKO) mice using high-resolution MS and LC. In this study, we demonstrated that the mutation upregulated the overall production of MG secretions (also known as meibogenesis) and noticeably altered their lipidomic profile, but had a more subtle effect on sebogenesis. The major changes in meibum of DKO mice included abnormal accumulation of shorter chain, sebaceous-type cholesteryl esters and wax esters (WEs), and a marked increase in the biosynthesis of monounsaturated and diunsaturated Meibomian-type WEs. Importantly, the MGs of DKO mice maintained their ability to produce typical extremely long chain Meibomian-type lipids at seemingly normal levels. These observations indicated preferential activation of a previously dormant biosynthetic pathway that produce shorter chain, and more unsaturated, sebaceous-type WEs in the MGs of DKO mice, without altering the elongation patterns of their extremely long chain Meibomian-type counterparts. We conclude that the Sdr16c5/Sdr16c6 pair may control a point of bifurcation in one of the meibogenesis subpathways at which biosynthesis of lipids can be redirected toward either abnormal sebaceous-type lipidome or normal Meibomian-type lipidome in WT mice.

Egg envelope formation of medaka Oryzias latipes requires ZP proteins originating from both the liver and ovary.

Teleost oocytes are surrounded by a structure called chorion or egg envelopes, which is composed of zona pellucida (ZP) proteins. As a result of the gene duplication in teleost, the expression site of the zp genes, coding the major component protein of egg envelopes, changed from the ovary to the maternal liver. In Euteleostei, there are three liver-expressed zp genes, named choriogenin (chg) h, chg hm, and chg l, and the composition of the egg envelope is mostly made up of these Chgs. In addition, ovary-expressed zp genes are also conserved in the medaka genomes, and their proteins have also been found to be minor components of the egg envelopes. However, the specific role of liver-expressed versus ovary-expressed zp genes was unclear. In the present study, we showed that ovary-synthesized ZP proteins first form the base layer of the egg envelope and then Chgs polymerize inwardly to thicken the egg envelope. To analyze the effects of dysfunction of the chg gene, we generated some chg knockout medaka. All knockout females failed to produce normally fertilized eggs by the natural spawning. The egg envelopes lacking Chgs were significantly thinner, but layers formed by ZP proteins synthesized in the ovary were found in the thin egg envelope of knockout as well as wildtype eggs. These results suggest that the ovary-expressed zp gene is well conserved in all teleosts, including those species in which liver-derived ZP proteins are the major component, because it is essential for the initiation of egg envelope formation.

Functional analysis of the protocatechuate branch of the ß-ketoadipate pathway in Aspergillus niger.

Bacteria and fungi catabolize plant-derived aromatic compounds by funneling into one of seven dihydroxylated aromatic intermediates, which then undergo ring fission and conversion to TCA cycle intermediates. Two of these intermediates, protocatechuic acid and catechol, converge on ß-ketoadipate which is further cleaved to succinyl-CoA and acetyl-CoA. These ß-ketoadipate pathways have been well characterized in bacteria. The corresponding knowledge of these pathways in fungi is incomplete. Characterization of these pathways in fungi would expand our knowledge and improve the valorization of lignin-derived compounds. Here, we used homology to characterize bacterial or fungal genes to predict the genes involved in the ß-ketoadipate pathway for protocatechuate utilization in the filamentous fungus Aspergillus niger. We further used the following approaches to refine the assignment of the pathway genes: whole transcriptome sequencing to reveal genes upregulated in the presence of protocatechuic acid; deletion of candidate genes to observe their ability to grow on protocatechuic acid; determination by mass spectrometry of metabolites accumulated by deletion mutants; and enzyme assays of the recombinant proteins encoded by candidate genes. Based on the aggregate experimental evidence, we assigned the genes for the five pathway enzymes as follows: NRRL3_01405 (prcA) encodes protocatechuate 3,4-dioxygenase; NRRL3_02586 (cmcA) encodes 3-carboxy-cis,cis-muconate cyclase; NRRL3_01409 (chdA) encodes 3-carboxymuconolactone hydrolase/decarboxylase; NRRL3_01886 (kstA) encodes ß-ketoadipate:succinyl-CoA transferase; and NRRL3_01526 (kctA) encodes ß-ketoadipyl-CoA thiolase. Strain carrying ΔNRRL3_00837 could not grow on protocatechuic acid, suggesting that it is essential for protocatechuate catabolism. Its function is unknown as recombinant NRRL3_00837 did not affect the in vitro conversion of protocatechuic acid to ß-ketoadipate.

Exploring the Functions of Mutant p53 through TP53 Knockout in HaCaT Keratinocytes.

Approximately 50% of tumors carry mutations in TP53; thus, evaluation of the features of mutant p53 is crucial to understanding the mechanisms underlying cell transformation and tumor progression. HaCaT keratinocytes represent a valuable model for research in this area since they are considered normal, although they bear two gain-of-function mutations in TP53. In the present study, transcriptomic and proteomic profiling were employed to examine the functions of mutant p53 and to investigate the impact of its complete abolishment. Our findings indicate that CRISPR-mediated TP53 knockout results in significant changes at the transcriptomic and proteomic levels. The knockout of TP53 significantly increased the migration rate and altered the expression of genes associated with invasion, migration, and EMT but suppressed the epidermal differentiation program. These outcomes suggest that, despite being dysfunctional, p53 may still possess oncosuppressive functions. However, despite being considered normal keratinocytes, HaCaT cells exhibit oncogenic properties.

Effect of knocking out mouse Slc44a4 on colonic uptake of the microbiota-generated thiamine pyrophosphate and colon physiology.

Humans and mammals obtain vitamin B1 from dietary and gut microbiota sources. A considerable amount of the microbiota-generated vitamin exists in the form of thiamine pyrophosphate (TPP), and colonocytes are capable of absorbing TPP via a specific carrier-mediated process that involves the colonic TPP transporter (cTPPT encoded by SLC44A4). Little is known about the relative contribution of the SLC44A4 transporter toward total colonic carrier-mediated TPP uptake and its role in colon physiology. To address these issues, we generated an Slc44a4 knockout (KO) mouse model (by Cre-Lox recombination) and found a near-complete inhibition in colonic carrier-mediated [3H]TPP uptake in the Slc44a4 KO compared with wild-type (WT) littermates. We also observed a significant reduction in KO mice's body weight and a shortening of their colon compared with WT. Using RNAseq and Ingenuity pathway analysis (IPA) approaches, we found that knocking out the colonic Slc44a4 led to changes in the level of expression of many genes, including upregulation in those associated with intestinal inflammation and colitis. Finally, we found that the Slc44a4 KO mice were more susceptible to the effect of the colitogenic dextran sodium sulfate (DSS) compared with WT animals, a finding that lends support to the recent prediction by multiple genome-wide association studies (GWAS) that SLC44A4 is a possible colitis susceptibility gene. In summary, the results of these investigations show that Slc44a4 is the predominant or only transporter involved in the colonic uptake of TPP, that the transporter is important for colon physiology, and that its deletion increases susceptibility to inflammation.NEW & NOTEWORTHY This study shows that Slc44a4 is the predominant or only transport system involved in the uptake of the gut microbiota-generated thiamine pyrophosphate (TPP) in the colon and that its deletion affects colon physiology and increases its susceptibility to inflammation.

Eighteen genes primarily expressed in the testis are not required for male fertility in mice.

There are approximately 20,000 protein-coding genes in humans and mice. More than 1000 of these genes are predominantly expressed in the testis or are testis-specific and thought to play an important role in male reproduction. Through the production of gene knockout mouse models and phenotypic evaluations, many genes essential for spermatogenesis, sperm maturation, and fertilization have been discovered, greatly contributing to the elucidation of their molecular mechanisms. On the other hand, there are many cases in which single-gene knockout models do not affect fertility, indicating that tissue-specific genes are not always critical. Here, we selected 18 genes whose mRNA expression is restricted to the testis or higher than in other tissues, but whose function in male reproduction is unknown. We then created single-gene KO mouse models using the CRISPR/Cas9 system. The established KO males were subjected to mating tests and screened for effects on fecundity, revealing that these genes were not essential for spermatogenesis and male fertility. This knowledge will contribute to understanding the functions of genes characteristic of the testis and identify the cause of male infertility.

Complement networks in gene-edited pig xenotransplantation: enhancing transplant success and addressing organ shortage.

The shortage of organs for transplantation emphasizes the urgent need for alternative solutions. Xenotransplantation has emerged as a promising option due to the greater availability of donor organs. However, significant hurdles such as hyperacute rejection and organ ischemia-reperfusion injury pose major challenges, largely orchestrated by the complement system, and activated immune responses. The complement system, a pivotal component of innate immunity, acts as a natural barrier for xenotransplantation. To address the challenges of immune rejection, gene-edited pigs have become a focal point, aiming to shield donor organs from human immune responses and enhance the overall success of xenotransplantation. This comprehensive review aims to illuminate strategies for regulating complement networks to optimize the efficacy of gene-edited pig xenotransplantation. We begin by exploring the impact of the complement system on the effectiveness of xenotransplantation. Subsequently, we delve into the evaluation of key complement regulators specific to gene-edited pigs. To further understand the status of xenotransplantation, we discuss preclinical studies that utilize gene-edited pigs as a viable source of organs. These investigations provide valuable insights into the feasibility and potential success of xenotransplantation, offering a bridge between scientific advancements and clinical application.

Generation of streptocarbazoles with cytotoxicities by pathway engineering and insights into their biosynthesis.

Streptocarbazoles are a class of indolocarbazole (ICZ) compounds produced by Streptomyces strains that feature unique cyclic N-glycosidic linkages between the 1,3-carbon atoms of the glycosyl moiety and the two indole nitrogen atoms. Although several streptocarbazole compounds display effective cytotoxic activity, their biosynthesis remains unclear. Herein, through the inactivation of the aminotransferase gene spcI in the staurosporine biosynthetic gene cluster spc followed by heterologous expression, two new streptocarbazole derivatives (1 and 3) and three known ICZs (2, 4, and 5) were generated. Their structures were determined by a combination of spectroscopic methods, circular dichroism measurements, and single-crystal X-ray diffraction. Compounds 1-4 displayed moderate cytotoxicity against HCT-116 cell line, and compounds 3 and 4 were effective against Huh 7 cell line. Double-gene knockout experiments allowed us to propose a biosynthetic pathway for streptocarbazole productions. Furthermore, by overexpression of the involving key enzymes, the production of streptocarbazoles 1 and 3 were improved by approximately 1.5-2.5 fold. IMPORTANCE: Indolocarbazoles (ICZs) are a group of antitumor agents, with several analogs used in clinical trials. Therefore, the identification of novel ICZ compounds is important for drug discovery. Streptocarbazoles harbor unique N-glycosidic linkages (N13-C1' and N12-C3'), distinguishing them from the representative ICZ compound staurosporine; however, their biosynthesis remains unclear. In this study, two new streptocarbazoles (1 and 3) with cytotoxic activities were obtained by manipulating the staurosporine biosynthetic gene cluster spc followed by heterologous expression. The biosynthetic pathway of streptocarbazoles was proposed, and their productions were improved through the overexpression of the key enzymes involved. This study enriches the structural diversity of ICZ compounds and would facilitate the discovery of new streptocarbazoles via synthetic biological strategies.