Search Results (149)

Background/Objectives: Congenital anomalies of the kidney and urinary tract (CAKUTs) represent the leading cause of pediatric chronic kidney disease, yet the molecular mechanisms underlying these malformations remain incompletely understood. While genetic studies have identified numerous CAKUT-associated genes, conventional knockout approaches often result in embryonic lethality or fail to reveal tissue-specific gene functions. This review aims to synthesize findings from conditional knockout mouse studies that have elucidated the spatiotemporal requirements of key signaling pathways during kidney development. Methods: We conducted a narrative synthesis of studies employing Cre-loxP conditional gene targeting in mouse models, identified through systematic searches of PubMed and cross-referencing of key primary research. Studies were selected based on their use of lineage-specific Cre drivers (Six2-Cre, Hoxb7-Cre, Foxd1-Cre) to investigate nephron progenitor maintenance, ureteric bud branching morphogenesis, and stromal–epithelial interactions. Results: Conditional knockout studies have redefined CAKUT pathogenesis as a disorder of dose-dependent signaling, temporal regulation, and inter-compartmental communication. WNT/β-catenin signaling operates in a biphasic, dose-dependent manner in nephron progenitors, with Six2-Cre-mediated β-catenin deletion causing premature progenitor depletion. BMP and FGF pathways demonstrate dose-dependent and context-specific functions in progenitor maintenance, while GDNF/RET signaling is essential for ureteric bud outgrowth and branching. Importantly, stromal-specific deletions have uncovered non-cell-autonomous mechanisms regulating nephron formation. Haploinsufficiency studies demonstrate that partial pathway disruption can reduce nephron endowment without overt CAKUT, predisposing to adult-onset hypertension and chronic kidney disease. Conclusions: Conditional gene targeting has mechanistically redefined CAKUT from a collection of structural malformations to a spectrum of disorders arising from quantitative perturbations in lineage-specific signaling networks. These findings establish that phenotypic severity is determined by the degree of pathway disruption, the developmental timing of insult, and the compartment affected, providing a framework for interpreting oligogenic interactions and variable penetrance in human CAKUTs. Full article

Mitochondria comprise ~1/3rd of the volume of an adult ventricular cardiomyocyte. The gene Immt encodes the Mic60/Mitofilin protein that is hypothesized to organize the mitochondrial contact site and cristae organization system (MICOS) complex that generates mitochondrial cristae junctions between the inner and outer membranes. To investigate the function of the Immt gene in the mouse heart, we generated and characterized mice in which this gene was specifically deleted in the mouse heart using a loxP-targeted allele (Immt^fl/fl) and either the constitutive heart-specific Myh6-Cre transgene or the conditional Myh6-MerCreMer transgene, each of which showed lethality in several weeks. Hearts from these mice showed progressive hypertrophic cardiomyopathy and failure with lost contractility and lung edema. At the ultrastructural level, hearts from these mice showed extreme abnormalities in mitochondrial architecture characterized by lost cristae junctions, stacking of the inner mitochondrial membranes, mitophagy and areas with complete absence of mitochondria. Analysis of mitochondria showed loss of the MICOS complex of proteins as well as loss of mitochondrial membrane potential (Δψ) and increased expression of mitophagy proteins and mitochondrial biogenesis transcription factors. Hearts from these mice also showed widespread cardiomyocyte necrosis and induction of the universal mitochondrial stress response at the mRNA level, as well as major alterations in cardiac metabolites, suggesting greater use of glucose, ketones and amino acids. We conclude that the Immt gene is required for cardiac mitochondrial structure and function, although the ensuing mitochondrial stress response provides molecular clues as to how the heart can compensate metabolically and maintain viability for weeks after mitochondria are absent or unfunctional. Full article

Amyotrophic Lateral Sclerosis (ALS) is a devastating neuromuscular disorder characterized by the progressive loss of motor neurons and skeletal muscle, ultimately leading to respiratory failure and death, typically within 3–5 years following diagnosis. While the death of motor neurons is the pathological hallmark, ALS is increasingly recognized as a systemic disorder involving non-motor systems. Gastrointestinal dysfunction has been widely observed in both ALS patients and animal models. However, because gut abnormalities and neuromuscular degeneration are intertwined during ALS disease progression, it remains unclear whether these gut abnormalities are merely a consequence of neuromuscular degeneration or whether they play a crucial role in initiating it. In this study, we investigated whether an ALS-associated mutation expressed exclusively in the gut can directly affect neuromuscular function. We generated a novel transgenic mouse model, Gut-hG93A, which overexpresses the human ALS mutation hSOD1^G93A specifically in the epithelial cells of the intestine at a level comparable to the endogenous mouse SOD1. We found that the specific overexpression of hSOD1^G93A in gut epithelial cells did not cause abnormalities in the structure of the tight junctions or in gut permeability. Furthermore, there were no significant differences between Gut-hG93A and control mice regarding lifespan, body weight, or neuromuscular activities, including grip strength, daily travel distance and in vivo muscle contractility. These findings suggest that the ALS-associated hSOD1^G93A mutation, when expressed solely in the gut epithelium, is not sufficient to initiate neuromuscular degeneration of systemic ALS-like pathology. Full article

Signal transducer and activator of transcription 2 (STAT2) is a key component of the type I interferon (IFN-I/III) signaling pathway, which is pivotal in host defense against cancer and viral infections and in shaping immune responses. Building on our previously reported conditional Stat2 knockout (KO) mouse, we expand its utility by validating additional tissue-specific models and exploring novel functional contexts. Mice carrying loxP-flanked Stat2 alleles were crossed with CMV-Cre, Cdx2-Cre or CD11c-Cre mice. Deletion of STAT2 was validated by PCR genotyping and western blotting in the relevant tissues. To confirm defective IFN-I signaling with STAT2 deletion, IFN-β stimulation of splenocytes from CMV-Cre Stat2 KO mice showed a lack of induction of canonical IFN-I target genes, confirming functional disruption of the pathway. In vivo, global Stat2 deletion significantly impaired the antitumor efficacy of IFN-β treatment. Similarly, lung fibroblasts isolated from globally deleted Stat2 KO mice showed defective antiviral responses to IFN-β. Tissue-specific Cre models demonstrated selective ablation of STAT2 in target compartments without affecting its expression in non-target tissues. Together, these studies expand our published conditional Stat2 KO findings and highlight the value of this model as a versatile platform for dissecting STAT2-dependent signaling pathways in a tissue- and disease-specific manner. Full article

Serotonin reuptake inhibitors (SSRIs) are commonly prescribed to pregnant women experiencing depression. Such drugs, however, might adversely affect placenta and fetal brain development. Parietal trophoblast giant cells (pTGCs) in the mouse placenta are postulated to internalize maternal serotonin (5-HT) via transport through SERT, encoded by Slc6a4, and to provide the initial source of 5-HT to the emerging brain via the placental–brain axis. Genetic deletion of Slc6a4 in pTGCs has been hypothesized to impact placental and fetal brain development. A transgenic mouse line with high-affinity SERT, encoded by Slc6a4, was selectively deleted by pairing mice with Cre recombinase linked to Prl2c2, with LoxP sites flanking the Slc6a4 gene. PRL2C2 is solely expressed by pTGCs and other giant cells of the placenta. To compare placental and fetal brain development in selective Slc6a4 KO and WT mice, 5-HT content in the placenta and fetal brains of conceptuses was measured. No significant differences in 5-HT content were evident between knockout (KO) and wild-type (WT) placentas or fetal brains. However, there were significantly fewer pTGCs in KO placentas compared to WT (p ≤ 0.05). Sexually dimorphic differences in gene expression were evident in the placenta and fetal brain between KO and WT counterparts, with female conceptuses showing the most dramatic responses, including decrease in Prl7a2, Prl5a1, Prl3a1, Slc28a3, and Ceacam 15 in female placental samples. These findings suggest that ablation of Slc6a4 in pTGC disrupts the placenta–brain axis in a sex-dependent manner. The results might have important clinical ramifications for pregnant women being treated with SSRIs. Full article

The Ataxin-2-like (ATXN2L) protein is required to survive embryonic development, as documented in mice with the constitutive absence of the ATXN2L Lsm, LsmAD, and PAM2 domains due to knock-out (KO) of exons 5–8 with a frameshift. Its less abundant paralog, Ataxin-2 (ATXN2), has an extended N-terminus, where a polyglutamine domain is prone to expansions, mediating vulnerability to the polygenic adult motor neuron disease ALS (Amyotrophic Lateral Sclerosis) or causing the monogenic neurodegenerative processes of Spinocerebellar Ataxia Type 2 (SCA2), depending on larger mutation sizes. Here, we elucidated the physiological function of ATXN2L by deleting the LsmAD and PAM2 motifs via loxP-mediated KO of exons 10–17 with a frameshift. Crossing heterozygous floxed mice with constitutive Cre-deleter animals confirmed embryonic lethality among offspring. Crossing with CamK2a-CreERT2 mice and injecting tamoxifen for conditional deletion achieved chimeric ATXN2L absence in CamK2a-positive frontal cortex neurons and reduced spontaneous horizontal movement. Global proteome profiling of frontal cortex homogenate showed ATXN2L levels decreased to 75% and dysregulations enriched in the alternative splicing pathway. Nuclear proteins with Sm domains are critical to performing splicing; therefore, our data suggest that the Like-Sm (Lsm, LsmAD) domains in ATXN2L serve a role in splice regulation, despite their perinuclear location. Full article

Beyond well-known genetic drivers, microRNA dysregulation has emerged as a key contributor to thyroid tumorigenesis. Central to this process is Dicer1, a ribonuclease essential for microRNA maturation, whose expression is often reduced in papillary thyroid carcinoma (PTC). Evidence from previous studies suggest Dicer1 functions as a context-dependent haplo-insufficient tumor suppressor gene: partial loss may promote tumor development, whereas complete loss may disrupt essential cellular functions, causing cell death and tumor suppression. However, the effects of partial or complete Dicer1 loss in thyroid cancer remain unclear. To explore this, we genetically inactivated one (heterozygous) or both (homozygous) Dicer1 alleles specifically in thyroid follicular cells of a RET/PTC3 transgenic mouse model using an inducible Cre-Lox system. Our findings deepen the current understanding of the RET/PTC3-driven PTC model by revealing an increased number of vimentin-positive cells and disruption in redox homeostasis. Additionally, whereas heterozygous Dicer1 loss did not alter tumor progression in RET/PTC3 mice, total loss reduced tumor growth and led to accumulated DNA damage and cell death. These findings highlight the crucial role of Dicer1 dosage in thyroid cancer progression and underscore its potential as a therapeutic target for aggressive PTC and other malignancies characterized by aberrant Dicer1 expression. Full article

We aimed to characterize peritoneal macrophages from two novel mouse models that enable macrophage-specific overexpression of ABCA1 and ABCG1 via Cre recombinase. Since ABCA1/ABCG1 expression in macrophages is acknowledged to be anti-atherogenic, overexpression of these two transporters may result in a potent atheroprotective effect. However, there are no current animal models that permit overexpression of ABCA1/ABCG1 to precisely occur in macrophages. The purpose of this work was to use ex vivo strategies to characterize the peritoneal macrophages from two novel mouse models: ABCA1-LSL mice and ABCG1-LSL mice. Overexpression of ABCA1/ABCG1 in peritoneal macrophages is controlled by Cre recombinase, due to the LoxP-Stop-LoxP (LSL) system regulating ABC-transporter overexpression. In this study, we first characterized cells isolated from the peritoneal cavities of mice via immunofluorescent staining with macrophage markers CD11b and F4/80 to confirm that we were successful with peritoneal macrophage isolation. We next isolated peritoneal macrophages from ABCA1-LSL mice and ABCG1-LSL mice, and then we incubated these cells with gesicle particles containing Cre recombinase to measure ABC-transporter expression via immunoblotting and measure apoAI/HDL-mediated efflux using cholesterol efflux assays. In our experiments, we observed increases in ABCA1 protein expression and apoAI-mediated cholesterol efflux within ABCA1-LSL peritoneal macrophages, and increased ABCG1 protein expression and HDL-mediated cholesterol efflux in ABCG1-LSL peritoneal macrophages, when compared to corresponding control peritoneal macrophage groups. In conclusion, this report shows that ABCA1-LSL mice and ABCG1-LSL mice may possibly be utilized to cross with macrophage-specific Cre mice to study ABC-transporter overexpression precisely in macrophages, thereby providing valuable tools to dissect the impact of macrophage-specific ABC-transporter overexpression on atherogenesis. Full article

Lactic acid bacteria (LAB) are central to food, feed, and health biotechnology, yet their genomes have long resisted rapid, precise manipulation. This review charts the evolution of LAB genome-editing strategies from labor-intensive RecA-dependent double-crossovers to state-of-the-art CRISPR and CRISPR-associated transposase systems. Native homologous recombination, transposon mutagenesis, and phage-derived recombineering opened the door to targeted gene disruption, but low efficiencies and marker footprints limited throughput. Recent phage RecT/RecE-mediated recombineering and CRISPR/Cas counter-selection now enable scar-less point edits, seamless deletions, and multi-kilobase insertions at efficiencies approaching model organisms. Endogenous Cas9 systems, dCas-based CRISPR interference, and CRISPR-guided transposases further extend the toolbox, allowing multiplex knockouts, precise single-base mutations, conditional knockdowns, and payloads up to 10 kb. The remaining hurdles include strain-specific barriers, reliance on selection markers for large edits, and the limited host-range of recombinases. Nevertheless, convergence of phage enzymes, CRISPR counter-selection and high-throughput oligo recombineering is rapidly transforming LAB into versatile chassis for cell-factory and therapeutic applications. Full article

The endocannabinoid system (ECS) is known to regulate crucial bodily functions, including healthy muscle activity. However, its precise roles in normal skeletal muscle function and the development of muscle disorders remain unclear. Previously, we developed a tamoxifen-inducible, skeletal muscle-specific CB₁ receptor knockdown (skmCB1-KD) mouse model using the Cre/LoxP system. In this study, we aimed to clarify the mechanisms behind the observed reduction in muscle force generation in these mice. To investigate this, we analyzed calcium dynamics following electrical stimulation-induced muscle fatigue, assessed store-operated calcium entry (SOCE), and performed functional analysis of mitochondrial respiration. Our findings suggest that the reduced muscle performance observed in vivo likely arises from interconnected alterations in ATP production by mitochondria. Moreover, in skmCB1-KD mice, we detected a significant decrease in a component of the respiratory chain (complex IV) and a slowed dissipation of mitochondrial membrane potential upon the addition of an un-coupler (FCCP). Full article

Background: Sepsis is a life-threatening condition that is characterized by systemic inflammation and organ dysfunction, with adrenal dysfunction being a significant complication. This study aimed to investigate the role of necroptosis and hydrogen sulfide (H₂S) in sepsis-induced adrenal dysfunction. Methods: A cecal ligation and puncture (CLP)-induced sepsis mouse model was employed. Adrenocortical-specific mixed lineage kinase domain-like pseudokinase (MLKL) knockout (MLKL-KO) and cystathioneine β-synthase (CBS) knockout (CBS-KO) mice were generated using Cre-loxP technology and adrenocortical-specific Cre tool mice. In vitro experiments utilized TNFα-stimulated Y1 adrenocortical cells. The treatments included the H₂S donor NaHS, TNFα inhibitor R-7050, necroptosis inhibitor NSA and CBS inhibitor AOAA. Pathological assessment involved hematoxylin–eosin (H&E) staining and a Western blot analysis of necroptosis markers (the phosphorylation of MLKL (p-MLKL) and phosphorylation of receptor-interacting protein kinases 1 (p-RIPK1)). Results: Sepsis induced adrenal congestion, elevated TNFα levels, and activated necroptosis (increased p-MLKL/p-RIPK1) in wild-type mice. H₂S treatment attenuated adrenal damage, reduced TNFα, and suppressed necroptosis. MLKL knockout reduced septic adrenal dysfunction, whereas CBS knockout exacerbated septic adrenal dysfunction. In vitro, TNFα induced Y1 cell necroptosis, which was reversed by H₂S or NSA. AOAA exacerbated TNFα-induced necroptosis in Y1 cells. Conclusions: H₂S inhibits TNFα-mediated necroptosis, thereby preserving adrenal integrity in sepsis. Targeting the TNFα–necroptosis axis and enhancing endogenous H₂S production may represent novel therapeutic strategies for sepsis-associated adrenal dysfunction. Full article

Implantation is a complex and tightly regulated process essential for the establishment of pregnancy. It involves dynamic interactions between a receptive uterus and a competent embryo, orchestrated by ovarian hormones such as estrogen and progesterone. These hormones regulate proliferation, differentiation, and gene expression within the three primary uterine tissue types: myometrium, stroma, and epithelium. Advances in genetic manipulation, particularly the Cre/loxP system, have enabled the in vivo investigation of the role of genes in a uterine compartmental and cell type-specific manner, providing valuable insights into uterine biology during pregnancy and disease. The development of endometrial organoids has further revolutionized implantation research. They mimic the native endometrial structure and function, offering a powerful platform for studying hormonal responses, implantation, and maternal-fetal interactions. Combined with omics technologies, these models have uncovered the molecular mechanisms and signaling pathways that regulate implantation. This review provides a comprehensive overview of uterine-specific genetic tools, endometrial organoids, and omics. We explore how these advancements enhance our understanding of implantation biology, uterine receptivity, and decidualization in reproductive research. Full article

Background/Objectives: The inhibitor of growth family member 3 (ING3) acts as an epigenetic reader through physical interactions with histone-modifying enzymes and subsequent chromatin remodelling processes. It is involved in various cellular functions, such as cell cycle control, cell growth, and apoptosis. Although ING3 was assigned tumour suppressor candidate status in some types of cancers, including prostate cancer, some studies suggest it acts to promote growth. To address these contradictory reports regarding its role in the initiation and progression of prostate cancer, we specifically addressed the question of whether ablation of ING3 in the mouse prostate is sufficient to initiate malignant transformation of the prostate and support its (candidate) tumour suppressor status. Methods: To generate the prostate-specific Ing3 knockout mouse, paternal inheritance of the PB-Cre4 transgene was used, while for the generation of a global knockout control, a female mouse harbouring the PB-Cre4 transgene was utilized. To determine the recombination efficiency of the Cre-LoxP system in the prostate at the Ing3 locus, a duplex probe-based digital PCR assay capable of counting undisrupted Ing3 copies was designed. The impact of DNA recombination on the protein level was investigated by immunohistochemical staining of prostate tissue samples. Results: In the prostate-specific knockout, digital PCR analysis revealed mosaic gene deletion. We found recombination efficiencies in the anterior, dorsolateral, and ventral prostate lobes ranging from approximately 15 to 30%. ING3 staining in the prostate was faint with no detectable differences in signal intensity between the knockout specimen and wild-type controls. This low ING3 expression in the prostate is consistent with observations of X-gal staining of an Ing3-LacZ reporter allele. Immunohistochemistry showed increased expression of DNA-damage-associated markers γH2AX and 53BP1. However, no gross anatomical abnormalities or prostate intraepithelial neoplasia (PIN) lesions in the prostate of tissue-specific knockout animals compared to wild-type controls were observed. Conclusions: Altogether, our data provide evidence that disruption of ING3 expression in prostate cells does not lead to malignant transformation and challenges the idea that ING3 acts primarily in a tumour-suppressive manner. Furthermore, this work supports the crucial role of ING3 in maintaining genomic stability, and we confirmed the embryonic lethal phenotype of homozygous Ing3 null mice that is rescued by ectopic expression of ING3. Full article

Background/Objectives: Incidence of vector-borne diseases, including rickettsioses and anaplasmosis, has been increasing in many parts of the world. The obligate intracellular nature of rickettsial pathogens has hindered the development of robust genetic tools for the study of gene function and the identification of therapeutic targets. Transposon mutagenesis has contributed to recent progress in the identification of virulence factors in this important group of pathogens. Methods: Combining the efficiency of the himar1 transposon method with a recombinase-mediated system, we aimed to develop a genetic tool enabling the exchange of the transposon with a cassette encoding non-native sequences. Results: This approach was used in Rickettsia parkeri to insert a himar1 transposon encoding fluorescent protein and antibiotic resistance genes for visualization and selection, flanked by mismatched loxP sites to enable subsequent recombinase-mediated cassette exchange (RMCE). RMCE mediated by a plasmid-encoded Cre recombinase was then employed to replace the transposon with a different cassette containing alternate fluorescent and selection markers and epitopes of Anaplasma phagocytophilum antigens. The resulting genetically modified R. parkeri was trialed as a live-attenuated vaccine against spotted fever rickettsiosis and anaplasmosis in mice. Conclusions: The use of this system provides a well-established and relatively efficient way of inserting non-native sequences into the rickettsial genome, with applications for the study of gene function and vaccine development. Full article

ADAM10 is a multi-functional proteinase that can cleave approximately 100 different substrates. Previously, it was demonstrated that ADAM10 is expressed by ameloblasts, which are required for enamel formation. The goal of this study was to determine if ADAM10 is necessary for enamel development. Deletion of Adam10 in mice is embryonically lethal and deletion of Adam10 from epithelia is perinatally lethal. We therefore deleted Adam10 from ameloblasts. Ameloblast-specific expression of the Tg(Amelx-iCre)872pap construct was confirmed. These mice were crossed with Adam10 floxed mice to generate Amelx-iCre; Adam10^fl/fl mice (Adam10 cKO). The Adam10 cKO mice had discolored teeth with softer than normal enamel. Notably, the Adam10 cKO enamel density and volume were significantly reduced in both incisors and molars. Moreover, the incisor enamel rod pattern became progressively more disorganized, moving from the DEJ to the outer enamel surface, and this disorganized rod structure created gaps and S-shaped rods. ADAM10 cleaves proteins essential for cell signaling and for enamel formation such as RELT and COL17A1. ADAM10 also cleaves cell-cell contacts such as E- and N-cadherins that may support ameloblast movement necessary for normal rod patterns. This study shows, for the first time, that ADAM10 expressed by ameloblasts is essential for proper enamel formation. Full article