Lineage-specific cell disruption in living mice by Cre-mediated expression of diphtheria toxin A chain

Induction of MASH-like pathogenesis in the Nwd1-/- mouse liver

Endoplasmic reticulum (ER) stores Ca2+ and plays crucial roles in protein folding, lipid transfer, and it's perturbations trigger an ER stress. In the liver, chronic ER stress is involved in the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH). Dysfunction of sarco/endoplasmic reticulum calcium ATPase (SERCA2), a key regulator of Ca2+ transport from the cytosol to ER, is associated with the induction of ER stress and lipid droplet formation. We previously identified NACHT and WD repeat domain-containing protein 1 (Nwd1) localized at the ER and mitochondria. However, the physiological significance of Nwd1 outside the brain remains unclear. In this study, we revealed that Nwd1-/- mice exhibited pathological manifestations comparable to MASH. Nwd1 interacts with SERCA2 near ER membranes. Nwd1-/- livers exhibited reduced SERCA2 ATPase activity and a smaller Ca2+ pool in the ER, leading to an exacerbated state of ER stress. These findings highlight the importance of SERCA2 activity mediated by Nwd1 in the pathogenesis of MASH.

Androgens suppress the sialyltransferases ST3GAL1 and ST3GAL4 and modulate mucin 10 glycosylation in the submandibular gland, related to sex differences in commensal microbiota composition in mice

Sex differences exist in the commensal microbiota that impact on multiple physiological processes in the host. Here, we examined the mechanism by which the sex differences are formed. In addition to the epithelial ductal cell, the acinar cell mass in the submandibular gland was associated with androgen-androgen receptor (AR) signaling. Sex differences in the formation of submandibular mucin 10 (MUC10) were identified using SDS-PAGE. Neuraminidase treatment, which hydrolyzes terminal sialic acid, influenced the mobility shift of MUC10. Androgen-AR signaling negatively regulated ST3 β-galactoside α-2,3-sialyltransferase 1 (St3gal1) and St3gal4 in the submandibular gland. There was a trend and significant sex differences in α-diversity (Shannon, P = .09) and β-diversity (unweighted UniFrac) in oral microbiota composition, respectively. Some female-preferring bacteria including Akkermansia muciniphila can assimilate mucin by degrading terminal sialic acids. Our results indicate that androgen-AR signaling suppresses ST3GAL1 and ST3GAL4, which can influence sex differences in commensal microbiota composition.

Lymphatic endothelial cell-specific NRAS p.Q61R mutant embryos show abnormal lymphatic vessel morphogenesis

Generalized lymphatic anomaly (GLA) and kaposiform lymphangiomatosis (KLA) are rare congenital disorders that arise through anomalous embryogenesis of the lymphatic system. A somatic activating NRAS p.Q61R variant has been recently detected in GLA and KLA tissues, suggesting that the NRAS p.Q61R variant plays an important role in the development of these diseases. To address this role, we studied the effect of the NRAS p.Q61R variant in lymphatic endothelial cells (LECs) on the structure of the lymphatics during embryonic and postnatal lymphangiogenesis applying inducible, LEC-specific NRAS p.Q61R variant in mice. Lox-stop-Lox NrasQ61R mice were crossed with Prox1-CreERT2 mice expressing tamoxifen-inducible Cre recombinase specifically in LECs. Whole-mount immunostaining of embryonic back skin using an antibody against the LEC surface marker VEGFR3 showed considerably greater lymphatic vessel width in LEC-specific NRAS p.Q61R mutant embryos than in littermate controls. These mutant embryos also showed a significant reduction in the number of lymphatic vessel branches. Furthermore, immunofluorescence staining of whole-mount embryonic back skin using an antibody against the LEC-specific nuclear marker Prox1 showed a large increase in the number of LECs in LEC-specific NRAS p.Q61R mutants. In contrast, postnatal induction of the NRAS p.Q61R variant in LECs did not cause abnormal lymphatic vessel morphogenesis. These results suggest that the NRAS p.Q61R variant in LECs plays a role in development of lymphatic anomalies. While this model does not directly reflect the human pathology of GLA and KLA, there are overlapping features, suggesting that further study of this model may help in studying GLA and KLA mechanisms.

Generating an organ-deficient animal model using a multi-targeted CRISPR-Cas9 system

Gene-knockout animal models with organ-deficient phenotypes used for blastocyst complementation are generally not viable. Animals need to be maintained as heterozygous mutants, and homozygous mutant embryos yield only one-fourth of all embryos. In this study, we generated organ-deficient embryos using the CRISPR-Cas9-sgRNAms system that induces cell death with a single-guide RNA (sgRNAms) targeting multiple sites in the genome. The Cas9-sgRNAms system interrupted cell proliferation and induced cell ablation in vitro. The mouse model had Cas9 driven by the Foxn1 promoter with a ubiquitous expression cassette of sgRNAms at the Rosa26 locus (Foxn1Cas9; Rosa26_ms). It showed an athymic phenotype similar to that of nude mice but was not hairless. Eventually, a rat cell-derived thymus in an interspecies chimera was generated by blastocyst complementation of Foxn1Cas9; Rosa26_ms mouse embryos with rat embryonic stem cells. Theoretically, a half of the total embryos has the Cas9-sgRNAms system because Rosa26_ms could be maintained as homozygous.

Myelin-Specific microRNA-23a/b Cluster Deletion Inhibits Myelination in the Central Nervous System during Postnatal Growth and Aging

Microribonucleic acids (miRNAs) comprising miR-23a/b clusters, specifically miR-23a and miR-27a, are recognized for their divergent roles in myelination within the central nervous system. However, cluster-specific miRNA functions remain controversial as miRNAs within the same cluster have been suggested to function complementarily. This study aims to clarify the role of miR-23a/b clusters in myelination using mice with a miR-23a/b cluster deletion (KO mice), specifically in myelin expressing proteolipid protein (PLP). Inducible conditional KO mice were generated by crossing miR-23a/b clusterflox/flox mice with PlpCre-ERT2 mice; the offspring were injected with tamoxifen at 10 days or 10 weeks of age to induce a myelin-specific miR-23a/b cluster deletion. Evaluation was performed at 10 weeks or 12 months of age and compared with control mice that were not treated with tamoxifen. KO mice exhibit impaired motor function and hypoplastic myelin sheaths in the brain and spinal cord at 10 weeks and 12 months of age. Simultaneously, significant decreases in myelin basic protein (MBP) and PLP expression occur in KO mice. The percentages of oligodendrocyte precursors and mature oligodendrocytes are consistent between the KO and control mice. However, the proportion of oligodendrocytes expressing MBP is significantly lower in KO mice. Moreover, changes in protein expression occur in KO mice, with increased leucine zipper-like transcriptional regulator 1 expression, decreased R-RAS expression, and decreased phosphorylation of extracellular signal-regulated kinases. These findings highlight the significant influence of miR-23a/b clusters on myelination during postnatal growth and aging.

In situ FRET measurement of cellular tension using conventional confocal laser microscopy in newly established reporter mice expressing actinin tension sensor

FRET-based sensors are utilized for real-time measurements of cellular tension. However, transfection of the sensor gene shows low efficacy and is only effective for a short period. Reporter mice expressing such sensors have been developed, but sensor fluorescence has not been measured successfully using conventional confocal microscopy. Therefore, methods for spatiotemporal measurement of cellular tension in vivo or ex vivo are still limited. We established a reporter mouse line expressing FRET-based actinin tension sensors consisting of EGFP as the donor and mCherry as the acceptor and whose FRET ratio change is observable with confocal microscopy. Tension-induced changes in FRET signals were monitored in the aorta and tail tendon fascicles, as well as aortic smooth muscle cells isolated from these mice. The pattern of FRET changes was distinctive, depending on tissue type. Indeed, aortic smooth muscle cells exhibit different sensitivity to macroscopic tensile strain in situ and in an isolated state. This mouse strain will enable novel types of biomechanical investigations of cell functions in important physiological events.

An intact pituitary vasopressin system is critical for building a robust circadian clock in the suprachiasmatic nucleus

The circadian clock is a biological timekeeping system that oscillates with a circa-24-h period, reset by environmental timing cues, especially light, to the 24-h day-night cycle. In mammals, a "central" clock in the hypothalamic suprachiasmatic nucleus (SCN) synchronizes "peripheral" clocks throughout the body to regulate behavior, metabolism, and physiology. A key feature of the clock's oscillation is resistance to abrupt perturbations, but the mechanisms underlying such robustness are not well understood. Here, we probe clock robustness to unexpected photic perturbation by measuring the speed of reentrainment of the murine locomotor rhythm after an abrupt advance of the light-dark cycle. Using an intersectional genetic approach, we implicate a critical role for arginine vasopressin pathways, both central within the SCN and peripheral from the anterior pituitary.

Greb1 Transiently Accelerates Pancreatic β-Cell Proliferation in Diabetic Mice Exposed to Estradiol

Decrease of pancreatic β cells leads to diabetes. In an inducible cAMP early suppressor (ICER-Iγ) transgenic mouse model of severe type 2 diabetes with reduced insulin production and depleted β cells, supplementation with high concentrations of 17β-estradiol (E2) markedly enhances β-cell proliferation and normalizes glucose levels. The current study explored the underlying mechanisms leading to a dynamic increase of β cells and pathologic changes in diabetic mice exposed to E2. Gene expression profiling of pancreatic islets of 6-month-old ICER-transgenic mice recovering from diabetes due to elevated E2 levels identified growth regulation by estrogen in breast cancer 1 (Greb1) as a gene significantly up-regulated during the recovery phase. To substantiate this, β-cell-specific Greb1-deficient mice were generated, and Greb1 was shown to be essential for recovery of depleted β cells in diabetic mice. Graft growth and glucose lowering were observed in 50 islets with increased Greb1 expression transplanted adjacent to E2 pellets beneath the kidney capsule of streptozotocin-induced diabetic mice. Greb1 expression due to a drastic increase in exogenous or endogenous E2 was transient and closely correlated with changes in E2-related and some cell cycle-related genes. These findings provide new insights into in vivo proliferation of deficient β cells and suggest the possibility of new therapeutic approaches targeting pancreatic β cells that could revolutionize the concept of diabetes treatment, which has been considered difficult to cure completely.

The Helicobacter pylori CagA oncoprotein disrupts Wnt/PCP signaling and promotes hyperproliferation of pyloric gland base cells

Helicobacter pylori strains that deliver the oncoprotein CagA into gastric epithelial cells are the major etiologic agents of upper gastric diseases including gastric cancer. CagA promotes gastric carcinogenesis through interactions with multiple host proteins. Here, we show that CagA also disrupts Wnt-dependent planar cell polarity (Wnt/PCP), which orients cells within the plane of an epithelium and coordinates collective cell behaviors such as convergent extension to enable epithelial elongation during development. Ectopic expression of CagA in Xenopus laevis embryos impaired gastrulation, neural tube formation, and axis elongation, processes driven by convergent extension movements that depend on the Wnt/PCP pathway. Mice specifically expressing CagA in the stomach epithelium had longer pyloric glands and mislocalization of the tetraspanin proteins VANGL1 and VANGL2 (VANGL1/2), which are critical components of Wnt/PCP signaling. The increased pyloric gland length was due to hyperproliferation of cells at the gland base, where Lgr5⁺ stem and progenitor cells reside, and was associated with fewer differentiated enteroendocrine cells. In cultured human gastric epithelial cells, the N terminus of CagA interacted with the C-terminal cytoplasmic tails of VANGL1/2, which impaired Wnt/PCP signaling by inducing the mislocalization of VANGL1/2 from the plasma membrane to the cytoplasm. Thus, CagA may contribute to the development of gastric cancer by subverting a Wnt/PCP-dependent mechanism that restrains pyloric gland stem cell proliferation and promotes enteroendocrine differentiation.

Deficiency of MicroRNA-23-27-24 Clusters Exhibits the Impairment of Myelination in the Central Nervous System

Several microRNAs (miRNAs), including miR-23 and miR-27a have been reportedly involved in regulating myelination in the central nervous system. Although miR-23 and miR-27a form clusters in vivo and the clustered miRNAs are known to perform complementary functions, the role of these miRNA clusters in myelination has not been studied. To investigate the role of miR-23-27-24 clusters in myelination, we generated miR-23-27-24 cluster knockout mice and evaluated myelination in the brain and spinal cord. Our results showed that 10-week-old knockout mice had reduced motor function in the hanging wire test compared to the wild-type mice. At 4 weeks, 10 weeks, and 12 months of age, knockout mice showed reduced myelination compared to wild-type mice. The expression levels of myelin basic protein and myelin proteolipid protein were also significantly lower in the knockout mice compared to the wild-type mice. Although differentiation of oligodendrocyte progenitor cells to oligodendrocytes was not inhibited in the knockout mice, the percentage of oligodendrocytes expressing myelin basic protein was significantly lower in 4-week-old knockout mice than that in wild-type mice. Proteome analysis and western blotting showed increased expression of leucine-zipper-like transcription regulator 1 (LZTR1) and decreased expression of R-RAS and phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) in the knockout mice. In summary, loss of miR-23-27-24 clusters reduces myelination and compromises motor functions in mice. Further, LZTR1, which regulates R-RAS upstream of the ERK1/2 pathway, a signal that promotes myelination, has been identified as a novel target of the miR-23-27-24 cluster in this study.

Embryonic β-Catenin Is Required for Priming of the Uterus to Implantation

Repeated implantation failure is a major cause of infertility among healthy women. Uterine β-catenin (CTNNB1) plays a critical role in implantation. However, the role of embryonic CTNNB1 during implantation remains unclear. We addressed this topic by analyzing mice carrying Ctnnb1-deficient (Ctnnb1^Δ/Δ) embryos. Ctnnb1^Δ/Δ embryos were produced by intercrossing mice bearing Ctnnb1-deficient eggs and sperms. We found that Ctnnb1^Δ/Δ embryos developed to the blastocyst stage; thereafter, they were resorbed, leaving empty decidual capsules. Moreover, leukemia inhibitory factor, a uterine factor essential for implantation, was undetectable in Ctnnb1^Δ/Δ blastocysts. Furthermore, CDX2, a transcription factor that determines the fate of trophectoderm cells, was not observed in Ctnnb1^Δ/Δ blastocysts. Intrauterine injection with uterine fluids (from control mice) and recombinant mouse leukemia inhibitory factor proteins rescued the uterine response to Ctnnb1^Δ/Δ blastocysts. These results suggest that embryonic CTNNB1 is required for the secretion of blastocyst-derived factor(s) that open the implantation window, indicating that the uterine response to implantation can be induced using supplemental materials. Therefore, our results may contribute to the discovery of a similar mechanism in humans, leading to a better understanding of the pathogenesis of repeated implantation failure.

Hepatic phosphatidylcholine catabolism driven by PNPLA7 and PNPLA8 supplies endogenous choline to replenish the methionine cycle with methyl groups

Choline supplies methyl groups for regeneration of methionine and the methyl donor S-adenosylmethionine in the liver. Here, we report that the catabolism of membrane phosphatidylcholine (PC) into water-soluble glycerophosphocholine (GPC) by the phospholipase/lysophospholipase PNPLA8-PNPLA7 axis enables endogenous choline stored in hepatic PC to be utilized in methyl metabolism. PNPLA7-deficient mice show marked decreases in hepatic GPC, choline, and several metabolites related to the methionine cycle, accompanied by various signs of methionine insufficiency, including growth retardation, hypoglycemia, hypolipidemia, increased energy consumption, reduced adiposity, increased fibroblast growth factor 21 (FGF21), and an altered histone/DNA methylation landscape. Moreover, PNPLA8-deficient mice recapitulate most of these phenotypes. In contrast to wild-type mice fed a methionine/choline-deficient diet, both knockout strains display decreased hepatic triglyceride, likely via reductions of lipogenesis and GPC-derived glycerol flux. Collectively, our findings highlight the biological importance of phospholipid catabolism driven by PNPLA8/PNPLA7 in methyl group flux and triglyceride synthesis in the liver.

Ascl1-expressing cell differentiation in initially developed taste buds and taste organoids

Mammalian taste bud cells are composed of several distinct cell types and differentiated from surrounding tongue epithelial cells. However, the detailed mechanisms underlying their differentiation have yet to be elucidated. In the present study, we examined an Ascl1-expressing cell lineage using circumvallate papillae (CVP) of newborn mice and taste organoids (three-dimensional self-organized tissue cultures), which allow studying the differentiation of taste bud cells in fine detail ex vivo. Using lineage-tracing analysis, we observed that Ascl1 lineage cells expressed type II and III taste cell markers both CVP of newborn mice and taste organoids. However, the coexpression rate in type II cells was lower than that in type III cells. Furthermore, we found that the generation of the cells which express type II and III cell markers was suppressed in taste organoids lacking Ascl1-expressing cells. These findings suggest that Ascl1-expressing precursor cells can differentiate into both type III and a subset of type II taste cells.

Inka2 expression in smooth muscle cells and its involvement in cell migration

The cell motility of smooth muscle cells (SMCs) is essential for vascular and internal organ development and tissue regeneration in response to damage. Cell migration requires dynamic changes in the actin-cytoskeleton via the p-21 activated kinase (Pak)-Cofilin signaling cascade, which is the central axis of the actin filaments. We previously identified that the Inka2 gene was preferentially expressed in the central nervous system (CNS) and revealed that Inka2 directly binds Pak4 to suppress its kinase activity, thereby regulating actin de-polymerization in dendritic spine formation of the forebrain neurons. However, its physiological significance outside the CNS remains unclear. Here we determined the Inka2 expression profile in various organs using in situ hybridization analysis and lacZ staining on Inka2^flox/+ mice. Robust Inka2 expression was consistently detected in the SMCs of many peripheral organs, including the arteries, esophagus, stomach, intestine, and bladder. The scratch assay was used on primary cultured SMCs and revealed that Inka2^-/- SMC exhibits accelerated cell migration ability without a change in the cell proliferation rate. Inka2^-/- SMCs displayed Cofilin activation/phosphorylation, a downstream molecule of Pak4 signal cascade. These results suggest that Inka2 regulates SMC motility through modulating actin reorganization as the endogenous inhibitor of Pak4.

Testis-enriched ferlin, FER1L5, is required for Ca2+-activated acrosome reaction and male fertility

Spermatozoa need to undergo an exocytotic event called the acrosome reaction before fusing with eggs. Although calcium ion (Ca2+) is essential for the acrosome reaction, its molecular mechanism remains unknown. Ferlin is a single transmembrane protein with multiple Ca2+-binding C2 domains, and there are six ferlins, dysferlin (DYSF), otoferlin (OTOF), myoferlin (MYOF), fer-1-like 4 (FER1L4), FER1L5, and FER1L6, in mammals. Dysf, Otof, and Myof knockout mice have been generated, and each knockout mouse line exhibited membrane fusion disorders such as muscular dystrophy in Dysf, deafness in Otof, and abnormal myogenesis in Myof. Here, by generating mutant mice of Fer1l4, Fer1l5, and Fer1l6, we found that only Fer1l5 is required for male fertility. Fer1l5 mutant spermatozoa could migrate in the female reproductive tract and reach eggs, but no acrosome reaction took place. Even a Ca2+ ionophore cannot induce the acrosome reaction in Fer1l5 mutant spermatozoa. These results suggest that FER1L5 is the missing link between Ca2+ and the acrosome reaction.

miR-23a/b clusters are not essential for the pathogenesis of osteoarthritis in mouse aging and post-traumatic models

Osteoarthritis (OA), the most prevalent aging-related joint disease, is characterized by insufficient extracellular matrix synthesis and articular cartilage degradation and is caused by various risk factors including aging and traumatic injury. Most microRNAs (miRNAs) have been associated with pathogenesis of osteoarthritis (OA) using in vitro models. However, the role of many miRNAs in skeletal development and OA pathogenesis is uncharacterized in vivo using genetically modified mice. Here, we focused on miR-23-27-24 clusters. There are two paralogous miR-23-27-24 clusters: miR-23a-27a-24-2 (miR-23a cluster) and miR-23b-27b-24-1 (miR-23b cluster). Each miR-23a/b, miR-24, and miR-27a/b is thought to function coordinately and complementary to each other, and the role of each miR-23a/b, miR-24, and miR-27a/b in OA pathogenesis is still controversial. MiR-23a/b clusters are highly expressed in chondrocytes and the present study examined their role in OA. We analyzed miRNA expression in chondrocytes and investigated cartilage-specific miR-23a/b clusters knockout (Col2a1-Cre; miR-23a/bflox/flox: Cart-miR-23clus KO) mice and global miR-23a/b clusters knockout (CAG-Cre; miR-23a/bflox/flox: Glob-miR-23clus KO) mice. Knees of Cart- and Glob-miR-23a/b clusters KO mice were evaluated by histological grading systems for knee joint tissues using aging model (12 and/or 18 month-old) and surgically-induced OA model. miR-23a/b clusters were among the most highly expressed miRNAs in chondrocytes. Skeletal development of Cart- and Glob-miR-23clus KO mice was grossly normal although Glob-miR-23clus KO had reduced body weight, adipose tissue and bone density. In the aging model and surgically-induced OA model, Cart- and Glob-miR-23clus KO mice exhibited mild OA-like changes such as proteoglycan loss and cartilage fibrillation. However, the histological scores were not significantly different in terms of the severity of OA in Cart- and Glob-miR-23clus KO mice compared with control mice. Together, miR-23a/b clusters, composed of miR-23a/b, miR-24, miR-27a/b do not significantly contribute to OA pathogenesis.

Inka2, a novel Pak4 inhibitor, regulates actin dynamics in neuronal development

The actin filament is a fundamental part of the cytoskeleton defining cell morphology and regulating various physiological processes, including filopodia formation and dendritic spinogenesis of neurons. Serine/threonine-protein kinase Pak4, an essential effector, links Rho GTPases to control actin polymerization. Previously, we identified the Inka2 gene, a novel mammalian protein exhibiting sequence similarity to Inka1, which serves as a possible inhibitor for Pak4. Although Inka2 is dominantly expressed in the nervous system and involved in focal-adhesion dynamics, its molecular role remains unclear. Here, we found that Inka2-iBox directly binds to Pak4 catalytic domain to suppress actin polymerization. Inka2 promoted actin depolymerization and inhibited the formation of cellular protrusion caused by Pak4 activation. We further generated the conditional knockout mice of the Inka2 gene. The beta-galactosidase reporter indicated the preferential Inka2 expression in the dorsal forebrain neurons. Cortical pyramidal neurons of Inka2^-/- mice exhibited decreased density and aberrant morphology of dendritic spines with marked activation/phosphorylation of downstream molecules of Pak4 signal cascade, including LIMK and Cofilin. These results uncovered the unexpected function of endogenous Pak4 inhibitor in neurons. Unlike Inka1, Inka2 is a critical mediator for actin reorganization required for dendritic spine development.

Actin filaments are an essential part of the cytoskeleton defining cell morphology and regulating various cellular processes, such as cell migration and synapse formation in the brain. Actin polymerization is controlled by the kinase activity of the Pak4 signaling cascade, including LIMK and Cofilin. Previously, we identified the Inka2 gene, which is strongly expressed in the mammalian central nervous system and a similar sequence as Inka1. Inka1 was reported to serve as a Pak4 inhibitor in cancer cell lines; however, the physiological function of Inka2 is unclear. In this study, we found that (i) Inka2 overexpression inhibits the formation of cell-protrusion caused by Pak4 activation; (ii) Inka2 directly binds to the catalytic domain of Pak4 to inhibit intracellular actin polymerization; (iii) Inka2 is specifically expressed in neurons in the forebrain region, including the cerebral cortex and hippocampus that are known to be essential for brain plasticity, such as learning and memory; and (iv) cortical neurons of Inka2-deficient mice showed decreased synapse formation and abnormal spine morphology, probably due to the marked phosphorylation of LIMK and Cofilin. These results indicate that Inka2 is an endogenous Pak4 inhibitor in neurons required for normal synapse formation through the modulation of actin reorganization.

Androgen receptor suppresses β-adrenoceptor-mediated CREB activation and thermogenesis in brown adipose tissue of male mice

Thermoregulation is a process by which core body temperature is maintained in mammals. Males typically have a lower body temperature than females. However, the effects of androgens, which show higher levels in males, on adrenergic receptor-mediated thermogenesis remain unclear. Here, we demonstrate that androgen-androgen receptor (AR) signaling suppresses the β-adrenergic agonist-induced rise of core body temperature using castrated and AR knockout (ARKO) male mice. Furthermore, in vitro mechanistic studies show that activated AR inhibits cAMP response element (CRE)-mediated transcription by suppressing cAMP response element-binding protein (CREB) phosphorylation. The elevation of body temperature induced by the β-adrenergic agonist CL316243 was higher in ARKO and castrated mice than in the control mice. Similarly, CL316243 induced a greater increase in Uncoupling protein 1 (Ucp1) expression and CREB phosphorylation in the brown adipose tissue of ARKO mice than in that of controls. We determined that activation of AR by dihydrotestosterone suppressed β3-agonist- or forskolin-induced CRE-mediated transcription, which was prevented by AR antagonist. AR activation also suppressed CREB phosphorylation induced by forskolin. Moreover, we found AR nuclear localization, but not transcriptional activity, was necessary for the suppression of CRE-mediated transcription. Finally, modified mammalian two-hybrid and immunoprecipitation analyses suggest nuclear AR and CREB form a protein complex both in the presence and absence of dihydrotestosterone and forskolin. These results suggest androgen-AR signaling suppresses β-adrenoceptor-induced UCP1-mediated brown adipose tissue thermogenesis by suppressing CREB phosphorylation, presumably owing to a protein complex with AR and CREB. This mechanism explains sexual differences in body temperature, at least partially.

Deficiency of CHAMP1, a gene related to intellectual disability, causes impaired neuronal development and a mild behavioural phenotype

CHAMP1 is a gene associated with intellectual disability, which was originally identified as being involved in the maintenance of kinetochore–microtubule attachment. To explore the neuronal defects caused by CHAMP1 deficiency, we established mice that lack CHAMP1. Mice that are homozygous knockout for CHAMP1 were slightly smaller than wild-type mice and died soon after birth on pure C57BL/6J background. Although gross anatomical defects were not found in CHAMP1^−/− mouse brains, mitotic cells were increased in the cerebral cortex. Neuronal differentiation was delayed in CHAMP1^−/− neural stem cells in vitro, which was also suggested in vivo by CHAMP1 knockdown. In a behavioural test battery, adult CHAMP1 heterozygous knockout mice showed mild memory defects, altered social interaction, and depression-like behaviours. In transcriptomic analysis, genes related to neurotransmitter transport and neurodevelopmental disorder were downregulated in embryonic CHAMP1^−/− brains. These results suggest that CHAMP1 plays a role in neuronal development, and CHAMP1-deficient mice resemble some aspects of individuals with CHAMP1 mutations.

Heterozygous loss of Zbtb38 leads to early embryonic lethality via the suppression of Nanog and Sox2 expression

OBJECTIVES

Mammalian DNA methyltransferases are essential to re-establish global DNA methylation patterns during implantation, which is critical for transmitting epigenetic information to the next generation. In contrast, the significance of methyl-CpG binding proteins (MBPs) that bind methylated CpG remains almost unknown at this stage. We previously demonstrated that Zbtb38 (also known as CIBZ)-a zinc finger type of MBP-is required for mouse embryonic stem (ES) cell proliferation by positively regulating Nanog expression. However, the physiological function of Zbtb38 in vivo remains unclear.

MATERIALS AND METHODS

This study used the Cre-loxP system to generate conditional Zbtb38 knockout mice. Cell proliferation and apoptosis were studied by immunofluorescence staining. Quantitative real-time PCR, immunoblotting and immunofluorescence were performed to investigate the molecular mechanisms.

RESULTS

Germline loss of the Zbtb38 single allele resulted in decreased epiblast cell proliferation and increased apoptosis shortly after implantation, leading to early embryonic lethality. Heterozygous loss of Zbtb38 reduced the expression of Nanog, Sox2, and the genes responsible for epiblast proliferation, differentiation, and cell viability. Although this early lethal phenotype, Zbtb38 is dispensable for ES cell establishment and identity.

CONCLUSIONS

These findings indicate that Zbtb38 is essential for early embryonic development via the suppression of Nanog and Sox2 expression.

MFN1 and MFN2 Are Dispensable for Sperm Development and Functions in Mice

MFN1 (Mitofusin 1) and MFN2 (Mitofusin 2) are GTPases essential for mitochondrial fusion. Published studies revealed crucial roles of both Mitofusins during embryonic development. Despite the unique mitochondrial organization in sperm flagella, the biological requirement in sperm development and functions remain undefined. Here, using sperm-specific Cre drivers, we show that either Mfn1 or Mfn2 knockout in haploid germ cells does not affect male fertility. The Mfn1 and Mfn2 double knockout mice were further analyzed. We found no differences in testis morphology and weight between Mfn-deficient mice and their wild-type littermate controls. Spermatogenesis was normal in Mfn double knockout mice, in which properly developed TRA98+ germ cells, SYCP3+ spermatocytes, and TNP1+ spermatids/spermatozoa were detected in seminiferous tubules, indicating that sperm formation was not disrupted upon MFN deficiency. Collectively, our findings reveal that both MFN1 and MFN2 are dispensable for sperm development and functions in mice.

Deficiency of lung-specific claudin-18 leads to aggravated infection with Cryptococcus deneoformans through dysregulation of the microenvironment in lungs

Cryptococcus deneoformans is an opportunistic fungal pathogen that infects the lungs via airborne transmission and frequently causes fatal meningoencephalitis. Claudins (Cldns), a family of proteins with 27 members found in mammals, form the tight junctions within epithelial cell sheets. Cldn-4 and 18 are highly expressed in airway tissues, yet the roles of these claudins in respiratory infections have not been clarified. In the present study, we analyzed the roles of Cldn-4 and lung-specific Cldn-18 (luCldn-18) in host defense against C. deneoformans infection. luCldn-18-deficient mice exhibited increased susceptibility to pulmonary infection, while Cldn-4-deficient mice had normal fungal clearance. In luCldn-18-deficient mice, production of cytokines including IFN-γ was significantly decreased compared to wild-type mice, although infiltration of inflammatory cells including CD4⁺ T cells into the alveolar space was significantly increased. In addition, luCldn-18 deficiency led to high K⁺ ion concentrations in bronchoalveolar lavage fluids and also to alveolus acidification. The fungal replication was significantly enhanced both in acidic culture conditions and in the alveolar spaces of luCldn-18-deficient mice, compared with physiological pH conditions and those of wild-type mice, respectively. These results suggest that luCldn-18 may affect the clinical course of cryptococcal infection indirectly through dysregulation of the alveolar space microenvironment.

Characterization and visualization of murine coagulation factor VIII-producing cells in vivo

Coagulation factors are produced from hepatocytes, whereas production of coagulation factor VIII (FVIII) from primary tissues and cell species is still controversial. Here, we tried to characterize primary FVIII-producing organ and cell species using genetically engineered mice, in which enhanced green fluorescent protein (EGFP) was expressed instead of the F8 gene. EGFP-positive FVIII-producing cells existed only in thin sinusoidal layer of the liver and characterized as CD31^high, CD146^high, and lymphatic vascular endothelial hyaluronan receptor 1 (Lyve1)⁺. EGFP-positive cells can be clearly distinguished from lymphatic endothelial cells in the expression profile of the podoplanin⁻ and C-type lectin-like receptor-2 (CLEC-2)⁺. In embryogenesis, EGFP-positive cells began to emerge at E14.5 and subsequently increased according to liver maturation. Furthermore, plasma FVIII could be abolished by crossing F8 conditional deficient mice with Lyve1-Cre mice. In conclusion, in mice, FVIII is only produced from endothelial cells exhibiting CD31^high, CD146^high, Lyve1⁺, CLEC-2⁺, and podoplanin⁻ in liver sinusoidal endothelial cells.

Dysfunction of the proteoglycan Tsukushi causes hydrocephalus through altered neurogenesis in the subventricular zone in mice

The lateral ventricle (LV) is flanked by the subventricular zone (SVZ), a neural stem cell (NSC) niche rich in extrinsic growth factors regulating NSC maintenance, proliferation, and neuronal differentiation. Dysregulation of the SVZ niche causes LV expansion, a condition known as hydrocephalus; however, the underlying pathological mechanisms are unclear. We show that deficiency of the proteoglycan Tsukushi (TSK) in ependymal cells at the LV surface and in the cerebrospinal fluid results in hydrocephalus with neurodevelopmental disorder-like symptoms in mice. These symptoms are accompanied by altered differentiation and survival of the NSC lineage, disrupted ependymal structure, and dysregulated Wnt signaling. Multiple TSK variants found in patients with hydrocephalus exhibit reduced physiological activity in mice in vivo and in vitro. Administration of wild-type TSK protein or Wnt antagonists, but not of hydrocephalus-related TSK variants, in the LV of TSK knockout mice prevented hydrocephalus and preserved SVZ neurogenesis. These observations suggest that TSK plays a crucial role as a niche molecule modulating the fate of SVZ NSCs and point to TSK as a candidate for the diagnosis and therapy of hydrocephalus.

Generation of functional liver organoids on combining hepatocytes and cholangiocytes with hepatobiliary connections ex vivo

In the liver, the bile canaliculi of hepatocytes are connected to intrahepatic bile ducts lined with cholangiocytes, which remove cytotoxic bile from the liver tissue. Although liver organoids have been reported, it is not clear whether the functional connection between hepatocytes and cholangiocytes is recapitulated in those organoids. Here, we report the generation of a hepatobiliary tubular organoid (HBTO) using mouse hepatocyte progenitors and cholangiocytes. Hepatocytes form the bile canalicular network and secrete metabolites into the canaliculi, which are then transported into the biliary tubular structure. Hepatocytes in HBTO acquire and maintain metabolic functions including albumin secretion and cytochrome P450 activities, over the long term. In this study, we establish functional liver tissue incorporating a bile drainage system ex vivo. HBTO enable us to reproduce the transport of hepatocyte metabolites in liver tissue, and to investigate the way in which the two types of epithelial cells establish functional connections.

Combining mouse hepatocyte progenitors and cholangiocytes ex vivo, the authors form an organoid that can drain bile ex vivo and transport metabolites, as in the liver.

Activating mutations in BRAF disrupt the hypothalamo-pituitary axis leading to hypopituitarism in mice and humans

Germline mutations in BRAF and other components of the MAPK pathway are associated with the congenital syndromes collectively known as RASopathies. Here, we report the association of Septo-Optic Dysplasia (SOD) including hypopituitarism and Cardio-Facio-Cutaneous (CFC) syndrome in patients harbouring mutations in BRAF. Phosphoproteomic analyses demonstrate that these genetic variants are gain-of-function mutations leading to activation of the MAPK pathway. Activation of the MAPK pathway by conditional expression of the BrafV600E/+ allele, or the knock-in BrafQ241R/+ allele (corresponding to the most frequent human CFC-causing mutation, BRAF p.Q257R), leads to abnormal cell lineage determination and terminal differentiation of hormone-producing cells, causing hypopituitarism. Expression of the BrafV600E/+ allele in embryonic pituitary progenitors leads to an increased expression of cell cycle inhibitors, cell growth arrest and apoptosis, but not tumour formation. Our findings show a critical role of BRAF in hypothalamo-pituitary-axis development both in mouse and human and implicate mutations found in RASopathies as a cause of endocrine deficiencies in humans.

Analysis of the sperm flagellar axoneme using gene-modified mice

Infertility is a global health issue that affects 1 in 6 couples, with male factors contributing to 50% of cases. The flagellar axoneme is a motility apparatus of spermatozoa, and disruption of its structure or function could lead to male infertility. The axoneme consists of a "9+2" structure that contains a central pair of two singlet microtubules surrounded by nine doublet microtubules, in addition to several macromolecular complexes such as dynein arms, radial spokes, and nexin-dynein regulatory complexes. Molecular components of the flagellar axoneme are evolutionally conserved from unicellular flagellates to mammals, including mice. Although knockout (KO) mice have been generated to understand their function in the formation and motility regulation of sperm flagella, the majority of KO mice die before sexual maturation due to impaired ciliary motility, which makes it challenging to analyze mature spermatozoa. In this review, we introduce methods that have been used to overcome premature lethality, focusing on KO mouse lines of central pair components.

Visualization of mechanical stress-mediated Ca2+ signaling in the gut using intravital imaging

Mechanosensory systems have been implicated in the maintenance of gut homeostasis, but details on the related mechanisms are scarce. Recently, we generated a conditional Ca2+ biosensor yellow cameleon 3.60 (YC3.60)-expressing transgenic mouse model and established a five-dimensional (5D; x, y, z, time, and Ca2+) intravital imaging system for investigating lymphoid tissues and enteric epithelial cell responses. To validate this gut-sensing system, we visualized responses of enteric nervous system (ENS) cells in Nestin-Cre/YC3.60flox mice with specific YC3.60 expression. The ENS, including the myenteric (Auerbach's) and submucous (Meissner's) plexuses, could be visualized without staining in this mouse line, indicating that the probe produced sufficient fluorescent intensity. Furthermore, the myenteric plexus exhibited Ca2+ signaling during peristalsis without stimulation. Nerve endings on the surface of enteric epithelia also exhibited Ca2+ signaling without stimulation. Mechanical stress induced transient salient Ca2+ flux in the myenteric plexus and in enteric epithelial cells in the Nestin-Cre/YC3.60 and the CAG-Cre/YC3.60 lines, respectively. Furthermore, the potential TRPM7 inhibitors were shown to attenuate mechanical stress-mediated Ca2+ signaling. These data indicate that the present intravital imaging system can be used to visualize mechanosensory Ca2+ signaling in ENS cells and enteric epithelial cells.

Ablation of Iah1, a candidate gene for diet-induced fatty liver, does not affect liver lipid accumulation in mice

Nonalcoholic fatty liver disease (NAFLD) is a pathological condition caused by excess triglyceride deposition in the liver. The SMXA-5 severe fatty liver mouse model has been established from the SM/J and A/J strains. To explore the genetic factors involved in fatty liver development in SMXA-5 mice, we had previously performed quantitative trait locus (QTL) analysis, using (SM/J×SMXA-5)F2 intercross mice, and identified Fl1sa on chromosome 12 (centromere-53.06 Mb) as a significant QTL for fatty liver. Furthermore, isoamyl acetate-hydrolyzing esterase 1 homolog (Iah1) was selected as the most likely candidate gene for Fl1sa. Iah1 gene expression in fatty liver-resistant A/J-12^SM mice was significantly higher than in fatty liver-susceptible A/J mice. These data indicated that the Iah1 gene might be associated with fatty liver development. However, the function of murine Iah1 remains unknown. Therefore, in this study, we created Iah1 knockout (KO) mice with two different backgrounds [C57BL/6N (B6) and A/J-12^SM (A12)] to investigate the relationship between Iah1 and liver lipid accumulation. Liver triglyceride accumulation in Iah1-KO mice of B6 or A12 background did not differ from their respective Iah1-wild type mice under a high-fat diet. These results indicated that loss of Iah1 did not contribute to fatty liver. On the other hands, adipose tissue dysfunction causes lipid accumulation in ectopic tissues (liver, skeletal muscle, and pancreas). To investigate the effect of Iah1 deficiency on white adipose tissue, we performed DNA microarray analysis of epididymal fat in Iah1-KO mice of A12 background. This result showed that Iah1 deficiency might decrease adipokines Sfrp4 and Metrnl gene expression in epididymal fat. This study demonstrated that Iah1 deficiency did not cause liver lipid accumulation and that Iah1 was not a suitable candidate gene for Fl1sa.

The HOIL-1L ligase modulates immune signalling and cell death via monoubiquitination of LUBAC

The linear ubiquitin chain assembly complex (LUBAC), which consists of HOIP, SHARPIN and HOIL-1L, promotes NF-κB activation and protects against cell death by generating linear ubiquitin chains. LUBAC contains two RING-IBR-RING (RBR) ubiquitin ligases (E3), and the HOIP RBR is responsible for catalysing linear ubiquitination. We found that HOIL-1L RBR plays a crucial role in regulating LUBAC. HOIL-1L RBR conjugates monoubiquitin onto all LUBAC subunits, followed by HOIP-mediated conjugation of linear chains onto monoubiquitin, and these linear chains attenuate the functions of LUBAC. The introduction of E3-defective HOIL-1L mutants into cells augmented linear ubiquitination, which protected the cells against Salmonella infection and cured dermatitis caused by reduced LUBAC levels due to SHARPIN loss. Our results reveal a regulatory mode of E3 ligases in which the accessory E3 in LUBAC downregulates the main E3 by providing preferred substrates for autolinear ubiquitination. Thus, inhibition of HOIL-1L E3 represents a promising strategy for treating severe infections or immunodeficiency.

Role of gut microbiota in sex- and diet-dependent metabolic disorders that lead to early mortality of androgen receptor-deficient male mice

The gut microbiota is involved in metabolic disorders induced by androgen deficiency after sexual maturation in males (late-onset hypogonadism). However, its role in the energy metabolism of congenital androgen deficiency (e.g., androgen-insensitive syndrome) remains elusive. Here, we examined the link between the gut microbiota and metabolic disease symptoms in androgen receptor knockout (ARKO) mouse by administering high-fat diet (HFD) and/or antibiotics. HFD-fed male, but not standard diet-fed male or HFD-fed female, ARKO mice exhibited increased feed efficiency, obesity with increased visceral adipocyte mass and hypertrophy, hepatic steatosis, glucose intolerance, insulin resistance, and loss of thigh muscle. In contrast, subcutaneous fat mass accumulated in ARKO mice irrespective of the diet and sex. Notably, all HFD-dependent metabolic disorders observed in ARKO males were abolished after antibiotics administration. The ratios of fecal weight-to-food weight and cecum weight-to-body weight were specifically reduced by ARKO in HFD-fed males. 16S rRNA sequencing of fecal microbiota from HFD-fed male mice revealed differences in microbiota composition between control and ARKO mice. Several genera or species (e.g., Turicibacter and Lactobacillus reuteri, respectively) were enriched in ARKO mice, and antibiotics treatment spoiled the changes. Furthermore, the life span of HFD-fed ARKO males was shorter than that of control mice, indicating that androgen deficiency causes metabolic dysfunctions leading to early death. These findings also suggest that AR signaling plays a role in the prevention of metabolic dysfunctions, presumably by influencing the gut microbiome, and improve our understanding of health consequences in subjects with hypogonadism and androgen insensitivity.

Induction of IκBζ Augments Cytokine and Chemokine Production by IL-33 in Mast Cells

IκBζ (encoded by the Nfkbiz) is a member of the nuclear IκB family, which is involved in the expression of secondary response genes based on signals from TLR or IL-1R. ST2L, an IL-33R, is a member of the IL-1R family and abundantly expressed in tissue-resident immune cells, such as mast cells and innate lymphoid cells; however, its downstream signaling pathway remains unelucidated. In this study, we examined the role of IκBζ in ST2L-mediated cytokine and chemokine production in mast cells. Murine bone marrow cells were differentiated ex vivo into bone marrow-derived mast cells (BMMCs). The treatment of BMMCs with IL-33 transiently induced robust IκBζ expression. Of the 40 cytokines and chemokines examined using a cytokine and chemokine array, the concentrations of IL-6, IL-13, CCL2, CCL3, and TNF-α in the supernatant were augmented by IL-33. The deletion of IκBζ in BMMCs resulted in a significant reduction of the production of these mediators and the expression of their mRNA. NF-κB p50 but not p65 translocated to the nucleus by IL-33 and was not affected by the deletion of IκBζ. However, induction of IκBζ and the resultant cytokine and chemokine productions were significantly inhibited by pretreatment with an NF-κB inhibitor. The deletion of IκBζ did not affect the phosphorylation of ERK, p38 MAPK, or JNK by IL-33, and the treatment with inhibitors of these mitogen-activated kinases failed to abolish the expression of Nfkbiz Our findings suggest that IκBζ augments IL-33-dependent cytokine and chemokine production in BMMCs through the action of NF-κB.

Critical role of CRAG, a splicing variant of centaurin-γ3/AGAP3, in ELK1-dependent SRF activation at PML bodies

CRMP-5-associated GTPase (CRAG), a short splicing variant of centaurin-γ3/AGAP3, is predominantly expressed in the developing brain. We previously demonstrated that CRAG, but not centaurin-γ3, translocates to the nucleus and activates the serum response factor (SRF)-c-Fos pathway in cultured neuronal cells. However, the physiological relevance of CRAG in vivo is unknown. Here, we found that CRAG/centaurin-γ3-knockout mice showed intensively suppressed kainic acid-induced c-fos expression in the hippocampus. Analyses of molecular mechanisms underlying CRAG-mediated SRF activation revealed that CRAG has an essential role in GTPase activity, interacts with ELK1 (a co-activator of SRF), and activates SRF in an ELK1-dependent manner. Furthermore, CRAG and ELK1 interact with promyelocytic leukaemia bodies through SUMO-interacting motifs, which is required for SRF activation. These results suggest that CRAG plays a critical role in ELK1-dependent SRF-c-fos activation at promyelocytic leukaemia bodies in the developing brain.

Adamts17 is involved in skeletogenesis through modulation of BMP-Smad1/5/8 pathway

Fibrillin microfibrils are ubiquitous elements of extracellular matrix assemblies that play crucial roles in regulating the bioavailability of growth factors of the transforming growth factor beta superfamily. Recently, several "a disintegrin and metalloproteinase with thrombospondin motifs" (ADAMTS) proteins were shown to regulate fibrillin microfibril function. Among them, ADAMTS17 is the causative gene of Weill-Marchesani syndrome (WMS) and Weill-Marchesani-like syndrome, of which common symptoms are ectopia lentis and short stature. ADAMTS17 has also been linked to height variation in humans; however, the molecular mechanisms whereby ADAMTS17 regulates skeletal growth remain unknown. Here, we generated Adamts17-/- mice to examine the role of Adamts17 in skeletogenesis. Adamts17-/- mice recapitulated WMS, showing shorter long bones, brachydactyly, and thick skin. The hypertrophic zone of the growth plate in Adamts17-/- mice was shortened, with enhanced fibrillin-2 deposition, suggesting increased incorporation of fibrillin-2 into microfibrils. Comprehensive gene expression analysis of growth plates using laser microdissection and RNA sequencing indicated alteration of the bone morphogenetic protein (BMP) signaling pathway after Adamts17 knockout. Consistent with this, phospho-Smad1 levels were downregulated in the hypertrophic zone of the growth plate and in Adamts17-/- primary chondrocytes. Delayed terminal differentiation of Adamts17-/- chondrocytes, observed both in primary chondrocyte and primordial metatarsal cultures, and was prevented by BMP treatment. Our data indicated that Adamts17 is involved in skeletal formation by modulating BMP-Smad1/5/8 pathway, possibly through inhibiting the incorporation of fibrillin-2 into microfibrils. Our findings will contribute to further understanding of disease mechanisms and will facilitate the development of therapeutic interventions for WMS.

Behavioral analysis in mice deficient for GAREM2 (Grb2-associated regulator of Erk/MAPK subtype2) that is a subtype of highly expressing in the brain

Grb2-associated regulator of Erk/MAPK (GAREM), is an adaptor protein related to the several cell growth factor receptor-signaling. The GAREM family has two subtypes, GAREM1 and GAREM2, both encoded in the human and mouse genome. Recent genome-wide research identified GAREM2 as a candidate of neurodegenerative diseases. Here, we use knockout (KO) mice to show the role of GAREM2, that is highly expressed in the brain. According to the comprehensive behavioral battery, they exhibited less anxiety both in elevated plus maze and open field tests, mildly increased social approaching behavior in the reciprocal social interaction test, and longer latency to immobility in the tail suspension test as compared to wild-type (WT). Additionally, the extension of neurites in the primary cultured neurons was suppressed in ones derived from GAREM2 KO mice. Furthermore, we also identified Intersectin, as a binding partner of GAREM2 in this study. Intersectin is also a multi-domain adaptor protein that regulates endocytosis and cell signaling, which can potentially alter the subcellular localization of GAREM2. The important molecules, such as the neurotrophin receptor and Erk family, that are involved in the signaling pathway of the neural cell growth in the mouse brain, have been reported to participate in emotional behavior. As GAREM plays a role in the cellular growth factor receptor signaling pathway, GAREM2 may have a common role related to the transduction of Erk signaling in the higher brain functions.

Normal B cell development and Pax5 expression in Thy28/ThyN1-deficient mice

Thy28, also known as ThyN1, is a highly conserved nuclear protein. We previously showed that in a chicken mature B cell line, Thy28 binds to the promoter of the gene encoding Pax5, a transcription factor essential for B cell development, and positively regulates its expression. Here, we generated a Thy28-deficient mouse line to analyze its potential role in B cell development in mice. Thy28-deficient mice showed normal development of B cells, and the expression of Pax5 was comparable between wild-type and Thy28-deficient primary B cells. Thus, species-specific mechanisms regulate Pax5 expression and B cell development.

Calaxin is required for cilia-driven determination of vertebrate laterality

Calaxin is a Ca2+-binding dynein-associated protein that regulates flagellar and ciliary movement. In ascidians, calaxin plays essential roles in chemotaxis of sperm. However, nothing has been known for the function of calaxin in vertebrates. Here we show that the mice with a null mutation in Efcab1, which encodes calaxin, display typical phenotypes of primary ciliary dyskinesia, including hydrocephalus, situs inversus, and abnormal motility of trachea cilia and sperm flagella. Strikingly, both males and females are viable and fertile, indicating that calaxin is not essential for fertilization in mice. The 9 + 2 axonemal structures of epithelial multicilia and sperm flagella are normal, but the formation of 9 + 0 nodal cilia is significantly disrupted. Knockout of calaxin in zebrafish also causes situs inversus due to the irregular ciliary beating of Kupffer's vesicle cilia, although the 9 + 2 axonemal structure appears to remain normal.

New Noonan syndrome model mice with RIT1 mutation exhibit cardiac hypertrophy and susceptibility to β-adrenergic stimulation-induced cardiac fibrosis

BACKGROUND

Noonan syndrome (NS) is a genetic disorder characterized by short stature, a distinctive facial appearance, and heart defects. We recently discovered a novel NS gene, RIT1, which is a member of the RAS subfamily of small GTPases. NS patients with RIT1 mutations have a high incidence of hypertrophic cardiomyopathy and edematous phenotype, but the specific role of RIT1 remains unclear.

METHODS

To investigate how germline RIT1 mutations cause NS, we generated knock-in mice that carried a NS-associated Rit1 A57G mutation (Rit1^A57G/+). We investigated the phenotypes of Rit1^A57G/+ mice in fetal and adult stages as well as the effects of isoproterenol on cardiac function in Rit1^A57G/+ mice.

FINDINGS

Rit1^A57G/+ embryos exhibited decreased viability, edema, subcutaneous hemorrhage and AKT activation. Surviving Rit1^A57G/+ mice had a short stature, craniofacial abnormalities and splenomegaly. Cardiac hypertrophy and cardiac fibrosis with increased expression of S100A4, vimentin and periostin were observed in Rit1^A57G/+ mice compared to Rit1^+/+ mice. Upon isoproterenol stimulation, cardiac fibrosis was drastically increased in Rit1^A57G/+ mice. Phosphorylated (at Thr308) AKT levels were also elevated in isoproterenol-treated Rit1^A57G/+ hearts.

INTERPRETATION

The A57G mutation in Rit1 causes cardiac hypertrophy, fibrosis and other NS-associated features. Biochemical analysis indicates that the AKT signaling pathway might be related to downstream signaling in the RIT1 A57G mutant at a developmental stage and under β-adrenergic stimulation in the heart. FUND: The Grants-in-Aid were provided by the Practical Research Project for Rare/Intractable Diseases from the Japan Agency for Medical Research and Development, the Japan Society for the Promotion of Science KAKENHI Grant.

Class II PI3Ks α and β Are Required for Rho-Dependent Uterine Smooth Muscle Contraction and Parturition in Mice

Class II phosphoinositide 3-kinases (PI3Ks), PI3K-C2α and PI3K-C2β, are highly homologous and distinct from class I and class III PI3Ks in catalytic products and domain structures. In contrast to class I and class III PI3Ks, physiological roles of PI3K-C2α and PI3K-C2β are not fully understood. Because we previously demonstrated that PI3K-C2α is involved in vascular smooth muscle contraction, we studied the phenotypes of smooth muscle-specific knockout (KO) mice of PI3K-C2α and PI3K-C2β. The pup numbers born from single PI3K-C2α-KO and single PI3K-C2β-KO mothers were similar to those of control mothers, but those from double KO (DKO) mothers were smaller compared with control mice. However, the number of intrauterine fetuses in pregnant DKO mothers was similar to that in control mice. Both spontaneous and oxytocin-induced contraction of isolated uterine smooth muscle (USM) strips was diminished in DKO mice but not in either of the single KO mice, compared with control mice. Furthermore, contraction of USM of DKO mice was less sensitive to a Rho kinase inhibitor. Mechanistically, the extent of oxytocin-induced myosin light chain phosphorylation was greatly reduced in USM from DKO mice compared with control mice. The oxytocin-induced rise in the intracellular Ca2+ concentration in USM was similar in DKO and control mice. However, Rho activation in the intracellular compartment was substantially attenuated in DKO mice compared with control mice, as evaluated by fluorescence resonance energy transfer imaging technique. These data indicate that both PI3K-C2α and PI3K-C2β are required for normal USM contraction and parturition mainly through their involvement in Rho activation.

Impaired male fertility and abnormal epididymal epithelium differentiation in mice lacking CRISP1 and CRISP4

Epididymal Cysteine Rich Secretory Proteins 1 and 4 (CRISP1 and CRISP4) associate with sperm during maturation and play different roles in fertilization. However, males lacking each of these molecules individually are fertile, suggesting compensatory mechanisms between these homologous proteins. Based on this, in the present work, we generated double CRISP1/CRISP4 knockout (DKO) mice and examined their reproductive phenotype. Our data showed that the simultaneous lack of the two epididymal proteins results in clear fertility defects. Interestingly, whereas most of the animals exhibited specific sperm fertilizing ability defects supportive of the role of CRISP proteins in fertilization, one third of the males showed an unexpected epididymo-orchitis phenotype with altered levels of inflammatory molecules and non-viable sperm in the epididymis. Further analysis showed that DKO mice exhibited an immature epididymal epithelium and abnormal luminal pH, supporting these defects as likely responsible for the different phenotypes observed. These observations reveal that CRISP proteins are relevant for epididymal epithelium differentiation and male fertility, contributing to a better understanding of the fine-tuning mechanisms underlying sperm maturation and immunotolerance in the epididymis with clear implications for human epididymal physiology and pathology.

Deletion of Long Isoform of Eukaryotic Elongation Factor 1Bδ Leads to Audiogenic Seizures and Aversive Stimulus-Induced Long-Lasting Activity Suppression in Mice

Alternative splicing enables a gene to give rise to diverse protein products. The Eef1d gene produces two isoforms: a short isoform that encodes translation elongation factor 1Bδ (eEF1Bδ1), and a long isoform that encodes the heat shock-responsive transcription factor eEF1BδL. Previously, we found that eEF1BδL was a splice variant that was specific to the brain and testis, and the protein encoded is thought to have a function in the central nervous system. In this study, we generated knockout (KO) mice of C57BL/6J background that selectively lacked a specific exon in Eef1d for the long isoform. These KO mice lacked eEF1BδL, but not eEF1Bδ1, in the brain. Although the KO mice showed normal anxiety-related and learning behavior in behavioral tests, some showed severe seizures in response to loud sounds (90 dBA), an audiogenic seizures (AGS) response. Furthermore, after the KO mice had been subjected to the fear conditioning test, they showed remarkably decreased locomotor activity in their home cage and in the open-field and elevated plus-maze tests. After the fear conditioning test, a significant decrease in brain weight, atrophy of the hippocampus and midbrain, and reduced cortical layer thickness were observed in the KO mice. We also found a compensatory increase in the eEF1Bδ1 level and elevated protein synthesis with the induction of endoplasmic reticulum stress markers in these mice. Our results suggest that eEF1BδL has an important role in normal brain function especially when exposed to external stimuli.

Loss of DDHD2, whose mutation causes spastic paraplegia, promotes reactive oxygen species generation and apoptosis

DDHD2/KIAA0725p is a mammalian intracellular phospholipase A₁ that exhibits phospholipase and lipase activities. Mutation of the DDHD2 gene causes hereditary spastic paraplegia (SPG54), an inherited neurological disorder characterized by lower limb spasticity and weakness. Although previous studies demonstrated lipid droplet accumulation in the brains of SPG54 patients and DDHD2 knockout mice, the cause of SPG54 remains elusive. Here, we show that ablation of DDHD2 in mice induces age-dependent apoptosis of motor neurons in the spinal cord. In vitro, motor neurons and embryonic fibroblasts from DDHD2 knockout mice fail to survive and are susceptible to apoptotic stimuli. Chemical and probe-based analysis revealed a substantial decrease in cardiolipin content and an increase in reactive oxygen species generation in DDHD2 knockout cells. Reactive oxygen species production in DDHD2 knockout cells was reversed by the expression of wild-type DDHD2, but not by an active-site DDHD2 mutant, DDHD2 mutants related to hereditary spastic paraplegia, or DDHD1, another member of the intracellular phospholipase A₁ family whose mutation also causes spastic paraplegia (SPG28). Our results demonstrate the protective role of DDHD2 for mitochondrial integrity and provide a clue to the pathogenic mechanism of SPG54.

Serum CTX levels and histomorphometric analysis in Src versus RANKL knockout mice

Src knockout (KO) and RANKL KO mice both exhibit near complete osteopetrosis in terms of 3D-bone volume (BV) fraction by micro-CT, whereas the serum CTX concentration of Src KO is apparently normal and that of RANKL KO is 30% of wild-type (WT) despite the fact that they lack osteoclasts. By histomorphometry we found that, whereas eroded surface (ES) and osteoid surface (OS) are zero values in RANKL KO, they are indistinguishable from WT in Src KO; because of marked increase in bone surface (BS), ES/BS and OS/BS of Src KO are 30-40% of WT. While RANKL KO lack both osteoclasts and osteoblasts, Src KO reveal increased numbers of osteoclasts and indistinguishable numbers of osteoblasts compared with WT; again, on the basis of BS, N.Oc/BS is comparable to WT and N.Ob/BS is markedly decreased in Src KO. The apparently increased number of total osteoclasts may be due to increased expression of RANKL found in Src KO bone in vivo. Src has a gene dosage-dependent effect on osteoclast function in vitro, with Src^-/- osteoclasts completely lacking bone-resorbing function as determined by CTX release on dentin. Thus, Src KO osteoclasts retain some bone-resorbing function in vivo. The number of osteocytes is proportionally increased in RANKL KO, while Src KO mice have relative osteocyte deficiency, raising the possibility that RANKL and Src has an unrecognized role in osteocyte survival.

Transgenic mouse lines expressing the 3xFLAG-dCas9 protein for enChIP analysis

We developed the engineered DNA-binding molecule-mediated chromatin immunoprecipitation (enChIP) technology to isolate specific genomic regions while retaining their molecular interactions. In enChIP, the locus of interest is tagged with an engineered DNA-binding molecule, such as a modified form of the clustered regularly interspaced short palindromic repeats (CRISPR) system containing a guide RNA (gRNA) and a catalytically inactive form of Cas9 (dCas9). The locus is then affinity-purified to enable identification of associated molecules. In this study, we generated transgenic mice expressing 3xFLAG-tagged Streptococcus pyogenes dCas9 (3xFLAG-dCas9) and retrovirally transduced gRNA into primary CD4+ T cells from these mice for enChIP. Using this approach, we achieved high yields of enChIP at the targeted genomic region. Our novel transgenic mouse lines provide a valuable tool for enChIP analysis in primary mouse cells.

Novel reporter and deleter mouse strains generated using VCre/VloxP and SCre/SloxP systems, and their system specificity in mice

DNA site-specific recombination by Cre/loxP is a powerful tool for gene manipulation in experimental animals. VCre/VloxP and SCre/SloxP are novel site-specific recombination systems, consisting of a recombinase and its specific recognition sequences, which function in a manner similar to Cre/loxP. Previous reports using Escherichia coli and Oryzias latipes demonstrated the existence of stringent specificity between each recombinase and its target sites; VCre/VloxP, SCre/SloxP, and Cre/loxP have no cross-reactivity with each other. In this study, we established four novel knock-in (KI) mouse strains in which VloxP-EGFP, SloxP-tdTomato, CAG-VCre, and CAG-SCre genes were inserted into the ROSA26 locus. VloxP-EGFP and SloxP-tdTomato KI mice were reporter mice carrying EGFP or tdTomato genes posterior to the stop codon, which was floxed by VloxP or SloxP fragments, respectively. CAG-VCre and CAG-SCre KI mice carried VCre or SCre genes that were expressed ubiquitously. These two reporter mice were crossed with three different deleter mice, CAG-VCre KI, CAG-SCre KI, and Cre-expressing transgenic mice. Through these matings, we found that VCre/VloxP and SCre/SloxP systems were functional in mice similar to Cre/loxP, and that the recombinases showed tight specificity for their recognition sequences. Our results suggest that these novel recombination systems allow highly sophisticated genome manipulations and will be useful for tracing the fates of multiple cell lineages or elucidating complex spatiotemporal regulations of gene expression.

Mice with an Oncogenic HRAS Mutation are Resistant to High-Fat Diet-Induced Obesity and Exhibit Impaired Hepatic Energy Homeostasis

Costello syndrome is a “RASopathy” that is characterized by growth retardation, dysmorphic facial appearance, hypertrophic cardiomyopathy and tumor predisposition. > 80% of patients with Costello syndrome harbor a heterozygous germline G12S mutation in HRAS. Altered metabolic regulation has been suspected because patients with Costello syndrome exhibit hypoketotic hypoglycemia and increased resting energy expenditure, and their growth is severely retarded. To examine the mechanisms of energy reprogramming by HRAS activation in vivo, we generated knock-in mice expressing a heterozygous Hras G12S mutation (Hras^G12S/+ mice) as a mouse model of Costello syndrome. On a high-fat diet, Hras^G12S/+ mice developed a lean phenotype with microvesicular hepatic steatosis, resulting in early death compared with wild-type mice. Under starvation conditions, hypoketosis and elevated blood levels of long-chain fatty acylcarnitines were observed, suggesting impaired mitochondrial fatty acid oxidation. Our findings suggest that the oncogenic Hras mutation modulates energy homeostasis in vivo.

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Mice expressing Hras G12S (Hras^G12S/+) showed Costello syndrome-like phenotypes, including craniofacial and cardiac defects.

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Hras^G12S/+ mice are resistant to high-fat diet (HFD)-induced obesity, showing microvesicular hepatic steatosis.

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Upon fasting, HFD-fed Hras^G12S/+ mice show abnormal hepatic fatty acid oxidation, hypoketosis and early hypoglycemia.

Costello syndrome is a congenital anomaly syndrome, which is caused by germline mutations in HRAS oncogene. Altered metabolic regulation has been suspected because patients with Costello syndrome exhibit hypoketotic hypoglycemia and increased resting energy expenditure, and growth retardation. Here, we generated a mouse model for Costello syndrome expressing a Hras G12S mutation, which showed craniofacial and heart abnormalities. On a high-fat diet, mutant mice exhibited a lean phenotype with poor weight gain and microvesicular hepatic steatosis. Under starvation conditions, impaired mitochondrial fatty acid oxidation has been observed. These results suggest that oncogenic RAS signaling in mice modulates energy homeostasis in vivo.

Yao HH, Jensen P. A new mouse line for cell ablation by diphtheria toxin subunit A controlled by a Cre-dependent FLEx switch

Recombinase responsive mouse lines expressing diphtheria toxin subunit A (DTA) are well established tools for targeted ablation of genetically defined cell populations. Here we describe a new knock-in allele at the Gt(Rosa)26Sor locus that retains the best features of previously described DTA alleles-including a CAG promoter, attenuated mutant DTA cDNA, and ubiquitous EGFP labeling-with the addition of a Cre-dependent FLEx switch for tight control of expression. The FLEx switch consists of two pairs of antiparallel lox sites requiring Cre-mediated recombination for inversion of the DTA to the proper orientation for transcription. We demonstrate its utility by Cre-dependent ablation of both a broad domain in the embryonic nervous system and a discrete population of cells in the fetal gonads. We conclude that this new DTA line is useful for targeted ablation of genetically-defined cell populations.

A new mouse line for cell ablation by diphtheria toxin subunit A controlled by a Cre-dependent FLEx switch

Recombinase responsive mouse lines expressing diphtheria toxin subunit A (DTA) are well established tools for targeted ablation of genetically defined cell populations. Here we describe a new knock-in allele at the Gt(Rosa)26Sor locus that retains the best features of previously described DTA alleles-including a CAG promoter, attenuated mutant DTA cDNA, and ubiquitous EGFP labeling-with the addition of a Cre-dependent FLEx switch for tight control of expression. The FLEx switch consists of two pairs of antiparallel lox sites requiring Cre-mediated recombination for inversion of the DTA to the proper orientation for transcription. We demonstrate its utility by Cre-dependent ablation of both a broad domain in the embryonic nervous system and a discrete population of cells in the fetal gonads. We conclude that this new DTA line is useful for targeted ablation of genetically-defined cell populations.