Abstract De novo SYT1 mutations cause Baker–Gordon syndrome (BAGOS), yet the pathogenic mechanisms are not well understood. We identified a child carrying a newly described SYT1 variant, D310N, which produced a consistently more severe clinical phenotype compared to a previously reported D366E variant. To investigate the biological basis of these differences, we generated Drosophila models harboring each variant. Heterozygous D310N flies displayed substantially greater locomotor impairment, higher incidences of seizure-like activity, more pronounced deficits in learning and memory, and synaptic dysfunction than flies expressing D366E. Importantly, we report the identification of a mid-larval developmental window during which variant expression induces life-long locomotor abnormalities. Yet, mutant SYT1 expressed in adult stage does not have an immediate effect on climbing, arguing that BAGOS is likely caused by developmentally disrupted networks rather than synaptic transmission alone. Finally, we show behavioral abnormalities specific to SYT1 variant expression in subset neurons. Together, findings from this integrated human-fly analysis recapitulate core clinical manifestations, uncover variant-specific disruptions in SV recycling, developmental timing, and circuit-level contributions, and advance understanding of SYT1 -associated neurodevelopmental disorders.

Precise control of allelic outcomes remains a major limitation of CRISPR-Cas9 genome editing, particularly for genes in which biallelic modification is lethal or confounds disease modeling. Here, we present CRISPR-SWITCH (Silent mutations With Intention To Create Heterozygotes), a genome engineering strategy that enables deliberate monoallelic editing by exploiting allele-specific CRISPR targeting. CRISPR-SWITCH operates through the initial introduction of a synonymous nucleotide substitution that creates a unique guide RNA recognition site, allowing subsequent selective editing of the engineered allele while preserving the wildtype copy. We applied CRISPR-SWITCH to generate a mouse model of Baker-Gordon syndrome, a dominant-negative neurodevelopmental disorder caused by pathogenic variants in synaptotagmin-1 (SYT1). Conventional CRISPR-Cas9 editing of the Syt1 locus produced complex allelic outcomes characterized by biallelic editing and mosaicism, preventing reliable generation of the defined heterozygous genotype required for disease modeling. In contrast, CRISPR-SWITCH enforced heterozygosity by first introducing a synonymous Y364Y mutation and then selectively targeting this allele to install the pathogenic D365E variant. This approach produced viable Syt1-D365E mice with exclusive monoallelic genome editing, predictable preservation of a wildtype allele, and balanced (1:1) expression of mutant and wildtype transcripts. Together, these results demonstrate proof-of-principle that CRISPR-SWITCH can enforce heterozygosity at endogenous loci and enable the generation of viable mammalian models for dominant-negative and dosage-sensitive genetic disorders.

Abstract The adult endometrium regenerates repeatedly, yet the cells and mechanisms that rebuild its epithelium remain poorly defined. To control the cell types available for regeneration, a genetic model to extensively ablate the uterine epithelium was combined with transplantation of lineage-labeled organoids. Ablation without organoid transplantation triggered re-epithelialization, but resulted in infertility. Transplanted endometrial epithelial organoids engrafted into the ablated uterus, reconstructed both the luminal and glandular epithelia, and restored fertility. Depleting organoids of the glandular lineage before transplantation revealed that luminal epithelial-derived cells acquire glandular identity and function after engraftment. The same luminal-to-glandular epithelial differentiation trajectory emerged during endogenous repair following targeted glandular ablation. Together, these findings establish luminal-to-glandular epithelial conversion as an intrinsic regenerative property of the adult uterine epithelium and establish an endometrial organoid transplantation platform with therapeutic potential.

The mammalian uterus contains glands in the endometrium that develop only or primarily after birth. In the mouse, endometrial glands govern post implantation pregnancy establishment via regulation of blastocyst implantation, stromal cell decidualization, and placental development. Here, we describe a new uterine glandular epithelium (GE) specific Cre recombinase mouse line that is useful to study endometrial gland development and function. Utilizing CRISPR-Cas9 genome editing, improved Cre recombinase (iCre) was inserted into the endogenous C-X-C motif chemokine ligand 15 (Cxcl15) gene. Cxcl15 mRNA, Cxcl15 protein, and Cxcl15-iCre recombinase activity were specific to the developing GE of the uterus. Cxcl15-iCre mice were crossed with floxed Foxa2 mice to conditionally delete Foxa2 specifically in the glands of the neonatal mouse uterus. This conditional deletion of Foxa2 in the developing neonatal uterus resulted in adult mice that lacked Foxa2 in the GE of the uterus, and the adult mice were infertile. The studies described here establish that Cxcl15-iCre mice are a valuable resource to elucidate and explore mechanisms regulating the development and function of glands in the uterus.

Fecal water syndrome (FWS) in horses is characterized by two-phase defecation, including both solid and liquid phases. While satisfactory explanations for FWS are unavailable, bacterial dysbiosis has been suggested as a contributing or causative factor. The objectives of this study were to determine whether fecal bacterial dysbiosis is associated with FWS in horses in the midwestern USA. Fecal samples were collected from horses with FWS and from unaffected horses at the same location. In total, 16S rRNA amplicon libraries produced from fecal bacterial DNA were sequenced using the Illumina sequencing platform. Significant differences in beta diversity were detected between affected and control horses (p = 7 × 10−4, F = 1.51), and differential abundance testing identified several features enriched in affected and control horses. These results agree with prior work regarding specific features in the bacterial microbiome associated with FWS, including Alloprevotella spp., and suggest fecal dysbiosis is associated with FWS.

La ribonucleoprotein 6, translational regulator (LARP6), a multifunctional mRNA-binding protein with well-described profibrotic effects, increases type I collagen mRNA half-life, translation, and deposition in noncardiac tissues. In the heart, LARP6 is expressed in cardiomyocytes, not primarily involved in fibrosis, where its role is unknown. To investigate the role of cardiomyocyte-derived LARP6 on cardiac function and remodeling, we generated a cardiomyocyte-specific LARP6 overexpressing transgenic mouse model (LARP6-Tg). Baseline longitudinal studies up to 10 mo of age revealed that constitutive overexpression of LARP6 had no significant effect on cardiac function or morphology despite inducing mild interstitial fibrosis versus wild-type (WT) littermates. Subsequently, we hypothesized that cardiomyocyte-specific LARP6-Tg mice would exhibit exacerbated cardiac remodeling and dysfunction in response to hypertensive stress via angiotensin II (Ang II) infusion. Ang II (1000 ng/kg/min for 21 days) induced hypertension and cardiac hypertrophy in WT and LARP6-Tg mice of both sexes. Unexpectedly, Ang II-induced cardiac dysfunction was prevented in LARP6-Tg mice. Cardiac gene expression profiling predicted increased fibrosis and cardiomyocyte death in Ang II-treated WT mice and inhibition of cardiomyocyte death in Ang II-treated LARP6-Tg mice versus saline-treated controls. Surprisingly, Ang II-induced interstitial fibrosis was reduced in LARP6-Tg mice and associated with attenuation of cardiomyocyte cell death and reduced fibroblast activation. These data support a mild profibrotic action of cardiomyocyte-specific LARP6 overexpression in unstressed mice and, paradoxically, that LARP6 overexpression is sufficient to prevent Ang II-induced cardiac interstitial fibrosis and dysfunction. Sustained induction of LARP6 has therapeutic potential in hypertensive heart disease.NEW & NOTEWORTHY LARP6 is a novel multifunctional RNA-binding protein whose role in the heart is poorly understood. Transgenic overexpression of LARP6 in cardiomyocytes caused mild cardiac fibrosis under basal conditions with no impact on cardiac function but, unexpectedly, blunted angiotensin-II-induced cardiac fibrosis and dysfunction. This protective effect of LARP6 overexpression was associated with significant shifts in the cardiac transcriptome alongside blunted fibroblast activation and cardiomyocyte apoptosis under hypertension conditions, highlighting LARP6 as a novel therapeutic target.

Our goal was to generate new rat strains for the study of human pathogenic viruses such as SARS-CoV-2 that use ACE2 for entry into host cells. An over-expression rat model was generated using random transgenesis to integrate copies of human ACE2 under the control of the ubiquitously expressed CAG promoter into the rat genome. After transgene copy number, mRNA, and protein expression were confirmed, rats were challenged with the SARS-CoV-2 isolate USA-WA1/2020. Wild type rats are not susceptible to high titer challenge, while rats hemizygous for the ACE2 transgene lost significant body weight and displayed overt clinical signs of infection. This rat model will advance the understanding of COVID-19 and SARS-CoV-2 pathogenesis as well as accelerate the development of vaccines and antiviral therapies and can serve as an animal model for studies of the physiological role of ACE2.

Previous studies demonstrated that activation of the mouse G protein-coupled formyl peptide receptor 2 (mFpr2) with aspirin-triggered resolvin D1 (AT-RvD1) blocks pro-inflammatory cytokine signaling while promoting salivary gland (SG) epithelial integrity both in vitro and in vivo. In addition, mice lacking Fpr2 display alterations of SG innate and adaptive immunity. Taken together, these results indicate that Fpr2 activation with AT-RvD1 restores saliva secretion and regulates SG immunity in mice. To demonstrate the value of AT-RvD1 for use in human SG, however, we need to extend the findings above in the direction of clinical use. To this end, the current study investigated whether treatment with AT-RvD1 reduces SG inflammation and restores saliva secretion in an acute sialadenitis mouse model expressing the human formyl peptide receptor 2 (hFPR2) protein. Results indicate that mice carrying the hFPR2 and treated with lipopolysaccharide (LPS) display acute sialadenitis-like features as shown by increased levels of proliferating inflammatory cells, loss of epithelial integrity and reduced saliva secretion. In contrast, when these mice are treated with AT-RvD1, the sialadenitis-like features are drastically reduced as evidenced by a significant decrease in proliferating inflammatory cells as well as restoration of saliva secretion to levels comparable to phosphate buffered saline (PBS)-treated healthy controls. Finally, changes observed in mice carrying the hFPR2 and treated with LPS and AT-RvD1 were comparable to those observed in wild-type mice carrying the mFpr2. Together, these results demonstrate that activation of hFPR2 with AT-RvD1 resolves acute sialadenitis in vivo.

The microorganisms colonizing the gastrointestinal tract of animals, collectively referred to as the gut microbiome, affect numerous host behaviors dependent on the central nervous system (CNS). Studies comparing germ-free mice to normally colonized mice have demonstrated influences of the microbiome on anxiety-related behaviors, voluntary activity, and gene expression in the CNS. Additionally, there is epidemiologic evidence supporting an intergenerational influence of the maternal microbiome on neurodevelopment of offspring and behavior later in life. There is limited experimental evidence however directly linking the maternal microbiome to long-term neurodevelopmental outcomes, or knowledge regarding mechanisms responsible for such effects. Here we show that that the maternal microbiome has a dominant influence on several offspring phenotypes including anxiety-related behavior, voluntary activity, and body weight. Adverse outcomes in offspring were associated with features of the maternal microbiome including bile salt hydrolase activity gene expression (bsh), abundance of certain bile acids, and hepatic expression of Slc10a1. In cross-foster experiments, offspring resembled their birth dam phenotypically, despite faithful colonization in the postnatal period with the surrogate dam microbiome. Genome-wide DNA methylation analysis of hippocampal DNA identified microbiome-associated differences in DNA methylation of 196 loci in total, 176 of which show conserved profiles between mother and offspring. Further, single-cell transcriptional analysis revealed accompanying differences in expression of several differentially methylated genes within certain hippocampal cell clusters, and vascular expression of genes associated with bile acid transport. Inferred cell-to-cell communication in the hippocampus based on coordinated ligand-receptor expression revealed differences in expression of neuropeptides associated with satiety. Collectively, these data provide proof-of-principle that the maternal gut microbiome has a dominant influence on the neurodevelopment underlying certain offspring behaviors and activities, and selectively affects genome DNA methylation and gene expression in the offspring hippocampus in conjunction with that neurodevelopment.

While rodents are used extensively for studying pain, there is a lack of reported direct comparisons of thermal and mechanical pain testing methods in rats of different genetic backgrounds. Understanding the range of interindividual variability of withdrawal thresholds and thermal latencies based on these testing methods and/or genetic background is important for appropriate experimental design. Testing was performed in two common rat genetic backgrounds: outbred Sprague-Dawley (SD) and inbred Fischer 344 (F344). Male and female, 10- to 14-wk-old F344 and SD rats were used to assess withdrawal thresholds in 3 different modalities: the Randall-Selitto test (RST), Hargreaves test (HT), and tail flick test (TFT). The RST was performed by using an operator-controlled handheld instrument to generate a noxious pressure stimulus to the left hind paw. The HT and the TFT used an electronically controlled light source to deliver a noxious thermal stimulus to the left hind paw or tail tip, respectively. Rats of each sex and genetic background underwent one type of test on day 0 and day 7. Withdrawal thresholds and thermal latencies were compared among tests. No significant differences were observed. Our findings can serve as a guide for researchers considering these nociceptive tests for their experiments.

Genome editing technology is widely used to produce genetically modified animals, including rats. Cytoplasmic or pronuclear injection of DNA repair templates and CRISPR-Cas reagents is the most common delivery method into embryos. However, this type of micromanipulation necessitates access to specialized equipment, is laborious, and requires a certain level of technical skill. Moreover, microinjection techniques often result in lower embryo survival due to the mechanical stress on the embryo. In this protocol, we developed an optimized method to deliver large DNA repair templates to work in conjunction with CRISPR-Cas9 genome editing without the need for microinjection. This protocol combines AAV-mediated DNA delivery of single-stranded DNA donor templates along with the delivery of CRISPRCas9 ribonucleoprotein (RNP) by electroporation to modify 2-cell embryos. Using this novel strategy, we have successfully produced targeted knock-in rat models carrying insertion of DNA sequences from 1.2 to 3.0 kb in size with efficiencies between 42% and 90%.

During the ejection phase of the cardiac cycle, left ventricular (LV) cardiac myocytes undergo loaded shortening and generate power. Our lab investigates factors that regulate loaded shortening and power in striated muscle cells. Few studies have measured sarcomere shortening during loaded contractions. For this study, we simultaneously monitored muscle length (ML) and sarcomere length (SL) during isotonic contractions in rat/mouse single permeabilized LV cardiac myocytes using the IonOptix SarcLen system.

ABSTRACT:Neuropathic pain is a devastating condition where current therapeutics offer little to no pain relief. Novel nonnarcotic therapeutic targets are needed to address this growing medical problem. Our work identified the G-protein-coupled receptor 160 (GPR160) as a potential target for therapeutic intervention. However, the lack of small-molecule ligands for GPR160 hampers our understanding of its role in health and disease. To address this void, we generated a global Gpr160 knockout (KO) mouse using CRISPR-Cas9 genome editing technology to validate the contributions of GPR160 in nociceptive behaviors in mice. Gpr160 KO mice are healthy and fertile, with no observable physical abnormalities. Gpr160 KO mice fail to develop behavioral hypersensitivities in a model of neuropathic pain caused by constriction of the sciatic nerve. On the other hand, responses of Gpr160 KO mice in the hot-plate and tail-flick assays are not affected. We recently deorphanized GPR160 and identified cocaine- and amphetamine-regulated transcript peptide (CARTp) as a potential ligand. Using Gpr160 KO mice, we now report that the development of behavioral hypersensitivities after intrathecal or intraplantar injections of CARTp are dependent on GPR160. Cocaine- and amphetamine-regulated transcript peptide plays a role in various affective behaviors, such as anxiety, depression, and cognition. There are no differences in learning, memory, and anxiety between Gpr160 KO mice and their age-matched and sex-matched control floxed mice. Results from these studies support the pronociceptive roles of CARTp/GPR160 and GPR160 as a potential therapeutic target for treatment of neuropathic pain.

Genome editing technology is widely used to produce genetically modified animals, including rats. Cytoplasmic or pronuclear injection of DNA repair templates and CRISPR-Cas reagents is the most common delivery method into embryos. However, this type of micromanipulation necessitates access to specialized equipment, is laborious, and requires a certain level of technical skill. Moreover, microinjection techniques often result in lower embryo survival due to the mechanical stress on the embryo. In this protocol, we developed an optimized method to deliver large DNA repair templates to work in conjunction with CRISPR-Cas9 genome editing without the need for microinjection. This protocol combines AAV-mediated DNA delivery of single-stranded DNA donor templates along with the delivery of CRISPR-Cas9 ribonucleoprotein (RNP) by electroporation to modify 2-cell embryos. Using this novel strategy, we have successfully produced targeted knock-in rat models carrying insertion of DNA sequences from 1.2 to 3.0 kb in size with efficiencies between 42% and 90%.

Genetic engineering in the rat has been revolutionized by the development of CRISPR-based genome editing tools. Conventional methods for inserting genome editing elements such as CRISPR/Cas9 reagents into rat zygotes include cytoplasmic or pronuclear microinjections. These techniques are labor-intensive, require specialized micromanipulator equipment, and are technically challenging. Here, we describe a simple and effective method for zygote electroporation in which CRISPR/Cas9 reagents are introduced into rat zygotes via pores produced by precise electrical pulses applied to the cells. Zygote electroporation allows for high-throughput efficient genome editing in rat embryos.

Specific bacterial taxa in the gastrointestinal tract have been strongly associated with cases of colorectal cancer (CRC) cancer in familial adenomatous polyposis and spontaneous disease cases in humans. This has been recapitulated in animal models of CRC with positive correlations with many commensals and pathogens. However, many of these studies are performed either in germ-free animals or employ an antibiotic regime, overlooking the complex interactions of the commensals within the colon. To simplify the challenges associated with the complexity of the microbiota in the GI tract we established the Pirc rat model of colon cancer on an Altered Schaedler Flora (ASF) gut microbiota (GM), maintained in a barrier room. To elucidate the role of the simplified (ASF) and conventional GMs on disease susceptibility, We conventionalized ASF Pirc littermates. We found that the conventionalized F1 rats had increased microbial diversity and decreased colonic adenoma multiplicity. Our findings show that the complexity and the interactions of the GM community and not a Firmicutes to Bacteroidetes ratio are an important factor affecting disease susceptibility.

Recent advances in CRISPR-Cas genome editing technology have been instrumental in improving the efficiency to produce genetically modified animal models. In this study we have combined four very promising approaches to come up with a highly effective pipeline to produce knock-in mouse and rat models. The four combined methods include: AAV-mediated DNA delivery, single-stranded DNA donor templates, 2-cell embryo modification, and CRISPR-Cas ribonucleoprotein (RNP) electroporation. Using this new combined approach, we were able to produce successfully targeted knock-in rat models containing either Cre or Flp recombinase sequences with knock-in efficiencies over 90%. Furthermore, we were able to produce a knock-in mouse model containing a Cre recombinase targeted insertion with over 50% knock-in efficiency directly comparing efficiencies to other commonly used approaches. Our modified AAV-mediated DNA delivery with 2-cell embryo CRISPR-Cas9 RNP electroporation technique has proven to be highly effective for generating both knock-in mouse and knock-in rat models.

In this study, the transcriptional repressor REST (Repressor Element 1 Silencing Transcription factor) was ablated in the mouse placenta to investigate molecular and cellular impacts on the offspring brain at different life stages. Ablation of placental REST deregulated several brain metabolites, including glucose and lactate that fuel brain energy, vitamin C (ascorbic acid) that functions in the epigenetic programming of the brain during postnatal development, and glutamate and creatine that help the brain to respond to stress conditions during adult life. Bulk RNA-seq analysis showed that a lack of placental REST persistently altered multiple transport genes, including those related to oxygen transportation in the offspring brain. While metabolic genes were impacted in the postnatal brain, different stress response genes were activated in the adult brain. DNA methylation was also impacted in the adult brain due to the loss of placental REST, but in a sex-biased manner. Single-nuclei RNA-seq analysis showed that specific cell types of the brain, particularly those of the choroid plexus and ependyma, which play critical roles in producing cerebrospinal fluid and maintaining metabolic homeostasis, were significantly impacted due to the loss of placental REST. These cells showed significant differential expression of genes associated with the metabotropic (G coupled protein) and ionotropic (ligand-gated ion channel) glutamate receptors, suggesting an impact of ablation of placental REST on the glutamatergic signaling of the offspring brain. The study expands our understanding of placental influences on the offspring brain.