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Hypophosphatemia: mouse model for human familial hypophosphatemic (vitamin D-resistant) rickets.

A new dominant mutation in the laboratory mouse, hypophosphatemia (gene symbol Hyp), has been identified. The Hyp gene is located on the X-chromosome and maps at the distal end. Mutant mice are characterized by hypophosphatemia, bone changes resembling rickets, diminished bone ash, dwarfism, and high fractional excretion of phosphate anion (low net tubular reabsorption). Phosphate supplementation of the diet from wearning prevents the appearance of severe skeletal abnormalities. The hypophosphatemic male mouse resembles human males with X-linked hypophosphatemia and the Hyp gene is presemably homologous with the X-linked human gene. The mouse model should facilitate study of the defect in transport of plasma inorganic phosphate anion.

Animals

Ultrastructural observations on giardiasis in a mouse model. II. Endosymbiosis and organelle distribution in Giardia muris and Giardia lamblia.

Ultrastructural observations of Giardia muris in a mouse model revealed endosymbiotic microbes not previously reported in Giardia. Endosymbionts 240--360 nm wide, 600--1,400 nm long, and with an internal structure similar to that of bacilli were not seen entering Giardia but were found and appeared to divide within Giardia. No evidence was found of digestion of the endosymbionts by the giardia host in either the trophozoite or the cyst form. Endosymbionts were concentrated centrally around the nuclear area and were uncommon in peripheral feeding regions. The same cellular organelles seen in G. muris were found in Giardia lamblia from human jejunal biopsy material, but no endosymbionts were identified in G. lamblia trophozoites from the seven patients examined. Endosymbionts within Giardia may be found to alter trophozoite pathogenicity, metabolism, range of infectivity, antigenic surface characteristics, and host specificity, as they do in other protozoa.

Animals

Evaluating the pathogenic significance of unique chromosomal variants in craniosynostosis using patient-derived induced pluripotent stem cells and mouse modelling.

PURPOSE: Unravelling causal links between unique structural/copy-number variants (SV/CNV) and associated phenotypes is essential for correct genetic counselling. We investigated two families in which patients with craniosynostosis had SV/CNV potentially dysregulating a fibroblast growth factor (FGF)-encoding gene; a 730 kb dup(4)(q21.21) including FGF5; and a complex 568 kb interspersed 13q12.11 duplication, located 841 kb from FGF9. METHODS: We combined bioinformatic predictions of altered topologically-associating domain (TAD) structure, with experimental analysis (RNA- and ATAC- [assay for transposase-accessible chromatin] sequencing) of patient induced pluripotent stem cell lines (iPSCs) differentiated to neural crest (NCC) and osteoprogenitor (OPC) identities. For the dup(4)(q21.21) we generated a mouse bearing an equivalent rearrangement using CRISPR-Cas9 targeting. RESULTS: TAD analysis suggested potential dysregulation of the FGF5/FGF9 gene by bringing it into a novel genomic milieu. The RNA- and ATAC-seq assays demonstrated FGF5/FGF9 upregulation (2.7-18x) and local opening of chromatin, in 3/4 cell lines. For the dup(4)(q21.21), a causal role was supported by the mouse model, whereas interpretation of the 13q12.11 SV is confounded by a co-existing FOXP2 pathogenic variant. CONCLUSION: Patient iPSC-differentiated NCC and OPC lines, combined with TAD-based modelling to generate testable functional hypotheses, provide valuable functional evidence when evaluating causation of unique SV/CNV in craniosynostosis.

copy-number variant

Optimized genomic editing of a common Duchenne muscular dystrophy mutation in patient-derived muscle cells and a new humanized mouse model.

Duchenne muscular dystrophy (DMD) is a fatal X-linked, recessive disease caused by mutations in the DMD gene encoding dystrophin, a membrane-associated protein necessary for maintaining muscle structure and function. One of the common DMD mutations is the deletion of exon 52 (Δ52), which introduces a premature stop codon in exon 53, preventing the expression of functional dystrophin protein. Patients with this mutation could benefit from skipping or reframing exon 53 to restore the dystrophin open reading frame. In this study, we investigated the efficacy of single-cut CRISPR gene editing with Staphylococcus pyogenes Cas9 (SpCas9)-LRVQR to restore dystrophin expression in patient-derived induced pluripotent stem cells (iPSCs) and a newly generated humanized DMD mouse model. We compared two injection routes for adeno-associated virus (AAV) serotype 9 to deliver gene-editing components to neonatal mice: intraperitoneal (IP) and facial vein (FV) injection. We observed efficient restoration of dystrophin protein expression across multiple skeletal muscle groups and the heart. The AAV9-mediated CRISPR single-cut approach ameliorated key DMD hallmarks, including histopathological phenotypes, impaired grip strength, and elevated serum creatine kinase levels. Our optimized strategies for dystrophin restoration in humanized DMD mice with exon 52 deletion represent a promising treatment for DMD.

AAV

Construction and evaluation of an independently generated transgenic mouse model carrying mutated human HRAS genes for short-term carcinogenicity assessment.

The study aimed to construct and evaluate an independently generated transgenic mouse model applied to the short-term carcinogenicity assessment. Mutated human HRAS fragment containing an intron point-mutation was inserted into C57BL/6JGpt mice via bacterial artificial chromosome transgenic technology, eventually generating BALB/c;B6J-Tg(hHRAS)16/Gpt mice, abbreviated as HRAS mice. The inserted human HRAS fragment in HRAS mice was characterized, revealing five tandem copies at chromosome 19. Baseline profiles, including biochemical, hematological, immunophenotypic, survival, and carcinogenic data of HRAS mice, were collected. To evaluate the tumor susceptibility in HRAS mice, we applied N-Nitroso-N-methylurea (MNU) to HRAS mice in a short-term carcinogenicity assessment conducted according to Good Laboratory Practice. The genetic characteristics of HRAS mice include five tandem arrays of mutated human HRAS fragments located in genomic coordinate 7,755,606 on chromosome 19 and the duplication of a 9-kilobase genome sequence (genomic coordinate 7,755,606-7,746,509) located on chromosome 19. HRAS mice showed a relatively lower incidence and range of spontaneous tumor formation during long-term observation compared to CByB6F1-Tg(HRAS)2Jic (Tg.rasH2) transgenic mice. The short-term carcinogenicity assessment showed a strong tumor response to MNU, with high incidences of lymphoma (≥ 90%) and stomach squamous cell papilloma (≥ 90%) in both male and female HRAS mice. The HRAS mice showed susceptibility to MNU and exhibited baseline characteristics distinct from those of Tg.rasH2 mice. The co-expression of HRAS and MKI67 at the cellular localization level was found in neoplasms of HRAS mice. These findings preliminarily evaluated the feasibility of HRAS mice applied to the short-term carcinogenicity assessment.

Animals

Quantitative proteomic analysis of the brain reveals the potential antidepressant mechanism of Jiawei Danzhi Xiaoyao San in a chronic unpredictable mild stress mouse model of depression.

OBJECTIVE: To reveal the antidepressant mechanisms of Jiawei DanZhiXiaoYaoSan (,JD) in chronic unpredictable mild stress (CUMS)-induced depression in mice. METHODS: Using the CUMS mouse model of depression, the antidepressant effects of JD were assessed using the sucrose preference test (SPT), forced swimming test (FST), and tail suspension test (TST). Tandem mass tag (TMT)-based quantitative proteomic analysis of the brain was performed following JD treatment. Hierarchical clustering, Gene Ontology function annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and protein-protein interactions (PPIs) were used to analyze differentially expressed proteins (DEPs), which were further validated using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting. RESULTS: Behavioral tests confirmed the anti-depressant effects of JD, and bioinformatics analysis revealed 59 DEPs, including 33 up-regulated and 26 down-regulated proteins, between the CUMS and JD-M groups. KEGG and PPI analyses revealed that neuro-filament proteins and the Ras signaling pathway may be key targets of JD in the treatment of depression. qRT-PCR and Western blotting results demonstrated that CUMS reduced the protein expression of neurofilament light (NEFL) and medium (NEFM) and inhibited the phosphorylation of extracellular regulated kinase 1/2 (ERK1/2), whereas JD promoted the phosphorylation of ERK1/2 and up-regulated the protein expression of NEFL and NEFM. CONCLUSIONS: The antidepressant mechanism of JD may be related to the up-regulation of p-ERK1/2 and neurofilament proteins.

Animals

Development of a new flippase-dependent mouse model for red fluorescence-based isolation of KRASG12D oncogene-expressing tumor cells.

Proto-oncogene KRAS, GTPase (KRAS) is one of the most intensively studied oncogenes in cancer research. Although several mouse models allow for regulated expression of mutant KRAS, selective isolation and analysis of transforming or tumor cells that produce the KRAS oncogene remains a challenge. In our study, we present a knock-in model of oncogenic variant KRASG12D that enables the "activation" of KRASG12D expression together with production of red fluorescent protein tdTomato. Both proteins are expressed from the endogenous Kras locus after recombination of a transcriptional stop box in the genomic DNA by the enzyme flippase (Flp). We have demonstrated the functionality of the allele termed RedRas (abbreviated KrasRR) under in vitro conditions with mouse embryonic fibroblasts and organoids and in vivo in the lung and colon epithelium. After recombination with adenoviral vectors carrying the Flp gene, the KrasRR allele itself triggers formation of lung adenomas. In the colon epithelium, it causes the progression of adenomas that are triggered by the loss of tumor suppressor adenomatous polyposis coli (APC). Importantly, cells in which recombination has successfully occurred can be visualized and isolated using the fluorescence emitted by tdTomato. Furthermore, we show that KRASG12D production enables intestinal organoid growth independent of epidermal growth factor (EGF) signaling and that the KRASG12D function is effectively suppressed by specific inhibitor MRTX1133.

Animals

Alternative 3' UTR polyadenylation is disrupted in the rNLS8 mouse model of ALS/FTLD.

Recent research has highlighted widespread dysregulation of alternative polyadenylation in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP). Here, we identify significant disruptions to 3` UTR polyadenylation in the ALS/FTLD-TDP mouse model rNLS8 that correlate with changes in gene expression and protein levels through the re-analysis of published RNA sequencing and proteomic data. A subset of these changes are shared with TDP-43 knock-down mice suggesting depletion of endogenous mouse TDP-43 is a contributor to polyadenylation dysfunction in rNLS8 mice. Some conservation exists between alternative polyadenylation in rNLS8 mice and human disease models including in disease relevant genes and biological pathways. Together, these findings support both TDP-43 loss and toxic gain-of-function phenotypes as contributors to the neurodegeneration in rNLS8 mice, nominating its continued utility as a preclinical model for investigating mechanisms of neurodegeneration in ALS/FTLD-TDP.

Animals

In search of anti-Trypanosoma cruzi drugs: new leads from a mouse model.

Nine of 25 carefully selected compounds (from a stock of more than 200 000 chemical species amassed principally as a result of testing against other parasitic diseases) were found to have significant suppressive activity against the parasites in the blood of a Trypanosoma cruzi mouse model. Eight of these compounds evaluated in this model had suppressive activity equal to or greater than the reference compound, nifurtimox. For the first time, suppressive activity against T. cruzi is reported for a 7-aminoquinoline, a phosphonium salt, and TAC pamoate; The biological model is believed to be able to serve as a means of identifying other new "leads* in seeking drugs broadly effective against T=ruzi infections in man.

5-Amino-3-((5-nitro-2-furyl)vinyl)-1,2,4-oxadiazol

Targeted insertion of an optimized donor DNA is effective in a humanized mouse model of dominant retinitis pigmentosa.

Retinitis pigmentosa (RP) affects 1 in 3,000 individuals worldwide, with 30%-40% of cases inherited as autosomal dominant (AD). Mutations in RHO (RP4) are the most common cause of ADRP. Because most RHO mutations exert gain-of-function or dominant-negative effects, conventional gene supplementation is insufficient, requiring mutant allele inactivation. Allele-specific editing is impractical, as each mutation requires a unique therapeutic strategy. We present a mutation-agnostic, RHO-specific approach using adeno-associated viral vector-mediated homology-independent targeted integration (AAV-HITI). Optimized donor DNA design enables targeted integration and efficient transgene expression from the endogenous RHO locus. In a humanized RP4 mouse model harboring the RHO P23H mutant allele alongside an endogenous wild-type mouse Rho allele, AAV-HITI significantly improves retinal structure, function, and visual acuity up to 1 year post-treatment. Comprehensive molecular analyses characterize on-target editing in mouse retina and off-target editing in a human cell line. These findings establish an effective, human-centric AAV-HITI platform for RP4 and support its evaluation in this and other dominant genetic conditions.

AAV

Prenatal arsenic exposure alters EZH2-H3K27me3 occupancy at TNF-α promoter leading to insulin resistance and metabolic syndrome in a mouse model.

The global prevalence of Metabolic Syndrome (MetS) is continuously rising and exposure to environmental toxicants such as arsenic could be contributing to this rapid surge. In this study, we have assessed the effects of prenatal arsenic exposure on insulin resistance and MetS parameters in a mouse model, and an underlying mechanism was identified. We found that prenatal arsenic exposure promotes insulin resistance and adipocyte dysfunction which leads to the early onset of MetS in male offspring. Primary adipocytes isolated from 20-week-old arsenic-exposed offspring showed hypertrophy, elevated basal lipolysis, and impaired insulin response along with enhanced expression of Tumor necrosis factor-alpha (TNF-α). TNF-α levels were consistently high at gestational day 15.5 (GD15.5) as well as primary adipocytes of 6-week-old arsenic-exposed male offspring. Along with TNF-α, downstream p-JNK1/2 levels were also increased, which led to inhibitory phosphorylation of IRS1and reduced GLUT4 translocation upon insulin stimulation in adipocytes. Insulin response and downstream signaling were restored upon TNF-α inhibition, confirming its central role. The persistent overexpression of TNF-α in adipocytes of arsenic-exposed mice resulted from diminished EZH2 occupancy and reduced H3K27me3 (gene silencing histone marks) at the TNF-α promoter. This further led to chromatin relaxation, recruitment of c-Jun and CBP/p300, formation of an enhanceosome complex, and TNF-α expression. Our findings show how prenatal arsenic exposure can epigenetically modulate TNF-α expression to promote adipocyte dysfunction and insulin resistance which contributes to the early onset of MetS in offspring.

Animals

Pentatricopeptide repeat protein targeting CUG repeat RNA ameliorates RNA toxicity in a myotonic dystrophy type 1 mouse model.

Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystemic disorder caused by the expansion of a CTG-triplet repeat in the 3' untranslated region of the dystrophia myotonica protein kinase (DMPK) gene. It results in the transcription of toxic RNAs that contain expanded CUG repeats (CUGexp). Splicing factors, such as muscleblind-like 1 (MBNL1), are sequestered by CUGexp, thereby disrupting the normal splicing program that is essential for various cellular functions. Pentatricopeptide repeat (PPR) proteins, originally found in plants, regulate RNA in organelles by binding in a sequence-specific manner. Here, we designed PPR proteins that specifically bind to the hexamer of CUG repeat RNAs (CUG-PPRs) and showed that CUG-PPR1 could ameliorate RNA toxicity induced by CUGexp in cell models of DM1. A single systemic recombinant adeno-associated virus (AAV9) vector-mediated gene delivery of CUG-PPR1 demonstrated long-term therapeutic effects on myotonia and restored splicing activity in a mouse model of DM1. These results highlight the potential of PPR molecules to target pathogenic RNA sequences in DM1 and potentially other RNA-mediated disorders.

Animals

A metagenomic analysis of the gut microbiota in a mouse model of fish allergy.

BACKGROUND: Fish are among the most frequent causes of immunoglobulin E (IgE)-mediated food allergies (Type I). Currently, there is no known cure for fish allergy and individuals who are sensitized have to practice strict, lifelong avoidance of fish products in their diets. The relationship between gut microbiome and food allergies is currently a major topic of discussion; these pathologies involve the development of dysbiosis, which is a microbial imbalance resulting from immune-related mechanisms. Recent studies have provided evidence that individuals suffering from food allergies, display an intestinal microbiota with a different microbial composition compared to healthy subjects. OBJECTIVES AND METHODS: In this work, we have described for the first time the differences in microbiome composition in a mouse model of fish allergy with previous sensitization to the main allergen, beta-Parvalbumin (β-PRVB), compared to mouse individuals without allergic response. RESULTS: The metagenomic analysis has shown differences in taxonomic composition between the treatments. Regarding phyla, an increase in the relative abundance of Patescibacteria, specifically Saccharimonas genus and Candidatus_Saccharimonas group, were observed in the allergic animals (Prvb_Alum group) when compared to the other groups. In contrast, the relative abundance of the RF39 group (Bacilli), Atopobiaceae family, Erysipelotrichaceae, and the Coriobacteriaceae_UCG-002 group, was higher in the animals that did not develop an allergic response, despite being exposed to the allergen (Prvb group). Furthermore, an increase in the relative abundance of Lachnospiraceae ASF356 group was observed in the control group compared to the other treatments. This family, has been reported to be inversely associated with the progression of intestinal inflammation and anaphylactic diseases. For the first time, the gut microbiota composition of individual mice with and without fish allergies is described in detail in this work. This study may shed light on the potential contribution of gut microbiota to the onset and avoidance of food allergies.

beta-parvalbumin

Propionyl-CoA carboxylase subunit B regulates anti-tumor T cells in a pancreatic cancer mouse model.

Most human pancreatic ductal adenocarcinoma (PDAC) are not infiltrated with cytotoxic T cells and are highly resistant to immunotherapy. Over 90% of PDAC have oncogenic KRAS mutations, and phosphoinositide 3-kinases (PI3Ks) are direct effectors of KRAS. Our previous study demonstrated that ablation of Pik3ca in KPC (KrasG12D; Trp53R172H; Pdx1-Cre) pancreatic cancer cells induced host T cells to infiltrate and completely eliminate the tumors in a syngeneic orthotopic implantation mouse model. Now, we show that implantation of Pik3ca-/- KPC (named αKO) cancer cells induces clonal enrichment of cytotoxic T cells infiltrating the pancreatic tumors. To identify potential molecules that can regulate the activity of these anti-tumor T cells, we conducted an in vivo genome-wide gene-deletion screen using αKO cells implanted in the mouse pancreas. The result shows that deletion of propionyl-CoA carboxylase subunit B gene (Pccb) in αKO cells (named p-αKO) leads to immune evasion, tumor progression, and death of host mice. Surprisingly, p-αKO tumors are still infiltrated with clonally enriched CD8+ T cells but they are inactive against tumor cells. However, blockade of PD-L1/PD1 interaction reactivated these clonally enriched T cells infiltrating p-αKO tumors, leading to slower tumor progression and improve survival of host mice. These results indicate that Pccb can modulate the activity of cytotoxic T cells infiltrating some pancreatic cancers and this understanding may lead to improvement in immunotherapy for this difficult-to-treat cancer.

Animals

Fibroblast growth factor 21 prevents catecholaminergic arrhythmias in a mouse model of PKP2 arrhythmogenic cardiomyopathy.

BACKGROUND: Pathogenic variants in plakophilin-2 (PKP2) cause arrhythmogenic cardiomyopathy (ACM) with intracellular calcium dysregulation as a major component of its arrhythmia phenotype. Recent adeno-associated virus (AAV)-based PKP2 gene therapy has shown promising results in a few different PKP2-associated ACM models. Fibroblast growth factor 21 (FGF21) has multiple cardioprotective effects and has recently emerged as a promising therapeutic agent for cardiovascular disease. OBJECTIVE: This study aimed to assess the efficacy and impact on calcium regulation of a novel AAV serotype 8 (AAV8)-based FGF21 gene therapy on adult cardiac-specific, tamoxifen-activated PKP2 knockout (PKP2-cKO) mice. METHODS: Experiments were performed using a PKP2-cKO murine model. AAV8-FGF21 was delivered to adult mice by a single tail vein injection 7 days before tamoxifen-activated PKP2-cKO. Cardiac functions were monitored using echocardiography and electrocardiography. Intracellular calcium transients were investigated in acute isolated adult mouse cardiomyocytes, and calcium fluorescent signals were acquired using the IonOptix system. RESULTS: Loss of PKP2 expression caused cardiac mechanical dysfunction and proarrhythmic phenotype in adult mouse models. AAV-mediated delivery of FGF21 mitigated the progression of biventricular structural changes, decreased the occurrence of adrenergic arrhythmias, and rescued intracellular calcium imbalance in the setting of PKP2 haploinsufficiency. In contrast, acute in vitro FGF21 treatment for 1 hour had no effect on intracellular calcium transients. CONCLUSION: These beneficial effects of AAV8-FGF21 on the PKP2-ACM phenotype suggest a therapeutic landscape for various targeted cardiomyopathies.

Animals

In Vivo Base Editing Partially Rescues Bone Dysplasia in a Mouse Model of Hutchinson-Gilford Progeria Syndrome.

Hutchinson-Gilford progeria syndrome (HGPS) is a premature aging disorder affecting tissues of mesenchymal origin. Most patients harbor a c.1824C>T/p.G608= variant, commonly described as G608G, in exon 11 of LMNA that leads to aberrant splicing and production of the toxic progerin protein. In addition to cardiovascular, dermal, and adipose tissue deterioration, HGPS mouse models also develop progressive bone dysplasia that occurs in patients. Here we characterize the efficacy of in&#xa0;vivo mutation correction with an adenine base editor (ABE) to rescue structural and functional defects in HGPS transgenic murine bone tissue. Treatment of double-copy transgenic osteoblast cultures with a lentiviral-delivered CRISPR-Cas9 ABE achieved nearly 40% gene correction in&#xa0;vitro, resulting in significant reduction of progerin transcripts and protein, in the absence of selective agents. Furthermore, gene correction improved progeroid osteoblasts' capacity to deposit and mineralize extracellular matrix compared to untreated cultures. In&#xa0;vivo, a single intravenous dose of AAV9-delivered ABE corrected the mutation, achieving ~14%, ~22%, ~10% and <&#x2009;1% correction in bone by six months of age when administered at P3, P14, 1 and 4&#x2009;months of age, respectively. Partially rescued bone structural and physical parameters were observed in P14-treated mice with concomitant normalization of gene transcriptional programs and intracellular signaling pathways involved in bone remodeling. This work demonstrates in&#xa0;vivo delivery of a locus-specific DNA base editor to bone tissue, delineates the timing of treatment required for maximum efficacy, and suggests that this system might be tailored for application to other monogenic bone disorders.

Animals

Altered neural electrophysiological properties in the anterior cingulate cortex in a mouse model of Prader-Willi syndrome.

Prader-Willi syndrome (PWS) is a neurodevelopmental genetic disease associated with multiple metabolic and behavioural abnormalities converging into a distinctive clinical phenotype characterized by insatiable appetite leading to hyperphagia and eventual morbid obesity. The PWS spectrum results from deficiencies in paternally imprinted chromosome 15q11-13 region clustering around non-coding RNA multiple-repeat gene Snord116. A PWS mouse model with paternal Snord116 deletion (Snord116del) revealed multiple expected behavioural traits but failed to reproduce obesity in experimental paradigms designed to uncover homeostatic hypothalamic mechanisms of hyperphagia, while the possibility for pathologic hedonic overdrive underlying hyperphagic behaviours was not studied. In Snord116del mice, we examined functional properties of pyramidal neurons (PyNs) in the anterior cingulate cortex (ACC), the brain area commonly associated with goal-oriented and choice-outcome processing, including the value assessment of food items. We found indications of higher dendritic complexity and stronger afferent excitatory connectivity compared to controls. A strong excitatory input into Snord116del PyNs was balanced by a more hyperpolarized resting membrane potential, rendering lower soma excitability, improved signal-to-noise discrimination and stronger low-pass filtering. The enhanced excitatory network-tuning ability originating from Snord116 deficiency may explain the previously reported better performance of Snord116del over wild-type mice in working-for-food behavioural tests, whereas in humans it might entail exaggerated reward-seeking behaviour since early childhood when food is the main attractant. Our analysis of previously published genomic databases revealed candidate genes responsible for the abnormal functional neuronal phenotype caused by Snord116 deletion, including K+ and Na+ voltage-dependent ion channels, protein kinases, phosphatases and components of the mechanistic target of rapamycin (mTOR) intracellular signalling pathway. KEY POINTS: Altered biophysical characteristics and parameters of neuronal connectivity in pyramidal neurons in the anterior cingulate cortex (ACC) in Snord116 deletion mice. Alterations include augmented afferent synaptic input, altered resting state and firing properties of ACC pyramidal neurons. Our findings uncover a possible mechanistic basis for altered ACC functionality in Prader-Willi syndrome.

Animals

Generation and validation of a Myh11Dre-Spp1Cre intersectional mouse model for lineage tracing of disease-associated smooth muscle cell states.

BACKGROUND: Phenotypic modulation of vascular smooth muscle cells (VSMCs) is a hallmark of vascular remodeling and cardiovascular disease. Recent lineage-tracing and single-cell transcriptomic studies have identified secreted phosphoprotein 1 (SPP1) as a prominent marker associated with disease-associated VSMC states, particularly those linked to fibrotic remodeling and vascular calcification. However, the cellular origins and fate of SPP1-associated VSMC populations remain incompletely understood. METHODS AND RESULTS: We generated a novel Spp1-rSTOPr-Cre (Spp1Cre) knock-in mouse line in which Cre recombinase is expressed from the endogenous Spp1 locus following Dre-mediated excision of a rox-flanked transcriptional STOP cassette. Correct targeting of the knock-in allele was validated by internal, 5' junction, 3' junction, and long-range PCR analyses, as well as Sanger sequencing. To establish an intersectional lineage-tracing strategy, Spp1Cre mice were crossed with Myh11DreERT2 and Rosa26-RSR-LSL-tdTomato-LSL-eGFP reporter mice, enabling permanent labeling of VSMC-derived populations following activation of the endogenous Spp1 locus. Under physiological conditions, eGFP-positive cells were detected at low frequency within the vascular wall and were predominantly negative for the contractile markers ACTA2 and MYH11. As a proof-of-principle application, eGFP-positive cells markedly expanded within atherosclerotic lesions induced by AAV-PCSK9D377Y and high-fat diet feeding. These lineage-traced cells remained largely ACTA2- and MYH11-negative, consistent with a modulated phenotype. Notably, only a minority of eGFP-positive cells expressed SPP1 or fibronectin at the time of analysis, demonstrating the utility of permanent lineage tracing for tracking cells with a history of endogenous Spp1 activation during vascular remodeling. CONCLUSION: We report the generation and validation of a novel Myh11Dre-Spp1Cre intersectional mouse model for lineage tracing of VSMC-derived populations that have activated the endogenous Spp1 locus. This genetic resource provides a valuable platform for investigating the origin, fate, and phenotypic evolution of Spp1-associated VSMC populations during vascular remodeling and cardiovascular disease.

Animals