Selected transgenic murine models of human autoimmune liver diseases

Murine models of human diseases are of outmost importance for both studying molecular mechanisms driving their development and testing new treatment strategies. In this review, we first discuss the etiology and risk factors for autoimmune liver disease, including primary biliary cholangitis, autoimmune hepatitis and primary sclerosing cholangitis. Second, we highlight important features of murine transgenic models that make them useful for basic scientists, drug developers and clinical researchers. Next, a brief description of each disease is followed by the characterization of selected animal models.

Metabolic convergence on lipogenesis in RAS, BCR-ABL, and MYC-driven lymphoid malignancies

Background Metabolic reprogramming is a central feature in many cancer subtypes and a hallmark of cancer. Many therapeutic strategies attempt to exploit this feature, often having unintended side effects on normal metabolic programs and limited efficacy due to integrative nature of metabolic substrate sourcing. Although the initiating oncogenic lesion may vary, tumor cells in lymphoid malignancies often share similar environments and potentially similar metabolic profiles. We examined cells from mouse models of MYC-, RAS-, and BCR-ABL-driven lymphoid malignancies and find a convergence on de novo lipogenesis. We explore the potential role of MYC in mediating lipogenesis by 13C glucose tracing and untargeted metabolic profiling. Inhibition of lipogenesis leads to cell death both in vitro and in vivo and does not induce cell death of normal splenocytes. Methods We analyzed RNA-seq data sets for common metabolic convergence in lymphoma and leukemia. Using in vitro cell lines derived in from conditional MYC, RAS, and BCR-ABL transgenic murine models and oncogene-driven human cell lines, we determined gene regulation, metabolic profiles, and sensitivity to inhibition of lipogenesis in lymphoid malignancies. We utilize preclinical murine models and transgenic primary model of T-ALL to determine the effect of lipogenesis blockade across BCR-ABL-, RAS-, and c-MYC-driven lymphoid malignancies. Statistical significance was calculated using unpaired t-tests and one-way ANOVA. Results This study illustrates that de novo lipid biogenesis is a shared feature of several lymphoma subtypes. Using cell lines derived from conditional MYC, RAS, and BCR-ABL transgenic murine models, we demonstrate shared responses to inhibition of lipogenesis by the acetyl-coA carboxylase inhibitor 5-(tetradecloxy)-2-furic acid (TOFA), and other lipogenesis inhibitors. We performed metabolic tracing studies to confirm the influence of c-MYC and TOFA on lipogenesis. We identify specific cell death responses to TOFA in vitro and in vivo and demonstrate delayed engraftment and progression in vivo in transplanted lymphoma cell lines. We also observe delayed progression of T-ALL in a primary transgenic mouse model upon TOFA administration. In a panel of human cell lines, we demonstrate sensitivity to TOFA treatment as a metabolic liability due to the general convergence on de novo lipogenesis in lymphoid malignancies driven by MYC, RAS, or BCR-ABL. Importantly, cell death was not significantly observed in non-malignant cells in vivo. Conclusions These studies suggest that de novo lipogenesis may be a common survival strategy for many lymphoid malignancies and may be a clinically exploitable metabolic liability. Trial registration This study does not include any clinical interventions on human subjects.

Poly (ADP-ribose) Interacts With Phosphorylated α-Synuclein in Post Mortem PD Samples

Poly (ADP-ribose) (PAR) is a negatively charged polymer that is biosynthesized by Poly (ADP-ribose) Polymerase-1 (PARP-1) and regulates various cellular processes. Alpha-synuclein (αSyn) is an intrinsically disordered protein (IDP) that has been directly implicated with driving the onset and progression of Parkinson’s disease (PD). The mechanisms by which α-synuclein (αSyn) elicits its neurotoxic effects remain unclear, though it is well established that the main components of Lewy bodies (LBs) and Lewy neurites (LNs) in PD patients are aggregated hyperphosphorylated (S129) forms of αSyn (pαSyn). In the present study, we used immunofluorescence-based assays to explore if PARP-1 enzymatic product (PAR) promotes the aberrant cytoplasmic accumulation of pαSyn. We also performed quantitative measurements using in situ proximity ligation assays (PLA) on a transgenic murine model of α-synucleinopathy (M83-SNCA∗A53T) and post mortem PD/PDD patient samples to characterize PAR–pαSyn interactions. Additionally, we used bioinformatic approaches and site-directed mutagenesis to identify PAR-binding regions on αSyn. In summary, our studies show that PAR–pαSyn interactions are predominantly observed in PD-relevant transgenic murine models of αSyn pathology and post mortem PD/PDD patient samples. Moreover, we confirm that the interactions between PAR and αSyn involve electrostatic forces between negatively charged PAR and lysine residues on the N-terminal region of αSyn.

Remodeling Alzheimer-amyloidosis models by seeding

Alzheimer’s disease (AD) is among the most prevalent neurodegenerative diseases, with brain pathology defined by extracellular amyloid beta deposits and intracellular tau aggregates. To aid in research efforts to improve understanding of this disease, transgenic murine models have been developed that replicate aspects of AD pathology. Familial AD is associated with mutations in the amyloid precursor protein and in the presenilins (associated with amyloidosis); transgenic amyloid models feature one or more of these mutant genes. Recent advances in seeding methods provide a means to alter the morphology of resultant amyloid deposits and the age that pathology develops. In this review, we discuss the variety of factors that influence the seeding of amyloid beta pathology, including the source of seed, the time interval after seeding, the nature of the transgenic host, and the preparation of the seeding inoculum.

Metabolic Convergence on Lipogenesis in RAS, BCR-ABL, and MYC-driven Lymphoid Malignancies

Background Metabolic re-programming is a central feature in many cancer subtypes and a hallmark of cancer. Many therapeutic strategies attempt to exploit this feature, although often having unintended side effects on normal metabolic programs and limited efficacy due to integrative nature of metabolic substrate sourcing. Although the initiating oncogenic lesion may vary, in lymphoid malignancies tumor cells often share similar environments and potentially similar metabolic profiles. Methods We searched publicly available data sets for common metabolic convergence in lymphoma and leukemia. Using in vitro cell lines derived in from conditional MYC, RAS, and BCR-ABL transgenic murine models we examine metabolic profiles of lipogenesis. We then utilize preclinical murine models and transgenic primary model of T-ALL to determine the effect of lipogenesis blockade across BCR-ABL, RAS, and c-MYC-driven lymphoid malignancies. Statistical significance was calculated using unpaired T tests and one-way ANOVA. Results We find that de novo lipid biogenesis is a shared feature of several lymphoma subtypes. Using cell lines derived in from conditional MYC, RAS, and BCR-ABL transgenic murine models we demonstrate shared responses to inhibition of lipogenesis by the acetyl-coA carboxylase inhibitor 5-(Tetradecloxy)-2-furic Acid (TOFA). We identify specific cell death responses to TOFA in vitro and in vivo and demonstrate delayed engraftment and progression in vivo in transplanted lymphoma cell lines. We also observed delayed progression of T-ALL in a primary transgenic mouse model upon TOFA administration. In a panel of human cell lines, we demonstrate sensitivity to TOFA treatment as a feature of MYC high expressing lymphoma cell lines. Conclusions These studies indicate that inhibition of lipogenesis may be a common survival strategy for many lymphomas and that high MYC expression is predictive of sensitivity to blockade of fatty acid synthesis. Trial Registration This study does not include any clinical interventions on human subjectsTrial RegistrationThis study does not include any clinical interventions on human subjects

Sentinel p16INK4a+ cells in the basement membrane form a reparative niche in the lung

Senescent cells are recognized drivers of aging-related decline in organ function, but deciphering the biology of senescence in vivo has been hindered by the paucity of tools to track and isolate senescent cells in tissues1–4. Deleting senescent cells from transgenic murine models have demonstrated therapeutic benefits in numerous age-related diseases5–11, but the identity, behavior, and function of the senescent cells deleted in vivo remain elusive. We engineered an ultra-sensitive reporter of p16INK4a, a biomarker of senescence12, to isolate and track p16INK4a+ cells in vivo. Surprisingly, p16INK4a+ mesenchymal cells appear in the basement membrane adjacent to epithelial progenitors in the lung shortly after birth, and these cells demonstrate senescent characteristics in vivo and ex vivo. Transcriptomic analysis of p16INK4a+ mesenchymal cells from non-aged lungs demonstrates a transition to a secretory phenotype upon airway epithelial injury. Heterotypic 3D organoid assays show that injured p16INK4a+ mesenchymal cells enhance epithelial progenitor proliferation, and we identified EREG as a novel airway progenitor mitogen produced by the secretory p16INK4a+ mesenchymal cells. Mesenchymal-specific deletion of the p16INK4a gene abrogates features of senescence in vivo, but also attenuates normal epithelial repair. Thus, p16INK4a+ mesenchymal cells can act as sentinels for the airway epithelial stem cell niche, poised to transition to a senescence-associated secretory phenotype to support barrier repair. Our data identify possible cellular targets in vivo for a rapidly growing list of senolytic therapies, but also raises important questions about the hidden cost of targeting senescent cells present in normal organs.

Identification of ADPKD-Related Genes and Pathways in Cells Overexpressing PKD2

Consistent with the gene dosage effect hypothesis, renal cysts can arise in transgenic murine models overexpressing either PKD1 or PKD2, which are causal genes for autosomal dominant polycystic kidney disease (ADPKD). To determine whether PKD gene overexpression is a universal mechanism driving cystogenesis or is merely restricted to rodents, other animal models are required. Previously, we failed to observe any renal cysts in a transgenic porcine model of PKD2 overexpression partially due to epigenetic silencing of the transgene. Thus, to explore the feasibility of porcine models and identify potential genes/pathways affected in ADPKD, LLC-PK1 cells with high PKD2 expression were generated. mRNA sequencing (RNA-seq) was performed, and MYC, IER3, and ADM were found to be upregulated genes common to the different PKD2 overexpression cell models. MYC is a well-characterized factor contributing to cystogenesis, and ADM is a biomarker for chronic kidney disease. Thus, these genes might be indicators of disease progression. Additionally, some ADPKD-associated pathways, e.g., the mitogen-activated protein kinase (MAPK) pathway, were enriched in the cells. Moreover, gene ontology (GO) analysis demonstrated that proliferation, apoptosis, and cell cycle regulation, which are hallmarks of ADPKD, were altered. Therefore, our experiment identified some biomarkers or indicators of ADPKD, indicating that high PKD2 expression would likely drive cystogenesis in future porcine models.

Congenital Hypopituitarism: Various Genes, Various Phenotypes

The ontogenesis and development of the pituitary gland is a highly complex process that depends on a cascade of transcription factors and signaling molecules. Spontaneous mutations and transgenic murine models have demonstrated a role for many of these factors, including HESX1, PROP1, PIT1, LHX3, LHX4, SOX2, SOX3, OTX2, PAX6, FGFR1, SHH, GLI2, and FGF8 in the etiology of congenital hypopituitarism. Genetic mutations in any of these factors can lead to congenital hypopituitarism, which is characterized by the deficiency in one or more pituitary hormones. The phenotype can be highly variable, consisting of isolated hypopituitarism or more complex disorders. The same phenotype can be attributed to different gene mutations; while a given gene mutation can induce different phenotypes. This review highlights the genetic variations that lead to congenital hypopituitarism and their associated defects. The overall incidence of mutations in known transcription factors in patients with hypopituitarism is low; therefore many gene mutations or even gene- epigenetic interactions have to be unraveled in the future to explain the vast majority of still unclear cases of congenital hypopituitarism.

Psoriasis: Keratinocytes or Immune Cells – Which Is the Trigger?

Background: Psoriasis is a common, chronic inflammatory skin disorder, which can significantly impact quality of life. Despite major breakthroughs in our understanding of the pathogenesis of psoriasis, the chronological order of the underlying mechanisms leading to the development of psoriatic plaques remains to be completely understood. Summary: Although psoriasis is classically perceived as a T-cell disease, it is now well recognized that T lymphocytes do not function in exclusivity. This theory is supported by evidence from transgenic murine models that develop marked psoriasiform disease. In addition, immune cells and cytokines regulate both early and late events involved in the pathogenesis of psoriasis. Key Messages: Psoriasis is a complex disease – a dynamic interplay between immune cells, keratinocytes, and various other skin-resident cells, such as endothelial and immune cells. The contribution of each cell type is crucial in the initiation and maintenance phases of psoriatic alterations.