A novel mouse model expressing human forms for complement receptors CR1 and CR2.

BACKGROUND: The complement cascade is increasingly implicated in development of a variety of diseases with strong immune contributions such as Alzheimer's disease and Systemic Lupus Erythematosus. Mouse models have been used to determine function of central components of the complement cascade such as C1q and C3. However, species differences in their gene structures mean that mice do not adequately replicate human complement regulators, including CR1 and CR2. Genetic variation in CR1 and CR2 have been implicated in modifying disease states but the mechanisms are not known. RESULTS: To decipher the roles of human CR1 and CR2 in health and disease, we engineered C57BL/6J (B6) mice to replace endogenous murine Cr2 with human complement receptors, CR1 and CR2 (B6.CR2CR1). CR1 has an array of allotypes in human populations and using traditional recombination methods (Flp-frt and Cre-loxP) two of the most common alleles (referred to here as CR1long and CR1short) can be replicated within this mouse model, along with a CR1 knockout allele (CR1KO). Transcriptional profiling of spleens and brains identified genes and pathways differentially expressed between mice homozygous for either CR1long, CR1short or CR1KO. Gene set enrichment analysis predicts hematopoietic cell number and cell infiltration are modulated by CR1long, but not CR1short or CR1KO. CONCLUSION: The B6.CR2CR1 mouse model provides a novel tool for determining the relationship between human-relevant CR1 alleles and disease.

Gain of function p.E138A alteration in Card14 leads to psoriasiform skin inflammation and implicates genetic modifiers in disease severity.

Psoriasis (PS) is a common inflammatory and incurable skin disease affecting 2-3% of the human population. Although genome-wide association studies implicate more than 60 loci, the full complement of genetic factors leading to disease is not known. Rare, highly penetrant, gain-of-function, dominantly acting mutations within the human caspase recruitment domain family, member 14 (CARD14) gene lead to the development of PS and psoriatic arthritis (PSA) (a familial p.G117S and de-novo p.E138A alteration). These residues are conserved in mouse and orthologous Knock-In (KI) mutations within Card14 were created. The Card14tm.1.1Sun allele (G117S) resulted in no clinically or histologically evident phenotype of the skin or joints in young adult or old mice. However, mice carrying the Card14tm2.1Sun mutant allele (E138A) were runted and developed thick, white, scaly skin soon after birth, dying within two weeks or less. The skin hyperplasia and inflammation was remarkable similarity to human PS at the clinical, histological, and transcriptomic levels. For example, the skin was markedly acanthotic and exhibited orthokeratotic hyperkeratosis with minimal inflammation and no pustules and transcripts affecting critical pathways of epidermal differentiation and components of the IL17 axis (IL23, IL17A, IL17C, TNF and IL22) were altered. Similar changes were seen in a set of orthologous microRNAs previously associated with PS suggesting conservation across species. Crossing the Card14tm2.1Sun/WT mice to C57BL/6NJ, FVB/NJ, CBA/J, C3H/HeJ, and 129S1/SvImJ generated progeny with epidermal acanthosis and marked orthokeratotic hyperkeratosis regardless of the hybrid strain. Of these hybrid lines, only the FVB;B6N(129S4) mice survived to 250 days of age or older and has led to recombinant inbred lines homozygous for Card14E138A that are fecund and have scaly skin disease. This implicates that modifiers of PS severity exist in mice, as in the familial forms of the disease in humans.

Loss of FAS/FASL signalling does not reduce apoptosis in Sharpin null mice.

Mice with mutations in SHANK-associated RH domain interactor (Sharpin) develop a hypereosinophilic auto-inflammatory disease known as chronic proliferative dermatitis. Affected mice have increased apoptosis in the keratinocytes of the skin, oesophagus and forestomach driven by extrinsic TNF receptor-mediated apoptotic signalling pathways. FAS receptor signalling is an extrinsic apoptotic signalling mechanism frequently involved in inflammatory skin diseases. Compound mutations in Sharpin and Fas or Fasl were created to determine whether these death domain proteins influenced the cutaneous phenotype in Sharpin null mice. Both Sharpin/Fas and Sharpin/Fasl compound mutant mice developed an auto-inflammatory phenotype similar to that seen in Sharpin null mice, indicating that initiation of apoptosis by FAS signalling is likely not involved in the pathogenesis of this disease.

Early induction of NRF2 antioxidant pathway by RHBDF2 mediates rapid cutaneous wound healing.

Rhomboid family protein RHBDF2, an upstream regulator of the epidermal growth factor (EGF) receptor signaling, has been implicated in cutaneous wound healing. However, the underlying molecular mechanisms are still emerging. In humans, a gain-of-function mutation in the RHBDF2 gene accelerates cutaneous wound healing in an EGFR-dependent manner. Likewise, a gain-of-function mutation in the mouse Rhbdf2 gene (Rhbdf2cub/cub) shows a regenerative phenotype (rapid ear-hole closure) resulting from constitutive activation of the EGFR pathway. Because the RHBDF2-regulated EGFR pathway is relevant to cutaneous wound healing in humans, we used Rhbdf2cub/cub mice to investigate the biological networks and pathways leading to accelerated ear-hole closure, with the goal of identifying therapeutic targets potentially effective in promoting wound healing in humans. Comparative transcriptome analysis of ear pinna tissue from Rhbdf2cub/cub and Rhbdf2+/+ mice at 0h, 15min, 2h, and 24h post-wounding revealed an early induction of the nuclear factor E2-related factor 2 (NRF2)-mediated anti-oxidative pathway (0h and 15min), followed by the integrin-receptor aggregation pathway (2h) as early-stage events immediately and shortly after wounding in Rhbdf2cub/cub mice. Additionally, we observed genes enriched for the Fc fragment of the IgG receptor IIIa (FCGR3A)-mediated phagocytosis pathway 24h post-wounding. Although cutaneous wound repair in healthy individuals is generally non-problematic, it can be severely impaired due to aging, diabetes, and chronic inflammation. This study suggests that activation of the NRF2-antioxidant pathway by rhomboid protein RHBDF2 might be beneficial in treating chronic non-healing wounds.

Rhbdf2 mutations increase its protein stability and drive EGFR hyperactivation through enhanced secretion of amphiregulin.

The rhomboid 5 homolog 2 (Rhbdf2) gene encodes an inactive rhomboid (iRhom) protease, iRhom2, one of a family of enzymes containing a long cytosolic N terminus and a dormant peptidase domain of unknown function. iRhom2 has been implicated in epithelial regeneration and cancer growth through constitutive activation of epidermal growth factor receptor (EGFR) signaling. However, little is known about the physiological substrates for iRhom2 or the molecular mechanisms underlying these functions. We show that iRhom2 is a short-lived protein whose stability can be increased by select mutations in the N-terminal domain. In turn, these stable variants function to augment the secretion of EGF family ligands, including amphiregulin, independent of metalloprotease a disintegrin and metalloproteinase 17 (ADAM17) activity. In vivo, N-terminal iRhom2 mutations induce accelerated wound healing as well as accelerated tumorigenesis, but they do not drive spontaneous tumor development. This work underscores the physiological prominence of iRhom2 in controlling EGFR signaling events involved in wound healing and neoplastic growth, and yields insight into the function of key iRhom2 domains.

Angiogenesis in the skin of SHARPIN-deficient mice with chronic proliferative dermatitis.

Angiogenesis is a common feature of pathological processes including wound healing, tumor formation, and chronic inflammation. Chronic inflammation can also be associated with dilation or proliferation of lymph vessels. We examined blood vessels and lymphatics and the expression of pro- and anti-angiogenic genes in the skin of SHARPIN-deficient mice which spontaneously develop a chronic proliferative dermatitis (cpdm). The number of blood vessels in the dermis of cpdm mice increased with age as the inflammation progressed. Lymphatics identified by labeling for LYVE1 and podoplanin were moderately dilated, but they were not increased in number. The expression of proangiogenic Vegfa, Flt1 and anti-angiogenic Sema3a mRNA was increased. VEGFA was primarily localized in keratinocytes of cpdm skin. There was also increased expression of Ece1 and Pdpn mRNA. Podoplanin was restricted to lymphatic endothelial cells in normal skin, but fibroblasts in cpdm skin also reacted with anti-podoplanin antibodies indicating that they were activated. The expression of other angiogenic and lymphangiogenic factors was not altered or decreased. These results indicate that cpdm mice may be a useful model to study the pathogenesis of angiogenesis in chronic inflammation.

Dermal lymphatic dilation in a mouse model of alopecia areata.

Mouse models of various types of inflammatory skin disease are often accompanied by increased dermal angiogenesis. The C3H/HeJ inbred strain spontaneously develops alopecia areata (AA), a cell mediated autoimmune disorder that can be controllably expanded using full thickness skin grafts to young unaffected mice. This provides a reproducible and progressive model for AA in which the vascularization of the skin can be examined. Mice receiving skin grafts from AA or normal mice were evaluated at 5, 10, 15, and 20 weeks after engraftment. Lymphatics are often overlooked as they are small slit-like structures above the hair follicle that resemble artifact-like separation of collagen bundles with some fixatives. Lymphatics are easily detected using lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1) by immunohistochemistry to label their endothelial cells. Using LYVE1, there were no changes in distribution or numbers of lymphatics although they were more prominent (dilated) in the mice with AA. Lyve1 transcripts were not significantly upregulated except at 10 weeks after skin grafting when clinical signs of AA first become apparent. Other genes involved with vascular growth and dilation or movement of immune cells were dysregulated, mostly upregulated. These findings emphasize aspects of AA not commonly considered and provide potential targets for therapeutic intervention.

3-Dimensional histological reconstruction and imaging of the murine pancreas.

Visualization of important disease-driving tissues in their native morphological state, such as the pancreas, given its importance in glucose homeostasis and diabetes, provides critical insight into the etiology and progression of disease and our understanding of how cellular changes impact disease severity. Numerous challenges to maintaining tissue morphology exist when one attempts to preserve or to recreate such tissues for histological evaluation. We have overcome many of these challenges and have developed new methods for visualizing the whole murine pancreas and single islets of Langerhans in an effort to gain a better understanding of how islet cell volume, spatial distribution, and vascularization are altered as diabetes progresses. These methods are readily adaptable without requirement for costly specialized equipment, such as magnetic resonance imaging, positron emission tomography, or computed tomography, and can be used to provide additional robust analysis of diabetes susceptibility in mouse models of Type 1 and Type II diabetes.

Genetic modifier loci of mouse Mfrp(rd6) identified by quantitative trait locus analysis.

The identification of genes that modify pathological ocular phenotypes in mouse models may improve our understanding of disease mechanisms and lead to new treatment strategies. Here, we identify modifier loci affecting photoreceptor cell loss in homozygous Mfrp(rd6) mice, which exhibit a slowly progressive photoreceptor degeneration. A cohort of 63 F2 homozygous Mfrp(rd6) mice from a (B6.C3Ga-Mfrp(rd6)/J × CAST/EiJ) F1 intercross exhibited a variable number of cell bodies in the retinal outer nuclear layer at 20 weeks of age. Mice were genotyped with a panel of single nucleotide polymorphism markers, and genotypes were correlated with phenotype by quantitative trait locus (QTL) analysis to map modifier loci. A genome-wide scan revealed a statistically significant, protective candidate locus on CAST/EiJ Chromosome 1 and suggestive modifier loci on Chromosomes 6 and 11. Multiple regression analysis of a three-QTL model indicated that the modifier loci on Chromosomes 1 and 6 together account for 26% of the observed phenotypic variation, while the modifier locus on Chromosome 11 explains only an additional 4%. Our findings indicate that the severity of the Mfrp(rd6) retinal degenerative phenotype in mice depends on the strain genetic background and that a significant modifier locus on CAST/EiJ Chromosome 1 protects against Mfrp(rd6)-associated photoreceptor loss.

Crisp1 and alopecia areata in C3H/HeJ mice.

Alopecia areata (AA), a cell mediated autoimmune disease, is the second most common form of hair loss in humans. While the autoimmune disease is responsible for the underlying pathogenesis, the alopecia phenotype is ultimately due to hair shaft fragility and breakage associated with structural deficits. Quantitative trait genetic analyses using the C3H/HeJ mouse AA model identified cysteine-rich secretory protein 1 (Crisp1), a hair shaft structural protein, as a candidate gene within the major AA locus. Crisp1 transcripts in the skin at various times during disease development were barely detectable. In situ hybridization identified Crisp1 expression within the medulla of hair shafts from clinically normal strains of mice but not C3H/HeJ mice with AA. Follow-up work with 5-day-old C3H/HeJ mice with normal hair also had essentially no expression of Crisp1. Other non-inflammatory based follicular dystrophy mouse models with similar hair shaft abnormalities also have little or no Crisp1 expression. Shotgun proteomics, used to determine strain difference in hair proteins, confirmed that there was very little CRISP1 within normal C3H/HeJ mouse hair in comparison to 11 other strains. However, mutant mice with hair medulla defects also had undetectable levels of CRISP1 in their hair. Crisp1 null mice had normal skin, hair follicles, and hair shafts indicating that the lack of the CRISP1 protein does not translate directly into defects in the hair shaft or hair follicle. These results suggest that CRISP1 may be an important structural component of mouse hair and that its strain-specific dysregulation may indicate a predisposition to hair shaft disease such as AA.

Transcriptional and functional consequences of Oncostatin M signaling on young Dnmt3a-mutant hematopoietic stem cells.

Age-associated clonal hematopoiesis (CH) occurs due to somatic mutations accrued in hematopoietic stem cells (HSCs) that confer a selective growth advantage in the context of aging. The mechanisms by which CH-mutant HSCs gain this advantage with aging are not comprehensively understood. Using unbiased transcriptomic approaches, we identified Oncostatin M (OSM) signaling as a candidate contributor to age-related Dnmt3a-mutant CH. We found that Dnmt3a-mutant HSCs from young adult mice (3-6 months old) subjected to acute OSM stimulation do not demonstrate altered proliferation, apoptosis, hematopoietic engraftment, or myeloid differentiation. Dnmt3a-mutant HSCs from young mice do transcriptionally upregulate an inflammatory cytokine network in response to acute in vitro OSM stimulation as evidenced by significant upregulation of the genes encoding IL-6, IL-1ß, and TNFα. OSM-stimulated Dnmt3a-mutant HSCs also demonstrate upregulation of the anti-inflammatory genes Socs3, Atf3, and Nr4a1. In the context of an aged bone marrow (BM) microenvironment, Dnmt3a-mutant HSCs upregulate proinflammatory genes but not the anti-inflammatory genes Socs3, Atf3, and Nr4a1. The results from our studies suggest that aging may exhaust the regulatory mechanisms that HSCs employ to resolve inflammatory states in response to factors such as OSM.

Mapping the genetic landscape establishing a tumor immune microenvironment favorable for anti-PD-1 response in mice and humans.

Identifying host genetic factors modulating immune checkpoint inhibitor (ICI) efficacy has been experimentally challenging because of variations in both host and tumor genomes, differences in the microbiome, and patient life exposures. Utilizing the Collaborative Cross (CC) multi-parent mouse genetic resource population, we developed an approach that fixes the tumor genomic configuration while varying host genetics. With this approach, we discovered that response to anti-PD-1 (aPD1) immunotherapy was significantly heritable in four distinct murine tumor models (H2 between 0.18-0.40). For the MC38 colorectal carcinoma system (H2 = 0.40), we mapped four significant ICI response quantitative trait loci (QTL) localized to mouse chromosomes (mChr) 5, 9, 15 and 17, and identified significant epistatic interactions between specific QTL pairs. Differentially expressed genes within these QTL were highly enriched for immune genes and pathways mediating allograft rejection and graft vs host disease. Using a cross species analytical approach, we found a core network of 48 genes within the four QTLs that showed significant prognostic value for overall survival in aPD1 treated human cohorts that outperformed all other existing validated immunotherapy biomarkers, especially in human tumors of the previously defined immune subtype 4. Functional blockade of two top candidate immune targets within the 48 gene network, GM-CSF and high affinity IL-2/IL-15 signaling, completely abrogated the MC38 tumor transcriptional response to aPD1 therapy in vivo. Thus, we have established a powerful cross species in vivo platform capable of uncovering host genetic factors that establish the tumor immune microenvironment configuration propitious for ICI response.

Oncostatin M is a Master Regulator of an Inflammatory Network in Dnmt3a -Mutant Hematopoietic Stem Cells.

Age-associated clonal hematopoiesis (CH) occurs due to somatic mutations accrued in hematopoietic stem cells (HSCs) that confer a selective advantage in the context of aging. The mechanisms by which CH-mutant HSCs gain this advantage with aging are not comprehensively understood. Using unbiased transcriptomic approaches, we identify Oncostatin M (OSM) signaling as a candidate contributor to aging-driven Dnmt3a -mutant CH. We find that Dnmt3a -mutant HSCs from young mice do not functionally respond to acute OSM stimulation with respect to proliferation, apoptosis, hematopoietic engraftment, or myeloid differentiation. However, young Dnmt3a -mutant HSCs transcriptionally upregulate an inflammatory cytokine network in response to acute OSM stimulation including genes encoding IL-6, IL-1ß and TNFα. In addition, OSM-stimulated Dnmt3a -mutant HSCs upregulate the anti-inflammatory genes Socs3, Atf3 and Nr4a1 , creating a negative feedback loop limiting sustained activation of the inflammatory network. In the context of an aged bone marrow (BM) microenvironment with chronically elevated levels of OSM, Dnmt3a -mutant HSCs upregulate pro-inflammatory genes but do not upregulate Socs3, Atf3 and Nr4a1 . Together, our work suggests that chronic inflammation with aging exhausts the regulatory mechanisms in young CH-mutant HSCs that resolve inflammatory states, and that OSM is a master regulator of an inflammatory network that contributes to age-associated CH.

A major X-linked locus affects kidney function in mice.

Chronic kidney disease is a common disease with increasing prevalence in the western population. One common reason for chronic kidney failure is diabetic nephropathy. Diabetic nephropathy and hyperglycemia are characteristics of the mouse inbred strain KK/HlJ, which is predominantly used as a model for metabolic syndrome due to its inherited glucose intolerance and insulin resistance. We used KK/HlJ, an albuminuria-sensitive strain, and C57BL/6J, an albuminuria-resistant strain, to perform a quantitative trait locus (QTL) cross to identify the genetic basis for chronic kidney failure. Albumin-creatinine ratio (ACR) was measured in 130 F2 male offspring. One significant QTL was identified on chromosome (Chr) X and four suggestive QTL were found on Chrs 6, 7, 12, and 13. Narrowing of the QTL region was focused on the X-linked QTL and performed by incorporating genotype and expression analyses for genes located in the region. From the 485 genes identified in the X-linked QTL region, a few candidate genes were identified using a combination of bioinformatic evidence based on genomic comparison of the parental strains and known function in urine homeostasis. Finally, this study demonstrates the significance of the X chromosome in the genetic determination of albuminuria.

Early gene expression differences in inbred mouse strains with susceptibility to pulmonary adenomas.

Lung cancer is the most common cause of cancer-related deaths in both men and women, and effective preventatives are rare due to the difficulty of early detection. Specific gene expression signatures have been identified in individuals that already developed lung cancer. To identify if gene expression differences could be detected in individuals before the onset of the disease, we obtained lung tissues for microarray analysis from young, healthy mice of 9 inbred strains with known differences in their susceptibility to spontaneous pulmonary adenomas when aged. We found that the most common differentially expressed genes among all possible 36 strain comparisons showed significant associations with cancer- and inflammation-related processes. Significant expression differences between susceptible and resistant strains were detected for Aldh3a1, Cxcr1 and 7, Dpt, and Nptx1-genes with known cancer-related functions, and Cd209, Cxcr1 and 7, and Plag2g1b-genes with known inflammatory-related functions. Whereas Aldh3a1, Cd209, Dpt, and Pla2g1b had increased expression, Cxcr1 and 7, and Nptx1 had decreased expression in strains susceptible to pulmonary adenomas. Thus, our study shows that expression differences between susceptible and resistant strains can be detected in young and healthy mice without manifestation of pulmonary adenomas and, thus, may provide an opportunity of early detection. Finally, the identified genes have previously been reported for human non-small cell lung cancer suggesting that molecular pathways may be shared between these two cancer types.

Distinct Tumor Necrosis Factor Alpha Receptors Dictate Stem Cell Fitness versus Lineage Output in Dnmt3a-Mutant Clonal Hematopoiesis.

Clonal hematopoiesis resulting from the enhanced fitness of mutant hematopoietic stem cells (HSC) associates with both favorable and unfavorable health outcomes related to the types of mature mutant blood cells produced, but how this lineage output is regulated is unclear. Using a mouse model of a clonal hematopoiesis-associated mutation, DNMT3AR882/+ (Dnmt3aR878H/+), we found that aging-induced TNFα signaling promoted the selective advantage of mutant HSCs and stimulated the production of mutant B lymphoid cells. The genetic loss of the TNFα receptor TNFR1 ablated the selective advantage of mutant HSCs without altering their lineage output, whereas the loss of TNFR2 resulted in the overproduction of mutant myeloid cells without altering HSC fitness. These results nominate TNFR1 as a target to reduce clonal hematopoiesis and the risk of associated diseases and support a model in which clone size and mature blood lineage production can be independently controlled to modulate favorable and unfavorable clonal hematopoiesis outcomes. SIGNIFICANCE: Through the identification and dissection of TNFα signaling as a key driver of murine Dnmt3a-mutant hematopoiesis, we report the discovery that clone size and production of specific mature blood cell types can be independently regulated. See related commentary by Niño and Pietras, p. 2724. This article is highlighted in the In This Issue feature, p. 2711.

A-Kinase Anchor Protein 1 deficiency causes mitochondrial dysfunction in mouse model of hyperoxia induced acute lung injury.

Background: Critically ill patients on supplemental oxygen therapy eventually develop acute lung injury (ALI). Reactive oxygen species (ROS) produced during ALI perturbs the mitochondrial dynamics resulting in cellular damage. Genetic deletion of the mitochondrial A-kinase anchoring protein 1 (Akap1) in mice resulted in mitochondrial damage, Endoplasmic reticulum (ER) stress, increased expression of mitophagy proteins and pro-inflammatory cytokines, exacerbating hyperoxia-induced Acute Lung Injury (HALI). Objective: Despite a strong causal link between mitochondrial dysfunction and HALI, the mechanisms governing the disease progression at the transcriptome level is unknown. Methods: In this study, RNA sequencing (RNA-seq) analysis was carried out using the lungs of Akap1 knockout (Akap1 -/-) mice exposed to normoxia or 48 h of hyperoxia followed by quantitative real time PCR and Ingenuity pathway analysis (IPA). Western blot analysis assessed mitochondrial dysfunction, OXPHOS complex (I-V), apoptosis and antioxidant proteins. Mitochondrial enzymatic assays was used to measure the aconitase, fumarase, citrate synthase activities in isolated mitochondria from Akap1 -/- vs. Wt mice exposed to hyperoxia. Results: Transcriptome analysis of Akap1 -/- exposed to hyperoxia reveals increases in transcripts encoding electron transport chain (ETC) and tricarboxylic acid cycle (TCA) proteins. Ingenuity pathway analysis (IPA) shows enrichment of mitochondrial dysfunction and oxidative phosphorylation in Akap1 -/- mice. Loss of AKAP1, coupled with oxidant injury, significantly decreases the activities of TCA enzymes. Mechanistically, a significant loss of dynamin-related protein 1 (Drp1) phosphorylation at the protein kinase A (PKA) site Serine 637 (Ser637), decreases in Akt phosphorylation at Serine 437 (Ser47) and increase in the expression of pro-apoptotic protein Bax indicate mitochondrial dysfunction. Heme oxygenase-1 (HO-1) levels significantly increased in CD68 positive alveolar macrophages in Akap1 -/- lungs, suggesting a strong antioxidant response to hyperoxia. Conclusion: Overall these results suggest that AKAP1 overexpression and modulation of Drp1 phosphorylation at Ser637 is an important therapeutic strategy for acute lung injury.

Matrix Metalloproteinase 7 Expression and Apical Epithelial Defects in Atp8b1 Mutant Mouse Model of Pulmonary Fibrosis.

Abnormalities in airway epithelia and lung parenchyma are found in Atp8b1 mutant mice, which develop pulmonary fibrosis after hyperoxic insult. Microarray and ingenuity pathway analysis (IPA) show numerous transcripts involved in ciliogenesis are downregulated in 14-month (14 M) -old Atp8b1 mouse lung compared with wild-type C57BL/6. Lung epithelium of Atp8b1 mice demonstrate apical abnormalities of ciliated and club cells in the bronchial epithelium on transmission electron microscopy (TEM). Matrix metalloproteinase 7 (MMP7) regulates of ciliogenesis and is a biomarker for idiopathic pulmonary fibrosis (IPF) in humans. Mmp7 transcript and protein expression are significantly upregulated in 14 M Atp8b1 mutant mouse lung. MMP7 expression is also increased in bronchoalveolar lavage fluid (BAL). Immunohistochemistry is localized MMP7 to bronchial epithelial cells in the Atp8b1 mutant. In conclusion, MMP7 is upregulated in the aged Atp8b1 mouse model, which displays abnormal ciliated cell and club cell morphology. This mouse model can facilitate the exploration of the role of MMP7 in epithelial integrity and ciliogenesis in IPF. The Atp8b1 mutant mouse is proposed as a model for IPF.

Comparison of unrestrained plethysmography and forced oscillation for identifying genetic variability of airway responsiveness in inbred mice.

Lung function detection in mice is currently most accurately measured by invasive techniques, which are costly, labor intensive, and terminal. This limits their use for large-scale or longitudinal studies. Noninvasive assays are often used instead, but their accuracy for measuring lung function parameters such as resistance and elastance has been questioned in studies involving small numbers of mouse strains. Here we compared parameters detected by two different methods using 29 inbred mouse strains: enhanced pause (Penh), detected by unrestrained plethysmography, and central airway resistance and lung elastance, detected by a forced oscillation technique. We further tested whether the phenotypic variations were determined by the same genomic location in genome-wide association studies using a linear mixed model algorithm. Penh, resistance, and elastance were measured in nonexposed mice or mice exposed to saline and increasing doses of aerosolized methacholine. Because Penh differed from airway resistance in several strains and because the peak genetic associations found for Penh, resistance, or elastance were located at different genomic regions, we conclude that using Penh as an indicator for lung function changes in high-throughput genetic studies (i.e., genome-wide association studies or quantitative trait locus studies) measures something fundamentally different than airway resistance and lung elastance.

Micronuclei in Kif18a mutant mice form stable micronuclear envelopes and do not promote tumorigenesis.

Micronuclei, whole or fragmented chromosomes spatially separated from the main nucleus, are associated with genomic instability and have been identified as drivers of tumorigenesis. Paradoxically, Kif18a mutant mice produce micronuclei due to asynchronous segregation of unaligned chromosomes in vivo but do not develop spontaneous tumors. We report here that micronuclei in Kif18a mutant mice form stable nuclear envelopes. Challenging Kif18a mutant mice via deletion of the Trp53 gene led to formation of thymic lymphoma with elevated levels of micronuclei. However, loss of Kif18a had modest or no effect on survival of Trp53 homozygotes and heterozygotes, respectively. Micronuclei in cultured KIF18A KO cells form stable nuclear envelopes characterized by increased recruitment of nuclear envelope components and successful expansion of decondensing chromatin compared with those induced by nocodazole washout or radiation. Lagging chromosomes were also positioned closer to the main chromatin masses in KIF18A KO cells. These data suggest that not all micronuclei actively promote tumorigenesis.