RI Mice Research Articles

Developmental coordination disorder: What can we learn from RI mice using motor learning tasks and QTL analysis.

Developmental Coordination Disorder (DCD) is a neurodevelopmental disorder of unknown etiology that affects one in 20 children. There is an indication that DCD has an underlying genetic component due to its high heritability. Therefore, we explored the use of a recombinant inbred family of mice known as the BXD panel to understand the genetic basis of complex traits (i.e., motor learning) through identification of quantitative trait loci (QTLs). The overall aim of this study was to utilize the QTL approach to evaluate the genome-to-phenome correlation in BXD strains of mice in order to better understand the human presentation of DCD. Results of this current study confirm differences in motor learning in selected BXD strains and strains with altered cerebellar volume. Five strains - BXD15, BXD27, BXD28, BXD75, and BXD86 - exhibited the most DCD-like phenotype when compared with other BXD strains of interest. Results indicate that BXD15 and BXD75 struggled primarily with gross motor skills, BXD28 primarily had difficulties with fine motor skills, and BXD27 and BXD86 strains struggled with both fine and gross motor skills. The functional roles of genes within significant QTLs were assessed in relation to DCD-like behavior. Only Rab3a (Ras-related protein Rab-3A) emerged as a high likelihood candidate gene for the horizontal ladder rung task. This gene is associated with brain and skeletal muscle development, but lacked nonsynonymous polymorphisms. This study along with Gill et al. (same issue) is the first studies to specifically examine the genetic linkage of DCD using BXD strains of mice.

Reevaluation of the effect of dietary restriction on different recombinant inbred lines of male and female mice.

Dietary restriction (DR) was reported to either have no effect or reduce the lifespan of the majority of the 41‐recombinant inbred (RI) lines studied by Liao et al. (Aging Cell, 2010, 9, 92). In an appropriately power longevity study (n > 30 mice/group), we measured the lifespan of the four RI lines (115‐RI, 97‐RI, 98‐RI, and 107‐RI) that were reported to have the greatest decrease in lifespan when fed 40% DR. DR increased the median lifespan of female RI‐115, 97‐RI, and 107‐RI mice and male 115‐RI mice. DR had little effect (<4%) on the median lifespan of female and male 98‐RI mice and male 97‐RI mice and reduced the lifespan of male 107‐RI mice over 20%. While our study was unable to replicate the effect of DR on the lifespan of the RI mice (except male 107‐RI mice) reported by Liao et al. (Aging Cell, 2010, 9, 92), we found that the genotype of a mouse had a major impact on the effect of DR on lifespan, with the effect of DR ranging from a 50% increase to a 22% decrease in median lifespan. No correlation was observed between the changes in either body composition or glucose tolerance induced by DR and the changes observed in lifespan of the four RI lines of male and female mice. These four RI lines of mice give the research community a unique resource where investigators for the first time can study the anti‐aging mechanism of DR by comparing mice in which DR increases lifespan to mice where DR has either no effect or reduces lifespan.

Phenotype-driven screening of 150 strains of mice for allergic lung inflammation identified strains representative of heterogeneous human asthma cohorts

Abstract Asthma is a highly prevalent and heterogeneous disease characterized by airway hyperreactivity (AHR) and an influx of immune cells including eosinophils and neutrophils in the bronchoalveolar lavage (BAL). Furthermore, there are patient subsets, such as severe asthmatics, who are unresponsive to corticosteroids or bronchodilators. Research efforts targeting these cohorts of asthma patients however are severely lacking due to an inadequacy in relevant biological mouse models. For the first time, we immunophenotyped 150+ inbred and RI mouse strains in the Hybrid Mouse Diversity Panel (HMDP) under steady state conditions and after house dust mite (HDM) challenge to assess the lung function, BAL cell composition, serum immunoglobulin levels, as well as quantification of lung and peripheral immune cells. These results revealed at least three unique groups of strains that, when exposed to the same allergen, respond with three distinct systemic and local phenotypes of lung inflammation, specifically a high Th-2 response, a low Th-2 response, and neutrophilia. These murine models of AHR mirror human cohorts of asthma previously underrepresented in ongoing research efforts. We are currently designing mechanistic studies focusing on identifying the genetic factors responsible for these distinct phenotypes. The results of these combined studies may lead to a better understanding of asthma heterogeneity and provide a foundation for further elucidation of the pathogenetic mechanisms of each phenotype of asthma utilizing relevant animal models.

The Hell Test (Seven Springs)

DANIEL POPPICK | 135 The Hell Test (Seven Springs) Daniel Poppick poetry 1. In the new music I’ve discovered nudity. Idiomatic footfall marking its route over a pane of glass, plunging into a darkened meadow. An interruption in the field filled with a vaporous microphone, titling the air with what it records—an animal running through the grass, stalking the glass, stepping onto it, lowering his snout, and whimpering as he smells the window under his feet. 2. I used to trespass regularly on a piece of property two towns over from where I grew up. Property is the syntax of the reddening horizon. But “property” isn’t the precise word. It was an estate, meadows and mansions, little monuments of infrastructure dotted along its outer edges: an abandoned stable, a shattered greenhouse, a rotting pump overgrown with flowering vines, an enormous house with a fountain in its garden, a pile of rubble, a swimming pool lined with marble. It was decadently abandoned. I told my parents about it at dinner. Alarmed, they told me not to go back, so I did as often as I could. I walked alone there, stoned at the end of my teens, meticulously surveilling myself for signs of profundity that no one credited me; if I could not articulate what I was, I would let the properties on which I trespassed speak for me. Was I of this ruined estate? The place looked like a horror movie even in broad daylight. I always stopped by a spot in the middle of a field, no building in sight, in which a skylight jutted out of the grass over what appeared to be a dank cellar below. There was a hatch a few feet away that I could have easily opened, but something stopped me. I listened for hours on end to music 136 | DANIEL POPPICK featuring psychedelic mandolin solos and lyrics about talking coyotes , played the role of Dan in an edgeless theater for an audience, such as it was, of one, and was, to what I think of as my present self, insu≠erable. I was magnetized to suburban ruins, especially if the ruins were under construction, as the knowledge that I was standing in the skeletal infrastructure of what might someday be some unknown family’s home filled me with a sharp longing that I loved because it would never be satisfied; I would never be able to gather enough of the multitudinous downed branches of adolescence to build the theater-in-the-round that I imagined adulthood to be. For instance, it was impossible to imagine owning a house. One day, walking through the woods of the estate alone, I felt a presence in the trees o≠ to my left. I looked up and saw, fifty paces through the forest, a structure so large and ominous that the mere outline of it made my blood run cold. I’d never felt that way about a building. A stone tower with nothing around it. I stepped back, then stepped forward. It was January, and along its rim ice seemed to bubble from the ground. I walked up to it and marveled at how close it had been without my noticing. I craned my neck and saw a tree growing on top of it. I had been raised as a Reform Jew—in other words, an agnostic worshipper of narrative—which meant that this image appealed. I wanted to see it up close. I pried open the door to the tower and found a metal water silo inside, corroded and percussively dripping. In a helix around it a rusted set of stairs spiraled up. I tested the first one, and it seemed sturdy enough to hold my weight. I started walking up, slowly, wondering if I could find a latch in the ceiling to get to the top in the dark. Twenty feet up I heard a wet crunch. The stair snapped under me and clattered into darkness—I grabbed the rail, and the entire staircase swung free from its bolt. I caught myself between the tank and stone exterior, and slowly slid myself down, the mechanism clanking in on itself, my heart pounding...

Silencing the ACAT1 Gene in Human SH-SY5Y Neuroblastoma Cells Inhibits the Expression of Cyclo-Oxygenase 2 (COX2) and Reduces β-Amyloid-Induced Toxicity Due to Activation of Protein Kinase C (PKC) and ERK

BackgroundAcyl-coenzymeA: cholesterol acyltransferase (ACAT) 1, a key enzyme converting excess free cholesterol to cholesterol esters, has been demonstrated to be associated with the pathogenesis of Alzheimer disease (AD). However, the mechanism underlying the protective role of ACAT1 blockage in AD progression remains elusive.Material/MethodsHuman neuroblastoma SH-SY5Y cells were treated for 24 h with increasing concentrations of aggregated Aβ25–35 (5, 15, 25, and 45 μmol) with or without the ACAT1 siRNA pretreatment. Cell viability analysis was measured by CCK-8 assay. The genome-wide correlation between ACAT1 and all other probe sets was measured by the Pearson correlation coefficient (r). Western blotting was used to detect the ACAT1 protein expression in the hippocampus of APP/PSN transgenic AD mice. The mRNA level for each target was analyzed by qPCR. Western blotting was used to detect the ACAT1, cyclo-oxygenase-2 (Cox2), Calcium voltage-gated channel subunits (CACNAs), and ERK/PKC proteins in SH-SY5Y cells with or without the ACAT1 siRNA pretreatment in the presence of Aβ25–35.ResultsThe expression of ACAT1 was significantly increased in the hippocampus of APP/PSN mice, and also showed an increasing trend when SH-SY5Y cells were exposed to Aβ25–35. Silencing ACAT1 significantly attenuated Aβ-induced cytotoxicity and cell apoptosis in SH-SY5Y cells. The genome-wide correlation analysis showed that Ptgs2 had the most significant correlation with Acat1 in the hippocampus of BXD RI mice. We further determined the regulatory effect of ACAT1 on COX2 expression by silencing or over-expressing ACAT1 in SH-SY5Y cells and found that silencing ACAT1 played a protective role in AD progression by regulating CACNAs and PKC/ERK signaling cascades.ConclusionsSilencing ACAT1 attenuates Aβ25–35-induced cytotoxicity and cell apoptosis in SH-SY5Y cells, which may due to the synergistic effect of ACAT1 and COX2 through PKC/ERK pathways.

Ethanol's Effect on Coq7 Expression in the Hippocampus of Mice.

Coenzyme Q (CoQ) is a well-studied molecule, present in every cell membrane in the body, best known for its roles as a mitochondrial electron transporter and a potent membrane anti-oxidant. Much of the previous work was done in vitro in yeast and more recent work has suggested that CoQ may have additional roles prompting calls for a re-assessment of its role using in vivo systems in mammals. Here we investigated the putative role of Coenzyme Q in ethanol-induced effects in vivo using BXD RI mice. We examined hippocampal expression of Coq7 in saline controls and after an acute ethanol treatment, noting enriched biologic processes and pathways following ethanol administration. We also identified 45 ethanol-related phenotypes that were significantly correlated with Coq7 expression, including six phenotypes related to conditioned taste aversion and ethanol preference. This analysis highlights the need for further investigation of Coq7 and related genes in vivo as well as previously unrecognized roles that it may play in the hippocampus.

Hemorrhage enhances cytokine, complement component 3, and caspase-3, and regulates microRNAs associated with intestinal damage after whole-body gamma-irradiation in combined injury.

Hemorrhage following whole-body γ-irradiation in a combined injury (CI) model increases mortality compared to whole-body γ-irradiation alone (RI). The decreased survival in CI is accompanied by increased bone marrow injury, decreased hematocrit, and alterations of miRNA in the kidney. In this study, our aim was to examine cytokine homeostasis, susceptibility to systemic bacterial infection, and intestinal injury. More specifically, we evaluated the interleukin-6 (IL-6)-induced stress proteins including C-reactive protein (CRP), complement 3 (C3), Flt-3 ligand, and corticosterone. CD2F1 male mice received 8.75 Gy 60Co gamma photons (0.6 Gy/min, bilateral) which was followed by a hemorrhage of 20% of the blood volume. In serum, RI caused an increase of IL-1, IL-2, IL-3, IL-5, IL-6, IL-12, IL-13, IL-15, IL-17A, IL-18, G-CSF, CM-CSF, eotaxin, IFN-γ, MCP-1, MIP, RANTES, and TNF-α, which were all increased by hemorrhage alone, except IL-9, IL-17A, and MCP-1. Nevertheless, CI further elevated RI-induced increases of these cytokines except for G-CSF, IFN- γ and RANTES in serum. In the ileum, hemorrhage in the CI model significantly enhanced RI-induced IL-1β, IL-3, IL-6, IL-10, IL-12p70, IL-13, IL-18, and TNF-α concentrations. In addition, Proteus mirabilis Gram(-) was found in only 1 of 6 surviving RI mice on Day 15, whereas Streptococcus sanguinis Gram(+) and Sphingomonas paucimobilis Gram(-) were detected in 2 of 3 surviving CI mice (with 3 CI mice diseased due to inflammation and infection before day 15) at the same time point. Hemorrhage in the CI model enhanced the RI-induced increases in C3 and decreases in CRP concentrations. However, hemorrhage alone did not alter the basal levels, but hemorrhage in the CI model displayed similar increases in Flt-3 ligand levels as RI did. Hemorrhage alone altered the basal levels of corticosterone early after injury, which then returned to the baseline, but in RI mice and CI mice the increased corticosterone concentration remained elevated throughout the 15 day study. CI increased 8 miRNAs and decreased 10 miRNAs in serum, and increased 16 miRNA and decreased 6 miRNAs in ileum tissue. Among the altered miRNAs, CI increased miR-34 in the serum and ileum which targeted an increased phosphorylation of ERK, p38, and increased NF-κB, thereby leading to increased iNOS expression and activation of caspase-3 in the ileum. Further, let-7g/miR-98 targeted the increased phosphorylation of STAT3 in the ileum, which is known to bind to the iNOS gene. These changes may correlate with cell death in the ileum of CI mice. The histopathology displayed blunted villi and villus edema in RI and CI mice. Based on the in silico analysis, miR-15, miR-99, and miR-100 were predicted to regulate IL-6 and TNF. These results suggest that CI-induced alterations of cytokines/chemokines, CRP, and C3 cause a homeostatic imbalance and may contribute to the pathophysiology of the gastrointestinal injury. Inhibitory intervention in these responses may prove therapeutic for CI and improve recovery of the ileal morphologic damage.

Thrombopoietin Receptor Agonist Mitigates Hematopoietic Radiation Syndrome and Improves Survival after Whole-Body Ionizing Irradiation Followed by Wound Trauma.

Ionizing radiation combined with trauma tissue injury (combined injury, CI) results in greater mortality and H-ARS than radiation alone (radiation injury, RI), which includes thrombocytopenia. The aim of this study was to determine whether increases in numbers of thrombocytes would improve survival and mitigate H-ARS after CI. We observed in mice that WBC and platelets remained very low in surviving RI animals that were given 9.5 Gy 60Co-γ-photon radiation, whereas only lymphocytes and basophils remained low in surviving CI mice that were irradiated and then given skin wounds. Numbers of RBC and platelets, hemoglobin concentrations, and hematocrit values remained low in surviving RI and CI mice. CI induced 30-day mortality higher than RI. Radiation delayed wound healing by approximately 14 days. Treatment with a thrombopoietin receptor agonist, Alxn4100TPO, after CI improved survival, mitigated body-weight loss, and reduced water consumption. Though this therapy delayed wound-healing rate more than in vehicle groups, it greatly increased numbers of platelets in sham, wounded, RI, and CI mice; it significantly mitigated decreases in WBC, spleen weights, and splenocytes in CI mice and decreases in RBC, hemoglobin, hematocrit values, and splenocytes and splenomegaly in RI mice. The results suggest that Alxn4100TPO is effective in mitigating CI.

Local immune response to primary infection and re-infection by Clonorchis sinensis in FVB mice

Although Clonorchis sinensis lives in the bile duct, few studies have investigated the local immune response in the liver and bile duct. To investigate the local immune response to C. sinensis, we investigated the activation and recruitment of various immune cells and cytokine levels in the liver and bile duct lymph nodes (BLN) in FVB mice after primary infection and re-infection. Male 4-week-old FVB mice were divided into 6 experimental groups: uninfected controls, primary infection lasting 1week (PI 1w), primary infection lasting 4weeks (PI 4w), praziquantel treatment after PI 4w (Tx), re-infection lasting 1week after Tx (RI 1w), and re-infection lasting 4weeks after Tx (RI 4w). Recovery rates were 80.0% and 73.0% in PI 1w and PI 4w mice, respectively, but significantly decreased during re-infection to 26.6% in RI 1w and 13.3% in RI 4w. This result suggested that the mice were resistant to re-infection. In the liver, Kupffer cells were augmented 70-fold in PI 1w mice (P<0.001). Kupffer cells expressed Th2-related cytokines (IL-10 and IL-13) during primary infection. In addition, serum levels of C. sinensis-specific IgG1 and IgG2a strongly increased in RI 1w mice. Secretion of C. sinensis-specific IgE reached a plateau at 4weeks after primary infection, and remained elevated in all infected groups. In conclusion, during infection with C. sinensis, Kupffer cells likely act as antigen-presenting cells, stimulating the Th2 cytokine production system.

Skin wound trauma, following high-dose radiation exposure, amplifies and prolongs skeletal tissue loss

The present study investigated the detrimental effects of non-lethal, high-dose (whole body) γ-irradiation on bone, and the impact that radiation combined with skin trauma (i.e. combined injury) has on long-term skeletal tissue health. Recovery of bone after an acute dose of radiation (RI; 8Gy), skin wounding (15–20% of total body skin surface), or combined injury (RI+Wound; CI) was determined 3, 7, 30, and 120days post-irradiation in female B6D2F1 mice and compared to non-irradiated mice (SHAM) at each time-point. CI mice demonstrated long-term (day 120) elevations in serum TRAP 5b (osteoclast number) and sclerostin (bone formation inhibitor), and suppression of osteocalcin levels through 30days as compared to SHAM (p<0.05). Radiation-induced reductions in distal femur trabecular bone volume fraction and trabecular number through 120days post-exposure were significantly greater than non-irradiated mice (p<0.05) and were exacerbated in CI mice by day 30 (p<0.05). Negative alterations in trabecular bone microarchitecture were coupled with extended reductions in cancellous bone formation rate in both RI and CI mice as compared to Sham (p<0.05). Increased osteoclast surface in CI animals was observed for 3days after irradiation and remained elevated through 120days (p<0.01). These results demonstrate a long-term, exacerbated response of bone to radiation when coupled with non-lethal wound trauma. Changes in cancellous bone after combined trauma were derived from extended reductions in osteoblast-driven bone formation and increases in osteoclast activity.

Ghrelin therapy improves survival after whole-body ionizing irradiation or combined with burn or wound: amelioration of leukocytopenia, thrombocytopenia, splenomegaly, and bone marrow injury.

Exposure to ionizing radiation alone (RI) or combined with traumatic tissue injury (CI) is a crucial life-threatening factor in nuclear and radiological events. In our laboratory, mice exposed to 60Co-γ-photon radiation (9.5 Gy, 0.4 Gy/min, bilateral) followed by 15% total-body-surface-area skin wounds (R-W CI) or burns (R-B CI) experienced an increment of ≥18% higher mortality over a 30-day observation period compared to RI alone. CI was accompanied by severe leukocytopenia, thrombocytopenia, erythropenia, and anemia. At the 30th day after injury, numbers of WBC and platelets still remained very low in surviving RI and CI mice. In contrast, their RBC, hemoglobin, and hematocrit were recovered towards preirradiation levels. Only RI induced splenomegaly. RI and CI resulted in bone-marrow cell depletion. In R-W CI mice, ghrelin (a hunger-stimulating peptide) therapy increased survival, mitigated body-weight loss, accelerated wound healing, and increased hematocrit. In R-B CI mice, ghrelin therapy increased survival and numbers of neutrophils, lymphocytes, and platelets and ameliorated bone-marrow cell depletion. In RI mice, this treatment increased survival, hemoglobin, and hematocrit and inhibited splenomegaly. Our novel results are the first to suggest that ghrelin therapy effectively improved survival by mitigating CI-induced leukocytopenia, thrombocytopenia, and bone-marrow injury or the RI-induced decreased hemoglobin and hematocrit.

Pegylated G-CSF inhibits blood cell depletion, increases platelets, blocks splenomegaly, and improves survival after whole-body ionizing irradiation but not after irradiation combined with burn.

Exposure to ionizing radiation alone (radiation injury, RI) or combined with traumatic tissue injury (radiation combined injury, CI) is a crucial life-threatening factor in nuclear and radiological accidents. As demonstrated in animal models, CI results in greater mortality than RI. In our laboratory, we found that B6D2F1/J female mice exposed to 60Co-γ-photon radiation followed by 15% total-body-surface-area skin burns experienced an increment of 18% higher mortality over a 30-day observation period compared to irradiation alone; that was accompanied by severe cytopenia, thrombopenia, erythropenia, and anemia. At the 30th day after injury, neutrophils, lymphocytes, and platelets still remained very low in surviving RI and CI mice. In contrast, their RBC, hemoglobin, and hematocrit were similar to basal levels. Comparing CI and RI mice, only RI induced splenomegaly. Both RI and CI resulted in bone marrow cell depletion. It was observed that only the RI mice treated with pegylated G-CSF after RI resulted in 100% survival over the 30-day period, and pegylated G-CSF mitigated RI-induced body-weight loss and depletion of WBC and platelets. Peg-G-CSF treatment sustained RBC balance, hemoglobin levels, and hematocrits and inhibited splenomegaly after RI. The results suggest that pegylated G-CSF effectively sustained animal survival by mitigating radiation-induced cytopenia, thrombopenia, erythropenia, and anemia.

Identification of genetic loci that modulate cell proliferation in the adult rostral migratory stream using the expanded panel of BXD mice

BackgroundAdult neurogenesis, which is the continual production of new neurons in the mature brain, demonstrates the strikingly plastic nature of the nervous system. Adult neural stem cells and their neural precursors, collectively referred to as neural progenitor cells (NPCs), are present in the subgranular zone (SGZ) of the dentate gyrus, the subventricular zone (SVZ), and rostral migratory stream (RMS). In order to harness the potential of NPCs to treat neurodegenerative diseases and brain injuries, it will be important to understand the molecules that regulate NPCs in the adult brain. The genetic basis underlying NPC proliferation is still not fully understood. From our previous quantitative trait locus (QTL) analysis, we had success in using a relatively small reference population of recombinant inbred strains of mice (AXBXA) to identify a genetic region that is significantly correlated with NPC proliferation in the RMS.ResultsIn this study, we expanded our initial QTL mapping of RMS proliferation to a far richer genetic resource, the BXD RI mouse strains. A 3-fold difference in the number of proliferative, bromodeoxyuridine (BrdU)-labeled cells was quantified in the adult RMS of 61 BXD RI strains. RMS cell proliferation is highly dependent on the genetic background of the mice with an estimated heritability of 0.58. Genome-wide mapping revealed a significant QTL on chromosome (Chr) 6 and a suggestive QTL on Chr 11 regulating the number of NPCs in the RMS. Composite interval analysis further revealed secondary QTLs on Chr 14 and Chr 18. The loci regulating RMS cell proliferation did not overlap with the suggestive loci modulating cell proliferation in the SGZ. These mapped loci serve as starting points to identify genes important for this process. A subset of candidate genes in this region is associated with cell proliferation and neurogenesis. Interconnectivity of these candidate genes was demonstrated using pathway and transcriptional covariance analyses.ConclusionsDifferences in RMS cell proliferation across the BXD RI strains identifies genetic loci that serve to provide insights into the interplay of underlying genes that may be important for regulating NPC proliferation in the adult mouse brain.

Analysis of Myocilin gene regulatory network using a genetic genomics approach

Background The pathogenesis of primary open angle glaucoma(POAG) and high myopia are very complex.To construct the regulatory network of virulence genes and relevant genes that involved in pathogenicity are helpful for reveal of the pathogenesis.Objective The aim of this study was to investigate myocilin(Myoc),a gene that contributes to POAG and high myopia in eyes of BXD Recombinant Inbred(BXD RI)mice and construct the regulatory network of Myoc.Methods The affymetrix microarray system was used to detect the differential expression of Myoc in the eyes of C57BL/6J(B6),DBA/2J(D2) and BXD RI mice.Expression quantitative trait loci (eQTL) mapping was performed to construct the regulatory network of Myoc gene.Results The average expression level of the Myoc gene in the BXD strains was 10.83,and the gene exhibited expression levels ranging from 8.39 in BXD55 mice tol 1.43 in B6 mice.The eQTL mapping for the Myoc gene showed a significant likelihood ratio statistic (LRS) of 21.78.The QTL was mapped in chromosome 2,and Myoc was located on chromosome 1,indicating that the Myoc gene was a trans-acting QTL.Olfml2a was identified to be a candidate upstream gene of Myoc by analysis of bioinformatics.Genetic regulatory network analysis demonstrated that a series of genes associated with Myoc probably played roles in the pathogenesis and development of POAG and high myopia.Conclusions The genetical genomics approach provides a powerful tool for constructing pathways that contribute to complex traits,such as POAG and high myopia. Key words: Genomics; Myoc gene; Network; Primary open angle glaucoma; High myopia; BXD RI mouse

Identification of genetic loci controlling intestinal calcium (Ca) absorption using BXD recombinant inbred (RI) mice fed high or low dietary Ca

Intestinal Ca absorption (Ca Abs) is affected by race and is similar between mothers and daughters suggesting genetic regulation of this trait. However, the impact of genetics on CaAbs and the adaptation of Ca Abs to inadequate dietary Ca intake is not known. We examined the role of genetics on Ca Abs efficiency in 51 lines of BXD RI mice. Mice were fed AIN93G diets with either 0.5% or 0.25% Ca from 4 to 12 wks of age (n=8/line/diet). Afterwards, Ca Abs was measured by Ca45 appearance in the blood 10 min after an oral gavage of 0.1 mM Ca. After correcting for covariates, considerable diversity was observed between the lines in Ca Abs on each diet. Narrow‐sense heritability for Ca Abs was 0.37 and 0.56 in the 0.5% and 0.25% Ca diets, respectively, demonstrating increased penetrance of genetic effects controlling Ca Abs with low Ca diets. Linkage mapping was conducted using both traditional and Bayesian methods. Quantitative trait loci (QTL) affecting Ca Abs were identified that were diet‐specific (0.25%: on Chr 5, 8 (distal), 9, 12, 17; 0.5% on Chr 8 (proximal), 10) and shared (Chr 4, 7). No known Ca regulatory genes were found around these QTL demonstrating the potential of this approach for discovery of new genes controlling Ca Abs. This study provides a foundation for determining genetic regulators that may underlie individual differences in Ca Abs and ultimately dietary Ca requirements. Supported by NIEHS award ES019103.Grant Funding Source : NIEHS

Genetic study of gutter-shaped root (GSR) in AKXL RI mouse strains using QTL analysis

In this study, quantitative trait locus (QTL) analysis was used to identify candidate chromosomes and for detecting the regions that include the gene or genes causing gutter-shaped root (GSR) in AKXL recombinant inbred mouse strains. One potential QTL was detected on chromosome 5 within a region of 13.0 cM, where the likelihood ratio statistic (LRS) score was higher than a suggestive level. This indicates that one of the candidate genes causing mouse GSR may be located in this region.

Immunoglobulin A: FcαRI Interactions Induce Neutrophil Migration Through Release of Leukotriene B4

Exacerbations of ulcerative colitis (UC) are dominated by massive neutrophil influx in the lamina propria with concomitant mucosal ulceration. The prevalent antibody in this area is immunoglobulin A (IgA). Interestingly, the IgA Fc receptor (Fc(alpha)RI) potently activates neutrophils. As such, we investigated whether IgA-Fc(alpha)RI interaction contributes to tissue damage in UC. Response of neutrophils to bovine serum albumin-, IgG-, or IgA-coated beads and Escherichia coli was investigated with 3-dimensional culture systems, real-time video microscopy, and (fluorescence) microscopy. In vivo studies were performed using human Fc(alpha)RI transgenic mice or nontransgenic littermates. Microscopic slides of UC patients were stained for IgA, Fc(alpha)RI, and neutrophils. In vitro and in vivo cross-linking of Fc(alpha)RI on neutrophils by serum IgA or uptake of IgA-coated E coli led to neutrophil migration. The responsible chemotactic factor was identified as leukotriene B4. Moreover, dimeric IgA (dIgA), which is produced in the lamina propria, but neither secretory IgA nor IgG, was equally capable of inducing neutrophil recruitment. We furthermore showed that Fc(alpha)RI(+)-neutrophils in the colon of UC patients had phagocytosed IgA-antigen complexes. Neutrophils are the first cells that arrive at inflammatory sites once pathogens have crossed the epithelial barrier. Fc(alpha)RI-dIgA interactions therefore may constitute an essential activation step to recruit more neutrophils, hereby eradicating impending infections. However, excessive IgA-antigen complexes can sustain a perpetuating inflammatory loop in UC, hereby seriously aggravating morbidity. Novel therapeutic strategies that block dIgA-Fc(alpha)RI interactions, and therefore diminish neutrophil migration and activation, may dampen the uncontrolled inflammatory processes in these patients.

Virus-specific IgE enhances airway responsiveness on reinfection with respiratory syncytial virus in newborn mice

Respiratory syncytial virus (RSV)-specific IgE is a component of the host response to RSV infection, but its role in the subsequent enhancement of altered airway responsiveness is unknown. To define the role of RSV-specific IgE in the enhancement of airway responsiveness on reinfection of newborn mice. Mice were infected as newborns with RSV and were reinfected 5 weeks later. The role of IgE was determined by documenting RSV-specific IgE response after neonatal infection, and by assessing airway responsiveness on reinfection. After neonatal infection, wild-type (WT) mice developed an RSV-specific IgE response. On reinfection, these mice developed enhanced airway hyperresponsiveness (AHR), airway eosinophilia, and mucus hyperproduction, and their T-cell cytokine response was skewed toward a T(H)2 phenotype. None of these altered responses developed on reinfection of IL-4(-/-)/IL-13(-/-) mice, and no RSV-specific IgE could be detected after neonatal infection of these mice. Fc epsilon RI(-/-) mice did not develop the enhanced AHR on reinfection, and airway eosinophilia and mucus production were significantly attenuated. These responses could be restored in deficient mice reconstituted with WT mast cells. In RSV-infected newborn WT mice, administration of anti-IgE prevented the enhancement of AHR and attenuated eosinophilia and mucus hyperproduction on reinfection, an effect that was associated with diminished T(H)2 cytokine production and increased IFN-gamma production. Respiratory syncytial virus-specific IgE enhances the development of T(H)2-biased airway responsiveness on reinfection of mice initially infected as newborns.

Coordinate expression of activating Fc gamma receptors I and III and inhibiting Fc gamma receptor type II in the determination of joint inflammation and cartilage destruction during immune complex-mediated arthritis.

To study the role of the activating Fc gamma receptor types I and III (Fc gamma RI and Fc gamma RIII, respectively) and the inhibiting Fc gamma receptor II (Fc gamma RII) in inflammation and in various aspects of cartilage destruction during arthritis that is solely induced by immune complexes. Immune complex-mediated arthritis (ICA) was passively induced by lysozyme-antilysozyme complexes in Fc gamma RI-, Fc gamma RIII-, and Fc gamma RII-knockout mice and their wild-type controls. Total knee joints were isolated to study inflammation and cartilage destruction (loss of proteoglycans [PGs], chondrocyte death, matrix metalloproteinase [MMP]-mediated neoepitope [VDIPEN] expression, and erosion). The presence of an active phenotype of macrophages was studied by detection of myeloid-related proteins 8 and 14 (MRP8 and MRP14, respectively). Influx and activation of inflammatory cells (MRP expression) during ICA was decreased in Fc gamma RIII-deficient mice and enhanced in mice lacking Fc gamma RII. Mild cartilage destruction reflected by loss of PGs was consistent with the degree of inflammation. Mice lacking Fc gamma RIII showed almost no PG depletion, whereas in Fc gamma RII(-/-) mice, PG depletion was increased 3-7-fold in various cartilage areas. Initiation of erosive cartilage destruction, as reflected by MMP-mediated VDIPEN expression, was reduced in Fc gamma RIII(-/-) and Fc gamma RI(-/-) mice, directing the two different critical steps of cellular influx and subsequent activation. These aspects were enhanced in Fc gamma RII(-/-) mice. In Fc gamma RI(-/-) and Fc gamma RIII(-/-) mice, VDIPEN expression was 90-99% lower, whereas in Fc gamma RII(-/-) mice, VDIPEN expression was increased 4-fold. Chondrocyte death was reduced in Fc gamma RIII(-/-) mice (68% lower) and enhanced in Fc gamma RII(-/-) mice (6-12-fold higher). Progression of arthritis and erosion of the cartilage surface were markedly elevated in Fc gamma RII(-/-) arthritic joints. During ICA, Fc gamma RIII is the dominant activating receptor mediating joint inflammation, whereas both Fc gamma RI and Fc gamma RIII are involved in cartilage destruction. Fc gamma RII inhibits both joint inflammation and severe cartilage destruction during ICA.

BXD recombinant inbred mice represent a novel T cell-mediated immune response tumor model.

To develop a better animal model for studying the effects of the host environment in neoplasia, we injected various genetically well-characterized H-2(d) RI strains of BXD mice with syngeneic breast cancer cells (TS/A) and monitored the growth of tumors over time. There was a marked difference in the growth of the implanted breast cancer cells among the 14 BXD RI strains, with 4 patterns of tumor development being observed: in type I, the implanted tumor cells grew rapidly in the first 2 weeks, necrosis of the tumors was observed and metastases to the intestinal lymph nodes and pancreas was observed, causing death; in type II, the implanted tumor cells grew slowly and attained a size after day 50 that required killing the animal, with tumor necrosis being rare and metastases absent; in type III, the implanted tumor cells grew initially but underwent a slow decline after 4 weeks; and in type IV, the implanted tumor cells failed to develop. Apoptosis of the implanted tumor cells was responsible for the regression of tumor nodules. The T-cell immune response minimized tumor development in types III and IV since T-cell depletion of the BXD RI mice resulted in aggressively growing tumors in these strains.