Altering mice by homologous recombination using embryonic stem cells

Sex and strain differences in renal hemodynamics in mice

The present study was to examine sex and strain differences in glomerular filtration rate (GFR) and renal blood flow (RBF) in C57BL6, 129/Sv, and C57BLKS/J mice, three commonly used mouse strains in renal research. GFR was measured by transdermal measurement of FITC-sinitrin clearance in conscious mice. RBF was measured by a flow probe placed in the renal artery under an anesthetic state. In C57BL6 mice, there were no sex differences in both GFR and RBF. In 129/Sv mice, females had significantly greater GFR than males at age of 24 weeks, but not at 8 weeks. However, males had higher RBF and lower renal vascular resistance (RVR). Similar to 129/Sv, female C57BLKS/J had significantly greater GFR at both 8 and 24 weeks, lower RBF, and higher RVR than males. Across strains, male 129/Sv had lower GFR and higher RBF than male C57BL6, but no significant difference in GFR and greater RBF than male C57BLKS/J. No significant difference in GFR or RBF was observed between C57BL6 and C57BLKS/J mice. Deletion of eNOS in C57BLKS/J mice reduced GFR in both sexes, but decreased RBF in males. Furthermore, there were no sex differences in the severity of renal injury in eNOS-/- dbdb mice. Taken together, our study suggests that sex differences in renal hemodynamics in mice are strain and age dependent. eNOS was not involved in the sex differences in GFR, but in RBF. Furthermore, the sexual dimorphism did not impact the severity of renal injury in diabetic nephropathy.

Production of large, defined genome modifications in rats by targeting rat embryonic stem cells

Rats were more frequently used than mice to model human disease before mouse embryonic stem cells (mESCs) revolutionized genetic engineering in mice. Rat ESCs (rESCs) were first reported over 10 years ago, yet they are not as frequently used as mESCs. CRISPR-based gene editing in zygotes is widely used in rats but is limited by the difficulty of inserting or replacing DNA sequences larger than about 10 kb. We report here the generation of germline-competent rESC lines from several rat strains. These rESC lines maintain their potential for germline transmission after serial targeting with bacterial artificial chromosome (BAC)-based targeting vectors, and CRISPR-Cas9 cutting can increase targeting efficiency. Using these methods, we have successfully replaced entire rat genes spanning up to 101 kb with the human ortholog.

Application of the transgenic pig model in biomedical research: A review

The large animal model has gradually become an essential part of preclinical research studies, relating to exploring the disease pathological mechanism, genic function, pharmacy, and other subjects. Although the mouse model has already been widely accepted in clinical experiments, the need for finding an animal model with high similarity compared with a human model is urgent due to the different body functions and systems between mice and humans. The pig is an optimal choice for replacement. Therefore, enhancing the production of pigs used for models is an important part of the large animal model as well. Transgenic pigs show superiority in pig model creation because of the progress in genetic engineering. Successful cases of transgenic pig models occur in the clinical field of metabolic diseases, neurodegenerative diseases, and genetic diseases. In addition, the choice of pig breed influences the effort and efficiency of reproduction, and the mini pig has relative obvious advantages in pig model production. Indeed, pig models in these diseases provide great value in studies of their causes and treatments, especially at the genetic level. This review briefly outlines the method used to create transgenic pigs and species of producing transgenic pigs and provides an overview of their applications on different diseases and limitations for present pig model developments.

Transfection by Electroporation

Electroporation-the use of high-voltage electric shocks to introduce DNA into cells-can be used with most cell types, yields a high frequency of both stable transformation and transient gene expression, and, because it requires fewer steps, can be easier than alternative techniques. This unit describes electroporation of mammalian cells, including ES cells, for the preparation of knock-out, knock-in, and transgenic mice. Protocols are described for the use of electroporation in vivo to perform gene therapy for cancer, as well as for DNA vaccination. © 2017 by John Wiley & Sons, Inc.

Passenger mutations and aberrant gene expression in congenic tissue plasminogen activator-deficient mouse strains

Essentials C57BL/6J-tissue plasminogen activator (tPA)-deficient mice are widely used to study tPA function. Congenic C57BL/6J-tPA-deficient mice harbor large 129-derived chromosomal segments. The 129-derived chromosomal segments contain gene mutations that may confound data interpretation. Passenger mutation-free isogenic tPA-deficient mice were generated for study of tPA function.

SUMMARY

Background The ability to generate defined null mutations in mice revolutionized the analysis of gene function in mammals. However, gene-deficient mice generated by using 129-derived embryonic stem cells may carry large segments of 129 DNA, even when extensively backcrossed to reference strains, such as C57BL/6J, and this may confound interpretation of experiments performed in these mice. Tissue plasminogen activator (tPA), encoded by the PLAT gene, is a fibrinolytic serine protease that is widely expressed in the brain. A number of neurological abnormalities have been reported in tPA-deficient mice. Objectives To study genetic contamination of tPA-deficient mice. Materials and methods Whole genome expression array analysis, RNAseq expression profiling, low- and high-density single nucleotide polymorphism (SNP) analysis, bioinformatics and genome editing were used to analyze gene expression in tPA-deficient mouse brains. Results and conclusions Genes differentially expressed in the brain of Plat(-/-) mice from two independent colonies highly backcrossed onto the C57BL/6J strain clustered near Plat on chromosome 8. SNP analysis attributed this anomaly to about 20 Mbp of DNA flanking Plat being of 129 origin in both strains. Bioinformatic analysis of these 129-derived chromosomal segments identified a significant number of mutations in genes co-segregating with the targeted Plat allele, including several potential null mutations. Using zinc finger nuclease technology, we generated novel 'passenger mutation'-free isogenic C57BL/6J-Plat(-/-) and FVB/NJ-Plat(-/-) mouse strains by introducing an 11 bp deletion into the exon encoding the signal peptide. These novel mouse strains will be a useful community resource for further exploration of tPA function in physiological and pathological processes.

Efficient production of chimeric mice from embryonic stem cells injected into 4- to 8-cell and blastocyst embryos

BACKGROUND

Production of chimeric mice is a useful tool for the elucidation of gene function. After successful isolation of embryonic stem (ES) cell lines, there are many methods for producing chimeras, including co-culture with the embryos, microinjection of the ES cells into pre-implantation embryos, and use of tetraploid embryos to generate the full ES-derived transgenic mice. Here, we aimed to generate the transgenic ES cell line, compare the production efficiency of chimeric mice and its proportion to yield the male chimeric mice by microinjected ES cells into 4- to 8-cell and blastocysts embryos with the application of Piezo-Micromanipulator (PMM), and trace the fate of the injected ES cells.

RESULTS

We successfully generated a transgenic ES cell line and proved that this cell line still maintained pluripotency. Although we achieved a satisfactory chimeric mice rate, there was no significant difference in the production of chimeric mice using the two different methods, but the proportion of the male chimeric mice in the 4- to 8-cell group was higher than in the blastocyst group. We also found that there was no tendency for ES cells to aggregate into the inner cell mass using in vitro culture of the chimeric embryos, indicating that they aggregated randomly.

CONCLUSIONS

These results showed that the PMM method is a convenient way to generate chimeric mice and microinjection of ES cells into 4- to 8-cell embryos can increase the chance of yielding male chimeras compared to the blastocyst injection. These results provide useful data in transgenic research mediated by ES cells.

Mouse systems for studying the genetics of hypertension and related disorders

The determination of cardiovascular diseases by multiple genetic and environmental factors makes it challenging to study the impact of any one genetic factor as a single variable. This review describes how to combine gene targeting in mice with carefully designed breeding strategies to determine the effect of precisely defined mutations as single variables. Studies of mice having mutations in cardiovascular genes should help to clarify the complex genetic determination of hypertension and related diseases. © 1996, Elsevier Science Inc. (Trends Cardiovasc Med 1996;6:232-238).

On the emerging role of rabbit as human disease model and the instrumental role of novel transgenic tools

The laboratory rabbit (Oryctolagus cuniculus) is widely used as a model for human diseases, because of its size, which permits non-lethal monitoring of physiological changes and similar disease characteristics. Novel transgenic tools such as, the zinc finger nuclease method and the sleeping beauty transposon mediated or BAC transgenesis were recently adapted to the laboratory rabbit and opened new opportunities in precise tissue and developmental stage specific gene expression/silencing, coupled with increased transgenic efficiencies. Many facets of human development and diseases cannot be investigated in rodents. This is especially true for early prenatal development, its long-lasting effects on health and complex disorders, and some economically important diseases such as atherosclerosis or cardiovascular diseases. The first transgenic rabbits models of arrhythmogenesis mimic human cardiac diseases much better than transgenic mice and hereby underline the importance of non-mouse models. Another emerging field is epigenetic reprogramming and pathogenic mechanisms in diabetic pregnancy, where rabbit models are indispensable. Beyond that rabbit is used for decades as major source of polyclonal antibodies and recently in monoclonal antibody production. Alteration of its genome to increase the efficiency and value of the antibodies by humanization of the immunoglobulin genes, or by increasing the expression of a special receptor (Fc receptor) that augments humoral immune response is a current demand.

Transfection by electroporation

Electroporation--the use of high-voltage electric shocks to introduce DNA into cells--can be used with most cell types, yields a high frequency of both stable transformation and transient gene expression, and, because it requires fewer steps, can be easier than alternate techniques. This unit describes electroporation of mammalian cells, including ES cells for the preparation of knock-out, knock-in, and transgenic mice. Protocols are described for the use of electroporation in vivo to perform gene therapy for cancer therapy and DNA vaccination. Also described are modifications for preparation and transfection of plant protoplasts.

Transfection by electroporation

Electroporation--the use of high-voltage electric shocks to introduce DNA into cells--can be used with most cell types, yields a high frequency of both stable transformation and transient gene expression, and, because it requires fewer steps, can be easier than alternate techniques. This unit describes electroporation of mammalian cells, including ES cells for the preparation of knock-out, knock-in, and transgenic mice. Protocols are described for the use of electroporation in vivo to perform gene therapy for cancer therapy and DNA vaccination. Also described are modifications for preparation and transfection of plant protoplasts.

Characterization of intestinal and pancreatic dysfunction in VPAC1-null mutant mouse

OBJECTIVES

These studies examined the effect of homozygous deletion of vasoactive intestinal peptide receptor type 1 (VPAC1) on development and function of intestines and pancreas.

METHODS

Genetically engineered VPAC1-null mutant mice were monitored for growth, development, and glucose homeostasis. Expression of VPAC1 was examined during embryonic development using VPAC1 promoter-driven β-galactosidase transgenic mice.

RESULTS

Homozygous deletion of VPAC1 resulted in fetal, neonatal, and postweaning death owing to failure to thrive, intestinal obstruction, and hypoglycemia. Histological findings demonstrated disorganized hyperproliferation of intestinal epithelial cells with mucus deposition and bowel wall thickening. The pancreas demonstrated small dysmorphic islets of Langerhans containing α, β, and δ cells. Expression of a VPAC1 promoter-driven transgene was observed in E12.5 and E14.5 intestinal epithelial and pancreatic endocrine cells. Vasoactive intestinal peptide receptor type 1-null mutant animals had lower baseline blood glucose levels compared to both heterozygous and wild-type littermates. Vasoactive intestinal peptide receptor type 1-deficient mice responded to oral glucose challenge with normal rise in blood glucose followed by rapid hypoglycemia and failure to restore baseline glucose levels. Insulin challenge resulted in profound hypoglycemia and inadequate glucose homeostasis in VPAC1-null mutant animals.

CONCLUSIONS

These observations support a role for VPAC1 during embryonic and neonatal development of intestines and endocrine pancreas.

Macrophage Mal1 deficiency suppresses atherosclerosis in low-density lipoprotein receptor-null mice by activating peroxisome proliferator-activated receptor-γ-regulated genes

OBJECTIVE

The adipocyte/macrophage fatty acid-binding proteins aP2 (FABP4) and Mal1 (FABP5) are intracellular lipid chaperones that modulate systemic glucose metabolism, insulin sensitivity, and atherosclerosis. Combined deficiency of aP2 and Mal1 has been shown to reduce the development of atherosclerosis, but the independent role of macrophage Mal1 expression in atherogenesis remains unclear.

METHODS AND RESULTS

We transplanted wild-type (WT), Mal1(-/-), or aP2(-/-) bone marrow into low-density lipoprotein receptor-null (LDLR(-/-)) mice and fed them a Western diet for 8 weeks. Mal1(-/-)→LDLR(-/-) mice had significantly reduced (36%) atherosclerosis in the proximal aorta compared with control WT→LDLR(-/-) mice. Interestingly, peritoneal macrophages isolated from Mal1-deficient mice displayed increased peroxisome proliferator-activated receptor-γ (PPARγ) activity and upregulation of a PPARγ-related cholesterol trafficking gene, CD36. Mal1(-/-) macrophages showed suppression of inflammatory genes, such as COX2 and interleukin 6. Mal1(-/-)→LDLR(-/-) mice had significantly decreased macrophage numbers in the aortic atherosclerotic lesions compared with WT→LDLR(-/-) mice, suggesting that monocyte recruitment may be impaired. Indeed, blood monocytes isolated from Mal1(-/-)→LDLR(-/-) mice on a high-fat diet had decreased CC chemokine receptor 2 gene and protein expression levels compared with WT monocytes.

CONCLUSION

Taken together, our results demonstrate that Mal1 plays a proatherogenic role by suppressing PPARγ activity, which increases expression of CC chemokine receptor 2 by monocytes, promoting their recruitment to atherosclerotic lesions.

Efficient silencing of gene expression by an ASON-bulge-DNAzyme complex

BACKGROUND

DNAzymes are DNA molecules that can directly cleave cognate mRNA, and have been developed to silence gene expression for research and clinical purposes. The advantage of DNAzymes over ribozymes is that they are inexpensive to produce and exhibit good stability. The "10-23 DNA enzyme" is composed of a catalytic domain of 15 deoxynucleotides, flanked by two substrate-recognition domains of approximately eight nucleotides in each direction, which provides the complementary sequence required for specific binding to RNA substrates. However, these eight nucleotides might not afford sufficient binding energy to hold the RNA substrate along with the DNAzyme, which would interfere with the efficiency of the DNAzyme or cause side effects, such as the cleavage of non-cognate mRNAs.

METHODOLOGY

In this study, we inserted a nonpairing bulge at the 5' end of the "10-23 DNA enzyme" to enhance its efficiency and specificity. Different sizes of bulges were inserted at different positions in the 5' end of the DNAzyme. The non-matching bulge will avoid strong binding between the DNAzyme and target mRNA, which may interfere with the efficiency of the DNAzyme.

CONCLUSIONS

Our novel DNAzyme constructs could efficiently silence the expression of target genes, proving a powerful tool for gene silencing. The results showed that the six oligo bulge was the most effective when the six oligo bulge was 12-15 bp away from the core catalytic domain.

Atlas of gene expression in the mouse kidney: new features of glomerular parietal cells

To gain molecular insight into kidney function, we performed a high-resolution quantitative analysis of gene expression in glomeruli and nine different nephron segments dissected from mouse kidney using Serial Analysis of Gene Expression (SAGE). We also developed dedicated bioinformatics tools and databases to annotate mRNA tags as transcripts. Over 800,000 mRNA SAGE tags were sequenced corresponding to >20,000 different mRNA tags present at least twice in at least one library. Hierarchical clustering analysis of tags demonstrated similarities between the three anatomical subsegments of the proximal tubule, between the cortical and medullary segments of the thick ascending limb of Henle's loop, and between the three segments constituting the aldosterone-sensitive distal nephron segments, whereas the glomerulus and distal convoluted tubule clusterized independently. We also identified highly specific mRNA markers of each subgroup of nephron segments and of most nephron segments. Tag annotation also identified numbers of putative antisense mRNAs. This database constitutes a reference resource in which the quantitative expression of a given gene can be compared with that of other genes in the same nephron segment, or between different segments of the nephron. To illustrate possible applications of this database, we performed a deeper analysis of the glomerulus transcriptome that unexpectedly revealed expression of several ion and water carriers; within the glomerulus, they were found to be preferentially expressed in the parietal sheet. It also revealed the major role of the zinc finger transcription factor Wt1 in the specificity of gene expression in the glomerulus. Finally, functional annotation of glomerulus-specific transcripts suggested a high proliferation activity of glomerular cells. Immunolabeling for PCNA confirmed a high percentage of proliferating cells in the glomerulus parietal sheet.

Germline competence of mouse ES and iPS cell lines: Chimera technologies and genetic background

In mice, gene targeting by homologous recombination continues to play an essential role in the understanding of functional genomics. This strategy allows precise location of the site of transgene integration and is most commonly used to ablate gene expression ("knock-out"), or to introduce mutant or modified alleles at the locus of interest ("knock-in"). The efficacy of producing live, transgenic mice challenges our understanding of this complex process, and of the factors which influence germline competence of embryonic stem cell lines. Increasingly, evidence indicates that culture conditions and in vitro manipulation can affect the germline-competence of Embryonic Stem cell (ES cell) lines by accumulation of chromosome abnormalities and/or epigenetic alterations of the ES cell genome. The effectiveness of ES cell derivation is greatly strain-dependent and it may also influence the germline transmission capability. Recent technical improvements in the production of germline chimeras have been focused on means of generating ES cells lines with a higher germline potential. There are a number of options for generating chimeras from ES cells (ES chimera mice); however, each method has its advantages and disadvantages. Recent developments in induced pluripotent stem (iPS) cell technology have opened new avenues for generation of animals from genetically modified somatic cells by means of chimera technologies. The aim of this review is to give a brief account of how the factors mentioned above are influencing the germline transmission capacity and the developmental potential of mouse pluripotent stem cell lines. The most recent methods for generating specifically ES and iPS chimera mice, including the advantages and disadvantages of each method are also discussed.

Serdin1/Lrrc10 is dispensable for mouse development

We have previously identified Serdin1/Lrrc10 as a cardiac-specific message that is expressed early in murine heart development and encodes a novel leucine-rich protein. A high degree of evolutionary conservation with respect to protein sequence, cardiac-specific expression, and cis-regulatory elements suggested that LRRC10 has an important and conserved function in cardiac development. Recently, the zebrafish lrrc10 knockdown models were described with a dramatic early defect in heart looping which supported the notion that Serdin1/Lrrc10 is likely to be essential for heart development in all vertebrates. To determine Lrrc10 function in mammalian cardiac development, we have disrupted the Lrrc10 gene in mice. We report here that, in striking contrast to the zebrafish lrrc10 knockdown, Lrrc10-null mice develop normally and exhibit no discernable phenotype.

Efficient production of mice from embryonic stem cells injected into four- or eight-cell embryos by piezo micromanipulation

The conventional method for producing embryonic stem (ES) cell-derived knockout or transgenic mice involves injection of ES cells into normal, diploid blastocysts followed by several rounds of breeding of resultant chimeras and thus is a time-consuming and inefficient procedure. F0 ES cell pups can also be derived directly from tetraploid embryo complementation, which requires fusion of two-cell embryos. Recently, F0 ES cell pups have been produced by injection of ES cells into eight-cell embryos using a laser-assisted micromanipulation system. We report a simple method for producing F0 ES cell germline-competent mice by piezo injection of ES cells into four- or eight-cell embryos. The efficiency of producing live, transgenic mice by this method is higher than that with the tetraploid blastocyst complementation method. This efficient and economical technique for directly producing F0 ES cell offspring can be applicable in many laboratories for creating genetically manipulated mice using ES cell technology and also for stringent testing of the developmental potency of new ES cell or other types of pluripotent stem cell lines.

Targeting genes in the renin-angiotensin system

PURPOSE OF REVIEW

The renin-angiotensin system plays a key role in the regulation of blood pressure and fluid homeostasis. Owing to its critical contribution to blood pressure control, abnormalities of any component in this system can lead to hypertension and cardiovascular diseases. In this review, we will highlight studies using this approach to uncover new perspectives on the physiology of the renin-angiotensin system.

RECENT FINDINGS

Over the past decade, application of techniques for manipulating the genome of living animals, including gene targeting through homologous recombination in embryonic stem cells, has provided unique insights into the complex biology of the renin-angiotensin system. Along with advances in understanding functions of the classical components of the system, gene targeting has clarified the functions of newly discovered angiotensin-converting enzyme homologues.

SUMMARY

Since pharmacological antagonists of the renin-angiotensin system are widely used in clinical medicine, advances in the gene-targeting experiments of the system have helped to clarify the mechanisms of action of these agents and may provide clues for improved approaches for the treatment of hypertension and kidney diseases.

Kidney-specific gene targeting: insight into thiazolidinedione-induced fluid retention

Conditional gene targeting technique, which is based on the use of Cre-loxP or Flp/FRT systems, has been increasingly used to study gene function of a particular cell type in vivo. The introduction of this technique to the kidney field is relatively recent but has already provided important insights into physiological or pathological functions of a number of genes in the kidney. This technique has recently been used to inactivate the peroxisome proliferator-activated receptor subtype gamma in the collecting duct, which leads to remarkable blockade of body weight gains and plasma volume expansion associated with thiazolidinediones. This finding not only helps understand pharmacology of the novel class of antidiabetic drugs, but also uncovers an important role of peroxisome proliferator-activated receptor subtype gamma in regulation of distal nephron fluid reabsorption. The present review represents an example for the use of the modern technique to address complex clinical problems. It is anticipated that over next few years this technique will be used by an increasing number of investigators for studying gene function in the kidney.

A de novo deafwaddler mutation of Pmca2 arising in ES cells and hitchhiking with a targeted modification of the Pparg gene

We observed severe ataxia in mice homozygous for modification of the Pparg locus. Genetic analysis and nucleotide sequencing revealed that ataxia is caused by a T692K substitution in plasma membrane calcium ATPase 2 (Pmca2), which is tightly linked to Pparg, but not by modified PPARgamma itself. We traced this mutation and found that it arose spontaneously during clonal expansion of the targeted embryonic stem (ES) cells. Consistent with the deafwaddler phenotype in other Pmca2 mutants, homozygous T692K Pmca2 mutants exhibit severe balance disorder, impaired neurologic reflexes, and motor coordination, and have profound hearing loss. Heterozygous mutants have normal movement and motor function but are severely deficient in hearing. Our findings represent a cautionary example since, although rare, spontaneous mutations do arise in ES cells during culture and hitchhike onto the targeted gene mutation.

Stability and homogeneity of transgene expression in isogenic cells

Genetically engineered cells are an important tool not only for basic research applications, but also for biotechnology and molecular medicine. Among the issues yet to be solved for this technology are the consequences of randomly integrating DNA into a cell's genome. The problems encountered range from unpredictable expression levels to safety concerns. Recombinase-mediated chromosome engineering is a popular tool for generating stably transfected isogenic cell lines. Using this approach, single-copy integration of foreign DNA fragments can be achieved at predetermined chromosomal loci in the genome. We used such a technology based on the Flp/Flp recombinase target (FRT) recombination system in human 293 cells for comparative promoter studies. The expected integration patterns were obtained with high frequency. In contrast, the phenotypic characterization of expression of the integrated reporter transgene showed remarkable differences between isogenic cell lines, ranging from homogenous expression to mosaic to even complete expression silencing. As long as cell clones with homogenous expression were kept under selective conditions, their expression characteristics could be maintained over a long period. However, this desirable phenotype was progressively lost upon withdrawal of selective pressure. These results were also reflected by the expression instability of the reporter cassette originally inserted in the recipient cell line. Thus, selection for appropriate integration events that ensure reproducible and long-term gene expression has to go beyond the verification of isogenicity.

The insulin-like growth factor-I gene and osteoporosis: a critical appraisal

Osteoporosis, a disorder of skeletal fragility, is common in the elderly, and its prevalence is increasing as more individuals with low bone mineral density (BMD), the strongest predictor of fracture risk, are detected. Previous basic and clinical studies imply there is a significant role for insulin-like growth factor-I (IGF-I) in determining BMD. Recently, polymorphisms upstream of the P1 promoter region of the human IGF-I gene have been found to be associated with serum levels of IGF-I, BMD and fracture risk in various ethnic groups. Multiple quantitative trait loci (QTLs) have been identified that underlie serum IGF-I in a mouse intercross between two inbred strains. The most promising QTL on mouse chromosome 6 has provided clues for unraveling the molecular mechanisms that regulate osteoblast differentiation. Genomic engineering resulting in IGF-I deficient mice, and mice with targeted over-expression of IGF-I reinforce the essential role of IGF-I in bone development at both the embryonic and postnatal stages. Thus, it is apparent that significant new insights into the role of the IGF-I gene in bone remodeling occur through several distinct mechanisms: (1) the skeletal IGF regulatory system; (2) the systemic growth hormone/IGF-I axis; (3) parathyroid hormone signaling; (4) sex steroids; and (5) the OPG/RANKL/RANK cytokine system. Molecular dissection of the IGF regulatory system and its signaling pathway in bone may reveal novel therapeutic targets for the treatment of osteoporosis.

Impact of genetic background on nephropathy in diabetic mice

With the goal of identifying optimal platforms for developing better models of diabetic nephropathy in mice, we compared renal effects of streptozotocin (STZ)-induced diabetes among five common inbred mouse strains (C57BL/6, MRL/Mp, BALB/c, DBA/2, and 129/SvEv). We also evaluated the renal consequences of chemical and genetic diabetes on the same genetic background (C57BL/6). There was a hierarchical response of blood glucose level to the STZ regimen among the strains (DBA/2 > C57BL/6 > MRL/MP > 129/SvEv > BALB/c). In all five strains, males demonstrated much more robust hyperglycemia with STZ than females. STZ-induced diabetes was associated with modest levels of albuminuria in all of the strains but was greatest in the DBA/2 strain, which also had the most marked hyperglycemia. Renal structural changes on light microscopy were limited to the development of mesangial expansion, and, while there were some apparent differences among strains in susceptibility to renal pathological changes, there was a significant positive correlation between blood glucose and the degree of mesangial expansion, suggesting that most of the variability in renal pathological abnormalities was because of differences in hyperglycemia. Although the general character of renal involvement was similar between chemical and genetic diabetes, Akita mice developed more marked hyperglycemia, elevated blood pressures, and less variability in renal structural responses. Thus, among the strains and models tested, the DBA/2 genetic background and the Akita (Ins2(+/C96Y)) model may be the most useful platforms for model development.

Diabetic nephropathy: of mice and men

Accumulating evidence supports intrinsic genetic susceptibility as an important variable in the progression of diabetic nephropathy in people. Mice provide an experimental platform of unparalleled power for dissecting the genetics of mammalian diseases; however, phenotypic analysis of diabetic mice lags behind that already established for humans. Standardized benchmarks of hyperglycemia, albuminuria, and measurements of renal failure remain to be developed for different inbred strains of mice. The most glaring deficiency has been the lack of a diabetic mouse model that develops progressively worsening renal insufficiency, the sine qua non of diabetic nephropathy in humans. Differences in susceptibility of these inbred strains to complications of diabetes mellitus provide a possible avenue to dissect the genetic basis of diabetic nephropathy; however, the identification of those strains and/or mutants most susceptible to renal injury from diabetes mellitus is lacking. Identification of a mouse model that faithfully mirrors the pathogenesis of DN in humans will undoubtedly facilitate the development of new diagnostic and therapeutic interventions.

Mouse models of diabetic nephropathy

Mice provide an experimental model of unparalleled flexibility for studying mammalian diseases. Inbred strains of mice exhibit substantial differences in their susceptibility to the renal complications of diabetes. Much remains to be established regarding the course of diabetic nephropathy (DN) in mice as well as defining those strains and/or mutants that are most susceptible to renal injury from diabetes. Through the use of the unique genetic reagents available in mice (including knockouts and transgenics), the validation of a mouse model reproducing human DN should significantly facilitate the understanding of the underlying genetic mechanisms that contribute to the development of DN. Establishment of an authentic mouse model of DN will undoubtedly facilitate testing of translational diagnostic and therapeutic interventions in mice before testing in humans.

In vivo pattern of lipopolysaccharide and anti-CD3-induced NF-kappa B activation using a novel gene-targeted enhanced GFP reporter gene mouse

NF-kappa B is a family of transcription factors involved in regulating cell death/survival, differentiation, and inflammation. Although the transactivation ability of NF-kappa B has been extensively studied in vitro, limited information is available on the spatial and temporal transactivation pattern in vivo. To investigate the kinetics and cellular localization of NF-kappa B-induced transcription, we created a transgenic mouse expressing the enhanced GFP (EGFP) under the transcriptional control of NF-kappa B cis elements (cis-NF-kappa B(EGFP)). A gene-targeting approach was used to insert a single copy of a NF-kappa B-dependent EGFP reporter gene 5' of the X-linked hypoxanthine phosphoribosyltransferase locus in mouse embryonic stem cells. Embryonic fibroblasts, hepatic stellate cells, splenocytes, and dendritic cells isolated from cis-NF-kappa B(EGFP) mice demonstrated a strong induction of EGFP in response to LPS, anti-CD3, or TNF-alpha that was blocked by the NF-kappa B inhibitors BAY 11-7082 and NEMO-binding peptide. Chromatin immunoprecipitation analysis demonstrated RelA binding to the cis-NF-kappa B(EGFP) promoter. Adenoviral delivery of NF-kappa B-inducing kinase strongly induced EGFP expression in the liver of cis-NF-kappa B(EGFP) mice. Similarly, mice injected with anti-CD3 or LPS showed increased EGFP expression in mononuclear cells, lymph node, spleen, and liver as measured by flow cytometry and/or fluorescence microscopy. Using whole organ imaging, LPS selectively induced EGFP expression in the duodenum and proximal jejunum, but not in the ileum and colon. Confocal analysis indicated EGFP expression was primarily found in lamina propria mononuclear cells. In summary, the cis-NF-kappa B(EGFP) mouse will serve as a valuable tool to address multiple questions regarding the cell-specific and real-time activation of NF-kappa B during normal and diseased states.

Mapping of the Physcomitrella patens proteome

The moss Physcomitrella patens is unique among land plants due to the high rate of homologous recombination in its nuclear DNA. The feasibility of gene targeting makes Physcomitrella an unrivalled model organism in the field of plant functional genomics. To further extend the potentialities of this seed-less plant we aimed at exploring the P. patens proteome. Experimental conditions had to be adopted to meet the special requirements connected to the investigations of this moss. Here we describe the identification of 306 proteins from the protonema of Physcomitrella. Proteins were separated by two dimensional electrophoresis, excised form the gel and analysed by means of mass spectrometry. This reference map will lay the basis for further profound studies in the field of Physcomitrella proteomics.

Genetic Approaches to Studying Mouse Models of Human Seizure Disorders

In conclusion, we have discussed a reverse genetics approach to studying seizure disorders in mice (Fig. 1), employing a targeted mutagenesis method to exploit the genetic defects identified in human epilepsy families. After detailed characterization of the nature of the human mutation and the mouse counterpart gene, a targeting vector containing the human disease allele is created. The endogenous mouse gene is replaced by the human disease allele through homologous recombination in ES cells, leading to the generation of chimeric animals. Mice carrying one copy or both copies of the human mutation can be bred to study the phenotypic effect of heterozygous and homozygous mutations. At this stage, one may want to split the newly created mice into two groups. One group will go through seizure phenotyping tests, while the other group will be used to generate disease allele-carrying mice on a different genetic background. Phenotypic characterization of mice on different inbred strains includes behavioral monitoring and EEG analysis looking for the occurrence of spontaneous seizures, as well as routine cage examination looking for handling-provoked seizure and ECT- and PTZ- induced seizure paradigms looking for sensitivity to these stimuli. A complete evaluation of the seizure phenotype at the whole-animal level establishes the relevance of the mouse model to the human condition. Further investigation including imaging, electrophysiology and AED response in these mouse models will shed light on the mechanistic basis of the convulsive disorder. Current epilepsy research in mouse genetics offers promise for understanding the molecular mechanisms that underlie epileptogenesis in humans. A large-scale forward genetic effort to create novel mouse mutants with seizure phenotypes by in vivo chemical mutagenesis with ethyl-nitroso urea (ENU) is underway at the Jackson Laboratory (http://www.jax.org/nmf/). Genetic mapping and isolation of the affected genes in these seizure-prone models will provide additional molecular pathways involved in seizures. The mutant mice generated through both forward and reverse genetic approaches will be a valuable resource for the biomedical community to study epilepsy at the molecular level and to characterize the pathological consequences of seizures in the whole organism.

A review of morphological techniques for detection of peroxisomal (and mitochondrial) proteins and their corresponding mRNAs during ontogenesis in mice: application to the PEX5-knockout mouse with Zellweger syndrome

In the era of application of molecular biological gene-targeting technology for the generation of knockout mouse models to study human genetic diseases, the availability of highly sensitive and reliable methods for the morphological characterization of the specific phenotypes of these mice is of great importance. In the first part of this report, the role of morphological techniques for studying the biology and pathology of peroxisomes is reviewed, and the techniques established in our laboratories for the localization of peroxisomal proteins and corresponding mRNAs in fetal and newborn mice are presented and discussed in the context of the international literature. In the second part, the literature on the ontogenetic development of the peroxisomal compartment in mice, with special emphasis on liver and intestine is reviewed and compared with our own data reported recently. In addition, some recent data on the pathological alterations in the liver of the PEX5(-/-) mouse with a peroxisomal biogenesis defect are briefly discussed. Finally, the methods developed during these studies for the localization of mitochondrial proteins (respiratory chain complexes and MnSOD) are presented and their advantages and pitfalls discussed. With the help of these techniques, it is now possible to identify and distinguish unequivocally peroxisomes from mitochondria, two classes of cell organelles giving by light microscopy a punctate staining pattern in microscopical immunohistochemical preparations of paraffin-embedded mouse tissues.

Role of the fatty acid binding protein mal1 in obesity and insulin resistance

The metabolic syndrome is a cluster of metabolic and inflammatory abnormalities including obesity, insulin resistance, type 2 diabetes, hypertension, dyslipidemia, and atherosclerosis. The fatty acid binding proteins aP2 (fatty acid binding protein [FABP]-4) and mal1 (FABP5) are closely related and both are expressed in adipocytes. Previous studies in aP2-deficient mice have indicated a significant role for aP2 in obesity-related insulin resistance, type 2 diabetes, and atherosclerosis. However, the biological functions of mal1 are not known. Here, we report the generation of mice with targeted null mutations in the mal1 gene as well as transgenic mice overexpressing mal1 from the aP2 promoter/enhancer to address the role of this FABP in metabolic regulation in the presence or absence of obesity. To address the role of the second adipocyte FABP in metabolic regulation in the presence and deficiency of obesity, absence of mal1 resulted in increased systemic insulin sensitivity in two models of obesity and insulin resistance. Adipocytes isolated from mal1-deficient mice also exhibited enhanced insulin-stimulated glucose transport capacity. In contrast, mice expressing high levels of mal1 in adipose tissue display reduced systemic insulin sensitivity. Hence, our results demonstrate that mal1 modulates adipose tissue function and contributes to systemic glucose metabolism and constitutes a potential therapeutic target in insulin resistance.

Knock out models to dissect chemokine receptor function in vivo

Chemokines are a family of small proteins involved in numerous biological processes ranging from hematopoiesis, angiogenesis and lymphocyte trafficking to the extravasation and tissue infiltration of leukocytes in response to inflammatory agents, tissue damage and bacterial or viral infection. Chemokines exert their effects by binding to specific G-protein-coupled seven-transmembrane receptors. In vitro studies suggest that the chemokine system is highly redundant in that most chemokines bind to more than one receptor and most receptors bind multiple chemokines. Therefore, targeted deletion of chemokine receptors has proved to be a useful tool for determining the distinct biological role of these molecules in vivo.

Whole-animal cellular and molecular imaging to accelerate drug development

In the past decade, new technologies (genomics), chemistries and high-throughput (HT) in vitro assays have played a large role in changing the paradigm of drug discovery and development. These technologies have enabled many more targets and potential lead compounds to be introduced into drug development. However, since 1996, the number of drug approvals per year has been decreasing. This reduced pipeline has now compromised the ability of biopharmaceutical companies to deliver the double-digit growth levels that investors expect. This review explores what is lacking in the drug discovery and development process that has caused such a dearth of new chemical entities (NCEs), and looks at how new in vivo imaging technologies might provide an answer in the form of more predictive animal models.

Novel approaches for identifying genes regulating lymphocyte development and function

The draft sequence of the human and mouse genomes provides an unparalleled opportunity for understanding the genetic control of immune-cell development. Strategies can begin with a gene sequence and pursue a putative immune-system function by employing mRNA-expression profiling or creating gene knockouts in embryonic stem cells. The latter can be produced by utilising the Cre/Lox system, a tetracycline operon, a gene-trap method or chemical mutagenesis. Alternatively, mutant phenotypes (derived using the mutagen ethylnitrosourea) can be traced back to gene sequences.