Chromosome mapping of the rod photoreceptor cGMP phosphodiesterase beta-subunit gene in mouse and human: tight linkage to the Huntington disease region (4p16.3).

The retinal degeneration mouse (gene symbol, rd) is an animal model for certain forms of human hereditary retinopathies. Recent findings of a nonsense mutation in the rd mouse PDE beta-subunit gene (Pdeb) prompted us to investigate the chromosome locations of the mouse and human genes. We have utilized backcross analysis in mice to verify and define more precisely the location of the Pdeb locus 6.1 +/- 2.3 cM distal of Mgsa on mouse chromosome 5. We have determined that the human gene (PDEB) maps to 4p16.3, very close to the Huntington disease (HD) region. Analysis of the comparative map for mice and humans shows that the mouse homologue of the HD gene will reside on chromosome 5. Linkage of the mouse Pdeb locus with other homologues in the human 4p16.3 region is maintained but gene order is not, suggesting at least three possible sites for the corresponding mouse HD gene.     

FVB.129P2-Pde6b(+) Tyr(c-ch)/Ant, a sighted variant of the FVB/N mouse strain suitable for behavioral analysis

Mice of the FVB/N strain are severely visual impaired as a result of tyrosinase gene defects, leading to a deficiency of the key enzyme for melanin synthesis in skin and eye and of cyclic guanosine monophosphate phosphodiesterase gene defects, which results in albinism (Tyr(c/c)) and retinal degeneration (Pde6b(rd1/rd1)), respectively. Nevertheless, FVB/N mice are commonly used for the generation of transgenic animals because of their large, strong pronuclei and high breeding performance. However, due to visual impairment of the FVB/N animals, the resulting transgenic animals cannot be used in tests that depend on vision, including tests of cognitive behavior. Therefore, we have bred a sighted version of the FVB/N strain by an outcross between FVB/N and 129P2/OlaHsd, followed by repeated backcrosses to FVB/N mice while selecting against albinism and homozygosity of the retinal degeneration mutation. After 11 generations of backcrossing, sighted animals were intercrossed to generate the congenic FVB.129P2-Pde6b(+) Tyr(c-ch)/Ant strain, which is pigmented (Tyr(c-ch)/(c-ch)) and devoid of the genetic predisposition to retinal degeneration. The accurate visual abilities of the FVB.129P2-Pde6b(+) Tyr(c-ch)/Ant mice, for which we propose the name FVBS/Ant, demonstrated a clear visual evoked potential in the presence of normal eye histology and improved performance in the Morris water maze test.     

Differences among eight inbred strains of mice in motor ability and motor learning on a rotorod

The rotorod is commonly used to assess motor ability in mice. We examined a number of inbred strains to determine whether there is genetic variability in rotorod performance and motor learning. Mice received three trials per day for three days in a modified accelerating rotorod paradigm, and active rotation performance was calculated for each day. Male and female 129S1/SvImJ, A/J, BALB/cByJ, C3H/HeJ, C57BL/6J, CBA/J, DBA/2J and FVB/NJ mice were tested. Strain and sex differences were observed in motor performance. Motor learning also differed across strains, as some strains showed an improvement in performance over the three days while other strains did not. In certain strains the weight and body length of the mouse correlated with rotorod performance. The role of vision in motor performance on the rotorod was assessed by a comparison of C3H/HeJ mice (with retinal degeneration) and congenic C3A.BLiA- Pde6b ⁺ (Pdeb+) mice (without retinal degeneration). The sight-impaired C3H mice stayed on the rotorod longer than did their sighted Pdeb+ partners, although both strains improved across days. Thus, we have demonstrated a genetic component in rotorod performance, and we have shown that factors other than inherent motor ability can contribute to rotorod performance in mice.     

Genetic Background Affects Human Glial Fibrillary Acidic Protein Promoter Activity

The human glial fibrillary acidic protein (hGFAP) promoter has been used to generate numerous transgenic mouse lines, which has facilitated the analysis of astrocyte function in health and disease. Here, we evaluated the expression levels of various hGFAP transgenes at different ages in the two most commonly used inbred mouse strains, FVB/N (FVB) and C57BL/6N (B6N). In general, transgenic mice maintained on the B6N background displayed weaker transgene expression compared with transgenic FVB mice. Higher level of transgene expression in B6N mice could be regained by crossbreeding to FVB wild type mice. However, the endogenous murine GFAP expression was equivalent in both strains. In addition, we found that endogenous GFAP expression was increased in transgenic mice in comparison to wild type mice. The activities of the hGFAP transgenes were not age-dependently regulated. Our data highlight the importance of proper expression analysis when non-homologous recombination transgenesis is used.     

Increased sensitivity to N-methyl-D-aspartate receptor-mediated excitotoxicity in a mouse model of Huntington's disease

Previous work suggests N-methyl-D-aspartate receptor (NMDAR) activation may be involved in degeneration of medium-sized spiny striatal neurons in Huntington's disease (HD). Here we show that these neurons are more vulnerable to NMDAR-mediated death in a YAC transgenic FVB/N mouse model of HD expressing full-length mutant huntingtin, compared with wild-type FVB/N mice. Excitotoxic death of these neurons was increased after intrastriatal injection of quinolinate in vivo, and after NMDA but not AMPA exposure in culture. NMDA-induced cell death was abolished by an NR2B subtype-specific antagonist. In contrast, NMDAR-mediated death of cerebellar granule neurons was not enhanced, consistent with cell-type and NMDAR subtype specificity. Moreover, increased NMDA-evoked current amplitude and caspase-3 activity were observed in transgenic striatal neurons. Our data support a role for NR2B-subtype NMDAR activation as a trigger for selective neuronal degeneration in HD.     

Effect of murine strain on metabolic pathways of glucose production after brief or prolonged fasting

Background strain is known to influence the way a genetic manipulation affects mouse phenotypes. Despite data that demonstrate variations in the primary phenotype of basic inbred strains of mice, there is limited data available about specific metabolic fluxes in vivo that may be responsible for the differences in strain phenotypes. In this study, a simple stable isotope tracer/NMR spectroscopic protocol has been used to compare metabolic fluxes in ICR, FVB/N (FVB), C57BL/6J (B6), and 129S1/SvImJ (129) mouse strains. After a short-term fast in these mice, there were no detectable differences in the pathway fluxes that contribute to glucose synthesis. However, after a 24-h fast, B6 mice retain some residual glycogenolysis compared with other strains. FVB mice also had a 30% higher in vivo phosphoenolpyruvate carboxykinase flux and total glucose production from the level of the TCA cycle compared with B6 and 129 strains, while total body glucose production in the 129 strain was approximately 30% lower than in either FVB or B6 mice. These data indicate that there are inherent differences in several pathways involving glucose metabolism of inbred strains of mice that may contribute to a phenotype after genetic manipulation in these animals. The techniques used here are amenable to use as a secondary or tertiary tool for studying mouse models with disruptions of intermediary metabolism.     

Sucrose octaacetate avoidance in nontaster mice is not enhanced by two type-A Prp transgenes from taster mice

The Soa bitter-sensitivity and Prp salivary-protein loci map to distal mouse chromosome six. No recombination has been found between sucrose octaacetate (SOA)-avoidance phenotype and PRP haplotype in any mouse population. Soa and Prp, therefore, are either very near each other or identical. To assess the latter possibility, two type-A, proline-rich protein genes (MP2 and M14), situated approximately 30 kb apart at the Prp locus, were separately transferred from an SOA-taster inbred strain (SWR) to an SOA-nontaster inbred strain (FVB). Five MP2-transgenic mice and seven M14-transgenic mice were insensitive to 1 mM SOA in two-bottle tests, thus retaining the nontaster FVB phenotype. Each transgenic mouse was mated to control FVB mice. Their transgene-positive F1 and F2 offspring also were insensitive. Transgene expression varied among the founder lines, but SWR-like expression levels, higher than background FVB expression levels, were found in submandibular gland tissue of adult transgenic mice from two MP2 lines and one M14 line. F3 mice from one of these MP2 lines were mated to F2 mice from the M14 line. Nine offspring inherited both transgenes. All nine were insensitive to 1 mM SOA. These findings indicated that expression of mRNAs for both type-A Prp genes alone or together did not enhance SOA taste sensitivity in nontaster mice.     

Strain-Dependent Differences in the Efficiency of Transgenic Mouse Production

Transgenic mouse production via pronuclear microinjection is a complex process consisting of a number of sequential steps. Many different factors contribute to the effectiveness of each step and thus influence the overall efficiency of transgenic mouse production. The response of egg donor females to superovulation, the fertilization rate, egg survival after injection, ability of manipulated embryos to implant and develop to term, and concentration and purity of the injected DNA all contribute to transgenic production efficiency. We evaluated and compared the efficiency of transgenic mouse production using four different egg donor mouse strains: B6D2/F1 hybrids, Swiss Webster (SW) outbred, and inbred FVB/N and C57BL/6. The data included experiments involving 350 DNA transgene constructs performed by a high capacity core transgenic mouse facility. Significant influences of particular genetic backgrounds on the efficiency of different steps of the production process were found. Except for egg production, FVB/N mice consistently produced the highest efficiency of transgenic mouse production at each step of the process. B6D2/F2 hybrid eggs are also quite efficient, but lyze more frequently than FVB/N eggs after DNA microinjection. SW eggs on the other hand block at the 1-cell stage more often than eggs from the other strains. Finally, using C57BL/6 eggs the main limiting factor is that the fetuses derived from injected eggs do not develop to term as often as the other strains. Based on our studies, the procedure for transgenic mouse production can be modified for each egg donor strain in order to overcome any deficiencies, and thus to increase the overall efficiency of transgenic mouse production.     

Spontaneous pituitary abnormalities and mammary hyperplasia in FVB/NCr mice: implications for mouse modeling

The FVB/N mouse strain is widely used in the generation of transgenic mouse models. We have observed that mammary glands of wild-type virgin female FVB/NCr mice frequently have the morphologic and histologic appearance of a gland during pregnancy. By 13 months of age, the mammary glands of more than 40% of the mice examined had lobuloalveolar hyperplasia that was characterized by the presence of secretory alveoli and distended ducts apparently containing secretory material. The prevalence of this phenotype further increased with age. The mammary phenotype was highly correlated with the presence of proliferative, prolactin-secreting lesions in the pituitary gland. In mice aged 18 to 23 months, hyperplasia of the pars distalis was seen in 11 of 21 mice (52%), and a further 4 of 21 mice (19%) had pituitary adenomas. Pituitary hyperplasia was already evident in some mice as young as nine months. The pituitary phenotype was also associated with high prevalence (4/6 mice) of spontaneous mammary tumors in aged multiparous, but not virgin FVB/NCr mice. This high prevalence of pituitary abnormalities and their effects on the mammary gland have important consequences for the interpretation of new phenotypes generated in transgenic models using this mouse substrain.     

Effects of an S84E mutation of bovine growth hormone in transgenic mice

The ability of mutant bovine growth hormones (bGH) to serve as either agonist or antagonist has been demonstrated in transgenic mice. We have prepared two transgenic strains of FVB/N mice, one expressing wild-type bGH and a second with a glutamic acid mutation at serine 84 in helix 2. Comparison of their phenotypes to those of nontransgenic littermates indicates that wild-type bGH induces a previously described phenotype for hyper-somatotrophic mice. In contrast, the replacement of the side chain hydroxyl at serine 84 with acetic acid produced a phenotype that expressed bGH at appreciable concentrations, but failed to elicit the phenotype observed with either an agonist or an antagonist of bGH. These results indicate that serine 84 is crucial for the activity of bGH despite this site being distal to the receptor binding surfaces.     

Genome scan identifies a locus affecting gamma-globin level in human beta-cluster YAC transgenic mice

Genetic factors affecting postnatal γ-globin expression—a major modifier of the severity of both β-thalassemia and sickle cell anemia—have been difficult to study. This is especially so in mice, an organism lacking a globin gene with an expression pattern equivalent to that of human γ-globin. To model the human β-cluster in mice, with the goal of screening for loci affecting human γ-globin expression in vivo, we introduced a human β-globin cluster YAC transgene into the genome of FVB/N mice. The β-cluster contained a Greek hereditary persistence of fetal hemoglobin (HPFH) γ allele, resulting in postnatal expression of human γ-globin in transgenic mice. The level of human γ-globin for various F₁ hybrids derived from crosses between the FVB/N transgenics and other inbred mouse strains was assessed. The γ-globin level of the (C3HeB/FeJ × FVB/N)F₁ transgenic mice was noted to be significantly elevated. To map genes affecting postnatal γ-globin expression, we performed a 20-centiMorgan (cM) genome scan of a (C3HeB/FeJ × FVB/N)F₁ transgenics × FVB/N backcross, followed by high-resolution marker analysis of promising loci. From this analysis we mapped a locus within an 18-cM interval of mouse Chromosome (Chr) 1 (LOD = 4.3) that contributes 10.9% of variation in γ-globin level. Combining transgenic modeling of the human β-globin gene cluster with quantitative trait analysis, we have identified and mapped a murine locus that impacts on human γ-globin level in vivo. Received: 26 January, 2000 / Accepted: 2 May 2000     

Persistent mammary hyperplasia in FVB/N mice

The inbred FVB/N mouse strain is widely used for creating transgenic mice. Over the past decade, persistent mammary hyperplasia has been detected in many multiparous FVB/N female mice sent to the University of California, Davis (UCD) Mutant Mouse Pathology Laboratory (MMPL) by a number of different laboratories. However, the experimental details concerning most specimens were not always available. To confirm these empiric findings, experiments were carried out to evaluate the mammary glands of FVB/N mice under controlled conditions. Persistent mammary hyperplasia that related to parity was found. Weeks after their first to fourth pregnancy, 10 FVB/N female mice from the Lawrence Berkeley National Laboratory (LBNL) colony were studied and the mammary glands were evaluated. The percentage of fat pad filled was estimated, using image analysis. Serum samples and the pituitary gland from other FVB/N mice from the LBNL were assayed for prolactin concentration. Multiparous FVB/N females consistently had persistent mammary hyperplasia. Four of seven females in the LBNL colony had hyperplasia after three pregnancies. A few foci of squamous nodules and sporadic carcinomas also were observed. Thus, some FVB/N females may have persistent mammary hyperplasia after three pregnancies without detectable pituitary abnormalities. Mammary carcinomas also may develop sporadically. These background phenotypes must be considered when interpreting the effect of genetic manipulation in FVB/N mice.     

Strain-dependent differences in responses to exercise training in inbred and hybrid mice

The aim of this study was to characterize the response to exercise training in several mouse strains and estimate the genetic contribution to phenotypic variation in the responses to exercise training. Male mice from three inbred strains [C57Bl/6J (BL6), FVB/NJ (FVB), and Balb/cJ (Balb/c)] and three hybrid F(1) strains [CB6F1/J (CB6 = female Balb/c x male BL6), B6F F(1) (female BL6 x male FVB), and FB6 F(1) (female FVB x male BL6)] completed an exercise performance test before and after a 4-wk treadmill running program. Distance was used as the primary estimate of endurance exercise performance. FVB mice showed the greatest response to training, with five- to sevenfold greater increases in distance run compared with BL6 and Balb/c strains. Specifically, BL6, FVB, and Balb/c strains increased distance by 33, 172, and 23%, respectively. A similar pattern of changes across strains was observed for run time (17, 87, and 11%) and work (99, 287, and 57%). As a group, F(1) hybrid mice derived from BL6 and FVB strains showed an intermediate response to training (61%). However, further analysis indicated that training responses in FB6 F(1) mice (80%) were approximately 2.5-fold greater than responses in B6F F(1) mice (33%, P = 0.08). A similar pattern of changes between FB6 and B6F F(1) mice was observed for run time (44.5 and 17%) and work (141 and 59%). These data demonstrate that there are large strain-dependent differences in training responses among inbred mouse strains, suggesting that genetic background contributes significantly to adaptation to exercise. Furthermore, the contrasting responses in B6F and FB6 F(1) strains show that a maternal component strongly influences strain-dependent differences in training responses.     

Genetic Immunization of Wild-Type and Hepatitis C Virus Transgenic Mice Reveals a Hierarchy of Cellular Immune Response and Tolerance Induction against Hepatitis C Virus Structural Proteins

To study the effect of genetic immunization on transgenic expression of hepatitis C virus (HCV) proteins, we evaluated the immunological response of HCV transgenic mice to HCV expression plasmids. FVB/n transgenic mice expressing HCV structural proteins (core, E1, and E2) and wild-type (WT) FVB/n mice were immunized intramuscularly with plasmids expressing core (pHCVcore) or core/E1/E2 (pHCVSt). After immunization, HCV-specific humoral and cellular immune response was studied. Both WT and transgenic mice immunized with either HCV construct produced antibodies and exhibited T-cell proliferative responses against core or envelope. In WT mice immunized with pHCVSt, cytotoxic T-lymphocyte (CTL) activities were detected against E2 but not against core or E1, whereas strong CTL activities against core could be detected in WT mice immunized with pHCVcore. In pHCVSt-immunized, transgenic mice, CTL activities against the core or envelope were completely absent, but core-specific CTL activities could be detected in pHCVcore-immunized transgenic mice. A similar pattern of immune responses was also observed in other mouse strains, including a transgenic line expressing human HLA-A2.1 molecules (AAD mice). Despite the presence of a peripheral cellular immunity against HCV, no liver pathology or lymphocytic infiltrate was observed in these transgenic mice. Our study suggests a hierarchy of CTL response against the HCV structural proteins (E2 > core > E1) in vivo when the proteins are expressed as a polyprotein. The HCV transgenic mice can be induced by DNA immunization to generate anti-HCV antibodies and anticore CTLs. However, they are tolerant at the CTL level against the E2 protein despite DNA immunization.     

COX-2 inhibitors and genetic background reduce mammary tumorigenesis in cyclooxygenase-2 transgenic mice

Cyclooxygenase-2 (COX-2) overexpression is a widely recognized feature of human breast cancer and inhibitors of the enzyme have antitumor effects in a subset of tumor settings. Previously, we demonstrated that direct overexpression of COX-2 under control of the mammary-specific MMTV promoter/enhancer, was itself oncogenic and lead to the induction of mammary tumors in multiparous, outbred CD1 mice. In the present study, we provide evidence that COX-2 dependent tumor progression can also be studied in FVB/N, an inbred strain widely used for analysis of breast cancer progression. In these mice, the human COX-2 transgene was strongly induced during pregnancy/lactation and mammary tumors developed after multiple pregnancies. However, crossing the COX-2 FVB/N mice with the C57BL6 strain resulted in loss of the mammary tumorigenic phenotype despite the fact that the human COX-2 gene was induced. Treatment of the COX-2 transgenic mice in the FVB/N strain with celecoxib (1600 ppm), a COX-2 selective inhibitor, resulted significant reduction in tumor size and multiplicity when compared to transgenic mice fed with control chow. SC-560 (20 ppm), a COX-1 selective inhibitor did not have significant effect on tumorigenesis. These studies suggest that FVB/N is a susceptible mouse strain well suited to the study of COX-2 mediated tumor progression and may provide a tool for the identification of interacting genes and therapeutic treatments for this clinically important target.     

Lateral Femoral Hernias in a Line of FVB/NHsd Mice: A New Confounding Lesion Linked to Genetic Background?

Several strains of transgenic mice derived from an inbred FVB/NHsd colony developed large masses on 1 or both flanks. Although originally suspected to be a phenotypic anomaly related to genetic modifications, nontransgenic littermates subsequently were affected with equal frequency, inculpating the FVB/NHsd founder colony. The masses were subcutaneous, soft, and exophytic and appeared over the course of a few weeks. Female mice were affected more frequently than males. Gross examination revealed the masses to consist of uni- or bilateral hernias of variable size, occasionally containing small or large intestine (or both), cecum, mesenteric adipose tissue, male reproductive organs, and ureters. All hernial sacs pouched through the femoral triangle laterally to the femoral vessels and therefore were classified as lateral femoral hernias. Lateral femoral hernias have not previously been described in the veterinary literature and have never been described as background lesions in a strain of mice. Our findings suggest likely genetic drift in this strain of FVB/NHsd mice, causing a background lesion that confounded phenotypic analyses of transgenic mice derived from this strain.     

Sequencing and characterisation of the FVB/NJ mouse genome

ABSTRACT: BACKGROUND: The FVB/NJ mouse strain has its origins in a colony of outbred Swiss mice established in 1935 at the National Institutes of Health. Mice derived from this source were selectively bred for sensitivity to histamine diphosphate and the B strain of Friend leukemia virus. This led to the establishment of the FVB/N inbred strain, which was subsequently imported to the Jackson Laboratory and designated FVB/NJ. The FVB/NJ mouse has several distinct characteristics, such as large pronuclear morphology, vigorous reproductive performance, and consistently large litters that make it highly desirable for transgenic strain production and general purpose use. RESULTS: Using next-generation sequencing technology, we have sequenced the genome of FVB/NJ to approximately 50-fold coverage, and have generated a comprehensive catalog of single nucleotide polymorphisms, small insertion/deletion polymorphisms, and structural variants, relative to the reference C57BL/6J genome. We have examined a previously identified quantitative trait locus for atherosclerosis susceptibility on chromosome 10 and identify several previously unknown candidate causal variants. CONCLUSION: The sequencing of the FVB/NJ genome and generation of this catalog has increased the number of known variant sites in FVB/NJ by a factor of four, and will help accelerate the identification of the precise molecular variants that are responsible for phenotypes observed in this widely-used strain.     

Host defenses in experimental scrub typhus: mapping the gene that controls natural resistance in mice

Natural resistance of mice to lethal ifections of Rickettsia tsutsugamushi, strain Gilliam, is controlled by a single, autosomal, dominant gene, which we have designated Ric, with r and s representing the resistant nd susceptible alleles, respectively. Using three sets of recombinant inbred mouse strains (BXD, BXH, and BXJ), the Ric locus was mapped to Chromosome 5 closely linked to the retinal degeneration (rd) locus. This linkage was confirmed by a backcross analysis. Based on the RI strains and the C57BL/6Ty-le congenic strain (the only proven Ric-rd cross-over), we estimate the recombination frequency between Ric and rd to be 0.015. Three presumptive Ric-rd recombinants detected among 93 backcross mice may represent caes of incomplete penetrance of the resistance allele rather than recombination. Analyis of th C57BL/6JTy-le congenic strain indicates that Ric is proximal to rd on Chromosome 5. If so, the correct gene order is Pgm-1-W-Ric-rd-Gus.     

A Comprehensive Behavioral Test Battery to Assess Learning and Memory in 129S6/Tg2576 Mice

Transgenic Tg2576 mice overexpressing human amyloid precursor protein (hAPP) are a widely used Alzheimer’s disease (AD) mouse model to evaluate treatment effects on amyloid beta (Aβ) pathology and cognition. Tg2576 mice on a B6;SJL background strain carry a recessive rd1 mutation that leads to early retinal degeneration and visual impairment in homozygous carriers. This can impair performance in behavioral tests that rely on visual cues, and thus, affect study results. Therefore, B6;SJL/Tg2576 mice were systematically backcrossed with 129S6/SvEvTac mice resulting in 129S6/Tg2576 mice that lack the rd1 mutation. 129S6/Tg2576 mice do not develop retinal degeneration but still show Aβ accumulation in the brain that is comparable to the original B6;SJL/Tg2576 mouse. However, comprehensive studies on cognitive decline in 129S6/Tg2576 mice are limited. In this study, we used two dementia mouse models on a 129S6 background—scopolamine-treated 129S6/SvEvTac mice (3–5 month-old) and transgenic 129S6/Tg2576 mice (11–13 month-old)–to establish a behavioral test battery for assessing learning and memory. The test battery consisted of five tests to evaluate different aspects of cognitive impairment: a Y-Maze forced alternation task, a novel object recognition test, the Morris water maze, the radial arm water maze, and a Y-maze spontaneous alternation task. We first established this behavioral test battery with the scopolamine-induced dementia model using 129S6/SvEvTac mice and then evaluated 129S6/Tg2576 mice using the same testing protocol. Both models showed distinctive patterns of cognitive impairment. Together, the non-invasive behavioral test battery presented here allows detecting cognitive impairment in scopolamine-treated 129S6/SvEvTac mice and in transgenic 129S6/Tg2576 mice. Due to the modular nature of this test battery, more behavioral tests, e.g. invasive assays to gain additional cognitive information, can easily be added.