Differences in saccharin preference and genetic alterations of the Tas1r3 gene among senescence-accelerated mouse strains and their parental AKR/J strain.

The senescence-accelerated mouse (SAM) is used as an animal model of senescence acceleration and age-associated disorders. SAM is derived from unexpected crosses between the AKR/J and unknown mouse strains. There are nine senescence-prone (SAMP) strains and three senescence-resistant (SAMR) strains. Although SAMP strains exhibit strain-specific and age-related pathological changes, the genes responsible for the pathologic changes in SAMP strains have not been comprehensively identified. In the present study, we evaluated sweet taste perception using the two-bottle test. We compared genotypes of the taste related gene, Tas1r3, using SAM strains and the parental AKR/J strain. The two-bottle test revealed that SAMR1 (R1), SAMP6 (P6), SAMP8 (P8), and SAMP10 (P10) mice were saccharin-preferring strains, whereas AKR/J did not prefer saccharin. All genotypes of the R1, P6, P8, and P10 strains at the polymorphic sites in Tas1r3, which is known to influence saccharin preference, were identical to those of C57BL6/J, a well-known saccharin-preferring strain, and were completely different from those of the parental AKR/J strain. These genetic alterations in SAM strains appear to arise from an unknown strain that is thought to have been crossed with AKR/J initially.

Impact of intra- and interstrain cross-fostering on mouse maternal care.

The importance of maternal care in shaping an individual's phenotype in health and disease is becoming more and more apparent in both human and animal studies. However, in mouse studies using inbred strains or knockout mice to analyze the genetic influences on the development of normal and aberrant behavioral phenotypes, maternal behavior is very poorly characterized and often ignored. This study provides an extensive analysis of spontaneous maternal behavior of inbred mice in three conditions: (1) comparing two commonly used strains, (2) analyzing the impact of adopting pups from the same strain (intrastrain cross-fostering) and (3) analyzing the impact of adopting pups from a different strain (interstrain cross-fostering). For each condition, maternal behavior was analyzed continuously over 23-h periods on postnatal days 2, 4, 6 and 9. We report that (1) the maternal behavior of C57BL/6J and DBA/2J dams toward their biological offspring is highly similar, (2) intrastrain cross-fostering has minimal impact on maternal behavior of C57BL/6J and DBA/2J dams, (3) interstrain cross-fostering does not modify the strain differences in maternal care observed between AKR and C3H/He mothers and (4) the pup strain does influence the amount of maternal behavior shown by both mothers in interstrain cross-fostering. These latter findings demonstrate that both mother strain and pup strain are key determinants of maternal behavior.

The development of a highly informative mouse Simple Sequence Length Polymorphism (SSLP) marker set and construction of a mouse family tree using parsimony analysis.

To identify highly informative markers for a large number of commonly employed murine crosses, we selected a subset of the extant mouse simple sequence length polymorphism (SSLP) marker set for further development. Primer pairs for 314 SSLP markers were designed and typed against 54 inbred mouse strains. We designed new PCR primer sequences for the markers selected for multiplexing using the fluorescent dyes FAM, VIC, NED, and ROX. The number of informative markers for C57BL/6J x DBA/2J is 217, with an average spacing of 6.8 centiMorgans (cM). For all other pairs of strains, the mean number of informative markers per cross is 197.0 (SD 37.8) with a mean distance between markers of 6.8 cM (SD 1.1). To confirm map positions of the 224 markers in our set that are polymorphic between Mus musculus and Mus spretus, we used The Jackson Laboratory (TJL) interspecific backcross mapping panel (TJL BSS); 168 (75%) of these markers had not been previously mapped in this cross by other investigators, adding new information to this community map resource. With this large data set, we sought to reconstruct a phylogenetic history of the laboratory mouse using Wagner parsimony analysis. Our results are largely congruent with the known history of inbred mouse strains.

Interstrain variation in murine aerobic capacity.

PURPOSE: The contribution of genetic factors to aerobic capacity is unknown. The purpose of this study was to measure maximal aerobic performance among inbred strains of mice to provide basic heritability estimates. METHODS: Eight female mice, 8 to 10 wk old, in 10 inbred strains (A/J, AKR/J, Balb/cJ, C(3)H/HeJ, C57Bl/6J, C57L/J, C(3)Heb/FeJ, CBA/J, DBA/2J, and SWR/J) were run on a treadmill until exhaustion. The protocol started at 22 m.min(-1) and increased in speed approximately 6 m.min(-1) every 4 min. After 4 min at 42.4 m.min(-1), the grade was increased 2% every 4 min thereafter until the mouse could not run off of the shock grid (150 V; 1.5 mA). RESULTS: There were significant differences between inbred strains in maximal duration of exercise accomplished (P < 0.0001). The order of strain-specific exercise duration was Balb/cJ > SWR/J > CBA/J > C57L/J > C3H/HeJ > C3Heb/FeJ > C57Bl/6J > AKR/J > DBA/2J > A/J. Two measures of heritability in the broad sense, intraclass correlation (0.73), and the coefficient of genetic determination (0.58) were both significant. CONCLUSION: These data indicate that there is a strong genetic contribution to aerobic capacity in mice.

Anomalous (preduodenal) portal vein: autosomal recessive mutation in AKR/J mice.

BACKGROUND AND PURPOSE: Anomalous (preduodenal) portal vein was found in AKR/J mice. It is a rare congenital malformation in humans, and to the authors' knowledge, has never been reported in laboratory animals. Morphology, clinical signs of disease, and heritability of this anomaly were examined. METHODS: Fifty-three strains of inbred mice (6,026 mice) in our mouse colony were examined for preduodenal portal vein and its association with clinical signs of disease (vomiting or abdominal pain) and other anomalies. Heritability also was tested by use of cross-backcross matings of AKR/J mice with clinically normal PT mice. RESULTS: The portal vein was found at the ventral side of the duodenum in most (98%) AKR/J mice, whereas it ran at the dorsal side of the duodenum in 52 other inbred mouse strains in our mouse colony. Clinical signs of disease and other congenital anomalies were not detected in this strain of mice, although position has a high association with other congenital anomalies in humans. Heritability testing of this anomaly in AKR/J mice indicated single autosomal recessive inheritance. CONCLUSIONS: Preduodenal portal vein found in AKR/J mice is a single autosomal recessive mutation, but is not associated with clinical signs of disease and other congenital malformations.

Genetic mapping of 262 loci derived from expressed sequences in a murine interspecific cross using single-strand conformational polymorphism analysis.

We have demonstrated previously that noncoding sequences of genes are a robust source of polymorphisms between mouse species when tested using single-strand conformation polymorphism (SSCP) analysis, and that these polymorphisms are useful for genetic mapping. In this report we demonstrate that presumptive 3'-untranslated region sequence obtained from expressed sequence tags (ESTs) can be analyzed in a similar fashion, and we have used this approach to map 262 loci using an interspecific backcross. These results demonstrate SSCP analysis of genes or ESTs is a simple and efficient means for the genetic localization of transcribed sequences, and is furthermore an approach that is applicable to any system for which there is sufficient sequence polymorphism.

Lifespan and lesions in genetically heterogeneous (four-way cross) mice: a new model for aging research.

Genetically heterogeneous animal models provide many advantages for research on aging but have been used infrequently. We present here lifespan and lesion data from a study of mice bred as a cross between (AKR/J x DBA/2J)F1 females and (C57BL/6J x SJL/J)F1 males. In such a four-way cross population, each mouse is genetically unique, but replicate populations of essentially similar genetic structure can be generated quickly, at low cost, and of arbitrary size from commercially available, genetically stable hybrid parents. We employed a protocol in which mice judged to be severely ill were euthanatized to obtain tissue in optimal condition for necropsy, and we were able to infer a likely cause of illness in 42 of 44 animals. Malignant lymphoma, including at least four histopathologically distinct subtypes, was the most common cause and was also a frequent incidental finding in mice dying of other causes. Neoplastic disease, benign or malignant, was the sole or a contributing cause of illness in 90% of the mice for which a cause could plausibly be assigned. A wide range of lethal and nonlethal degenerative lesions was also noted. The coefficient of variation for lifespan in these genetically heterogeneous mice was 26%, similar to that seen in analyses of recombinant inbred mouse lines. Baseline lifespan and pathology data on four-way cross mice is a useful prelude to the exploitation of this rodent model in tests of genetic and mechanistic hypotheses about aging.

Autoimmune diabetes-prone NOD mice express the Lyt2 alpha (Lyt2.1) and Lyt3 alpha (Lyt3.1) alleles of CD8.

Predisposition to Type I insulin-dependent diabetes (IDD) has a strong underlying genetic basis involving class II major histocompatibility complex (MHC) genes as well as several non-MHC genetic systems. In the non-obese diabetic (NOD) mouse, a model for human IDD, genes associated with the appearance of immune cell infiltrates in the pancreatic islets (insulitis) and/or overt IDD have been mapped to chromosomes 1, 3, 6, 11, and 17. A recent report has suggested that CD8+ lymphocytes of the NOD mouse might be deficient in the expression of the CD8 beta molecule, a protein encoded by a gene on chromosome 6. The CD8 beta molecule is a T-cell surface marker, the lack of which could affect selection in the thymus, possibly permitting auto-reactive T-cell clones to populate the peripheral lymphoid tissues. For this reason, we examined the expression of the CD8 molecule by lymphocytes in the NOD mouse. Results indicate that the NOD mouse is not deficient in its transcription of detectable mRNA encoding either the CD8 alpha or beta subunits. However, the NOD mouse expresses the Lyt2 alpha and Lyt3 alpha alleles, suggesting that a portion of chromosome 6 centromeric to the diabetes-susceptibility genetic region is derived from an ancestry common to AKR and, like AKR, the CD8 alpha and CD8 beta 3.1 (but not CD8 beta 3.2) subunits are detected on the cell surface of T lymphocytes of the NOD mouse. Interestingly, though, the CD8 beta 3.1 molecule may not be expressed in the NOD mouse to the same extent as it is expressed in the AKR/J mouse, suggesting the possibility that the NOD mouse possesses a defect somewhere between transcription and cell surface expression of the CD8 beta molecule.

Molecular genetic characterization of the senescence-accelerated mouse (SAM) strains.

Senescence-Accelerated Mouse (SAM) is a murine model of accelerated senescence, which consists of the senescence-prone P series and the senescence-resistant R series of strains. In order to characterize these SAM strains molecular genetically, we have performed a series of Southern hybridization experiments using oligonucleotide probes designed to recognize the endogenous mouse retrovirus sequences. The repertoires of endogenous retroviruses in different SAM strains indicated that each SAM strain is distinct. Comparisons of the SAM strains with the parental AKR/J strain revealed significant differences between them, suggesting the involvement of other strains in the course of the development of SAM. While some of the endogenous retroviruses were found in all of the SAM strains, others were found to be distributed uniquely, indicating their potential usefulness as genetic markers in the analysis of strain-specific phenotypes, and possibly of the phenomenon of accelerated senescence itself.

Genetics of dietary obesity in AKR/J x SWR/J mice: segregation of the trait and identification of a linked locus on chromosome 4.

We describe a new multiple gene mouse model of differential sensitivity to dietary obesity that provides a tool for dissecting the genetic basis for body composition and obesity. AKR/J and SWR/J male mice, as well as male progeny of intercrosses between these strains, were fed a high-fat diet for 12 weeks beginning at 5 weeks of age. Body weight and energy intake were assessed weekly. At the conclusion of the dietary manipulation, an adiposity index was calculated by dividing the weight of seven dissected adipose depots by the carcass weight. AKR/J mice had approximately sixfold greater adiposity than SWR/J mice. Examination of the segregation of the adiposity trait in the progeny of crosses between these strains indicates that the trait is determined by a minimum of one to four genetic loci and that there is significant dominance of the AKR/J genotype. A preliminary analysis with markers linked to the known mouse obesity genes ob, db, tub, and fat showed no linkage with these loci. However, a quantitative trait locus was found that maps distal to the db gene on Chromosome (Chr) 4. This locus has been designated dietary obese 1 or Do1.

Assignment of a gene that determines erythrocytic guanosine-5'-triphosphate concentration (Gtpc) to mouse chromosome 9.

Nine inbred mouse strains surveyed for erythrocytic guanosine-5'-triphosphate (GTP) concentration were found to segregate into two discrete groups. Strains having low GTP levels between 1.4 and 3.4 nmol/10(9) cells were C3H/HeJ, C3H/HeHa, A/J, and WB/ReJ. Strains having high GTP levels between 11.0 and 14.8 nmol/10(9) cells were AKR/J, DBA/2J, CBA/J, C57BL/6J, and C57L/J. Erythrocytic ATP levels did not vary significantly among these groups. Crosses between low and high GTP strains gave F1 progeny having intermediate levels of GTP, and the progeny of F1's backcrossed to parental strains segregated in a 1:1 ratio for GTP concentration. We designated the GTP concentration determining trait, Gtpc. Typing the C57BL/6J x C3H/HeJ (B x H) recombinant inbred strains for GTP levels revealed 0/12 strain distribution pattern differences for loci on both chromosomes 5 and 9. Backcross analysis did not provide evidence for linkage of Gtpc to W (dominant white spotting) on chromosome 5 with 15/45 recombinants. A test for linkage of Gtpc to transferrin (Trf) on chromosome 9 gave evidence of linkage with an observed recombination frequency of 14.6 +/- 5.5 and a 99% confidence interval of 3.9-33.9 cM.

Organization of the V gene segments in mouse T-cell antigen receptor alpha/delta locus.

The mouse T-cell receptor (TCR) alpha/delta locus was mapped using 17 V alpha and 4 V beta subfamily-specific probes. Four complementary methods were used: (1) an estimate of the V gene repertoire by Southern blot analysis of genomic DNA with subfamily-specific probes; (2) an analysis of V gene segments deleted by TCR gene rearrangements from a panel of T-cell tumors and hybridomas; (3) an analysis of overlapping clusters of cosmid clones; and (4) an analysis of large DNA fragments separated by field-inversion gel electrophoresis. The alpha/delta locus spans about 1 Mb. The distance between the 3'-most V gene segment (V delta 1) and the delta constant gene (C delta) is no more than 150 kb. Sixty-six V gene segments have been mapped physically on cosmids. The members of individual V alpha gene segment subfamilies are dispersed throughout the locus. In contrast, the V delta gene segments V delta 1 to 5 are clustered at the 3' end of the V gene segment cluster. At least two DNA segment duplications, 45 to 80 kb in length, are present in the locus. These data provide information on the evolution of the alpha/delta locus and on organization features that might influence the expression of specific V gene segments in gamma delta cells.

Lymphomagenesis in AKR.Fv-1b congenic mice.

In the AKR.Fv-1b congenic strain the Fv-1n allele of the AKR/J mice was substituted with the Fv-1b allele, thereby limiting viral replication and spread of the endogenous N-tropic murine leukemia virus. As a result of this genetic change AKR.Fv-1b mice develop a low spontaneous incidence (7%) of T-cell lymphomas and about 28% of Ly-1+ B-cell lymphomas are observed in old mice. Characteristic changes in thymus subpopulations of AKR/J mice (related to the formation of the dual tropic mink cell focus inducing (MCF) type virus in the thymus) were not observed in the thymus of AKR.Fv-1b mice. In contrast to the low susceptibility to spontaneous T-cell lymphoma development, these mice were highly sensitive to fractionated irradiation or to radiation leukemia virus (a mixture of N- and B-tropic viruses) induced T-cell lymphoma. Potential lymphoma cells (that would ultimately develop into Ly-1+ B-cell lymphomas) were demonstrated in bone marrow and spleens of 16-24-month-old mice. Analysis of the Ly-1+ IgM+ B-cell population in spleens of 18-month-old mice revealed a significant increase in this population (35% versus 2% in young spleens). The spontaneous Ly-1+ B-cell lymphoma incidence could be enhanced (up to 77%) by in vivo administration of anti-CD8 monoclonal antibody or IL-4 to 18-month-old mice. Virological analysis of T/B-cell lymphomas for class I MCF viruses indicated that Class I MCF development was tightly correlated with T-lymphoma development (except radiation induced tumors that showed no MCF provirus involvement). In contrast, Ly-1+ B-cell lymphoma development was independent of Class I MCF pathogenic virus involvement.

Autosomal dominant mouse cataract (Lop-10). Consistent differences of expression in heterozygotes.

The clinical and histologic features are reported of an autosomal dominant mouse cataract that was first observed as a new mutation in a cross between BALB/cJ and AKR/J. In the homozygous state, the eyes were microphthalmic, and a dense white cataract was present when the eyes opened at day 12. Histologic changes were apparent from birth and as early as 18 days' gestation. Liquefaction started by day 4, and herniation of lens contents posteriorly was seen at day 11. Heterozygous mice had variable expression depending both on their genetic background and age. When the single gene was expressed fully, the cataract appeared as a fetal nuclear white opacity; partial expression gave a nuclear haze to snowflake nuclear opacities. Lop-10 appeared to be an excellent model for studying variable expression of a dominant gene.

Morphometric studies in inbred and hybrid house mice. VIII. Effects of litter size on brain size and body size.

Litter size, brain size, and body size were examined in inbred and hybrid house mice of three different ages in order to test whether litter size exhibits a positive genetic, but negative environmental association with both brain and body size. As estimated from among-line covariation, litter size showed a positive, but non-significant genetical association with brain and body size. It also showed a significant, negative environmental association with brain and body size, as hypothesized. Over all inbreds and hybrids, litter size explained 8% and 14%, respectively, of the within-strain (environmental) variation in brain and body size. It was concluded that the negative phenotypic association of litter size with brain size and especially body size is the reflection of a well-known negative maternal environmental effect whereby mice with large body sizes tend to produce larger litters of mice with smaller body sizes.

Resistance to NK and metastatic potential of fibrosarcoma cells is associated with products encoded by the H-2D region.

We have used the murine 3-methylcholanthrene induced T10 fibrosarcoma tumor cell system originating in (C3II/en x C57BL/6)F1 mice (H-2b x H-2k) to elucidate the possible correlation between metastatic potential, expression of individual H-2 antigens and susceptibility to NK cells. Transfection of the non metastatic and NK sensitive IC9 cells (Db+, Kk, Kb, Kk-) with the H-2Dk gene, altered the metastatic phenotype of the parental cells, yet had no effect on the susceptibility of these tumor cells to lysis by NK and did not elicit a specific CTL response in syngeneic hosts. Variants of the metastatic and NK resistant IE7 clone (Db+, Kk-, Kb-, Kk-), lacking H-2Dk, were selected by treatment with monoclonal anti H-2Dk antibodies and complement. These variants were sensitive to NK and poorly or non metastatic. Transfection of Dk negative variants with the H-2Dk gene, resulted in the isolation of several clones which expressed a wide range of metastatic phenotypes but maintained sensitivity to NK. In addition, by cloning the cDNA of the H-2Dk gene of the metastatic T10-IE7 variant cells and analyzing its nucleotide sequence, we found four single nucleotide changes. Two of them are not expected to alter the encoded amino acids, whereas the others should result in two amino acid substitutions in the alpha-2 domain of the class I H-2Kd protein product. These changes might account, at least partially, for the failure of the transfection of H-2Dk to restore resistance to NK.(ABSTRACT TRUNCATED AT 250 WORDS)