H-2-associated differences in replicated strains of mice divergently selected for body weight

A random-bred strain (Q) was established and divided into six replicates. Each replicate was divergently selected for 6-week weight (for over 30 generations) and each had an unselected control. We have investigated the H-2 haplotype of individual mice of the 18 selected Q strains to determine whether selection for size had also selected for H-2 or H-2-linked genes. From the results it appeared that only the H-2 ^b and H-2 ^q haplotypes were present in the foundation stock. A large number of individuals of the six small sublines were of H-2 bhaplotype, while the majority of those of the six large sublines were of the H-2 ^q haplotype. Individuals in the six control strains were H-2 ^b , H-2 ^q or both (i. e., H-2 heterozygotes and/or H-2 recombinants). These results suggest that control of body size is associated with H-2 or an H-2-linked gene(s).     

Functional polymorphisms in inbred rat strains and their allele frequencies in commercially available outbred stocks.

Polymorphisms that have been proven to influence gene functions are called functional polymorphisms. It is significant to know the distribution of functional polymorphisms in the rat, widely used in animal models for human diseases. In this study, we assessed 16 functional polymorphisms consisting of 3 coat color and 13 disease-associated genes in 136 rat strains, as a part of the genetic profiling program of the National Bio Resource Project for the Rat (NBRP-Rat). Polymorphisms of Cdkn1a, Fcgr3, Grp10, Lss, and Fdft1, which were proven to function in prostate tumorigenesis, glomerulonephritis, hyperphagia, and cholesterol biosynthesis, were shared among various inbred strains. These findings indicated that most rat strains harbored the disease-associated alleles and suggested that many unidentified functional polymorphisms might exist in inbred rat strains. The functional polymorphisms shared in inbred strains were also observed within outbred stocks available commercially. Therefore, this implies that experimental plans based on either rat inbred strains or outbred stocks need to be carefully designed with a full understanding of the genetic characteristics of the animals. To select the most suitable strains for experiments, the NBRP-Rat will periodically improve and update the genetic profiles of rat strains.     

Use of intercross outbred mice and single nucleotide polymorphisms to map skin cancer modifier loci

Car-R and Car-S outbred mouse lines, phenotypically selected for resistance and susceptibility to skin carcinogenesis respectively, show significant linkage disequilibrium (LD) at genetic markers mapping on chromosomal regions where skin cancer modifier loci (Skts3, Skts1, and Psl1 on Chrs 5, 7, and 9 respectively) have been mapped in standard crosses. Analysis of these regions for genetic linkage with skin cancer phenotypes in 245 (Car-R × Car-S)F₂ intercross mice, by using single nucleotide polymorphisms (SNPs), revealed significant linkage at a possible allelic form of the Skts1 locus, whose mapping region was shortened to a <5.5-cM interval near the Tyr locus. The Car-derived Skts1 locus was linked with papilloma multiplicity and latency by a recessive inheritance of the susceptibility allele. Putative loci on Chr 5 (Skts3) and 9 (Psl1) showed no significant linkage. These results point to the important role of the Stks1 locus in mouse skin tumorigenesis in independent crosses. The shortened Skts1 mapping region should facilitate the identification of candidate genes. Received: 23 June 2000 / Accepted: 22 November 2000     

Assessment of retinal degeneration in outbred albino mice

Evaluation of a pharmaceutical's safety includes assessment of the potential for ophthalmologic toxicity. These nonclinical studies commonly use various outbred stocks of mice. Pretest indirect ophthalmoscopic examinations in the commonly used outbred stock Hsd:ICR(CD-1) indicated that retinal degeneration was a problem in this particular outbred stock of mice. This prompted the authors to examine other stocks of outbred mice routinely used in the performance of nonclinical safety studies. Groups of mice were observed over a 13-week period to determine the progression and changing incidence of retinal degeneration. Light intensity in the room and caging was measured during the study, and it was determined that light did not play a direct role in the progression of the retinal degeneration observed during the study. Histomorphologic examination of the mouse eyes was performed at the end of the study to confirm the presence of retinal degeneration observed after ophthalmoscopic examination. The incidence of retinal atrophy in the various outbred stocks of mice was: Crl:CFW(SW)BR (98.3%), Tac(SW)fBR (80%), Tac:Icr:Ha(ICR)fBR (75%), Hsd:ICR(CD-1) (43.3%), and Crl:CF-1BR (3.0%). Retinal atrophy was not observed in the following outbred mice stocks: Crl:CD-1(ICR)BR, HsdWin:CFW1, and Hsd:NSA(CF-1). On the basis of these findings, it is highly recommended that pretest ophthalmologic screening be performed on mice to obviate pre-existing conditions from confounding or invalidating nonclinical study results.     

Genetic drift in an outbred stock of mice.

Survey in protein polymorphism in the nucleus colony of the Him: OF 1-mouse outbred stock showed that 8 of 53 loci were variable in the stock. Allele frequencies of these eight loci (Idh-1, Mup-1, Pgm-1; Ldr-1, Gpi-1s, Hbb, Mod-1, Ce-2) changed between generations investigated. The average percentage of heterozygote animals for these loci decreased with generation. These suggested that genetic drift occurred in the breeding stock. Examination in the breeding record sheets showed that genetic drift was caused by mistakes in mating probably due to repeated personnel changes and insufficient training of the animal technicians. Mice had not been paired according to the schemes prescribed, pairing among relatives and reduction of the number of litters used for mating occurred. The increase in homozygosity showed only little effect on breeding parameters: The interval between pairing and first and second litter increased significantly.     

Detection of mouse hepatitis virus antibody by protein A-ELISA in 6 prevalent inbred strains or outbred stocks of mice.

Protein A was applied as a reagent for the secondary reaction in ELISA (protein A-ELISA). Mouse hepatitis virus antibody in 6 prevalent mouse strains or stocks reared in a MHV-contaminated room was effectively detected by protein A-ELISA, whereas significant strain differences in the antibody detection rate were demonstrated using the complement fixation test. C57BL/6 mice were particularly reactive in the protein A-ELISA test.     

The influence of graft size on the induction of immunity versus tolerance to H-Y in H-2 k strains of mice

Unprimed female CBA mice do not reject large (10 mm²) syngeneic male skin grafts. However, a high proportion do reject small (4 mm²) grafts. Nevertheless, rejection does not invariably result in an anamnestic response. In some cases, the immunity induced by the rejection of a small graft was overcome, and tolerance was induced by a subsequent challenge with a large graft. This suggests that the transplantation response to minor antigens is subject to active regulation, and screening of other H-2 ^k strains indicates that the nature of the response (i. e., immunity or tolerance) is determined by a gene or genes mapping outside the major histocompatibility complex.     

Method for inducing experimental pneumococcal meningitis in outbred mice

Background  

Streptococcus pneumoniae is the leading cause of bacterial meningitis. Pneumococcal meningitis is associated with the highest mortality among bacterial meningitis and it may also lead to neurological sequelae despite the use of antibiotic therapy. Experimental animal models of pneumococcal meningitis are important to study the pathogenesis of meningitis, the host immune response induced after infection, and the efficacy of novel drugs and vaccines.     

H-2-Linked regulation of serum gp70 production in mice

By using many congenic strains of C57BL/10 (B10) mice and NZB mice, we have demonstrated a genetic system that controls the production of serum gp70. Our system has been tentatively designated as Sgp-1 and is composed of three phenotypes, Sgp-1a, 1b, and 1c. This system appears to be closely linked to, but not in the H-2 region on chromosome 17. Sgp-1a, which is associated with H-2d, correlates with relatively large amounts of serum gp70 in B10 congenic lines. Sgp-1b, which appeared in most of the H-2 types tested, corresponds with low serum gp70 output in B10 congenic lines and F1 hybrid offspring of B10 and NZB crosses and with increased gp70 production after lipopolysaccharide (LPS) stimulation. Sgp-1c, which is associated with H-2s, also relates to small amounts of serum gp70 in B10 congenic lines and their F1 hybrids from NZB matings, but shows lack of serum gp70 responsiveness to LPS. This failure to accelerate serum gp70 production after injection of LPS is independent of other acute phase responses and polyclonal activation of B cells.     

Genetic variability within and between outbred Wistar strains of rats.

The allelic frequencies at 6 isozyme loci (Es-1, Es-2, Es-3, Es-4, Es-Si and Amy-1) were examined in 4 outbred Wistar strains and additionally 2 SD strains as controls. From the allelic frequencies, the averages of the heterozygosities in individual strains and the geometric genetic distances between every pair of all possible strain combinations were calculated. The averages of the heterozygosities in 2 SD strains were both intermediate (around 0.2) and the genetic distance between them was rather short. But among the Wistar strains, the averages of the heterozygosities were highly variable and the genetic relationships among them were very variable in their genetic distances. From these results, it was suggested that the outbred Wistar strains were different each other in their genetic constitutions and that no suggestion was obtained to descriminate genetically the Wistar strains from the SD strains.     

DNA sequence analysis of the C3H H-2Kk and H-2Dk loci. Evolutionary relationships to H-2 genes from four other mouse strains

We generated nucleotide sequences for H-2Kk and H-2Dk from the C3H mouse, as well as for a genomic clone of H-2Db, in order to conduct an evolutionary analysis of the H-2 genes from three haplotypes, k, d, and b. H-2Kk from both the C3H and AKR strains, H-2Kd, H-2Kb, H-2Dk, H-2Ld, H-2Dd, H-2Db, and H-2Dp DNA sequences were aligned, and the alignments used to construct phylogenetic trees inferring the evolutionary relationships among the nine genes by two independent methods. Both approaches yielded trees with similar topologies. In addition, the sequence alignments revealed patterns of nucleotide substitutions which implicate both point mutation and recombination in the divergence of the H-2 genes. Future considerations for evolutionary analysis of class I genes are discussed.