Genotype modulates the aggression-promoting quality of progesterone in pregnant mice

During late pregnancy, female mice of the DBA/2J inbred strain are more likely to exhibit aggressive behavior toward a standard stimulus intruder male than C57BL/6J females. This strain difference can not be accounted for by differences in circulating levels of progesterone (P) since pregnant DBA/2J and C57BL/6J females exhibit similar patterns of the steroid throughout pregnancy. Upon receiving subcutaneously implanted Silastic capsules containing P, virgin DBA/2J mice are more likely than virgin C57BL/6J to respond to the steroid by exhibiting aggression. Strain differences in the aggressive behavior exhibited by pregnant mice may be related to genotype-based variation in central neural tissue sensitivity to P.     

Effect of a single severe stress on behaviour of males and females in the mouse inbred strains CBA/Lac and C57BL/6J

The effect of single severe stress in the form of forced swimming on the behavior of males and females in the mouse inbred strains CBA/Lac and C57BL/6J were examined in the open field test. Measurements were carried out within two hours after the stress exposure (Trial 1) and repeated 2 hours thereafter (Trial 2). Intact males and females of the both mouse strains which tested in the open field twice too were used as control. An increased latency was found until first escape from the center both in males and females of the CBA/Lac strain within two hours after the end of forced swimming. This parameter was still high in females in the Trial2. Four out of seven behavior parameters were changed in females of the C57BL/6J strain two hours after the stress exposure, but their behavior was similar to control in the Trial 2. The males of the C57BL/6J strain demonstrated the least changed behavior in the open field test after the stress exposure with the exception of increased number of grooming in the Trial 1. Further on, a detailed analysis of repeated testing in the open field within intact and stressed mice of both strains was performed. This comparison allowed revealing hereditary and gender peculiarities in the mouse behavior after single severe stress exposure. The results are discussed in respect to the possible genetically inherent increased traitanxiety in females of C57BL/6J strain and the state of anxiety in females of CBA/Lac strain.     

Participation of embryonic genotype in the pregnancy block phenomenon in mice.

Pregnancy block by male pheromones in mice differs in incidence depending on the combination of strains. Female mice of BALB/cA strain mated with BALB/cA males show a 100% pregnancy block when exposed to males of inbred strain DDK shortly after copulation (Chung et al., Biol Reprod 1997; 57:312-319). In the present study, BALB/cA females mated with the males of other strains--CBA/J, C3H/HeN, C57BL/6Cr, and IXBL--showed higher pregnancy rates (66.6-87. 5%) even when they were exposed to DDK males. In the pharmacological induction of pregnancy block with dopamine agonist (bromocriptine, 4 mg/kg BW), BALB/cA females mated with BALB/cA males showed a 100% pregnancy block. In contrast, BALB/cA females mated with CBA/J, C3H/HeN, and C57BL/6Cr males showed higher pregnancy rates (40-70%). These results suggest that the better pregnancy rate of BALB/cA females mated with alien males may be due to the stronger viability of F(1) embryos. This interpretation was confirmed by an embryo transfer experiment in which a higher implantation rate was observed when BALB/cA embryos grown in BALB/cA females exposed to BALB/cA males were transferred into recipient BALB/cA females exposed to DDK males. These results suggest that the embryonic genotype or viability of the embryo is one factor contributing to the occurrence of pregnancy block by male pheromones in mice.     

Allogeneic matings and immunization have different effects on nulliparous and multiparous mice

CBA/J female mice have a high rate of spontaneous fetal loss when mated with DBA/2 males. We have confirmed that this fetal resorption rate can be significantly reduced by immunizing the female with C57BL rather than DBA leukocytes. The current studies have been extended to show the effect of continued immunization into second pregnancies. Three new findings emerge: second pregnancies in unimmunized CBA/J females X DBA/2 males proceed with a low percentage of spontaneous resorptions; continued immunization of multigravid, multiparous mice is associated with a high percentage of late onset fetal resorptions; and comparison of sex ratios between treated and untreated pregnancies showed no significant shift. These results suggest that untreated CBA/J females mated to DBA/2 males can be immunized to trophoblast antigens during first pregnancies, and that such immunization leads to "normal" reproductive outcome in subsequent untreated pregnancies. Persistent immunization with leukocytes appears to increase the percentage of fetal wastage in subsequent pregnancies regardless of whether the mother receives paternal or nonpaternal leukocytes. Intentional chronic immunization with male leukocytes does not influence the sex ratio of viable offspring. These data are discussed with reference to immunotherapy for women who suffer unexplained, recurrent spontaneous abortions.     

Decline in male mouse pheromone with age

An age-related decline in urinary-borne pheromone was found in male C57BL/6J mice aged from 2 to 30 months. Pheromone activity, estimated by bioassay, declined sharply after about 10 months of age. Two other strains of mice tested (DBA/2J and CBA/HT6J) also appeared to show an age-related decline in pheromone activity. Within each strain, however, pheromone activity was consistently similar to or higher than that of the C57BL/6J male mice. The DBA/2J and BALB/cWt strains appeared to be high pheromone producers, and the C57BL/6J and CBA/HT6J strains, low producers. This report is the first demonstration of a decline with age in male mouse pheromone activity. This decline appears to be synchronized with the well-defined loss of reproductive function in female mice.     

Background matters: the effects of estrogen receptor alpha gene disruption on male sexual behavior are modified by background strain

One approach to study interactions between behavior and genetics is to use inbred mice with different genetic backgrounds. To examine the effect of background on a specific gene, we conducted a series of experiments with a well-characterized knockout (KO) mouse, the estrogen receptor alpha KO (ERalphaKO). The ERalphaKO mouse has so far been examined in one inbred line, C57BL/6J. Here, we examined the behavior of ERalphaKO mice within three different backgrounds mixed with C57BL/6J; DBA/2J, BALB/c, and A/J. First, we assessed masculine sexual behavior in both intact male and testosterone-treated female offspring. More ERalphaKO males in the DBA/2J (5/12) and BALB/c (5/13) backcrosses displayed intromissions and many ejaculated as compared with males in a C57BL/6J and A/J mixed background. Many fewer ERalphaKO females than males displayed masculine sexual behavior in any of the three hybrid crosses. We assessed fertility in males from the C57BL/6J by DBA/2J cross and found that one of 12 ERalphaKO males sired a litter. Several other characteristics of sexual behavior and physiology were unaffected by genetic background in ERalphaKO mice. Our data suggest that genetic background has dramatic effects on male sexual behavior and its dependence on the ERalpha gene.     

Measurement of thymus weight, lumbar node weight and progesterone levels in syngeneically pregnant, allogeneically pregnant, and pseudopregnant mice.

Female CBA mice were mated to fertile CBA males, to vasectomized CBA males, to fertile C57BL males or to vasectomized C57BL males. After allogeneic or syngeneic mating the extent of thymic involution on the 10th day of pregnancy and pseudopregnancy was similar. Lumbar lymph node weight was not affected by pseudopregnancy but increased similarly in allogeneic and syngeneic pregnancies. Serum progesterone levels on the 10th day of pseudopregnancy were similar to those of non-pregnant females, and significantly lower than those of pregnant females. On the 4th to 7th days progesterone levels in pseudopregnant animals were equal to those in pregnant animals. Progesterone levels and thymic involution were similar in syngeneically and allogeneically pregnant females. Progesterone levels were negatively correlated with thymus weight but reached significance only when the mating was allogeneic. It is suggested that there is an interaction between progesterone concentrations and the degree of thymic involution during pregnancy.     

过继转输的父系抗原耐受T细胞诱导受体母-胎免疫耐受的机制研究

To study the effect of adoptive transfer of paternal antigen-tolerant T cells on recipient reactive T cells, CBA/JxDBA/2 mating was recruited as an abortion-prone model, and CBA/JxBALB/c mating as a successful pregnancy model. The abortion-prone CBA/J females mated with DBA/2 males were injected intraperitoneally with rat anti-mouse CD80 and CD86 mAb or rat isotype IgG at day 4 after gestation (time of implantation). The purified T cells were obtained from spleen of the pregnant CBA/J mice using magnetic beads at day 9 after gestation and labeled with CFSE in vitro. The CFSE-labeled T cells were intravenously injected into other CBA/J females mated with DBA/2 males at day 4 after gestation. The proliferation of recipient splenocytes in response to DBA/2 stimulator cells was evaluated at day 9 after gestation in vitro, and the expressions of intracellular cytokines and costimulatory molecules in CFSE +/- T cells were analyzed by flow cytometry. The results showed that adoptive transfer of either paternal antigen-tolerant T cells or T cells from BALB/c-mated CBA/J mice significantly suppressed the proliferation of recipient splenocytes in response to DBA/2 stimulator cells and resulted in lower frequency of cells positive for IL-2, IFN-gamma, CD28 and higher frequency of IL-10,CTLA-4-producing cells in both CFSE+ CD3+ population and CFSE- CD3+ population compared with adoptive transfer of T cells from isotype IgG-treated CBA/J mice, whereas the frequency of IL-4-producing cells did not appear significant change. Our findings suggest that paternal antigen-tolerant T cells transferred in recipient not only function as antigen-specific suppresser cells but also disable the recipient reactive T cells, which co-suppresses maternal rejection to the allogeneic fetus, thus resulting in the decrease of the embryo resorption rate of the abortion-prone mice to that of the normal pregnancy mice.     

Genetic control of sex-chromosomal univalency in the spermatocytes of C57BL/6J and DBA/2J mice

The genetic control of sex-chromosomal univalency was examined in the primary spermatocytes of the mouse. The C57BL/6J strain expresses 3% X-Y univalency and DBA/2J expresses 37% univalency. The reciprocal F1 and the eight types of reciprocal backcross males were examined. In the C57BL/6J--DBA/2J strain pair, X--Y univalency is controlled by three genetic systems. Autosomal factors of unknown number that are dominant in DBA/2J increase the probability of univalency from 3% in C57BL/6J to 12%. The DBA/2J-Y chromosome, in place of the C57BL/6J-Y chromosome, has an additive effect to increase the probability of univalency from 12 to 37% in the DBA/2J strain. Two X-chromosome factors that differ between C57BL/6J and DBA/2J regulate the probability of univalency. The X-chromosome factors appear to be separated by sufficient distance so that, with the DBA/2J-Y chromosome and dominant DBA/2J autosomal factors, there are two recombinant classes of X--Y univalency at 20 and 60%. The genetic factors in the univalency trait may be involved in the regulation or structure of the terminal attachment sites between the X and Y chromosomes.     

DBA/2J and DBA/2Ha lymphocytes differ in their ability to induce graft-vs-host disease

Graft-vs-host disease (GVHD) is a common occurrence after bone marrow transplantation despite the use of MHC-matched donors and recipients. This indicates that non-MHC loci play an important role in the regulation and development of GVHD. Non-MHC loci have been shown to regulate GVHD in a murine model where acute GVHD results from i.v. injection of C57BL/6J spleen cells into B6D2F1/J [C57BL/6J X DBA/2J)F1) recipients while chronic GVHD results from injection of DBA/2J spleen cells. In contrast to the hyperproduction of Ig and auto-antibodies that is characteristic of the chronic GVHD that occurs after injection of DBA/2J cells, injection of DBA/2Ha cells was found to induce CTL and suppressor cells characteristic of the acute GVHD that results from injection of C57BL/6 cells into B6D2F1/J recipients. Genetic analysis indicated that one autosomal locus is responsible for the different GVHD responses of DBA/2J and DBA/2Ha cells and that the DBA/2Ha allele is dominant. Further studies indicate that the different responses by DBA/2J and DBA/2Ha cells is not due to functional differences between the two sets of cells but by a radiosensitive B6D2F1 recipient immune response which discriminates between the DBA/2J and DBA/2Ha spleen cells.     

Preimplantation embryonic mortality--method of studying interstrain differences in the reparative activity of mouse ova

Cytological analysis of preimplantation embryonic death in 101/HY, C57BL/6JY and CBA/lacY females crossed with hybird males F1 (BALB/cYxDBA/2Y) was carried out. Embryonic death was induced by thiophosphamide at a dose of 2 mg/kg, i. p. The maximum preimplantation death was recorded in 101/HY females (38.8%), the minimum in CBA/LacY females (21.9%). In C57BL/6JY females, the maximum preimplantation death accounted for 31.3%. Thus the same chromosome damage induced by thiophosphamide in late spermatids of F1CD2 males caused quantitative differences in embryonic mortality in females of different genotypes. The data obtained evidence that fertilized eggs are capable of repairing part of damage induced by paternal chromosomes. It was demonstrated that the preimplantation embryonic death can be used for studying strain differences from the reparative activity of mouse eggs.     

Variations in the response of five strains of mice to Leishmania mexicana.

Five strains of mice were studied in their ability to support Leishmania mexicana infection. Four strains, AKR, C57BL/6, DBA/2 and NMRI, were relatively resistant to cutaneous leishmaniasis. These strains developed delayed type hypersensitivity responses to leishmanial antigens and produced agglutinating antibodies. On the other hand Balb/c mice, highly susceptible to infection, failed to develop delayed type hypersensitivity responses and showed an impaired production of antibodies. Hybrids produced by mating C57BL/6 males and Balb/c females were no more susceptible than C57BL/6 mice, suggesting that resistance is inherited as a dominant character.     

A sex-limited serum protein variant in the mouse: Hormonal control of phenotypic expression

The sex-limited protein (Slp) antigen of the mouse is first detected in the serum of strain DBA/2J males at 5–6 weeks of age and reaches full adult levels by 10 weeks. This antigen is normally absent in females. Immature DBA/2J males castrated at 3 1/2 weeks of age failed to develop Slp antigen, while DBA/2J females treated with testosterone propionate starting at 3 1/2 weeks developed normal adult male levels of Slp antigen. Similar hormone-influenced effects were demonstrated in adult males and females of the same strain. Experiments indicated that testosterone does not act directly in the serum to expose Slp antigenic sites. Testosterone treatment of both males and females of strain C57BL/10JSf, which does not carry the gene for the presence of the Slp antigen, failed to stimulate the appearance of the antigen. Thus, the presence of Slp antigen in the serum is dependent on both the proper genotype and the presence of male hormone.Supported by U.S.P.H.S. Research Grant GM-15419, U.S.P.H.S. Training Grant 2T01-GM-00071 (H.C.P.), and U.S.P.H.S. Career Development Award K3-HE-24,980 (D.C.S.).     

Genetic control of allogenic inhibition of hematopoietic stem cells]

Adult mice of C57BL/6, CBA (CBA X C57BL/6) F1, (CBA X C57BL/6) F2, F1 X CBA and F1 X C57BL/6 strains were lethally irradiated and reconstituted with a constant dose of 3-10(5) C57BL/6 bone marrow cells. At the 9th day after the bone marrow transplantation the colony count was performed in spleen of irradiated recipients. In the spleen of F1, CBA and C57BL/6 mice were registered low (0--8, intermediate (6--18) and high (22-40) numbers of colonies respectively. The segregation ratios in F2 progeny were close to 2 (low): 1(intermediate): 1(high). The segregation ratios in backcross (F1 X CBA) were close to 1(low): 1(intermediate)numbers of colonies. Backcrosses (F1 X C57BL/6) were distributed to low and high numbers of colonies with the ratio 1:1. The number of spleen colonies of males and females was the same in all segregating progeny. The results of hybrid analysis suggest that a single pair of allelic genes is involved in genetic control of allogenic inhibition, and that the resistance (manifestation of inhibition) to C57BL/6 stem cells is conferred by the dominant allele.     

Cryptosporidium infections in inbred strains of mice.

Cryptosporidium, a protozoan parasite of man and animals, is an important etiological agent of diarrhea throughout the world, particularly in children and immunocompromised individuals such as AIDS patients. Unfortunately, because of the lack of both in vivo laboratory models and reliable in vitro parasite culture systems, virtually nothing is known about the immunological events occurring during disease. In order to identify reliable animal models for infection, we studied C. parvum infections in 19 different strains of mice representing 12 H-2 haplotypes: A/J, AKR/J, B10.D2/J, B10.M/J, C3H/HeJ, C57BL/65, C57BL/6J-bgJ, CBA/NJ, DBA/1J, DBA/2J, HRS/J, HTG/J, NZB/B1NJ, NZW/J, P/J, RIII/J, SJL/J, SWR/J, and WB/ReJ, and in one gerbil: Meriones unguiculatus. Fecal samples and histological sections of the intestine taken on day 7 post-Cryptosporidium inoculation indicated that only the beige mouse (C57BL/6J-bgJ) harbored significant numbers of parasites compared to the other strains. The numbers of parasites harbored in these NK cell-deficient beige mice were, however, considerably lower than those seen in neonatal mice. Adult inbred mouse strains susceptible to Cryptosporidium infections are discussed.     

Genetic and epigenetic factors affecting blastomere fragmentation in two-cell stage mouse embryos

We report here that mouse embryos can exhibit a significant incidence of blastomere fragmentation at the two-cell stage. The incidence of this is influenced by both the maternal and paternal genotype. Embryos from C57BL/6 mothers exhibit a very low incidence of fragmentation at the two-cell stage in crosses involving males of C57BL/6, DBA/2, AKR/J, or SJL strains but exhibit a significantly increased incidence of fragmentation in crosses involving C3H/HeJ males. Increased fragmentation is seen in embryos from C3H/HeJ females crossed with C57BL/6 males but not with C3H/HeJ males. Embryos obtained from reciprocal (C57BL/6 x C3H/HeJ) F1 hybrid females also exhibit an increased incidence of fragmentation at the two-cell stage when the hybrid females are mated to either C57BL/6 or C3H/HeJ males. Interestingly, the results differ significantly between reciprocal F1 hybrid females, indicating a parental origin effect, possibly a result of either genomic imprinting or differences in mitochondrial origin. We conclude that the incidence of blastomere fragmentation at the two-cell stage in the mouse is under the control of more than one genetic locus. We also conclude that blastomere fragmentation is affected by both parental genotypes. These results are relevant to understanding the genetic control blastomere fragmentation, which may contribute to evolutionary processes, affect the success of procedures such as cloning, and affect the outcome of assisted reproduction techniques.     

Gene expression changes in the host response between resistant and susceptible inbred mouse strains after influenza A infection

Inbred mouse strains exhibit differences in susceptibility to influenza A infections. However, the molecular mechanisms underlying these differences are unknown. Therefore, we infected a highly susceptible mouse strain (DBA/2J) and a resistant strain (C57BL/6J) with influenza A H1N1 (PR8) and performed genome-wide expression analysis. We found genes expressed in lung epithelium that were specifically down-regulated in DBA/2J mice, whereas a cluster of genes on chromosome 3 was only down-regulated in C57BL/6J. In both mouse strains, chemokines, cytokines and interferon-response genes were up-regulated, indicating that the main innate immune defense pathways were activated. However, many immune response genes were up-regulated in DBA/2J much stronger than in C57BL/6J, and several immune response genes were exclusively regulated in DBA/2J. Thus, susceptible DBA/2J mice showed a hyper-inflammatory response. This response is similar to infections with highly pathogenic influenza virus and may serve as a paradigm for a hyper-inflammatory host response to influenza A virus.     

Insufficient peroxiredoxin-2 expression in uterine NK cells obtained from a murine model of abortion

The CBA/J × DBA/2 mouse mating combination is prone to spontaneous embryo loss, in contrast to the MHC-identical CBA/J × BALB/c mating combination, which yields successful pregnancies. The underlying mechanisms for these observations are unclear. In this study, multi-vision immunohistochemical staining (IHC), flow cytometry and Western blot analysis were used to detect peroxiredoxin-2 (PRX-2) expression in the uterine natural killer (uNK) cells from CBA/J × DBA/2 and CBA/J × BALB/c mice. In IHC analysis, co-localization of PRX-2 and lectin from Dolichos biflorus agglutinin (DBA-lectin) was confirmed and the frequency of PRX-2(+) DBA-lectin(+) cells was significantly lower in CBA/J × DBA/2 than CBA/J × BALB/c. In flow cytometry and Western blotting, PRX-2 was found expressed at a significantly lower level in CBA/J × DBA/2 mice. PRX-2 inhibition with a neutralizing antibody significantly decreased PRX-2 expression, increased the cytotoxicity of uNK cells, and increased the percentage of embryo loss in CBA/J × DBA/2J mice. Our data suggest that PRX-2 may be involved in the modulation of maternal-fetal tolerance and that insufficient expression of this protein may correlate with increased embryo loss in CBA/J × DBA/2J mice.     

Modification of survival rate of mouse embryos developing in heterozygous females for ovum mutant gene

The DDK syndrome (polar infertility) is caused by an incompatibility system due to the ovum mutant (Om) locus. For brevity, the following gene symbols are used in the present report: DDK allele, Om; C57BL/6Cr allele, +. In this investigation, we first attempted to introduce the Om allele of DDK strain into the genetic background of C57BL/6Cr strain. The attempt resulted in the production of no young at the third generation of successive backcrosses. Secondly, mating experiments were performed with heterozygous (Om/+) females having background genes of C57BL/6Cr and DDK strains in the ratios 1:1(B1D), 3:1(B3D), 7:1(B7D), and 15:1(B15D). The survival rate of the embryos as judged by the percentage number of live fetuses/number of corpora lutea at Day 12 of pregnancy was 41.3 +/- 3.2%, 27.3 +/- 3. 2%, 16.4 +/- 3.3%, and 11.3 +/- 3.2% (mean +/- SEM) in the B1D, B3D, B7D, and B15D females, respectively, when they were mated with C57BL/6Cr males. Furthermore, the increased embryonic mortality in the heterozygous (Om/+) females with more background genes of C57BL/6Cr strain was found to be due to a failure in blastocyst formation, as in the DDK syndrome. The parallelism between the proportion of C57BL/6Cr background genes and embryonic mortality has led to a hypothesis proposing the participation of a modifier gene, namely that a mechanism similar to allelic exclusion may be working in the synthesis of cytoplasmic factor of eggs and that only the Om allele is activated during oogenesis to produce DDK-type cytoplasmic factor in heterozygous (Om/+) females having a modifier gene in the homozygous state.     

Extinction of passive avoidance response in various mouse strains

Dependence of the passive avoidance extinction dynamics on a mouse strain was shown. Mice C57BL/6J and AKR/J extinguished more quickly relative to DBA/2J, CBA/Lac and BALB/c, and this extinction was stable. Individual instability of extinction was characteristic of C3H/HeJ mice. Extinction of the passive avoidance in mice CBA/Lac and BALB/c was slower: with a delay in the beginning and prolonged retention of memory trace of the shock exposure. In DBA/2J mice, the extinction was impaired. These data suggest that DBA/2J, CBA/Lac and BALB/c mice constitute groups of risk with high predisposition to impairment of extinction of memory of aversive events, which is thought to be a symptom of a depressive-like state.