Double Congenic Strain Research Articles

MC4R mutant mice develop ovarian teratomas

Teratomas in mice, composed of different tissue types, are derived from primordial germ cells (PGCs) in the foetal gonads. The strongest candidate gene in the testicular teratoma locus (Ter) responsible for testicular teratoma formation was identified as mutation in Dnd1, Dnd1R178*. However, the phenotype of mice with a mutated Dnd1 gene was germ cell loss. This suggests that other genes are involved in teratoma formation. Testicular teratomas can also be induced experimentally (experimentally testicular teratomas: ETTs) in 129/Sv mice by transplanting E12.5 foetal testes into adult testes. Previously, we mapped the ett1 locus, which is the locus responsible for ETT formation on chromosome 18. By exome sequence analysis of the 129 and LTXBJ (LT) strains, we identified a missense mutation in the melanocortin 4 receptor (MC4R) gene among 8 genes in the ett1 region. The missense mutation causes a substitution of glycine 25 by serine. Thus, this gene is a candidate for ETT formation. We established the LT-ett1 congenic strain, which introduced the locus responsible for ETT formation genetically into the genomes of a testicular teratoma non-susceptible strain. In this study, we crossed LT-ett1 and a previously established LT-Ter strain to establish the double congenic strain LT-Ter-ett1. Also, we established a strain with a point mutation in the MC4R gene of the LT strain by genome editing, LT-MC4RG25S. Furthermore, double genetically modified strain LT-Ter-MC4RG25S was established to address the relation between Ter and MC4R. Surprisingly, highly developed ovarian teratomas (OTs), instead of testicular teratomas, appeared not only in the LT-Ter-MC4RG25S and LT-MC4RG25S strains but also in the LT-ett1 and LT-Ter-ett1 strains. The incidence of OT formation was high in double genetically modified strains. The results demonstrated that MC4R is one of the genes responsible for OT formation. It was suggested that the effect of the missense mutation in MC4R on teratoma formation was promoted by abnormal germ cell formation by the mutation in DND1.

OP.2A.02] FURTHER REDUCTION OF THE WIDTH OF STROKE-SUSCEPTIBILITY QUANTITATIVE TRAIT LOCI AND IDENTIFICATION OF CANDIDATE GENES IN THE STROKE-PRONE SPONTANEOUSLY HYPERTENSIVE RAT

Objective: In the previous study, we identified two major quantitative trait loci (QTLs) for stroke susceptibility on chr 1 and 18 in the stroke-prone spontaneously hypertensive rat (SHRSP). Most of difference in stroke susceptibility between SHR and SHRSP was explained with these two QTLs. In this study, we attempted to narrow down the QTL regions, and to identify candidate genes in the target regions. Design and method: Sixteen subcongenic and double subcongenic strains were established to cover the QTLs on chr 1 and 18. Stroke susceptibility was evaluated by stroke latency under 1% salt loading. Sequence variations in coding regions of genes were analyzed on whole-genome sequence data of SHRSP and SHR, and confirmed with direct sequencing. Comprehensive gene expression analysis was done on kidney tissue from SHRSP, SHR and two double congenic strains for the QTLs on chr 1 and 18 with Rat GE 44K microarray slides (v.3, Agilent Technologies). The results were confirmed with RT-PCR. Results: Analysis of stroke latency in a double subcongenic strain confirmed that the QTLs for the stroke susceptibility were in a 68 Mbp region on chr 1 and a 20 Mbp region on chr 18. Analysis on subcongenic strains covering these regions suggested that the most probable candidate region on chr 1 was a 240 kbp fragment between D1Got80 and Rat33. Microarray analysis indicated that expression of 3 genes in this region differed significantly between SHRSP and SHR as well as between the two double congenic strains in which the QTLs on chr 1 and 18 were reciprocally exchanged. In addition, analysis on the whole-genome sequence data suggested that 2 genes in this candidate region harbored a missense variant between SHR and SHRSP. In contrast to the QTL on chr 1, it was difficult to narrow down the QTL on chr 18. Conclusions: In conclusion, we successfully narrowed down the QTL on chr 1 and identified several candidate genes in the region. The QTL on chr 18 might harbor multiple causative genes that made the analysis difficult.

New animal models reveal that coenzyme Q2 (Coq2) and placenta-specific 8 (Plac8) are candidate genes for the onset of type 2 diabetes associated with obesity in rats.

Obesity is a major risk factor for the onset of type 2 diabetes; however, little is known about the gene(s) involved. Therefore, we developed new animal models of obesity to search for diabetogenic genes associated with obesity. We generated double congenic rat strains with a hyperglycaemic quantitative trait locus (QTL) derived from the Otsuka Long-Evans Tokushima Fatty rat and a fa/fa (Lepr-/-) locus derived from the Zucker Fatty rat; phenotypic analysis for plasma glucose and insulin levels and RNA and protein levels were determined using reverse transcription quantitative PCR and Western blotting analyses, respectively. The double congenic strain F344-fa-nidd2 (Lepr-/- and Nidd2/of) exhibited significantly higher glucose levels and significantly lower hypoglycaemic response to insulin than the obese control strain F344-fa (Lepr-/-). These phenotypes were clearly observed in the obese strains but not in the lean strains. These results indicate that the Nidd2/of locus harbours a diabetogenic gene associated with obesity. We measured the expression of 60 genes in the Nidd2/of QTL region between the strains and found that the mRNA expression levels of five genes were significantly different between the strains under the condition of obesity. However, three of the five genes were differentially expressed in both obese and lean rats, indicating that these genes are not specific for the condition of obesity. Conversely, the other two genes, coenzyme Q2 (Coq2) and placenta-specific 8 (Plac8), were differentially expressed only in the obese rats, suggesting that these two genes are candidates for the onset of type 2 diabetes associated with obesity in rats.

Susceptibility to seizure-induced excitotoxic cell death is regulated by an epistatic interaction between Chr 18 (Sicd1) and Chr 15 (Sicd2) loci in mice.

Seizure-induced cell death is believed to be regulated by multiple genetic components in addition to numerous external factors. We previously defined quantitative trait loci that control susceptibility to seizure-induced cell death in FVB/NJ (susceptible) and C57BL/6J (resistant) mice. Two of these quantitative trait loci assigned to chromosomes 18 (Sicd1) and 15 (Sicd2), control seizure-induced cell death resistance. In this study, through the use of a series of novel congenic strains containing the Sicd1 and Sicd2 congenic strains and different combinations of the Sicd1 or Sicd2 sub region(s), respectively, we defined these genetic interactions. We generated a double congenic strain, which contains the two C57BL/6J differential segments from chromosome 18 and 15, to determine how these two segments interact with one another. Phenotypic comparison between FVB-like littermates and the double congenic FVB.B6-Sicd1/Sicd2 strain identified an additive effect with respect to resistance to seizure-induced excitotoxic cell death. It thus appears that C57BL/6J alleles located on chromosomes 18 and 15 interact epistatically in an additive manner to control the extent of seizure-induced excitotoxic cell death. Three interval-specific congenic lines were developed, in which either segments of C57BL/6J Chr 18 or C57BL/6J Chr 15 were introduced in the FVB/NJ genetic background, and progeny were treated with kainate and examined for the extent of seizure-induced cell death. All of the interval-specific congenic lines exhibited reduced cell death in both area CA3 and the dentate hilus, associated with the C57BL/6J phenotype. These experiments demonstrate functional interactions between Sicd1 and Sicd2 that improve resistance to seizure-induced excitotoxic cell death, validating the critical role played by gene-gene interactions in excitotoxic cell death.

Tumor loci and their interactions on mouse chromosome 19 that contribute to testicular germ cell tumors.

BackgroundComplex genetic factors underlie testicular germ cell tumor (TGCT) development. One experimental approach to dissect the genetics of TGCT predisposition is to use chromosome substitution strains, such as the 129.MOLF-Chr 19 (M19). M19 carries chromosome (Chr) 19 from the MOLF whereas all other chromosomes are from the 129 strain. 71% of M19 males develop TGCTs in contrast to 5% in 129 strain. To identify and map tumor loci from M19 we generated congenic strains harboring MOLF chromosome 19 segments on 129 strain background and monitored their TGCT incidence.ResultsWe found 3 congenic strains that each harbored tumor promoting loci that had high (14%-32%) whereas 2 other congenics had low (4%) TGCT incidences. To determine how multiple loci influence TGCT development, we created double and triple congenic strains. We found additive interactions were predominant when 2 loci were combined in double congenic strains. Surprisingly, we found an example where 2 loci, both which do not contribute significantly to TGCT, when combined in a double congenic strain resulted in greater than expected TGCT incidence (positive interaction). In an opposite example, when 2 loci with high TGCT incidences were combined, males of the double congenic showed lower than expected TGCT incidence (negative interaction). For the triple congenic strain, depending on the analysis, the overall TGCT incidence could be additive or could also be due to a positive interaction of one region with others. Additionally, we identified loci that promote bilateral tumors or testicular abnormalities.ConclusionsThe congenic strains each with their characteristic TGCT incidences, laterality of tumors and incidence of testicular abnormalities, are useful for identification of TGCT susceptibility modifier genes that map to Chr 19 and also for studies on the genetic and environmental causes of TGCT development. TGCTs are a consequence of aberrant germ cell and testis development. By defining predisposing loci and some of the locus interactions from M19, this study further advances our understanding of the complex genetics of TGCTs, which is the most common cancer in young human males.

Genetic Interaction between Hyperglycemic QTLs Is Manifested under a High Calorie Diet in OLETF-Derived Congenic Rats

The condition of hyperglycemia results from multiple genetic and environmental factors. In recent years much progress has been made with regards to the search for candidate genes involved in the expression of various common diseases including type 2 diabetes. However less is known about the specific genetic and environmental connections that are important for the development of the disease. In the present study, we used hyperglycemic congenic rats to address this issue. When given a normal diet, two hyperglycemic QTLs (quantitative trait locus), Nidd2/of and Nidd10/of, showed mild obesity and/or increased blood glucose in the oral glucose tolerance test. In a double congenic strain possessing both loci, these indices were not significantly different from those of either single congenic strain. In contrast, the double congenic strain fed a high-calorie diet showed significantly greater body weight than the single congenic strains or normoglycemic control rats. Although postprandial glucose levels of the double congenic rat were not further aggravated even on the high fat diet, it was notable that the postprandial insulin levels were drastically elevated. From these results, we constructed a novel model animal especially for the study of prediabetic hyperinsulemia, in which two QTLs and an additional dietary condition are involved. This may help to shed light on the genetic basis and gene-to-diet interaction during the early stage of type 2 diabetes.

Genetic Loci Modulate Macrophage Activity and Glomerular Damage in Experimental Glomerulonephritis

The Wistar Kyoto (WKY) rat is uniquely susceptible to experimentally induced crescentic glomerulonephritis. Two major quantitative trait loci (QTLs) on chromosomes 13 (Crgn1) and 16 (Crgn2) with logarithm of odds >8, as well as five other loci (Crgn3 through 7), largely explain this genetic susceptibility. To understand further the effects of Crgn1 and Crgn2, we generated a double-congenic strain by introgressing these loci from glomerulonephritis-resistant Lewis rats onto the WKY genetic background. Induction of nephrotoxic nephritis in the double-congenic rats (WKY.LCrgn1,2) produced markedly fewer glomerular crescents, reduced macrophage infiltration, and decreased expression of glomerular TNF-alpha and inducible nitric oxide synthase expression compared with control animals. Bone marrow and kidney transplantation studies between parental and WKY.LCrgn1,2 strains, together with in vitro experiments, demonstrated that Crgn1 and Crgn2 contribute exclusively to circulating cell-related glomerular injury by regulating macrophage infiltration and activation. The residual genetic susceptibility to crescentic glomerulonephritis in WKY.LCrgn1,2 rats associated with macrophage activity (especially with enhanced metalloelastase expression) rather than macrophage infiltration. Taken together, these results demonstrate that a genetic influence on macrophage activation, rather than number, determines glomerular damage in immune-mediated glomerulonephritis.

Contrasting epistatic interactions between rat quantitative trait loci controlling mammary cancer development

We previously defined quantitative trait loci (QTLs) that control susceptibility to 7,12-dimethylbenz(alpha)anthracene-induced mammary carcinoma in SPRD-Cu3 (susceptible) and WKY (resistant) rats. Two of these QTLs, assigned to chromosomes (Chr) 10 and 18, control tumor growth rate and invasiveness. In this study we characterized a congenic strain in which a large segment of WKY Chr 10 was introduced in the SPRD-Cu3 genetic background and demonstrated that this chromosome segment controls this tumor trait. The WKY allele at this QTL (Mcsta1) reduces the growth rate of the fastest growing tumors by 26%. We also previously showed that two SPRD-Cu3-WKY congenic strains containing a WKY chromosome segment derived either from Chr 5 or from Chr 18 exhibit a reduction in tumor multiplicity (QTLs Msctm1 and Mcstm2, respectively) (with no reduction in tumor growth rate in the Chr 18 congenic). In this study we generated a double congenic strain, which contains the two WKY differential segments from Chr 5 and 18, to determine how these two segments interact with one another. Interestingly, two types of epistatic interactions were found: no additive effect was seen with respect to tumor multiplicity, while a reduction in tumor growth rate was observed. It thus appears that WKY alleles located on Chr 5 and Chr 8 interact epistatically in a contrasting manner to modulate tumor multiplicity (in a nonadditive manner) and growth rate (in a synergic manner). Tumor growth rate is thus influenced by two QTLs, on Chr 10 (Mcsta1) and on Chr 18 (Mcsta2), the action of the latter being dependent on the presence of the Chr5 QTL (Mcstm1). The expression level of positional and functional candidate genes was also analyzed. On Chr 5, Pla2g2a is subject to a syntenic control while expression of the Tp53 (Chr 10) and Pmai1/Noxa (Chr 18) genes appears to be controlled by several mammary cancer resistance QTLs.

Abstract 2732: Interacting Blood Pressure Loci in the Stroke-Prone Spontaneously Hypertensive Rat.

Background: In a previous genome wide linkage study we identified blood pressure quantitative trait loci (QTL) mapping to rat chromosome 2 and chromosome 3 in an F2 cross derived from SHRSP and WKY strains. We also identified a significant interaction between loci on chromosomes 2 and 3 using Pseudomarker (v 0.9) statistical framework. The aim of this study was to generate a double congenic strain to confirm chromosome 3 QTL and investigate the interaction between loci on the implicated chromosomes. Methods : A marker-assisted breeding strategy was used to generate the SP.WKYGla2a/3a double congenic strain (D2Rat13-D2Rat157, D3Mgh16-D3Wox28), using SHRSP as recipient and WKY as the donor strain. Haemodynamic measurements were carried out using radiotelemetry over a 5-week baseline period followed by 3 weeks of salt-loading (1%). Results : Radiotelemetry data for systolic blood pressure and pulse pressure are illustrated in figure a + b respectively. Systolic blood pressure was significantly reduced in the SP.WKYGa2a/3a strain (n=7) compared to SHRSP (n=13) (p = 0.0001, F = 97.77, repeated measures ANOVA). Pulse pressure was also significantly reduced compared to SHRSP (p=0.0001, F=34.17) and achieved levels comparable to WKY (n=10). Pulse pressure diurnal variation observed in SHRSP during salt-loading was abolished in the double congenic strain (AUC; p=0.0001, F=13.56). Conclusions : Almost complete reversal of SHRSP hypertensive haemodynamic profiles has been achieved in the SP.WKYGla2a/3a double congenic strain. This strain will allow interrogation of complex gene-gene, gene-environment interactions contributing to salt-sensitive hypertension in the SHRSP.

Novel double-congenic strain reveals effects of spontaneously hypertensive rat chromosome 2 on specific lipoprotein subfractions and adiposity

We have developed a new, double-congenic rat strain BN-Lx.SHR2, which carries two distinct segments of chromosome 2 introgressed from the spontaneously hypertensive rat strain (SHR) into the genetic background of congenic strain BN-Lx, which was previously shown to express variety of metabolic syndrome features. In 16-wk-old male rats of BN-Lx and BN-Lx.SHR2 strains, we compared their glucose tolerance and triacylglycerol and cholesterol concentrations in 20 lipoprotein subfractions and the lipoprotein particle sizes under conditions of feeding standard and high-sucrose diets. Introgression of two distinct SHR-derived chromosome 2 segments resulted in decreased adiposity together with aggravation of glucose intolerance in the double-congenic strain. The BN-Lx.SHR2 rats were more sensitive to sucrose-induced rise in triacylglycerolemia. Although the total cholesterol concentrations of the two strains were comparable after the standard diet and even lower in BN-Lx.SHR2 after sucrose feeding, detailed analysis revealed that under both dietary conditions, the double-congenic strain had significantly higher cholesterol concentrations in low-density lipoprotein fractions and lower high-density lipoprotein fractions. We established a new inbred model showing dyslipidemia and mild glucose intolerance without obesity, attributable to specific genomic regions. For the first time, the chromosome 2 segments of SHR origin are shown to influence other than blood pressure-related features of metabolic syndrome or to be involved in relevant nutrigenomic interactions.

Interaction between blood pressure quantitative trait loci in rats in which trait variation at chromosome 1 is conditional upon a specific allele at chromosome 10

We have used inbred and congenic rat strains in F2 segregation studies to discover epistasis in a polygenic model of hypertension. Previously, we have found evidence that the presence of a blood pressure quantitative trait locus (QTL) on chromosome 1 is conditional upon the allele status of chromosome 10. To prove the existence of an epistatic interaction we have analyzed congenic strains for chromosome 1 and 10 carrying high blood pressure QTL alleles from the spontaneously hypertensive rat on a normotensive background of the Wistar–Kyoto (WKY) rat. Additionally, a double congenic strain was developed with both chromosome 1 and 10 high blood pressure QTL alleles on the WKY background. Analysis of variance for blood pressure phenotypes as determined by radiotelemetry showed a significant effect for chromosome 10 but not chromosome 1 QTL alleles and demonstrated a significant interaction between the two loci (P<0.05). The interaction accounted for 5 mmHg of blood pressure. Thus, the identification of epistasis is critical to the understanding of the quantitative nature of blood pressure genetics.

Interaction between blood pressure quantitative trait loci in rats in which trait variation at chromosome 1 is conditional upon a specific allele at chromosome 10.

We have used inbred and congenic rat strains in F(2) segregation studies to discover epistasis in a polygenic model of hypertension. Previously, we have found evidence that the presence of a blood pressure quantitative trait locus (QTL) on chromosome 1 is conditional upon the allele status of chromosome 10. To prove the existence of an epistatic interaction we have analyzed congenic strains for chromosome 1 and 10 carrying high blood pressure QTL alleles from the spontaneously hypertensive rat on a normotensive background of the Wistar-Kyoto (WKY) rat. Additionally, a double congenic strain was developed with both chromosome 1 and 10 high blood pressure QTL alleles on the WKY background. Analysis of variance for blood pressure phenotypes as determined by radiotelemetry showed a significant effect for chromosome 10 but not chromosome 1 QTL alleles and demonstrated a significant interaction between the two loci (P<0.05). The interaction accounted for 5 mmHg of blood pressure. Thus, the identification of epistasis is critical to the understanding of the quantitative nature of blood pressure genetics.

Testicular cancer susceptibility in the 129.MOLF-Chr19 mouse strain: additive effects, gene interactions and epigenetic modifications.

Testicular germ cell tumors (TGCTs) are the most common solid cancers affecting young men. Although the evidence for genetic predisposition to TGCTs in humans is compelling, the genetic control of susceptibility is poorly understood. The 129S1/SvImJ (129/Sv) inbred strain of mice is an excellent model for studying TGCT susceptibility. We previously reported a new mouse strain, the 129.MOLF-Chr19 chromosome substitution strain, which develops spontaneous TGCTs at a high frequency (70-80%) as compared with the much lower rate in the 129/Sv strain (5%). To characterize the genetic control of TGCT susceptibility, we created a panel of single- and double-congenic strains derived from 129.MOLF-Chr19. The frequency of TGCTs in these strains suggests that several genes with additive and epistatic effects located at distinct sites on chromosome 19 control susceptibility. However, an alternative interpretation involving epigenesis is based on a striking correlation between TGCT frequency and the length of the MOLF-derived congenic segment, regardless of their chromosomal location on Chr 19 in each congenic strain. We also show that bilateral TGCT cases result from the coincidental co-occurrence of unilateral TGCTs rather than from the action of distinct genes that control susceptibility to bilateral versus unilateral TGCT cases. Finally, we propose that these TGCTs result from disrupted testicular and spermatogenic developmental programs.

Statistical modeling of interlocus interactions in a complex disease: rejection of the multiplicative model of epistasis in type 1 diabetes.

In general, common diseases do not follow a Mendelian inheritance pattern. To identify disease mechanisms and etiology, their genetic dissection may be assisted by evaluation of linkage in mouse models of human disease. Statistical modeling of multiple-locus linkage data from the nonobese diabetic (NOD) mouse model of type 1 diabetes has previously provided evidence for epistasis between alleles of several Idd (insulin-dependent diabetes) loci. The construction of NOD congenic strains containing selected segments of the diabetes-resistant strain genome allows analysis of the joint effects of alleles of different loci in isolation, without the complication of other segregating Idd loci. In this article, we analyze data from congenic strains carrying two chromosome intervals (a double congenic strain) for two pairs of loci: Idd3 and Idd10 and Idd3 and Idd5. The joint action of both pairs is consistent with models of additivity on either the log odds of the penetrance, or the liability scale, rather than with the previously proposed multiplicative model of epistasis. For Idd3 and Idd5 we would also not reject a model of additivity on the penetrance scale, which might indicate a disease model mediated by more than one pathway leading to beta-cell destruction and development of diabetes. However, there has been confusion between different definitions of interaction or epistasis as used in the biological, statistical, epidemiological, and quantitative and human genetics fields. The degree to which statistical analyses can elucidate underlying biologic mechanisms may be limited and may require prior knowledge of the underlying etiology.

Construction of a double congenic strain to prove an epistatic interaction on blood pressure between rat chromosomes 2 and 10.

Previously we presented suggestive evidence from an F2 segregating population for an interaction on blood pressure (BP) between quantitative trait loci (QTL) on rat chromosomes (Chr) 2 and 10. To prove the existence of such an interaction, we developed congenic strains for Chr 2 and 10 by introgressing the low BP QTL alleles into the Dahl salt-sensitive (S) strain. A double congenic strain was also constructed with both the Chr 2 and 10 low BP QTL alleles on the S background. The four strains (S, Chr 2 congenic, Chr 10 congenic, and Chr 2/10 double congenic) were studied for BP response to increased salt intake. An analysis of variance showed significant main effects of Chr 2, Chr 10, and a significant interaction between Chr 2 and 10 on BP and heart weight (all P < 0.0001). The interaction accounted for 24 mmHg of BP and 79 mg of heart weight. Thus, the discovery and proof of epistatic interactions are clearly critical to understanding the genetics of blood pressure.

The C57BL/6 nude, beige mouse: a model of combined T cell and NK effector cell immunodeficiency.

This article describes the construction and establishment of a double congenic nude, beige C57BL/6 (B6 nu, bg) mouse strain. The mice do not show higher fragility than C57BL/6 nude mice and the double congenic strain can be maintained under conventional mouse housing conditions. Although the B6 nu, bg display a very low natural killer activity which cannot be enhanced by an interferon inducer (poly(I-C], they lack responsiveness to a T cell mitogen (concanavalin A); and they also show extremely low responsiveness to a B cell mitogen (0128: B12 Escherichia coli lipopolysaccharide) probably as a result of combined effects of the beige and nude genes in the C57BL/6 genetic context.

The CH series of murine B cell lymphomas: identification of cross-reactive idiotypes and restricted antigen specificities.

Mice of the double congenic strain, B10.H-2aH-4bp/Wts (2a4b), display a high incidence of lymphoma following intense adoptive immunization with sheep erythrocytes (SRBC). The tumors which arise comprise a heterogenous group, including the UNC series of T cell lymphomas (Corley 1983), the CH series of B cell lymphomas (Lanier 1982), and a set of lymphomas which are not readily characterized as belonging to either the B cell or T cell lineage (unpublished data). Presently available data are insufficient to define the etiology of this disease, but we previously had found that heterologous anti-idiotype sera raised against the surface IgM of CHI and of CH2 each reacted with one other of the first 11 B cell lymphomas described (CH9 and CH5, respectively) (Arnold 1982). This suggested that a limited subset of the total normal idiotype repertoire might be expressed by CH lymphomas. We also had found that the surface immunoglobulin of CH12 was specifically reactive with an epitope present on SRBC, suggesting that adoptive immunization had led to the expansion of a subset of B cells with neoplastic potential (Arnold 1983).

Use of H-2:H-7 congenic mice to study H-2-mediated resistance to Friend leukemia virus.

Congenic and double congenic mice expressing different H-7 alleles with varying H-2 haplotypes on the C57BL/10 (B10) background were tested for their susceptibility to Friend virus (FV) infection. Mice expressing the H-7b allele derived from BALB/c were susceptible to FV infection whereas mice expressing the H-7a allele of B10 were absolutely resistant. Coexpression of H-7b and the H-2a and H-2d haplotypes determined high susceptibility; mice expressing both H-7b and H-2b were relatively resistant compared to H-7b mice expressing H-2a or H-2d. Parallel experiments with BALB/c and BALB.B recipients did not demonstrate differences in susceptibility associated with H-2d and H-2b. Mapping experiments with the H-2h4 and H-2i5 recombinants indicated that the gene determining relative resistance to FV-induced spleen focus formation mapped to the K-end (KbAb) of H-2b. Female recipients expressing H-7b, regardless of their H-2 haplotype, were more susceptible to FV infection than their syngeneic male counterparts. These experiments demonstrate the utility of congenic and double congenic strains that define H-7 and Fv-2 on different H-2 haplotype backgrounds for the analysis of Fv-2:H-7:H-2 interactions in determining susceptibility to FV infection.

Antigen-Induced Murine B Cell Lymphomas

Abstract Two unusual murine lymphomas, designated CH1 and CH2, were produced in the newly developed double congenic strain of mice, B10 H-2a H-4bp/Wts. Both tumors lack the T cell-specific antigen (thy-1), but express cell surface immunoglobulin and the H-2K, H-2D, and Ia specificities determined by the H-2a haplotype. Further studies have demonstrated that these tumors represent “early” B cells in that they express surface IgM (µ heavy and λ light chains), but do not bear surface δ, γ, or α heavy chains. CH1 and CH2 lack surface C3 receptors and results from assays for Fc receptors have proven variable. A competition radioimmunoassay directed against the gp71 group-specific antigen of Friend leukemia virus has shown that there is a murine leukemia virus associated with these tumors, however, we have been unable to establish a causal relationship between the virus and this malignancy. A comparison of the surface characteristics of these tumors with other mammalian B cell lymphomas is presented.

The production, testing, and utility of double congenic mouse strains

Two new double congenic strains, B10-H-2 a H-7 b /Wts and B10-H-2 d H-7 b /Wts, were selected to differ from B10.A and B10.D2/o, respectively, at theH-7 locus. The survival time ofH-7-incompatible skin grafts is dependent upon theH-2 haplotype of recipient and donor.