Consomic Mice Research Articles

B6-MSM Consomic Mouse Strains Reveal Multiple Loci for Genetic Variation in Sucrose Octaacetate Aversion

Based on crosses among inbred strains derived principally from M. m. domesticus, sucrose octaacetate (SOA) aversion in laboratory mice has been thought for many years to be controlled by a single genetic locus (Soa) located on distal chromosome (Chr) 6. To expand knowledge of the genetic basis underlying SOA aversion, we have studied the M. m. molossinus derived strain (MSM) and MSM consomic strains on a M. m. domesticus (C57BL/6J: B6) host background. Using two-bottle preference procedures, MSM mice avoided 0.1mM and 1mM SOA while B6 mice were indifferent to 0.1mM and exhibited slight aversion to 1mM SOA. Preference tests of 16 available consomic strains implicated Chr 2, 4 and 15 in SOA aversion in addition to the prominent effect of the known Soa locus on Chr 6 (implicated by study of two congenic strains). The originally defined Soa locus is presumably associated with one or more members of the cluster of Tas2r genes on distal Chr 6 that code for bitter taste receptors. Our results point to the possible role of established Tas2r genes on Chr 2 and 15, as well as to genes not coding for bitter receptors (Chr 4), in SOA aversion. SOA aversion emerges from this consomic screen as being definitively under polygenic control. The genetic diversity captured by the MSM model system is shown to be a valuable tool to complement the limited genetic variation in the commonly used stocks derived from M m. domesticus.

Reduced Dental Caries Susceptibility in Chromosome 2-Substituted Consomic Mice

In this study, to clarify the effects on dental caries susceptibility of mouse chromosome 2 in vivo, we used chromosome 2 substitution mice (termed consomic mice), B6-Chr2C3H. The consomic mice used in this study were based on high dental caries susceptibility strain C57BL/6CrSlc (B6), and only chromosome 2 from the low dental caries susceptibility strain C3H/HeSlc (C3H) was substituted. We induced dental caries in three inbred mice strains : B6, C3H and B6-Chr2C3H. All mice were weaned at 21 days, were fed on Diet#2000, and were infected with Streptococcus mutans JC-2 to induce dental caries. The mandible bones were extracted at 49 days and observed by microscope and Micro-focus X-ray computed tomography images. The caries status was evaluated by calculating the dental caries score using the modified Keyes method. Mean dental caries scores of B6-Chr2C3H, B6 and C3H were 8.1±3.4 (mean±S.D.), 46.5±1.3 and 2.2±1.0, respectively. Statistical analysis revealed that the dental caries score of B6-Chr2C3H was significantly low compared with the score of B6 and there was no difference in dental caries score between C3H and B6-Chr2C3H. The first fissures of the first molar in B6 and B6-Chr2C3H were similar having a slight fossa at center area and which were differ from that of C3H. However, there was no significant difference in dental caries score at the fissure among B6-Chr2C3H, B6 and C3H. And, the amount of saliva of B6-Chr2C3H was significantly low than C3H, and significantly high than B6. These results suggested that the major genetic factor responsible for dental caries susceptibility is located on mouse chromosome 2.

Deficiency of Splicing Factor 1 Suppresses the Occurrence of Testicular Germ Cell Tumors

Testicular germ cell tumors (TGCT) originate from germ cells. The 129-Ter and M19 (129.MOLF-Chr19 consomic) mouse strains have extremely high incidences of TGCTs. We found that the expression levels of Sf1-encoded splicing factor 1 (SF1) can modulate the incidence of TGCTs. We generated mice with inactivated Sf1. Sf1 null mice (Sf1-/-) died before birth. Mice with one intact allele of Sf1 (Sf1+/-) were viable but expressed reduced levels of Sf1. When Sf1-deficient mice (Sf1+/-) were crossed to the 129-Ter and M19 strains, we observed decreased incidence of TGCTs in Sf1+/-;Ter and Sf1+/-;M19/+ mice compared with that in control cohorts. Therefore, Sf1 deficiency protects against TGCT development in both strains. Sf1 is expressed in the testes. We found that Sf1 levels vary significantly in the testes of inbred strains such as 129 and MOLF, and as such Sf1 is an oncogenic tumor-susceptibility factor from 129. Our results also highlight the complications involved in evaluating Sf1 levels and TGCT incidences. When a large number of tumor-promoting factors are present in a strain, the protective effect of lower Sf1 levels is masked. However, when the dosage of tumor-promoting factors is reduced, the protective effect of lower Sf1 levels becomes apparent. SF1 is involved in splicing of specific pre-mRNAs in cells. Alternate splicing generates the complex proteosome in eukaryotic cells. Our data indicate that Sf1 levels in mouse strains correlate with their incidences of TGCTs and implicate the importance of splicing mechanisms in germ cell tumorigenesis.

Direct evidence for susceptibility genes for type 2 diabetes on mouse chromosomes 11 and 14

Diabetogenic loci for type 2 diabetes have been mapped to mouse chromosome (Chr) 11 and 14 in the Nagoya-Shibata-Yasuda (NSY) mouse, an animal model of type 2 diabetes. We aimed to obtain direct evidence of these genes on each chromosome and to clarify their function and interaction in conferring susceptibility to type 2 diabetes. We established three consomic strains homozygous for diabetogenic NSY-Chr11, NSY-Chr14 or both on the control C3H background (C3H-11(NSY), C3H-14(NSY) and C3H-11(NSY)14(NSY), respectively), and monitored diabetes-related phenotypes longitudinally. The glucokinase gene was sequenced as a positional candidate gene on Chr11. C3H-11(NSY) mice showed hyperglycaemia associated with impaired insulin secretion and age-dependent insulin resistance without obesity. C3H-14(NSY) mice exhibited hyperglycaemia mainly due to insulin resistance, with a slight increase in percentage body fat. C3H-11(NSY)14(NSY) double consomic mice showed marked hyperglycaemia and obesity, which was not observed in single consomic strains. Sequences of the glucokinase gene were allelically variant between NSY and C3H mice. These data provide direct evidence that Chr11 and Chr14 harbour major susceptibility genes for type 2 diabetes. These two chromosomes interact to cause more severe hyperglycaemia and obesity, which was not observed with the presence of either single chromosome, indicating different modes of gene-gene interaction depending on the phenotype. Marked changes in the phenotypes retained in the consomic strains will facilitate fine mapping and the identification of the responsible genes and their interaction with each other, other genes and environmental factors.

Genetic Mapping of Social Interaction Behavior in B6/MSM Consomic Mouse Strains

Genetic studies are indispensable for understanding the mechanisms by which individuals develop differences in social behavior. We report genetic mapping of social interaction behavior using inter-subspecific consomic strains established from MSM/Ms (MSM) and C57BL/6J (B6) mice. Two animals of the same strain and sex, aged 10 weeks, were introduced into a novel open-field for 10 min. Social contact was detected by an automated system when the distance between the centers of the two animals became less than ~12 cm. In addition, detailed behavioral observations were made of the males. The wild-derived mouse strain MSM showed significantly longer social contact as compared to B6. Analysis of the consomic panel identified two chromosomes (Chr 6 and Chr 17) with quantitative trait loci (QTL) responsible for lengthened social contact in MSM mice and two chromosomes (Chr 9 and Chr X) with QTL that inhibited social contact. Detailed behavioral analysis of males identified four additional chromosomes associated with social interaction behavior. B6 mice that contained Chr 13 from MSM showed more genital grooming and following than the parental B6 strain, whereas the presence of Chr 8 and Chr 12 from MSM resulted in a reduction of those behaviors. Longer social sniffing was observed in Chr 4 consomic strain than in B6 mice. Although the frequency was low, aggressive behavior was observed in a few pairs from consomic strains for Chrs 4, 13, 15 and 17, as well as from MSM. The social interaction test has been used as a model to measure anxiety, but genetic correlation analysis suggested that social interaction involves different aspects of anxiety than are measured by open-field test.Electronic supplementary materialThe online version of this article (doi:10.1007/s10519-009-9312-x) contains supplementary material, which is available to authorized users.

Parent-of-origin effects on cardiac response to pressure overload in mice

Left ventricular (LV) hypertrophy (LVH) is an independent risk factor for cardiovascular mortality and is commonly caused by hypertension. In rodents, transverse aortic constriction (TAC) is a model regularly employed in mechanistic studies of the response of the LV to pressure overload. We previously reported that inbred strains of male mice manifest different cardiac responses to TAC, with C57BL/6J (B6) developing LV dilatation and impaired contractility and 129S1/SvImJ (129) males displaying concentric LVH. In the present study, we investigated sex and parent-of-origin effects on the response to TAC by comparing cardiac function, organ weights, expression of cardiac hypertrophy markers, and histology in female B6 and female 129 mice and in F1 progeny of reciprocal crosses between B6 and 129 mice (B6129F1 and 129B6F1). Five weeks after TAC, heart weight increased to the greatest extent in 129B6F1 mice and the least extent in 129 and B6129F1 mice. Female 129B6F1 and B6 mice were relatively protected from the increase in heart weight that occurs in their male counterparts with pressure overload. The response to TAC in 129 consomic mice bearing the B6 Y chromosome resembled that of 129 rather than 129B6F1 mice, indicating that the B6 Y chromosome does not account for the differences in the reciprocal cross. Our results suggest that susceptibility to LVH is more complex than simple Mendelian inheritance and that parental origin effects strongly impact the LV response to TAC in these commonly used inbred strains.

A Y-chromosome factor impairs iNKT cell development (85.15)

Abstract Invariant Natural Killer T (iNKT) cells are a fairly recently discovered unique subset of T lymphocytes. These granular cells are derived from the thymus and share properties of both NK and T cells. iNKT cell development is unique from mainstream T cell selection and the polygenic factors that influence NK T cell ontogeny are still unclear. Previous studies done in our laboratory has shown the absence of iNKT cells in male B6.IFN-αβR1-/- mice. Analysis of the iNKT cell compartment in a variety of mice demonstrated that the deficiency was linked to the Y-chromosome but independent of IFN-αβ. Here, we generated wild-type male B6 mice carrying the YNKT-chromosome as well as male B6.IFN-αβR1-/- mice that do not carry the YNKT-chromosome. We found that wild-type B6 (YNKT) male mice have a strong decrease in iNKT cell frequency. In contrast, the B6.IFN-αβ R1-/- male mice have a relatively normal repertoire, confirming that the deficiency is linked to the Y-chromosome and is independent of IFN-α/β In addition, preliminary data using two different strains of B6 consomic mice for the Y-chromosome show that they have a normal iNKT cell repertoire. This suggests that a consomic Y chromosome is not sufficient to influence iNKT cell development. We are currently investigating whether the phenotype observed is due to a Y chromosome mutation or an epistatic interaction with other genes. This work was supported by the National Institutes of Health Research Grant AI46709.

A Role for Stroma-Derived Annexin A1 as Mediator in the Control of Genetic Susceptibility to T-Cell Lymphoblastic Malignancies through Prostaglandin E2 Secretion

Cancer susceptibility is essentially attributable to multiple low-penetrance genes. Using interspecific consomic and congenic mice between the tumor-resistant SEG/Pas and the tumor-sensitive C57BL/6J strains, a region on chromosome 19 involved in the genetic resistance to gamma-irradiation-induced T-cell lymphomas (Tlyr1) has been identified. Through the development of nonoverlapping subcongenic strains, it has been further shown that Anxa1 may be a candidate resistance gene on the basis of its differential expression in thymus stroma cells after gamma-radiation exposure. In addition, thymus stroma cells of thymic lymphomas exhibited a significant reduction in the expression levels of Anxa1. Interestingly, the activity of Anxa1 relies on prostaglandin E(2) (PGE(2)) induction that brings about apoptosis in thymocytes. In fact, in vitro transfection experiments revealed that PGE(2) production was enhanced when HEK 293 cells were transfected with full-length cDNAs of Anxa1, with PGE(2) production in the cells transfected with the allele of the resistant strain (Anxa1(Tyr)) being higher than that in cells transfected with the allele of the susceptible strain (Anxa1(Phe)). Furthermore, the presence of this compound in the medium induced apoptosis of immature CD4(+)CD8(+)CD3(low) cells in a dose-dependent manner. These results improve our knowledge of the molecular mechanisms triggering T-cell lymphoblastic lymphoma development while highlighting the relevance of the stroma in controlling genetic susceptibility and the use of PGE(2) as a new therapeutic approach in T-cell hematologic malignancies.

Body and Major Organ Weights of A/J-Chr 11SM Consomic Mice

The body and major organ weights of A/J-Chr 11(SM) consomic mice were compared to those of the progenitor strains, A/J and SM/J. The weights of the body and organs, except for those of the brain and uterus, were significantly greater in A/J mice than in SM/J mice. However, those of consomic mice were highly variable. For example, the average body weight of consomic mice was significantly greater than that of SM/J mice and nearly equal to that of A/J mice. Chromosome 11 of SM/J mice induced various significant changes of the organ weights of A/J mice, especially those of the brain, lung, kidney, adrenal, and ovary, demonstrating the importance of this chromosome in determining the phenotypes.

Establishment of consomic mice to clarify host susceptibility to caries

Our previous study showed that inbred mice strains such as C57BL/6CrSlc (B6) and C3H/HeSlc (C3H) revealed high and low caries susceptibility, respectively. Quantitative trait locus (QTL) analysis was performed by a genome-wide scan on genetic crosses of B6 and C3H mice. The analysis showed that two effective values, one significant QTL was found on chromosome2, and the other suggestive QTL was detected on chromosome8. For the elucidation of the causative genes of dental caries susceptibility, we constructed mice termed consomic mice (B6-Chr.2 C3H ), in which the chromosome2 derived from B6 was replaced by that of C3H. For establishment of consomic mice, 2nd generation mice were obtained by mating B6 and F1 (B6×C3H). Microsatellite markers were used during confirmation of the genomic recombination. The recombination mice showing heterozygous genotype on the whole chromosome2 were crossed to the next generation continuously. Until the 13th generation, the mice were continuously genetically crossed by backcross and the genotype of all chromosomes was checked. The selected mice of the 13th generation were checked for heterozygous genotype of B6 and C3H on chromosome2, and whether all were homozygous for B6 on all chromosomes except chromosome2 and finally B6-Chr.2 C3H were established by intercrossing the selected mice of 13th generation. We established consomic mice that can be used as an experimental model for investigating the causative genes of dental caries susceptibility.

Search for candidate chromosomes that specify mesiodistal tooth crown length of the mandibular first molar using MSM, C57BL/6J and their consomic mice

Tooth size directly affects abnormalities in dental occlusion, and is decided by genetic and environmental factors. Malalignment of teeth occurs as a result of discrepancies in jaw bone and tooth size. In this study, F2 mice acquired by crossing C57BL/6J (B6) strain having large mesiodistal tooth crowns and MSM strain having small mesiodistal crowns were used to conduct quantitative trait locus (QTL) analysis and to identify chromosomes involved in determining mesiodistal tooth size. Analysis revealed that the QTL responsible for tooth size could be mapped chromosomes 3 and 17 in mice. Therefore, we measured mesiodistal crown length of the first molar of the mandible, and analyzed candidate chromosomes that decide the size of teeth in vivo using consomic mice between B6 and MSM strains. Mesiodistal crown length was largest in consomic mice of B6-Chr.3 MSM , thus some genes for mesiodistal crown development may be located on chromosome 3.

High-resolution genetic analysis of spontaneous activity using B6-MSM consomic mouse strains

High-resolution genetic analysis of spontaneous activity using B6-MSM consomic mouse strains

High-resolution mapping of anxiety-related traits using consomic mouse strains

Endogenous renal dopamine is a major physiological regulator of renal ion transport; however its intracellular signaling pathways are not thoroughly understood. The present study examined the role of 20-hydroxyeicosatetraenoic acid (20-HETE), the major cytochrome P450 (CYP4A) metabolite of arachidonic acid formed in the renal cortex, on the natriuretic response to dopamine in Sprague Dawley rats. Infusion of dopamine (1.5 μg/kg/min, i.v.) increased urine flow (1.9 fold over basal), sodium excretion (UNaV, 2.7 fold), fractional sodium excretion (FENa, 3.3 fold) and proximal and distal delivery of sodium by 1.5‐ and 2-fold respectively. Administration of two inhibitors of the synthesis of 20-HETE, 1-aminobenzotriazole (ABT) and N-hydroxy-N′-(‐4-butyl-2-methylphenyl)formamidine (HET0016) reduced the response to dopamine by 65%. Induction of the renal expression of CYP4A enzymes with clofibrate did not alter the response to dopamine. The natriuretic response to dopamine was lower in Dahl salt-sensitive rats in comparison to an SS.BN5 consomic strain in which transfer of chromosome 5 from Brown Norway to Dahl salt-sensitive rats upregulates the renal expression of CYP4A protein and the production of 20-HETE. Treatment with HET0016 blocked the renal effects of dopamine in SS.BN5 rats. We also examined the influence of 20-HETE in the natriuretic response to acute volume expansion that is in part mediated via the release of endogenous dopamine. The increase in urine flow, UNaV, FENa and distal FENa following volume expansion was markedly reduced in rats treated with ABT. These results suggest that 20-HETE plays at least a permissive role in the natriuretic response to dopamine.

Establishment of consomic mice to clarify host susceptibility to caries

Establishment of consomic mice to clarify host susceptibility to caries

Genetic mapping for aggressive behavior using B6-MSM consomic mouse strains

The goal of this study was to determine the adiposity of a range of rat strains, including a panel of consomics, to estimate heritability. To that end, we assessed the body fat distribution and organ weights of groups of adult male rats from 3 outbred strains, 11 inbred strains and 22 consomic strains. We measured the weights of the gonadal, retroperitoneal, mesenteric, femoral, subscapular and pericardial white fat depots, the subscapular brown fat depot, the kidneys, liver, heart, spleen, and brain. Strains were compared for the measured weight of each of these adipose depots and organs, and also for these weights adjusted statistically for body size. All individual adipose depot and organ weights were highly heritable, in most cases h2 > 0.50. The fourteen inbred and outbred rat strains were not very different in body length but there was a three-fold difference in body weight, and up to a twenty-fold difference in the weight of some adipose depots. Comparison of the FHH-Chr nBN consomic strains with the FHH host strain revealed 98 quantitative trait loci (QTLs) for body composition and organ weight, with the introgressed chromosome reducing weight or adiposity in most cases. These results can be used to guide the choice of appropriate rat strains for future studies of the genetic architecture of obesity and body size.

Systematic analysis of emotionality in consomic mouse strains established from C57BL/6J and wild‐derived MSM/Ms

Consomic strains have recently attracted attention as an advantageous method to screen for genes related to developmental, physiological, and behavioral phenotypes. Recently, a new set of consomic strains was established from the Japanese wild-derived mouse strain MSM/Ms and C57BL/6JJcl. By analyzing the entire consomic panel, we were able to identify a number of chromosomes associated with anxiety-like behaviors in the open-field (OF) test, a light–dark box and an elevated plus maze. Detailed observation of the OF behavior allowed us to identify chromosomes associated with those ethological traits, such as stretch attend, rearing, and jumping. Repeated OF test trials have different meanings for animals, and we found that some chromosomes responded to only the first or second trial, while others were consistent across both trials. By examining both male and female mice, sex-dependent effects were found in several measurements. Principal component analysis of anxiety-like behaviors extracted five factors: ‘general locomotor activity’, ‘thigmotaxis’, ‘risk assessment’, ‘open-arm exploration’ and ‘autonomic emotionality’. We mapped chromosomes associated with these five factors of emotionality.

Genetic mapping of vocalization to a series of increasing acute footshocks using B6.A consomic and B6.D2 congenic mouse strains.

Footshock response is used to study a variety of biological functions in mammals including drug self-administration, learning and memory and nociception. However, the genetics underlying variability in footshock sensitivity are not well understood. In the current studies, a panel of B6.A consomic mouse strains, two B6.D2 genome-tagged mouse lines, and the progenitor strains were screened for footshock sensitivity as measured by audible vocalization. It was found that A/J (A) mice and C57BL/6J (B6) mice with an A Chromosome 1 (Chr 1) were less sensitive to footshock compared to B6 animals. Furthermore, the offspring of Chr 1 consomic mice crossed with B6 mice had vocalization levels that were intermediate to A/J and B6 animals. A F2 mapping panel revealed two significant QTLs for footshock vocalization centered around D1Mit490 and D1Mit206 on Chr 1. The role of these Chr 1 loci in footshock sensitivity was confirmed in B6.D2 genome-tagged mouse lines.

Multigenic factors associated with a hydrocephalus-like phenotype found in inter-subspecific consomic mouse strains

Hydrocephalus is a significant clinical condition in humans and is known to be a multifactorial neurologic disorder. It has been thought that genetic factors are closely involved in the etiology of congenital hydrocephalus, but further investigation is required to elucidate the genetic architecture of hydrocephalus. By analyzing breeding records of a panel of inter-subspecific consomic mouse strains, we found that consomic strains with MSM/Ms (MSM) chromosomes 4, 5, 7, 11, 15, and 17 showed a significantly higher incidence of hydrocephalus, whereas both parental strains, MSM and C57BL/6J (B6), rarely showed this abnormality. Further analysis of the consomic Chr 17 strain revealed that apparently normal individuals of this strain also exhibited increased brain ventricle size compared to B6 and had larger individual variation of ventricle size within the strain. Thus, we concluded that hydrocephalus is an extreme phenotype of individual ventricle size variation. We then established and analyzed several subconsomic strains of Chr 17 to identify genetic factors related to hydrocephalus-like phenotype and successfully mapped one genetic locus around the proximal region of Chr 17.

Multigenic factors associated with a hydrocephalus-like phenotype found in inter-subspecific consomic mouse strains

Multigenic factors associated with a hydrocephalus-like phenotype found in inter-subspecific consomic mouse strains

Genetic analysis of inter-male aggression using consomic mouse strains established from C57BL/6J and MSM

Genetic analysis of inter-male aggression using consomic mouse strains established from C57BL/6J and MSM