The ROSA26 LacZ-neo R insertion confers resistance to mammary tumors in Apc Min/+ mice

B6.129S7-Gtrosa26 (ROSA26) mice carry a LacZ-neo ^R insertion on Chromosome (Chr) 6, made by promoter trapping with AB1 129 ES cells. Female C57BL/6J Apc ^Min /+ (B6 Min/+) mice are very susceptible to the induction of mammary tumors after treatment with ethylnitrosourea (ENU). However, ENU-treated B6 mice carrying both Apc ^Min and ROSA26 are resistant to mammary tumor formation. Thus, ROSA26 mice carry a modifier of Min-induced mammary tumor susceptibility. We have previously mapped the modifier to a 4-cM interval of 129-derived DNA that also contains the ROSA26 insertion. Here we report additional evidence for the effect of the ROSA26 insertion on mammary tumor formation. To test the hypothesis that the resistance was due to a linked modifier locus, we utilized two approaches. We have derived and tested two lines of mice that are congenic for 129-derived DNA within the minimal modifier interval and show that they are as susceptible to mammary tumors as are B6 mice. Additionally, we analyzed a backcross population segregating for the insertion and show that mice carrying the insertion are more resistant to mammary tumor development than are mice not carrying the insertion. Thus, the resistance is not due to a 129-derived modifier allele, but must be due to the ROSA26 insertion. In addition, the effect of the ROSA26 insertion can be detected in a backcross population segregating for other mammary modifiers. Received: 29 December 2000 / Accepted: 4 April 2001     

Identification of Mom12 and Mom13, two novel modifier loci of ApcMin-mediated intestinal tumorigenesis

Colorectal cancer is a heterogeneous disease resulting from a combination of genetic and environmental factors. The C57BL/6J (B6) Apc^Min/+ mouse develops polyps throughout the gastrointestinal tract and has been a valuable model for understanding the genetic basis of intestinal tumorigenesis. Apc^Min/+ mice have been used to study known oncogenes and tumor suppressor genes on a controlled genetic background. These studies often utilize congenic knockout alleles, which can carry an unknown amount of residual donor DNA. The Apc^Min model has also been used to identify modifer loci, known as Modifier of Min (Mom) loci, which alter Apc^Min-mediated intestinal tumorigenesis. B6 mice carrying a knockout allele generated in WW6 embryonic stem cells were crossed to B6 Apc^Min/+ mice to determine the effect on polyp multiplicity. The newly generated colony developed significantly more intestinal polyps than Apc^Min/+ controls. Polyp multiplicity did not correlate with inheritance of the knockout allele, suggesting the presence of one or more modifier loci segregating in the colony. Genotyping of simple sequence length polymorphism (SSLP) markers revealed residual 129X1/SvJ genomic DNA within the congenic region of the parental knockout line. An analysis of polyp multiplicity data and SSLP genotyping indicated the presence of two Mom loci in the colony: (1) Mom12, a dominant modifier linked to the congenic region on chromosome 6 and (2) Mom13, which is unlinked to the congenic region and whose effect is masked by Mom12. The identification of Mom12 and Mom13 demonstrates the potential problems resulting from residual heterozygosity present in congenic lines.Key words: adenomatous polyposis coli, modifier of min, congenic mice, caveolin-1, cancer susceptibility     

Identification of Mom12 and Mom13, two novel modifier loci of ApcMin-mediated intestinal tumorigenesis

Colorectal cancer is a heterogeneous disease resulting from a combination of genetic and environmental factors. The C57BL/6J (B6) Apc^Min/+ mouse develops polyps throughout the gastrointestinal tract and has been a valuable model for understanding the genetic basis of intestinal tumorigenesis. Apc^Min/+ mice have been used to study known oncogenes and tumor suppressor genes on a controlled genetic background. These studies often utilize congenic knockout alleles, which can carry an unknown amount of residual donor DNA. The Apc^Min model has also been used to identify modifer loci, known as Modifier of Min (Mom) loci, which alter Apc^Min-mediated intestinal tumorigenesis. B6 mice carrying a knockout allele generated in WW6 embryonic stem cells were crossed to B6 Apc^Min/+ mice to determine the effect on polyp multiplicity. The newly generated colony developed significantly more intestinal polyps than Apc^Min/+ controls. Polyp multiplicity did not correlate with inheritance of the knockout allele, suggesting the presence of one or more modifier loci segregating in the colony. Genotyping of simple sequence length polymorphism (SSLP) markers revealed residual 129X1/SvJ genomic DNA within the congenic region of the parental knockout line. An analysis of polyp multiplicity data and SSLP genotyping indicated the presence of two Mom loci in the colony: 1) Mom12, a dominant modifier linked to the congenic region on chromosome 6, and 2) Mom13, which is unlinked to the congenic region and whose effect is masked by Mom12. The identification of Mom12 and Mom13 demonstrates the potential problems resulting from residual heterozygosity present in congenic lines.     

Exclusion of <Emphasis Type="Italic">Madh2, Madh4</Emphasis>, and <Emphasis Type="Italic">Madh7</Emphasis> as candidates for the modifier of <Emphasis Type="Italic">Min 2</Emphasis> (<Emphasis Type="Italic">Mom2</Emphasis>) locus

Abstract We recently identified the Modifier of Min 2 (Mom2) locus. Mom2 is a new modifier of intestinal tumorigenesis that resulted from a spontaneous mutation in a B6 Apc ^Min/+ mouse. The presence of one resistant Mom2 ^R allele results in a significant reduction in small intestinal polyp number and colon polyp incidence in Apc ^Min/+ mice. Through linkage analysis, we previously localized Mom2 to a 14-cM region on mouse Chromosome (Chr) 18, distal to the Apc gene. This region is syntenic with human Chr 18q, which frequently undergoes loss of heterozygosity (LOH) in several human cancers, including colorectal cancer. Residing in this region are the Madh2 and Madh4 genes, which have both been implicated in human colorectal cancer. Based on meiotic recombinations within the Mom2 region in the derivation of our congenic animals, we have narrowed the location of the Mom2 locus and excluded Madh2, Madh4, and Madh7, as well as Mbd1, Mbd2, Dcc, and Tcf4, as candidates for the Mom2 gene.     

Increased angiogenesis in Cdk4R24C/R24C:Apc+/Min intestinal tumors

Cyclin dependent kinase 4 (Cdk4) is a cell cycle regulator involved in early G1 cell cycle progression and has been indirectly implicated in angiogenesis in the Min mouse system, a mouse that harbors a mutation in the Apc gene. Apc^+/Min mice when crossed with Ink4a/arf-/- mice, exhibited increased angiogenesis of colorectal tumors suggesting that dysregulation of Cdk4 (due to loss of Ink4a-mediated suppression) may contribute to enhanced angiogenesis. To demonstrate a direct role for Cdk4 in angiogenesis, we crossed mice that have an activated Cdk4, Cdk4^R24C/R24C mice, with Apc^+/Min mice and examined levels of angiogenesis in intestinal tumors formed. Our results show an increase in the percentage of highly vascularized tumors in Cdk4^R24C/R24C:Apc^Min/+ and Cdk4^+/R24C:Apc^Min/+ mice compared to Cdk4^+/+:Apc^Min/+ mice. In addition immunohistochemical analysis showed an increase in CD-31 staining localized to endothelial cells of Cdk4^R24C/R24C:Apc^Min/+ mouse tumors, supporting the hypothesis of increased vasculature in these tumors. Further analysis showed an increase in the expression of the E2F1 target proteins Vegf-b and Cyclin A in Cdk4^R24C/R24C:Apc^+/Min intestinal tumors. Together these data suggest that the dysregulated Cdk4 gene plays an important role in angiogenesis during intestinal tumor formation and may in part act via increasing E2F1 target proteins. This is the first report to show that Cdk4 has a direct role in angiogenesis in vivo and may be an important drug target to reduce or prevent angiogenesis during intestinal tumor formation.     

Analysis of reciprocal congenic lines reveals the C3H/HeJ genome to be highly resistant to ApcMin intestinal tumorigenesis

Genetic background affects polyp development in the Multiple intestinal neoplasia (Apc(Min)) mouse model. The Modifier of Min 1 (Mom1) locus accounts for approximately 50% of the variation in polyp multiplicity. We generated reciprocal congenic lines, such that the recipient C57BL/6J (B6) strain carries a donor C3H/HeJ (C3H) Mom1 allele, and the recipient C3H strain carries a donor B6 Mom1 allele. Hybrid progeny from congenic females mated to B6 Apc(Min/+) males were analyzed. A single C3H Mom1 locus on the B6 background reduced small intestinal polyp numbers by 50% and colon polyp incidence by 66% compared to their susceptible B6 Mom1(S/S)Apc(Min/+) siblings. These findings show that the C3H genome contains a resistant Mom1(R) locus. The reciprocal congenic line, which carries the susceptible B6 Mom1(S) locus on the C3H background, reduced small intestinal polyp numbers by 80% and colon polyp incidence by 95% compared to B6 Mom1(S/S)Apc(Min/+) mice. These data demonstrate that unidentified modifiers in the C3H strain can suppress intestinal polyp multiplicity in Apc(Min/+) mice, and act in the absence of a resistant Mom1(R) locus.     

Role of nucleotide excision repair deficiency in intestinal tumorigenesis in multiple intestinal neoplasia (Min) mice

Mice deficient in the Xeroderma pigmentosum group A (Xpa) gene are defective in nucleotide excision repair (NER) and highly susceptible to skin carcinogenesis after dermal exposure to UV light or chemicals. Min (multiple intestinal neoplasia) mice, heterozygous for a germline nonsense mutation in the tumor suppressor gene adenomatous polyposis coli (Apc), develop intestinal tumors spontaneously and show additional intestinal tumors after exposure to the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). In this study, we investigated the impact of loss of XPA function on PhIP-induced intestinal tumorigenesis in F1 offspring of Min/+ (Apc^+/−) mice crossed with Xpa gene-deficient mice. Apc^+/− mice lacking both alleles of Xpa had higher susceptibility towards toxicity of PhIP, higher levels of PhIP–DNA adducts in the middle and distal small intestines, as well as in liver, and a higher number of small intestinal tumors at 11 weeks, compared with Apc^+/− mice with one or two intact Xpa alleles. Localization of tumors was not affected, being highest in middle and distal small intestines in all genotypes. At 11 weeks of age, the number of spontaneous intestinal tumors was not significantly increased by homozygous loss of Xpa, but untreated Apc^+/−/Xpa^−/− mice had significantly shorter life-spans than their XPA-proficient littermates. Heterozygous loss of Xpa did not affect any of the measured end points. In conclusion, the Xpa gene and the NER pathway are involved in repair of bulky PhIP–DNA adducts in the intestines and the liver, and most probably of DNA lesions leading to spontaneous intestinal tumors. These results confirm a role of the NER pathway also in protection against cancer in internal organs, additional to its well-known importance in protection against skin cancer. An effect of Apc^+/− on adduct levels, additional to that of Xpa^−/−, indicates that the truncated APC protein may affect a repair pathway other than NER.     

Mechanistic study of the anti‐cancer effect of Gynostemma pentaphyllum saponins in the ApcMin/+ mouse model

Gynostemma pentaphyllum saponins (GpS) have been shown to have anti‐cancer activity. However, the underlying mechanisms remain unclear. In this study, we used the Apc^Min/+ colorectal cancer (CRC) mouse model to investigate the anti‐cancer effect of GpS and we demonstrated that GpS treatment could significantly reduce the number and size of intestinal polyps in Apc^Min/+ mice. In order to identify the potential targets and mechanisms involved, a comparative proteomics analysis was performed and 40 differentially expressed proteins after GpS treatment were identified. Bioinformatics analyses suggested a majority of these proteins were involved in processes related to cellular redox homeostasis, and predicted Raf‐1 as a potential target of GpS. The upregulation of two proteins known to be involved in redox homeostasis, peroxiredoxin‐1 (Prdx1) and peroxiredoxin‐2 (Prdx2), and the downregulation of Raf‐1 were validated using Western blot analysis. After further investigation of the associated signaling networks, we postulated that the anti‐cancer effect of GpS was mediated through the upregulation of Prdx1 and Prdx2, suppression of Ras, RAF/MEK/ERK/STAT, PI3K/AKT/mTOR signaling and modulation of JNK/p38 MAPK signaling. We also examined the potential combinatorial effect of GpS with the chemotherapeutic 5‐fluorouracil (5‐FU) and found that GpS could enhance the anti‐cancer efficacy of 5‐FU, further suppressing the number of polyps in Apc^Min/+ mice. Our findings highlight the potential of GpS as an anti‐cancer agent, the potential mechanisms of its anti‐cancer activities, and its effect as an adjuvant of 5‐FU in the chemotherapy of CRC.     

Role of splenic stroma in the action of bacterial lipopolysaccharides on radiation mortality: a study in mice carrying the Slj allele

Abstract. Sl_j/+ mice display a slight macrocytic anaemia due to a defect in their haemopoietic organ stroma. They have a deficient endogenous spleen colony (CFU-end) formation following sublethal doses of gamma-radiation compared with their normal +/+ littermates, which is likely to be due to the low pre-irradiation CFU-S content of the Sl_j/+ spleen. CFU-S in these congenic mice do not differ in their sensitivity to gamma-irradiation or stem cell-activating factor. While injection of +/+ mice with 10 μg of lipopolysaccharide-W (LPS) one day prior to irradiation led to a substantial increase in their survival, the survival of Sl_j/+ mice was only slightly increased. Irradiation induced a similar dose-related reduction in the numbers of CFU-S in the spleen and femora of LPS-injected Sl_j/+ mice compared to similarly treated +/+ mice when measured directly after irradiation. At Day 9 after irradiation, injection of LPS led to a significantly higher CFU-end formation and higher numbers of CFU-S and nucleated cells in the Sl_j/+ spleens compared to LPS-injected +/+ mice. No such differences in the radioprotective effect of LPS were observed in the +/+ and Sl_j/+ mice with respect to the splenic and femoral ⁵⁹Fe-incorporation and the femoral CFU-S numbers at Day 9. These data strongly suggest a contribution by immigrating CFU-S to the CFU-S numbers and endogenous colony formation in at least the Sl_j/+ spleen after LPS injection and subsequent sublethal irradiation. The observations also imply that the splenic organ stroma may play a mediatory role in the radioprotective action of LPS. In addition, the data represent an extreme example of a lack of correlation between animal survival and haemopoietic parameters. Caution should be taken when applying endogenous colony counts as a means of screening potential anti-radiation drugs.     

Real-time Imaging of Myeloid Cells Dynamics in ApcMin/+ Intestinal Tumors by Spinning Disk Confocal Microscopy

Myeloid cells are the most abundant immune cells within tumors and have been shown to promote tumor progression. Modern intravital imaging techniques enable the observation of live cellular behavior inside the organ but can be challenging in some types of cancer due to organ and tumor accessibility such as intestine. Direct observation of intestinal tumors has not been previously reported. A surgical procedure described here allows direct observation of myeloid cell dynamics within the intestinal tumors in live mice by using transgenic fluorescent reporter mice and injectable tracers or antibodies. For this purpose, a four-color, multi-region, micro-lensed spinning disk confocal microscope that allows long-term continuous imaging with rapid image acquisition has been used. Apc^Min/+ mice that develop multiple adenomas in the small intestine are crossed with c-fms-EGFP mice to visualize myeloid cells and with ACTB-ECFP mice to visualize intestinal epithelial cells of the crypts. Procedures for labeling different tumor components, such as blood vessels and neutrophils, and the procedure for positioning the tumor for imaging through the serosal surface are also described. Time-lapse movies compiled from several hours of imaging allow the analysis of myeloid cell behavior in situ in the intestinal microenvironment.     

Genome-wide search for genes that modulate inflammatory arthritis caused by Ali18 mutation in mice

Many of inflammatory diseases, including inflammatory arthritis, are multifactorial bases. The Ali18 semidominant mutation induced by N-ethyl-N-nitrosourea in the C3HeB/FeJ (C3H) genome causes spontaneous inflammation of peripheral limbs and elevated immunoglobulin E (IgE) levels in mice. Although the Ali18 locus was mapped to a single locus on chromosome 4, the arthritic phenotype of Ali18/+ mice was completely suppressed in F1 hybrid genetic backgrounds. To determine the chromosomal locations of the modifier loci affecting the severity of arthritis, an autosomal genome scan of 22 affected Ali18/+ F2 mice was conducted using C57BL/6J as a partner strain. Interestingly, regions on chromosomes 1 and 3 in C3H showed significant genetic interactions. Moreover, 174 N2 (backcross to Ali18/Ali18) and 267 F2 animals were used for measurement of arthritis scores and plasma IgE levels, and also for genotyping with 153 genome-wide single nucleotide polymorphism (SNP) markers. In N2 populations, two significant trait loci for arthritis scores on chromosomes 1 and 15 were detected. Although no significant scores were detected in F2 mice besides chromosome 4, a suggestive score was detected on chromosome 3. In addition, a two-dimensional genome scan using F2 identified five suggestive scores of chromosomal combinations, chromosomes 1 × 10, 2 × 6, 3 × 4, 4 × 9, and 6 × 15. No significant trait loci affecting IgE levels were detected in both N2 and F2 populations. Identification of the Ali18 modifier genes by further detailed analyses such as congenic strains and expression profiling may dissect molecular complexity in inflammatory diseases.     

Genetic analysis of theT-H-2 region in non-t Chromosomes

A general breeding protocol useful in the construction of congenic lines of mice disparate in the 15 cMT-H-2 region of chromosome 17 in non-t chromosomes is described. Two such congenic lines, B6.TC2/Rn and B6.TC3/Rn, were derived from the C57BL/6J and B6.C-H-2 ^d/By strains using this protocol. Both B6.TC2 and B6.TC3 dissociate the quantitative activity locus for glyoxalase I (Qglo-1) from theH-2 complex, and hence possess BALB/cBy DNA centromeric toH-2. However, neither new strain is able to map anyH-2-associated restriction fragment length polymorphism with anH-2 cDNA probe even though both strains are recombinant in the 2 cMQglo-1-H-2K interval.     

Teratocarcinoma transplantation rejection loci: Genetic localization of the Gt-1 locus on chromosome 17 and the expression of alternate alleles

A series of congenic mice on the BALB/c genetic background have been employed to localize a teratocarcinoma transplantation rejection locus, Gt-1, to the K side of the H-2 locus on chromosome 17. Previous studies have placed the Gt-1 ^sv allele about 8 centimorgans away from the H-2 ^b or H-2 ^bv1 locus. Teratocarcinomas derived from 129/sv mice, Gt-1 ^sv (H-2K ^bv1/H-2D ^bv1), are rejected by BALB/c (H-2K ^d/H-2D^d) and BALB-G mice (H-2K ^d/H2D-^b, but form tumors in BALB-B (H-2K ^b/H2D ^b) and BALB/5R5 mice (H-2K ^b/H2D ^d). In the reciprocal tumor-rejection test, a BALB/c teratocarcinoma was rejected by immunized BALB·B mice, but formed tumors in the immunized isogenic BALB/c mouse. These studies demonstrate the reciprocal expression of two Gt-1 alleles, one Gt-1 ^c, in BALB/c mice, and the other, Gt-1 ^sv, in the congenic BALB·B mice. Shedlovsky and co-workers have placed the Gt-1 locus in a similar location on the K side of the H-2 locus on chromosome 17.     

Abnormal anxiety-related behavior in serotonin transporter null mutant mice: the influence of genetic background

Serotonin transporter (5-HTT) null mutant mice provide a model system to study the role genetic variation in the 5-HTT plays in the regulation of emotion. Anxiety-like behaviors were assessed in 5-HTT null mutants with the mutation placed on either a B6 congenic or a 129S6 congenic background. Replicating previous findings, B6 congenic 5-HTT null mutants exhibited increased anxiety-like behavior and reduced exploratory locomotion on the light ↔ dark exploration and elevated plus-maze tests. In contrast, 129S6 congenic 5-HTT null mutant mice showed no phenotypic abnormalities on either test. 5-HTT null mutants on the 129S6 background showed reduced 5-HT_1A receptor binding (as measured by quantitative autoradiography) and reduced 5-HT_1A receptor function (as measured by 8-OH-DPAT-indcued hypothermia). These data confirm that the 5-HTT null mutation produced alterations in brain 5-HT function in mice on the 129S6 background, thereby discounting the possibility that the absence of an abnormal anxiety-like phenotype in these mice was due to a suppression of the mutation by 129 modifier genes. Anxiety-like behaviors in the light ↔ dark exploration and elevated plus-maze tests were significantly higher in 129S6 congenic +/+ mice as compared to B6 congenic +/+ mice. This suggests that high baseline anxiety-like behavior in the 129S6 strain might have precluded detection of the anxiety-like effects of the 5-HTT null mutation on this background. Present findings provide further evidence linking genetic variation in the 5-HTT to abnormalities in mood and anxiety. Furthermore, these data highlight the utility of conducting behavioral phenotyping of mutant mice on multiple genetic backgrounds.     

High-resolution genetic mapping of the saccharin preference locus (Sac) and the putative sweet taste receptor (T1R1) gene (Gpr70) to mouse distal Chromosome 4

The Sac (saccharin preference) locus affecting mouse behavioral and neural responsiveness to sweeteners has been mapped to distal Chr 4. A putative sweet taste receptor, T1R1, has been recently cloned, and the gene encoding it, Gpr70, has also been mapped to mouse distal Chr 4. To assess Gpr70 as a candidate gene for Sac, we compared the Gpr70 sequences of C57BL/6ByJ and 129P3/J mouse strains with different alleles of Sac. Using Gpr70 sequence variation between the C57BL/6ByJ and 129P3/J strains, we conducted a high-resolution analysis of the chromosomal localization of the Gpr70 and Sac loci in the F₂ hybrids and 129.B6-Sac partially congenic mice originating from these two strains. The Gpr70 gene maps proximal to Sac, which demonstrates that they are different loci. Received: 24 April 2000 / Accepted: 14 September 2000     

Haematopoiesis In Mice Heterozygous For the W Trait: Defective Formation of Transient Endogenous Spleen Colonies

It has been determined that W/+ and W^v/+ heterozygous mice, as compared with normal +/+ homozygous littermates, form significantly lower numbers of transient 5-day endogenous spleen colonies in response to X-irradiation. This defect was evident for doses of irradiation between 2–6 Gy (200–600 rad) and was associated with a slightly increased radiosensitivity of the assayed precursor cells (TE-CFU) in W heterozygotic mice. Moreover, the defect was transplantable, i.e., intrinsic to the marrow cells and not to the microenvironment, and was not associated with a similar decrease in cells which form erythropoietic bursts in vitro (BFUe). This study provides a cellular basis for increased radiosensitivity of W/+ and W^v/+ mice and suggests that the ‘W’ mutation is semi-dominant, both with respect to the white spotting and TE-CFU formation.     

Mammary tumor modifiers in BALB/cJ mice heterozygous for p53

BALB/c mice are predisposed to developing spontaneous mammary tumors, which are further increased in a p53 heterozygous state. C57BL/6J mice are resistant to induced mammary tumors and develop less than 1% mammary tumors in both wild-type and p53 ^+/− states. To map modifiers of mammary tumorigenesis, we have established F₁ and F₂ crosses and backcrosses to BALB/cJ (N2-BALB/cJ) and C57BL/6J (N2-C57BL/6J) strains. All cohorts developed mammary carcinomas in p53 ^+/− females, suggesting that multiple loci dominantly and recessively contributed to mammary tumorigenesis. We mapped two modifiers of mammary tumorigenesis in the BALB/cJ strain. Mtsm1 (mammary tumor susceptibility modifier), a dominant-acting modifier, is located on chromosome 7. Mtsm1 is suggestive for linkage to mammary tumorigenesis (p = 0.001). We have analyzed the Mtsm1 region to locate candidate genes by comparing it to a rat modifier region, Mcs3, which shares syntenic conservation with Mtsm1. Expression data and SNPs were also taken into account. Five potential candidate genes within Mtsm1 are Aldh1a3, Chd2, Nipa2, Pcsk6, and Tubgcp5. The second modifier mapped is Mtsm2, a recessive-acting modifier. Mtsm2 is located on chromosome X and is significantly linked to mammary tumorigenesis (p = 1.03 × 10⁻⁷). Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Scram1 is a modifier of spinal cord resistance for astrocytoma on mouse Chr 5

Tumor location can profoundly affect morbidity and patient prognosis, even for the same tumor type. Very little is known about whether tumor location is determined stochastically or whether genetic risk factors can affect where tumors arise within an organ system. We have taken advantage of the Nf1-/+;Trp53-/+cis mouse model of astrocytoma/glioblastoma to map genetic loci affecting whether astrocytomas are found in the spinal cord. We identify a locus on distal Chr 5, termed Scram1 for spinal cord resistance to astrocytoma modifier 1, with a LOD score of 5.0 and a genome-wide significance of P?相似文献   

Assignment of the Ly-6--Ril-1--Sis--H-30--Pol-5/Xmmv-72--Ins-3--Krt-1--Int-1--Gdc-1 region to mouse chromosome 15

Previous work has demonstrated linkage between Ly-6, H-30, and a locus, Ril-1, that affects susceptibility to radiation-induced leukemia. Results of preliminary linkage analyses suggested further that the cluster might be linked to Ly-11 on the proximal portion of mouse chromosome 2. Using molecular probes to examine somatic cell lines and recombinant inbred and congenic strains of mice, we have re-evaluated these linkage relationships. A cloned genomic DNA fragment derived from a retroviral site has been used to define a novel locus, Pol-5, that is tightly linked to both H-30 and Ril-1 as shown by analysis of the B6.C-H-30 ^c congenic mouse strain. Following the segregation of the Pol-5 mouse-specific DNA fragment in a series of somatic cell hybrids carrying various combinations of mouse chromosomes on a rat or Chinese hamster background mapped Pol-5 to mouse chromosome 15. During the course of these studies, restriction fragment length polymorphisms were defined associated with several loci, including Pol-5, Ly-6, Sis, Ins-3, Krt-1, Int-1, and Gdc-1. Three of these loci, Sis, Int-1, and Gdc-1, have been previously mapped to chromosome 15 by others using somatic cell hybrids or isoenzyme analyses. Following the inheritance of these eight loci in recombinant inbred strains of mice allowed the definition of a linkage group on the chromosome with the order Ly-6-Ril-1--Sis--H-30--Pol-5--Ins-3--Krt-1--Int-1--Gdc-1. Analyses of alleles inherited as passengers in B6.C-H-30 ^c, C3H.B-Ly-6 ^b, and C57BL/6By-Eh/+ congenic mouse strains and in situ hybridization experiments support the above gene order and indicate further that the cluster is located on distal chromosome 15, with Ly-6 and Sis near Eh.Abbreviations A agouti - Abl cellular homolog of the Abelson leukemia virus oncogene - Ada adenosine deaminase - Ak-1 adenylate kinase-1 - AXB A/J × C57BL/6J recombinant inbred strain - B2m beta-2 microglobulin - BXA C57BL/6J × A/J recombinant inbred strain - BXD C57BL/6J × DBA/2J recombinant inbred strain - BXH C57BL/6J × C3H/HeJ recombinant inbred strain - CXB BALB/cBy × C57BL/6By recombinant inbred strain - DNA deoxyribonucleic acid - Eh hairy ears - Fpgs folypolyglutamyl synthetase - FXI fractionated x-irradiation - Gdc-1 glycerol phosphate dehydrogenase-1 - Il2r IL-2 receptor - Ins-3 a novel insulinlike gene - Int-1 mammary tumor integration site-1 - Itp inosine triphosphatase - Krt-1 the locus designated here includes a cluster of at least three keratin genes - LTR long terminal repeat - Ly lymphocyte - Lv-6 lymphocyte antigen-6 - Ly-11 lymphocyte antigen-11 - MIH minor histocompatibility - Myc cellular homolog of the Abelson leukemia virus oncogene; pa, pallid; - Pol-5 locus encoding retroviral polymerase-5 - RFLP restriction fragment length polymorphism - RI recombinant inbred mouse strains - Ril-1 radiation-induced leukemia susceptibility-1 locus - SDP strain distribution pattern - Sis cellular homolog of the simian sarcoma virus oncogene - SFFV spleen focus-forming virus - Tpi-1 triosephosphate isomerase-1 - Ve velvet