Mapping of novel loci involved in lung and colon tumor susceptibility by the use of genetically selected mouse strains.

Two non-inbred mouse lines, phenotypically selected for maximal (AIRmin) and minimal (AIRmax) acute inflammatory response, show differential susceptibility/resistance to the development of several chemically-induced tumor types. An intercross pedigree of these mice was generated and treated with the chemical carcinogen dimethylhydrazine, which induces lung and intestinal tumors. Genome wide high-density genotyping with the Restriction Site-Associated DNA genotyping (2B-RAD) technique was used to map genetic loci modulating individual genetic susceptibility to both lung and intestinal cancer. Our results evidence new common quantitative trait loci (QTL) for those phenotypes and provide an improved understanding of the relationship between genomic variation and individual genetic predisposition to tumorigenesis in different organs.

Genetic control of renal tumorigenesis by the mouse Rtm1 locus.

BACKGROUND: The genetic basis of susceptibility to renal tumorigenesis has not yet been established in mouse strains. Mouse lines derived by bidirectional phenotypic selection on the basis of their maximal (AIRmax) or minimal (AIRmin) acute inflammatory responsiveness differ widely in susceptibility to spontaneous and urethane-induced renal tumorigenesis. To map the functional loci modulating renal tumor susceptibility in these mice, we carried out a genome-wide genetic linkage study, using SNP arrays, in an (AIRmax x AIRmin)F2 intercross population treated with a single urethane dose at 1 week of age and phenotyped for renal tumors at 35 weeks of age. RESULTS: AIRmax mice did not develop renal tumors spontaneously nor in response to urethane, whereas in AIRmin mice renal tumors formed spontaneously (in 52% of animals) and after urethane induction (89%). The tumors had a papillary morphology and were positive for alpha-methylacyl-CoA racemase and negative for CD10. By analysis of 879 informative SNPs in 662 mice, we mapped a single quantitative trait locus modulating the incidence of renal tumors in the (AIRmax x AIRmin)F2 intercross population. This locus, which we named Renal tumor modifier QTL 1 (Rtm1), mapped to chromosome 17 at 23.4 Mb (LOD score = 15.8), with SNPs rs3696835 and rs3719497 flanking the LOD score peak. The A allele of rs3719497 from AIRmin mice was associated with a 2.5-fold increased odds ratio for renal tumor development. The LOD score peak included the Tuberous sclerosis 2 (Tsc2) gene which has already been implicated in kidney disease: loss of function by germline retroviral insertion is associated with spontaneous renal tumorigenesis in the Eker rat, and heterozygous-null Tsc2(+/-) mice develop renal cystadenomas. CONCLUSIONS: We mapped Rtm1 as a single major locus modulating renal tumorigenesis in a murine intercross population. Thus, the AIR mouse lines can be considered a new genetic model for studying the role of germline and somatic molecular alterations in kidney neoplastic disease.

Mapping of novel loci involved in lung and colon tumor susceptibility by the use of genetically selected mouse strains

Two non-inbred mouse lines, phenotypically selected for maximal (AIRmin) and minimal (AIRmax) acute inflammatory response, show differential susceptibility/resistance to the development of several chemically-induced tumor types. An intercross pedigree of these mice was generated and treated with the chemical carcinogen dimethylhydrazine, which induces lung and intestinal tumors. Genome wide high-density genotyping with the Restriction Site-Associated DNA genotyping (2B-RAD) technique was used to map genetic loci modulating individual genetic susceptibility to both lung and intestinal cancer. Our results evidence new common quantitative trait loci (QTL) for those phenotypes and provide an improved understanding of the relationship between genomic variation and individual genetic predisposition to tumorigenesis in different organs.

Novel Pycard gene polymorphism impairs Nlpr3 inflammasome-induced IL-1β production in mice selected for low inflammatory response

A SNP based linkage study in mouse lines phenotypically selected for maximal (AIRmax) or minimal (AIRmin) acute inflammatory response (AIR), mapped a major locus, Inflammatory response modulator 1 (Irm1) at 128Mb (3.5Mb interval) in chr 7 controlling AIR, measured by leukocyte and IL-6 levels in exudates and IL-1β production by circulating leukocytes after Nlpr3 inflammasome activation. Sequencing of this region in mice with extreme high or low IL-1β levels revealed 14 SNPs between the two groups, narrowing the locus interval to 420Kb. Candidate genes at Irm1 include Pycard with an undescribed exon 3 (C/T) mutation leading to E19K substitution at the pyrin domain, and Itgam, Rgs10 and BC017158 with intronic SNPs. In Pycard, the C allele was fixed in high responder AIRmax mice whereas the C and T alleles frequencies were 39% and 61%, respectively in AIRmin. We then investigated the effect of this novel Pycard SNP in inflammation phenotypes.Methods AIRmin mice bearing the 3 genotypes at Pycard: CC, CT, TT were produced by genotype-assisted mating. Inflammatory response was measured in AIRmax and in the 3 AIRmin sublines by the number of infiltrating cells and IL-6 concentration in the 24h exudate induced by sc Biogel P-100 bead injection and ex vivo IL-1β production by circulating leukocytes after E coli LPS (1 ug) and ATP (5mM) activation.Results IL-1β levels were similar in AIRmaxCC (4.5-±0.4 ng/ml) and AIRminCC (3.4±2.4 ng/ml) whereas AIRminCT produced 0.3±0.5 and AIRminTT <0.05 ng/ml IL-1β. Leukocyte influx and IL-6 levels in inflammatory exudates were not affected.Conclusion The E19K substitution in Pycard causes a negative effect in inflammasome activation for IL-1β production, without interfering in other inflammation phenotypes.