4th Annual BMRP Investigator Meeting - Abstract

Subcongenic Analysis of Cdcs1, A Major Colitis Susceptibility Modifier in Mice

Edward Leiter^1,a, Jason Beckwith¹, Lydia Petell¹, Ben King¹, John Kulik¹, Dan Shaffer¹, Derry Roopenian¹, and John Sundberg<sup>1

1</sup>The Jackson Laboratory, Bar Harbor, Maine

Genetic disruption of the gene encoding the regulatory cytokine, IL-10, produces a consistent, non-remitting typhlocolitis in C3H/HeJBir (C3H) mice.  In contrast, IL-10-deficient C57BL/6J (B6) mice are colitis resistant.  A locus on Chromosome (Chr.) 3, designated Cdcs-1, was the major modifier, with the Nfkb1 locus a primary candidate.  To fine map Cdcs1, we assessed colitis histopathology in a Chr. 3 subcongenic series on both the susceptible C3H and resistant B6 backgrounds.  We recently demonstrated that (1) a long congenic interval containing Cdcs1 modified colitis susceptibility in the expected direction (e.g., B6 alleles on C3H suppressed colitis; C3H alleles on B6 exacerbated colitis).  Using both bone marrow-derived macrophages (BMDM) and dendritic cell cultures from the two parental strains and the reciprocal congenic stocks, we further showed that the C3H Cdcs1 susceptibility locus suppressed Toll-like receptor (TLR)-mediated innate immune responses to bacterial ligands whereas the B6 resistance locus promoted them.

Analysis of alterations in colitis histopathology in new subcongenic stocks seemingly excluded Nfkb1 as the primary contributor.  Because Cdcs1 affects BMDM responses to TLR ligands, we assessed differential gene expression using Affymetrix Mouse Expression Set 430v2.0.  To confirm differences observed on the microarray, we performed customized real-time PCR on genes identified to be differentially expressed within 5 Mb of Nfkb1.  One novel candidate gene of unknown function significantly under-expressed in C3H was confirmed by RT-PCR.  Other potential candidates identified by RT-PCR, including Nfkb1 (0.01>P<0.05) will be discussed.

^aPrincipal Investigator