Presenter: Vivek Kumar
Vivek Kumar1, Fernando Pardo-Manuel de Villena3, Gary Churchill2, Joseph S. Takahashi1 1Department of Neuroscience and Howard Hughes Medical Institute, University of Texas, Southwestern Medical Center, Dallas, TX, USA, 2The Jackson Laboratory, Bar Harbor, ME, USA, 3Department of Genetics, UNC-Chapel Hill, Chapel Hill, NC, USA
Identification of QTLs at the single gene or nucleotide level has been difficult due to low mapping resolutions achieved by traditional F2 or N2 mapping approaches. Frequently confounding numbers of polymorphisms within the QTL interval make identification of the causative gene or nucleotide difficult. One alternate approach is to use closely related mouse substrains with high phenotypic but low genotypic variance. Due to high relatedness between substrains, there should be limited polymorphisms within the QTL interval allowing for the identification of the causal gene or even nucleotide. Here we use two C57BL/6 substrains, C57BL/6J from Jackson Labs and C57BL/6N from NIH, to map and clone a QTL for psychostimulant response. We developed a SNP marker panel that can be used to map QTLs between several C57BL/6 substrains including C57BL/6Cr, C57BL/6Tac and C57BL/6NJ. This marker panel was used to genotype the F2 cross and map a single locus mediating cocaine response (LOD 6.4). We sequenced the C57BL/6N genome and discovered a single missense mutation in CYFIP2 within the 1.5 LOD QTL support interval. Biochemical and physiological analysis revealed this mutation destabilizes CYFIP2 leading to changes in dendritic spine morphology shown to regulate behavior. Mice harboring heterozygous gene deletion of Cyfip2 have acute and sensitized cocaine response phenotypes, confirming CYFIP2 as a regulator of psychostimulant response in mammals.
Our data will be of interest to the general mouse community because embryonic stem cells from C57BL/6N are being used for the Mouse Knockout Project. Our approach will be of interest to the QTL community because there are hundreds of mouse substrains, many with documented phenotypic differences, all of which are amenable to the approach we pilot here.