Physiol. Genomics 31: 75-85, 2007.
First published May 29, 2007; doi:10.1152/physiolgenomics.00267.2006

1094-8341/07 $8.00
Received 6 December 2006;
accepted in final form 25 May 2007.
Physiological Genomics 31:75-85 (2007)
1094-8341/07 $8.00 © 2007 American Physiological Society
Identification of positional candidate genes for body weight and adiposity in subcongenic mice
Sally Chiu1,
Kyoungmi Kim1,
Kari A. Haus1,
Glenda M. Espinal1,
Lee V. Millon2 and
Craig H. Warden1,3
1 Rowe Program in Genetics, University of California, Davis, California
2 School of Veterinary Medicine, University of California, Davis, California
3 Section of Neurobiology, Physiology, and Behavior, University of California, Davis, California
We previously constructed a congenic mouse, B6.S-D2Mit194-D2Mit311 (B6.S-2) with 27 Mb of SPRET/Ei donor DNA on distal chromosome 2 in a C57BL/6J background that captured an obesity quantitative trait locus (QTL). Mice homozygous for SPRET/Ei alleles at the donor region had decreased body weight and obesity-related phenotypes (Diament AL, Farahani P, Chiu S, Fisler J, Warden CH. Mamm Genome 15: 452–459, 2004). In this study, we constructed five overlapping subcongenics with smaller SPRET/Ei donor regions to fine map the underlying gene(s). One of the five subcongenic lines derived from the B6.S-2 founding congenic, B6.S-2A, captured the body weight and adiposity phenotypes in a donor region with a maximum size of 7.4 Mb. Homozygous SPRET/Ei donor alleles in both the founding congenic and the derived B6.S-2A subcongenic exhibited significant decreases in body weight, multiple fat pad weights, and adiposity index (total fat pad weight divided by body weight). Interval-specific microarray analysis in four tissues for donor region genes from the founding B6.S-2 congenic identified several differentially expressed genes mapping to the B6.S-2A subcongenic donor region, including prohormone convertase 2 (PC2; gene name: Pcsk2). Quantitative real-time PCR confirmed a modest decrease of PC2 expression in brains of mice homozygous for SPRET/Ei donor alleles. Analysis of the relative levels of mRNA for B6 and SPRET/Ei in heterozygous congenic mice showed differentially higher expression of the C57BL/6J allele over the SPRET/Ei allele, indicating a cis regulation of differential expression. Using subcongenic mapping, we successfully narrowed a body weight and obesity QTL interval and identified PC2 as a positional candidate gene.
quantitative trait locus mapping; mouse chromosome 2; congenic strains; microarray
Copyright © 2007 by the American Physiological Society.