Genetics. Published Articles Ahead of Print: June 18, 2005, Copyright © 2005
doi:10.1534/genetics.104.040162


A more recent version of this article appeared on September 1, 2005.

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Functional Mapping of Quantitative Trait Loci That Interact With the hg Mutation to Regulate Growth Trajectories in Mice

Rongling Wu 1*, Changxing Ma 1, Wei Hou 1, Pablo Corva 2 and Juan Medrano 2

1 University of Florida
2 University of California at Davis

* To whom correspondence should be addressed. E-mail: rwu{at}stat.ufl.edu.

Submitted on December 20, 2004
Revised on March 25, 2005
Accepted on 14 May 2005


Abstract

The high growth (hg) mutation increases body size in mice by 30-50%. Given the complexity of the genetic regulation of animal growth, it is likely that the effect of this major locus is mediated by other quantitative trait loci (QTL) with smaller effects within a web of gene interactions. In this article, we extend our functional mapping model to characterize QTL that interact with the hg locus during ontogenetic growth. Our model is derived within the maximum likelihood context, incorporated by mathematical aspects of growth laws and implemented with the EM algorithm. In an F2 population founded by a congenic high growth (HG) line and non-HG line, a highly additive effect due to the $hg$ gene was detected on growth trajectories. Three QTL located on chromosomes 2 and X were identified to trigger significant additive and/or dominant effects on the process of growth. The most significant finding made from our model is that these QTL interact with the hg locus to affect the shapes of growth process. Our model provides a powerful means for understanding the genetic architecture and regulation of growth rate and body size in mammals.

Key Words: EM algorithm, functional mapping, growth trajectories, high growth (hg) locus, mice