ARS | Publication request: Mapping, Expression, and Molecular Variation of Potential Candidate Genes Underlying a Major Embryonic Development Rate Qtl in Rainbow Trout

Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract
Publication Acceptance Date: December 15, 2005
Publication Date: December 15, 2005
Citation: Nichols, K., Gahr, S.A., Rexroad III, C.E., Phillips, R., Thorgaard, G. 2005. Mapping, expression, and molecualr variation of potential candidate genes underlying a major embryonic development rate qtl in rainbow trout. Plant and Animal Genome Conference. Abstract ID W205, page 54.

Technical Abstract: A major embryonic development rate QTL has been identified in several crosses of rainbow trout, but potential candidate genes underlying this locus have not been previously identified. From candidate gene mapping efforts, we have identified two genes, a negative growth regulation and differentiation gene (Myd118) and growth hormone receptor (GHR1) that map to this QTL region on linkage group (LG) 8 of the OSUxCW doubled haploid map. Both Myd118 and GHR1 are duplicated in rainbow trout, and the duplicate genes map to LG6 and LG1, respectively. We have or plan to conduct comparative sequence analysis of each of these genes, assessing molecular variation among the OSU and CW clonal lines in coding and non-coding regions. Comparative sequence analysis of Myd118 (on LG8) exhibited no coding differences, with 99.6% nucleotide similarity in the coding region. We are in the process of evaluating sequence differences in GHR, which was only recently mapped. Sequence variation in upstream regulatory regions, accomplished by sequencing genomic BACs isolated for these genes, is also being evaluated. Semi-quantitative RT-PCR expression profiles of the duplicated Myd118 genes, tracked from fertilization to hatch, show similar trends in expression, but the copy mapping to LG8 is a much more rare transcript. Expression profiles of GHR during embryonic development are currently being assessed. This descriptive work on expression profiles and molecular variation for each of these genes will further determine if these genes are indeed true candidate genes for development rate differences, which may be explored further in functional genomics studies.