Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2001
Publication Date: 10/20/2001
Citation: Smith, T.P., Showalter, A.D., Sloop, K.W., Rohrer, G.A., Fahrenkrug, S.C., Meier, B.C., Rhodes, S.J. 2001. Identification of porcine lhx3 and sf1 as candidate genes for qtl affectinggrowth and reproduction traits in swine. Animal Genetics. 32:344-350. Interpretive Summary: Genetic variation in a region of porcine chromosome 1 has been shown to affect age at puberty, backfat thickness, and early growth rate in a research population at MARC in a previous manuscript. The current manuscript is a comparative mapping study to attempt to determine which gene or genes is causing this variation. Two potential candidate genes, called SF-1 and Lhx3, that have been shown to affect growth and sexual maturation in other species were chosen and mapped to this region of chromosome 1. The mapping and analysis of pituitary regulatory genes such as SF-1 and Lhx3 will support further investigations into the possible roles these genes play in important production characteristics, and is a first step in potential identification of the specific DNA sequence differences that lead to the observed variation. Characterization of the biochemical mechanisms of the encoded transcription factors may allow the development of genetic protocols or tests to improve productivity in the meat industry.
Technical Abstract: The distal portion of the long arm of porcine chromosome 1 has been shown to harbor several quantitative trait loci affecting growth and reproductive traits in swine. In order to identify potential candidate genes that might underlie these effects, a comparative mapping analysis was undertaken to define the extent of orthologous segments of human chromosome 9. A microsatellite associated with heat shock protein A5 was used to define the proximal boundary of the QTL region, which suggests the human ortholog of the gene(s) responsible for the observed effects lies between HSPA5 and the q arm telomere of human chromosome 9. Examination of this region revealed two candidate genes with known roles in production of hormones essential to growth and reproductive function. The steroidogenic factor 1 and Lhx3 LIM homeodomain transcription factor genes were mapped to 123 and 155 cM, respectively, of the SSC1 linkage group, placing both genes within the confidence interval for the observed QTL. To further evaluate Lhx3, we examined the expression profile during porcine embryonic development. Low levels were detected at early embryonic stages, when development of the nervous system is proceeding. A transient increase in expression level is observed during the time of pituitary organogenesis and again at the time of differentiation of anterior pituitary cells, with relatively high levels of expression persisting in the adult pituitary gland. This ontology is consistent with Lhx3 being a candidate gene for the QTL.