Responses to divergent selection for plasma concentrations of insulin-like growth factor-1 in mice

• Published in: Genetical Research Vol. 53; no. 3; pp. 187 - 192
• Main Authors: Blair, H. T., McCutcheon, S. N., Mackenzie, D. D. S., Gluckman, P. D., Ormsby, J. E., Brier, B. H.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.06.1989
• Subjects: Animals; Biological and medical sciences; Body Weight; Classical genetics, quantitative genetics, hybrids; Female; Fundamental and applied biological sciences. Psychology; Genetic Variation; Genetics of eukaryotes. Biological and molecular evolution; Insulin-Like Growth Factor I - blood; Insulin-Like Growth Factor I - genetics; Male; Mice; Mice, Inbred Strains; Selection, Genetic; Somatomedins - genetics; Vertebrata; Vertebrata; Mammalia; Genetic variability; Somatomedin C; Mouse; Body weight; Rodentia; Artificial selection; Selection criterion; Inbreeding; Heritability
• ISSN: 0016-6723; 1469-5073
• DOI: 10.1017/S0016672300028159

A divergent selection experiment with mice, using plasma concentrations of insulin-like growth factor-1 (IGF-1) at 42 days of age as the selection criterion, was undertaken for 7 generations. Lines were not replicated. To obtain sufficient plasma for the IGF-1 assay, blood from four individuals was volumetrically bulked to obtain a litter mean IGF-1 concentration. This necessitated the use of between family selection. Although inbreeding accumulated in a linear fashion in each of the high, control and low lines, the rates were different for each line (3·6, 1·6 and 5·3% per generation for the high, control and low lines, respectively). As a consequence, the effects of selection and inbreeding are confounded in this experiment. Divergence between the high and low lines in plasma concentrations of IGF-1 continued steadily until generation 5. In generations 6 and 7, there was a reduced degree of divergence and this contributed towards the low realized heritability value of 0.15 ± 0.12. Six-week liveweight showed a steady positive correlated response to selection for or against plasma concentrations of IGF-1 until generation 4 (high-low difference = 1·7 g = 12%). In generation 5, a substantial drop in 6-week liveweight in the low line relative to both the high and control lines occurred (high-low difference, 3·9; g, 25%). This difference was maintained until generation 7. This experiment suggests that genetic variation exists at 6 weeks of age in plasma concentrations of IGF-1 in mice. Furthermore, genetic covariation between plasma IGF-1 concentrations and liveweight at 6 weeks of age is likely to be positive. Further experiments have been initiated to examine these theories.