title: Correlated responses to selection for large body size in oMt1a-oGH transgenic mice: reproductive traits.
abstract: Correlated responses in female reproductive performance were evaluated following short-term selection within full-sib families for increased 8-week body weight in two replicates of four lines of mice: two ovine metallothionein-ovine growth hormone (oMt1a-oGH) transgene-carrier lines, one from a high-growth background (TM) and one from a control background (TC), and two non-transgenic lines, one from each of these genetic backgrounds (NM and NC, respectively). A fifth line (CC), not containing the transgene, served as a randomly selected control. The initial frequency of the oMt1a-oGH transgene construct in the TM and TC lines was 0.5. The frequency of transgenic females sampled at generations 7 and 8 of selection was 84.0% and 6.1% in the TC and TM lines, respectively. No significant female infertility differences were detected between transgene-carrier and non-transgenic lines or between transgenic and non-transgenic mice within carrier lines, whereas high-growth background lines had a higher infertility than control background lines (P < 0.05). Correlated responses in the TC transgene-carrier line were suggestive of reduced reproductive performance as indicated by increased post-implantation mortality (P < 0.05), number of dead fetuses plus implants (P < 0.05), and loss of fetuses from day 16 to parturition (P < 0.001). For the first two traits, the negative correlated responses were accounted for by the reduced performance of transgenic compared with non-transgenic females. Embryos carrying the transgene may also have a lower viability. In contrast, the NC non-transgenic line did not exhibit reduced reproductive performance for these traits. The low frequency of the transgene in the high-growth background TM line was associated with reduced fitness and a lower additive effect for 8-week body weight compared with the control background TC line.
authors.affiliation: Department of Animal Science, North Carolina State University, Raleigh 27695, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Parks
authors.forename: E J
authors.initials: EJ
authors.lastname: Eisen
authors.forename: I J
authors.initials: IJ
authors.lastname: Parker
authors.forename: L G
authors.initials: LG
authors.lastname: Hester
authors.forename: J D
authors.initials: JD
authors.lastname: Murray
mesh_terms: D000818:Animals; D001835:Body Weight; D005260:Female; D013006:Growth Hormone / Q000235:genetics / Q000502:physiology*; D007247:Infertility, Female; D008668:Metallothionein / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D010060:Ovulation; D012098:Reproduction / Q000502:physiology*; D012756:Sheep
chemical_list: D013006:Growth Hormone; D008668:Metallothionein