Hypodiploidy as a prominent attributor to chromosomal aneuploidy in transgenic rabbit embryos

Abstract

Transgenic animals play a vital role in basic research, agriculture and pharmaceutical industries. Rabbits have the advantage of other large laboratory species in that they have a short gestation period and yield large numbers of embryos. Production of transgenic rabbits has been directed towards using the rabbit as a model for large domestic animals or as a basic biological model for studying the mammalian gene regulation. In connection with their use, developmental and health disorders have also been reported in genetically modified animals. Random integration of a transgene can disrupt the function or regulation of an endogenous gene, resulting in insertion mutations or chromosomal aneuploidy. Chromosomal abnormalities affect the developmental potential of early embryos and serve as potential predictors of developmental outcome. This study was aimed at analyzing the cytogenetic profile of transgenic rabbit embryos, which is necessary for selecting optimal lines for dissemination in order to eliminate animals with chromosomal aberrations. Conventional Giemsa stained c-metaphase spreads obtained from blastomeres of intact as well as microinjected transgenic (EGFP and hFVIII) and non-transgenic embryos revealed a significantly higher (P < 0.01) rate of aneuploid cells in transgenic rabbits compared to non-transgenic animals. However, microinjection did not seem to influence the rate of aneuploidy, as the incidence of aneuploidy in non-transgenic blastomeres was significantly lower (P < 0.01) in comparison with intact ones (14.3 vs. 73.33%). The findings suggest hypodiploidy as the prominent attributor to the occurrence of aneuploidy. This is the first report of 100% chromosomal aneuploidy in the embryos of both EGFP and hFVIII transgenic rabbits.

Quality of rabbit vitrified/thawed transgenic embryos

“…Popelková et al (2005) reported that the ability to achieve the hatching in microinjected rabbit blastocysts (94.00%) is comparable with the control group of embryos (90.00%). Microinjection of a foreign gene into the pronucleus of eggs can result in chromosomal aneuploidy (Roychoudhury et al, 2008), and DNA rearrangement during integration can cause decreased yield of blastocyst stage embryos (Voss et al, 1990).…”

Occurrence of chromosomal aneuploidy in rabbit oocytes and embryos at different developmental stages

“…Over-spread metaphases were excluded, only chromosomes in metaphase plates, which were looked complete, were counted. Further, Roychoudhury et al (2008) reported 73.33% aneuploidy occurrence in cells isolated from intact control rabbit embryos in their paper, focused on the influence of transgenesis on the aneuploidy rate. Due to this, the chromosomes were dispersed on the slide within a limited space.…”

“…Further, Roychoudhury et al . (2008) reported 73.33% aneuploidy occurrence in cells isolated from intact control rabbit embryos in their paper, focused on the influence of transgenesis on the aneuploidy rate. Viuff et al .…”

“…Determined 62.5% aneuploidy in the 2cell and 34.65% in 4-cell rabbit embryos differs from 13.7% attained by Iwasaki & Nakahara's (1990) in 2to 4-cell bovine embryos. Further, Roychoudhury et al (2008) reported 73.33% aneuploidy occurrence in cells isolated from intact control rabbit embryos in their paper, focused on the influence of transgenesis on the aneuploidy rate. Viuff et al (2000) published that cytogenetic investigations may result in an unreliable estimation of the number of polyploid embryos because only a few cells from the embryo can be accurately analysed.…”