Efficient Production of Offspring from Japanese Wild-Derived Strains of Mice (Mus musculus molossinus) by Improved Assisted Reproductive Technologies1

Abstract

Because the genetic diversity of the laboratory mouse (Mus musculus) is very limited, wild-derived strains from this genus could provide invaluable experimental models for studies of mouse genetics and epigenetics such as quantitative trait locus analysis. However, such strains generally show poor reproductive performance under conventional husbandry conditions, so their use for large-scale analyses has been limited. This study was undertaken to devise assisted reproductive technologies (ARTs) for the efficient production of offspring in two wild-derived strains, MSM/Ms and JF1/Ms (Mus musculus molossinus). First, as females of these strains are poor responders to equine chorionic gonadotropin (eCG) stimulation, we examined the efficiency of superovulation by injecting anti-inhibin serum followed by human chorionic gonadotropin (hCG). Approximately four to six times more oocytes were ovulated than with eCG-hCG treatment in both strains, reaching ∼25-30 oocytes per female. Consequently, the procedures for in vitro fertilization using these superovulated oocytes and cryopreservation of embryos and spermatozoa could be optimized for both of the wild-derived strains. However, MSM/Ms embryos but not JF1/Ms embryos failed to develop to term after embryo transfer because of intrauterine death at mid to late gestation. We were able to overcome this obstacle by cotransfer of these embryos with those from laboratory strains combined with treatment of recipient females with an immunosuppressant (cyclosporin A). Thus, a series of ARTs essential for efficient production and preservation of the wild-derived strains were successfully devised. These technologies will facilitate systematic studies of mouse genetics and epigenetics using a wider range of genetic diversity than currently available in the genus Mus.

Littermate Influence on Infant Growth in Mice: Comparison of SJL/J and ICR as Cotransferred Carrier Embryos

“…When 2-cell embryos of the mSm/ms mouse strain, an inbred mouse strains derived from Japanese wild mice belonging to the same subspecies of Mus musculus (M. musculus molossinus), were transferred to an iCR female, no mSm/ms pups were born alive because of the intrauterine death of fetuses during late gestation. Hasegawa et al successfully rescued this incidence of fetal death with the combination of cyclosporine a and cotransfer of iCR embryos [10]. B6 & SJL/J cotransfer, B6 transfer, and SJL/J transfer to iCR recipients, however, resulted in live pups without the use of cyclosporine a in this study.…”

Wild-Derived Inbred Mice No Longer ART-Resistant1

“…The exact mechanism whereby GSH enhances fertilization is not known, but it has been suggested that it may be related to the modifications of zona pellucida [11]. The fertilization rates in the JF1/Ms strain reported by Hasegawa et al [1] were very high (.85%) with both fresh and frozen sperm, even without GSH. With MSM/Ms mice, however, sperm freezing decreased the fertilization rates, and this was partially rescued by inclusion of GSH.…”

“…Immunization against inhibin also stimulates follicle development and is successful in the induction of multiple ovulations in a variety of species [6][7][8][9]. Hasegawa et al [1], however, are the first to show that AIS administration is highly successful in facilitating follicle progression and oocyte production in wild-derived inbred mice. Whereas eCG/hCG treatment of MSM/Ms and JF1/Ms females yielded few oocytes (n ; 5), replacement of eCG with AIS resulted in ovulation of as many as 25 oocytes.…”

“…During normal in vivo development, the establishment and maintenance of pregnancy requires cross-talk between the conceptus and maternal environment [13]. Hasegawa et al [1] speculated that the reason for the fetal loss might be impaired maternal-fetal interaction, such as maternal intolerance to the fetus and/or insufficient trophoblast growth and expansion. They first tried overcoming the fetal loss problem by using females of different strains, including one consomic for MSM Chromosome 17 encoding the major histocompatibility complex.…”

“…Cotransfer of normal healthy embryos has also been shown to improve pregnancy rates, particularly with nuclear transfer-derived and transgenic embryos [15,16]. In the hands of Hasegewa et al [1], CsA and cotransfer treatments, applied individually, allowed the birth of the first few viable ART-derived MSM/ Ms fetuses. The combination of both treatments resulted in up to 29% of transferred embryos surviving to term.…”