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Highlights

Manipulating fowl reproduction.

Recent studies in the mouse have demonstrated that grafts of testis fragments or transplantation of spermatogonial cells can give rise to sperm capable of contributing to the development of a new individual. On p. 598 of this issue, Song and Silversides report the transplantation of testicular tissue between newly-hatched chicks and the subsequent generation of donor-derived offspring by inseminating hens with a suspension of cells harvested from the transplanted testis of mature birds. Transplants from black feathered Barred Plymouth Rock chicks placed under the skin or in the abdomen of castrated and immunocompromised White Leghorn chicks produced motile sperm. Fluid exuded from the surface of transplanted testicular tissue cut into small pieces was injected through an incision in the body wall into the magnum of the oviduct resulted in the production of fertile eggs that gave rise to chicks with black feathers. This study lays the groundwork that will lead to new experimental approaches and developing methods for preservation of poultry lines and of the germ cell line of endangered birds.

Yonghong Song and Frederick Silversides. Heterotopic Transplantation of Testes in Newly Hatched Chickens and Subsequent Production of Offspring via Intramagnal Insemination Biol Reprod 2007; 76:598–603. Published online ahead of print 13 December 2006; DOI 10.1095/biolreprod.106.058032

Pregnancy as a complex trait.

The complex processes involved in establishing a successful pregnancy are undoubtedly under genetic regulation, but this has been difficult to approach on a global scale. However, on p. 709 of this issue, Konno and colleagues report a study on placentation in two different genetic strains of inbred rats with inherent differences in litter size due to pregnancy loss. Disparate litter sizes were manifest in early pregnancy, leading to discovery of striking differences in placentation in the two strains of rats studied. The brown Norway (BN) rat, with low litter size, was found to possess a profound impairment in intrauterine trophoblast cell invasion, a growth restricted junctional zone compartment of the chorioallantoic placenta, and compensatory increases in uterine natural killer (NK) cells. Uterine NK cells are regulators of placental morphogenesis and endometrial angiogenesis in mice and humans and have been implicated in pregnancy diseases in the human, including preeclampsia. These studies provide an excellent genetic model for discovering novel mechanisms regulating placentation and fetal growth. Physiological genomics and gene discovery will be accelerated in these rat strains, because the BN rat genome represents the genome sequenced for the rat genome project and because chromosome-substituted rat strains have been generated with BN chromosomes; both resources provide powerful approaches for uncovering genes and networks regulating complex biological processes in pregnancy.

Toshihiro Konno, Lea A. Rempel, Juan A. Arroyo, and Michael J. Soares. Pregnancy in the Brown Norway Rat: A Model for Investigating the Genetics of Placentation. Biol Reprod 2007; 76:709–718. Published online ahead of print 3 January 2007; DOI 10.1095/biolreprod.106.056481

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