Distribution of blastodermal cells transferred to chick embryos for chimera production using windowed eggs

Improved surrogate eggshell incubation system for assisted reproductive technologies such as cloning, genome modification, and de-extinction efforts

A germinal disc located on the egg yolk surface drives genetic modification. Windowed and surrogate eggshell incubation methods have been developed, but these exhibit limited abilities to generate transgenic chickens. In the present study, we investigated the frequency of observing the germinal disc according to the preincubation positioning direction and time and found that it depended on those conditions, but only a few chicks (2.8-5.6%) hatched using the windowed method. Then, we attempted to improve surrogate method via one- or two-step procedures. All eggs, including surrogates that were 10 g heavier than the donor eggs, were obtained from a poultry flock of the same age. With the one-step surrogate method, where the donor egg was transferred only once through a 3.5 cm hole on the point end, at the first day of preincubation, into the surrogate egg, the survival rate at day 4 was 30.8%, and the hatching rate was 11.8%. With the two-step surrogate method (transfer was on the 1st and 4th day of incubation), the survival rate at day 4 was improved to 90.7%, and a hatching rate of 70.0% was achieved. Therefore, this method can be effective for in ovo artificial incubation.

Contribution of cells derived from the area pellucida to extraembryonic mesodermal cell lineages in heterospecific quail chick blastodermal chimeras

The current study has two main objectives: first, to determine if cells derived from the area pellucida are able to populate extraembryonic membranes, and second, to determine if donor cells have the potential to differentiate to endothelial (EC) and hematopoietic cells (HC) in the yolk sac and allantois, the two extraembryonic membranes functioning as hematopoietic organs in the avian embryo. To this end, quail chick chimeras were constructed by transferring dissociated cells from the areae pellucidae of the stage X-XII (EG&K) quail embryo into the subgerminal cavity of the unincubated chick blastoderm. The distribution of quail cells in the allantois, yolk sac, amnion, and chorion of resulting putative chimeras was examined using quail cell-specific antibody against a perinuclear antigen (QCPN) after 6 days of incubation. The presence of EC, HC, and smooth muscle cells among the QCPN(+) donor cells was examined using QH-1, a quail-specific marker identifying HC and EC and an anti-α-smooth muscle actin antibody. Evidence gathered in the present study demonstrates that quail cells derived from the areae pellucidae are able to populate all of the extraembryonic membranes of resulting heterospecific quail chick chimeras and, most importantly, give rise to HC, EC, and smooth muscle cells, all of the three main mesodermal lineages derived from the posterior mesoderm both in the yolk sac and allantois.

Improvement of hatchability of chicken eggs injected by blastoderm cells

In our first experiment, we studied the effect of injection method of blastoderm cells (BC) into the subgerminal cavity of White Leghorn embryos on hatchability of chicken chimeras. Freshly laid eggs were injected through a hole made in the equatorial plane of the eggshell (Method A). In Method B, eggs were stored pointed end down for 5 to 7 d prior to injection, and a hole was cut in the blunt end of the eggshell. An advantage of Method B was that the early embryonic mortality was reduced (P < or = 0.01) and resulted in higher hatchability (41.0%; 43/105) than Method A (9.8%; 14/143). In the second experiment, we studied chicken hatchabililty as influenced by windowing (no hole, Group 1; hole in the equatorial plane, Group 2; hole in the blunt end of egg, Groups 3 and 4) and egg turning (Groups 1 and 4) or not (Groups 2 and 3) during incubation. The hatchability percentages were as follows: 67.9 (Group 1) 0.0, (Group 2) 23.3, (Group 3), and 56.8 (Group 4). A statistically significant difference (P < or = 0.05) was noted between Group 1 or 4 and the other groups. We found no statistically significant differences in the weight changes (g) but did note certain differences in the egg weight loss (%) among different egg treatments. In the third experiment, we investigated the influence of origins of BC donors: Rhode Island Red (RIR), Barred Plymouth Rock (BPR), and Green-legged Partridgelike (GP) on hatchability of putative and somatic chimera chickens. The hatchability of chimeras was dependent on the adequate assortment of BC of the donor and ranged from 7.4% (RIR) to 56.1% (GP). In the case of BC injection of the GP breed, good hatchability was accompanied by very high percentage (86.9; 20/23) of somatic chimeras.