Abnormalities in liver morphogenesis attributed to the Bh (black at hatch) lethal gene in the Japanese quail.

Abstract

Homozygous Japanese quail embryos for Bh (black at hatch) gene died at 6-9 days of incubation in the intra Bh (black at hatch) strain matings and at 5-9 days of incubation in the matings arranged with F1 hybrids between Bh strain and alien colony. In both experiment, however, the lethal period was Stages 18-26 of ZACCHEI'S standard10). The lethal period of the Bh homozygous embryos is thought to be 4-9 days of incubation incorporating the previously reported results by MINEZAWA and WAKASUGI5). Characteristics of the Bh homozygous embryos were degeneration of the liver tissue and whole body subcutaneous haemorrhage. Two possibilities were presented concerning the lethality of the homozygous embryos. The first was that degeneration of the liver tissue might be the major factor. The second was that disintegration or dysfunction of the capillaries might be the major factor. These possibilities were discussed in relation to the normal process of the liver morphogenesis and the results obtained through the culture of embryonic liver grafts on the chorioallantoic membrane of the chick.In the liver of some embryos after 9 days of incubation, degenerated region was found at the posterior tip of the left lobe (focal degeneration). This abnormality was observed in about one-third of the Bh heterozygous and in about one-thirteenth of the wild type embryos at 10-12 days of incubation. At 15 days of incubation, the incidence decreased in heterozygotes. The abnormal tissue at this region seems to be replaced by the neighboringnormal tissue with progress of development.