Cloning and characterization of an apoptosis-associated gene in the human placenta

Placenta is a transient feto-maternal association that develops during mamm alian pregnancies. Human placental tissue during the first trimester of pre gnancy is an actively dividing and differentiating tissue, while near term, it represents a fully differentiated unit performing many life-sustaining functions for the fetus. Previous studies have demonstrated that the percen tage of placental cells that undergo apoptosis is greater at full term as c ompared to the first trimester of pregnancy. In this study, we undertook a study aimed at gaining an insight into the kind of genes expressed in the t wo developmentally distinct stages of gestation ie, the first trimester and term using Differential Display RT-PCR. Cloning and sequencing of one of t he differentially expressed cDNAs from term placental tissue revealed that it is a novel gene, referred to as T-18 in the text. In this study, we also examined the regulation of this gene during apoptosis in the human placent a. A model for analysis of placental apoptosis was established by incubatin g placental villi in serum-free culture medium. It was observed that apopto sis occurred rapidly following incubation of placental villi without tropic support, and the proposed free-radical scavenger, superoxide dismutase (SO D) suppressed apoptosis in the placenta. Interestingly, the levels of T-18 mRNA increased significantly during spontaneous induction of apoptosis and decreased when apoptosis was blocked by SOD. These data clearly suggest tha t there is a strong correlation between the expression of T-18 and placenta l apoptosis and that T-18, may play a significant role in this process. Fur thermore, the establishment of a defined in vitro explant culture model sho uld facilitate elucidation of factors, which regulate apoptosis in human pl acenta.