Tissue-specific Rescue Suggests That Placental Adenosine Deaminase Is Important for Fetal Development in Mice

Abstract

Adenosine deaminase (ADA, EC 3.5.4.4) is an essential enzyme of purine metabolism that is expressed at very high levels in the murine placenta where it accounts for over 95% of the ADA present at the fetal gestation site. We have recently shown that ADA-deficient fetuses, which also lack ADA in their adjoining placentas, die during late fetal development in association with profound purine metabolic disturbances and hepatocellular impairment. We have now investigated the potential importance of placental ADA by genetically restoring the enzyme to placentas of ADA-deficient fetuses. This genetic engineering strategy corrected most of the purine metabolic disturbances, prevented serious fetal liver damage, and rescued the fetuses from perinatal lethality. Our findings suggest that placental ADA is important for murine fetal development and illustrate a general strategy for the tissue specific correction of phenotypes associated with null mutations in mice.During mammalian development the first differentiation event gives rise to the trophectoderm, which in turn provides lineages for specialized extraembryonic cells known as trophoblasts. These cells make the physical connection between the embryo and the maternal environment and play important roles in the implantation process and placental function (1). Inadequate placental development is associated with a high incidence of early embryonic mortality (2-4) and serious pregnancy disorders such as preeclampsia (5). Although the formation of a functional placenta is essential for mammalian embryogenisis and fetal development, relatively little is known about the molecular mechanisms that govern trophoblast differentiation and subsequent function. Determining what proteins are produced in trophoblasts and elucidating their physiological roles is an important part of understanding how this cell lineage contributes to the formation of a functional placenta.One such protein that is highly abundant in the murine placenta is adenosine deaminase (ADA).1 ADA is an essential enzyme of purine metabolism that is expressed at very high levels in trophoblasts of the murine placenta (6, 7). The physiological importance of ADA in trophoblasts of the placenta is not known. However, recent evidence suggests that ADA is essential during fetal stages of development. ADA-deficient fetuses, which also lacked ADA in trophoblasts of their adjoining placentas, died perinatally in association with profound purine metabolic disturbances and hepatocellular impairment (8, 9). Considering that greater than 95% of ADA enzymatic activity found in the fetal gestation site resides in trophoblasts of the placenta, it is likely that placental ADA plays an essential role during fetal development. Here we show that genetically restoring ADA to placentas of ADA-deficient fetuses rescued them from perinatal lethality, thereby providing compelling evidence for the importance of placental ADA for fetal development. MATERIALS AND METHODS ADA Minigene Construction and Transgenic Mouse Generation-Theplasmid, Ϫ...

Adenosine-Dependent Airway Inflammation and Hyperresponsiveness in Partially Adenosine Deaminase-Deficient Mice

“…Male mice homozygous for the null Ada allele and carrying a placentalspecific ADA minigene that allows for prenatal rescue were intercrossed with females heterozygous for the null Ada allele (22). Southern blot analysis of genomic DNA obtained from tails at weaning was used to determine the genotypes of the resulting progeny (21).…”

“…ADA-deficient fetuses die prenatally due to the absence of ADA in their placentas (22). ADA-deficient fetuses were rescued from prenatal lethality by the expression of an ADA minigene in their placentas (21,22).…”

“…ADA-deficient fetuses were rescued from prenatal lethality by the expression of an ADA minigene in their placentas (21,22). With the loss of their placentas, these rescued pups were completely ADA-deficient and went on to die at 3 wk of age from severe pulmonary inflammation and damage that was linked to pronounced elevations in lung adenosine levels (21,26).…”

Adenosine deaminase, a key enzyme in DNA precursors control, is a new p73 target

“…Indeed, although the main function of ADA is the development of the immune systems in humans, it also seems to be associated with the differentiation of epithelial cells and monocytes, neurotransmission and maintenance of gestation (Moriwaki et al, 1999); besides, increasing evidences indicate that maintaining high levels of ADA in mice placenta is essential for embryonic and fetal development (Blackburn et al, 1995;Shi et al, 1997). All these observations indicate that the ADA protein is critical for development and cell proliferation.…”

Functional Map of a Placenta-specific Enhancer of the Human Leukemia Inhibitory Factor Receptor Gene

“…Mice lacking a functional leptin gene not only became massively obese (50), but also are infertile (51), but no placental abnormality was reported. ADA-deficient fetuses lacking ADA in their adjoining placenta die during late fetal development (52), while genetically restoring ADA to placentas of ADA-deficient fetuses rescued them from perinatal lethality (53). While GATA-3 knockout mice have severe abnormalities in the nervous system and fetal liver hematopoiesis (54), and GATA-2 knockout mice are defective in early hematopoietic cell proliferation and mast cell formation (55), both GATA-2 and GATA-3 knockout mice did not show placental abnormalities, thus supporting the presence of other GATA family members functioning in the placenta.…”