Clues to ancestral origin of placenta emerge in Stanford studyApril 15, 2008STANFORD, Calif. - Researchers at the Stanford University School of Medicine have uncovered the first clues about the ancient origins of a mother's intricate lifeline to her unborn baby, the placenta, which delivers oxygen and nutrients critical to the baby's health. The evidence suggests the placenta of humans and other mammals evolved from the much simpler tissue that attached to the inside of eggshells and enabled the embryos of our distant ancestors, the birds and reptiles, to get oxygen. "The placenta is this amazing, complex structure and it's unique to mammals, but we've had no idea what its evolutionary origins are," said Julie Baker, PhD, assistant professor of genetics. Baker is senior author of the study, which will be published in the May issue of Genome Research.
The placenta grows inside the mother's uterus and serves as a way of exchanging gas and nutrients between mother and fetus; it is expelled from the mother's body after the birth of a baby. It is the only organ to develop in adulthood and is the only one with a defined end date, Baker said, making the placenta of interest to people curious about how tissues and organs develop. Beyond being a biological curiosity, the placenta also plays a role in the health of both the mother and the baby. Some recent research also suggests that the placenta could be a key barrier in preventing or allowing molecules to pass to the unborn baby that influence the baby's disease risk well into adulthood. "The placenta seems to be critical for fetal health and maternal heath," Baker said. Despite its major impact, almost nothing was known about how the placenta evolved or how it functions. Baker and Kirstin Knox, graduate student and the study's first author, began addressing the question of the placenta's evolution by determining which genes are active in cells of the placenta throughout pregnancy in mice. They found that the placenta develops in two distinct stages. In the first stage, which runs from the beginning of pregnancy through mid-gestation, the placental cells primarily activate genes that mammals have in common with birds and reptiles. This suggests that the placenta initially evolved through repurposing genes the early mammals inherited from their immediate ancestors when they arose more than 120 million years ago. In the second stage, cells of the mammalian placenta switch to a new wave of species-specific genes. Mice activate newly evolved mouse genes and humans activate human genes. It makes sense that each animal would need a different set of genes, Baker said. "A pregnant orca has different needs than a mouse and so they had to come up with different hormonal solutions to solve their problems," she said. For example, an elephant's placenta nourishes a single animal for 660 days. A pregnant mouse gestates an average of 12 offspring for 20 days. Clearly, those two pregnancies would require very different placentas. Baker said these findings are particularly interesting given that cloned mice are at high risk of dying soon after the placenta's genetic transition takes place. "There's obviously a huge regulatory change that takes place," she said. What's surprising is that despite the dramatic shift taking place in the placenta, the tissue doesn't change in appearance. Understanding the placenta's origins and function could prove useful. Previous studies suggest the placenta may contribute to triggering the onset of maternal labor, and is suspected to be involved in a maternal condition called pre-eclampsia, which is a leading cause of premature births. Baker intends to follow up on this work by collaborating with Theo Palmer, PhD, associate professor of neurosurgery; Gill Bejerano, PhD, assistant professor of developmental biology, and Anna Penn, MD, PhD, assistant professor of pediatrics. Together, the group hopes to learn how the placenta protects the growing brain of the unborn baby, a protection that seems to extend into adulthood. Stanford University Medical Center Science News and Science Current Events Tag Cloud This tag cloud is a visual representation of term frequencies of random science news topics with common terms grouped together and emphasized by their display size. Oral Cancer Hepatitis B Planet Parkinson’s Disease Gastric Bypass Malpractice Amputation Back Pain Pulmonary Embolism Bison Staph Infection Tuberculosis Heart Muscle Lead Exposure Vitamin C Cocaine Ozone Hole Allergic Reaction Anthrax Metastasis Black Hole Salmonella Diabetes Parkinsons disease Hippocampus
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Related Placenta Current Events and Placenta News Articles Female human embryos adjust the balance of X chromosomes before implantation Dutch researchers have found the first evidence that a process of inactivating the X chromosome during embryo development and implantation, which was known to occur in mice but unknown in humans, does, in fact, take place in human female embryos prior to implantation in the womb. Complications early in pregnancy or in previous pregnancies adversely affect existing or subsequent pregnancies Complications in early pregnancy or in previous pregnancies can predict the likelihood of further problems in current or subsequent pregnancies, according to research carried out by an international group of experts. Human term placenta a new abundant source of hematopoietic cells Investigators at Children's Hospital Oakland Research Institute, Oakland, California found a way to obtain large numbers of hematopoietic stem cell from human term placenta. Tiny levels of carbon monoxide damage fetal brain A UCLA study has discovered that chronic exposure during pregnancy to miniscule levels of carbon monoxide damages the cells of the fetal brain, resulting in permanent impairment. Children's Hospital Oakland scientists first to discover new source for harvesting stem cells A groundbreaking study conducted by Children's Hospital & Research Center Oakland is the first to reveal a new avenue for harvesting stem cells from a woman's placenta, or more specifically the discarded placentas of healthy newborns. Three to six months to lose weight gained in pregnancy is normal Once the baby arrives, many new mothers want to return to their former weight quickly - just like film stars who appear in the media in bikinis just weeks after giving birth. Cocaine and heroin harm placenta Cocaine and heroin increase permeability of the placenta. Researchers writing in BioMed Central's open access journal Reproductive Biology and Endocrinology have shown that exposure to the drugs causes an increase in the passage of some chemicals into the fetus. 2 studies: The first finds twins born after fertility treatment have a higher risk of problems Twins born as a result of assisted reproductive technology (ART) are more likely to be admitted to neonatal intensive care and to be hospitalised in their first three years of life than spontaneously conceived twins New and improved tomato analyzer Tomatoes come in a variety of sizes and shapes, making them the perfect subject to test shape-analyzing software. Gladstone scientists identify key factors in heart cell creation Scientists at the Gladstone Institute of Cardiovascular Disease have identified for the first time key genetic factors that drive the process of generating new heart cells. More Placenta Current Events and Placenta News Articles |
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