Embryo Project Encyclopedia

Karl Oskar Illmensee studied the cloning and reproduction of fruit flies, mice, and humans in the US and Europe during the twentieth and twenty-first centuries. Illmensee used nuclear transfer techniques (cloning) to create early mouse embryos from adult mouse cells, a technique biologists used in later decades to help explain how embryonic cells function during development. In the early 1980s, Illmensee faced accusations of fraud when others were unable to replicate the results of his experiments with cloned mouse embryos. Illmensee also worked with human embryos, investigating how embryos split to form identical twins.

Fortunio Liceti studied natural philosophy and medicine in Italy during the first half of the seventeenth century. Liceti wrote greater than seventy works on a wide range of topics, including the human soul, reproduction, and birth defects observed in animals and human infants. In the seventeenth century, people commonly addressed birth defects using superstition and considered them as signs of evil, possibly caused by spiritual or supernatural entities. Liceti described infants with birth defects as prodigies and monsters to be admired and studied rather than feared. Liceti’s works established monsters as a possible subject of scientific inquiry and served as models for the future study of birth defects, a field later called teratology. Liceti was one of the first scholars to attempt to systematically categorize birth defects based on their causes, including multiple causes unrelated to the supernatural.

In his 1991 article Screening for Congenital Hypothyroidism, Delbert A. Fisher in the US reported on the implementation and impact of mass neonatal screening programs for congenital hypothyroidism (CH) from the early 1970s through 1991. CH is a condition that causes stunted mental and physical development in newborns unless treatment begins within the first three months of the newborn's life. In the early 1970s, regions in Canada and the US had implemented screening programs to diagnose and treat CH as quickly as possible after the infant's birth. By 1991 many other countries had adopted the early screening program, and Fisher estimated that 10 to 12 million newborns per year were tested in the early 1990s. The screening programs, along with physician education and improved screening techniques, such as radioimmunoassay, helped significantly reduce the incidence of abnormal newborn development resulting from untreated congenital hypothyroidism.

In Australia in the 1940s, Norman McAlister Gregg observed a connection between pregnant women who contracted the rubella virus, or German measles, and cataract formation in their children's eyes. Gregg published his findings in the 1941 article Congenital Cataract following German Measles in the Mother in Transactions of the Ophthalmological Society of Australia. In the article, Gregg analyzed seventy-eight cases of congenital cataracts and suggested that the mothers' environmental factors could cause birth defects, otherwise known as teratogenic effects. Gregg's paper on the teratogenic effects of an environmental agent, the rubella virus, changed the study of birth defects to include viruses as potential causes or teratogens.

Fetal surgeries are a range of medical interventions performed in utero on the developing fetus of a pregnant woman to treat a number of congenital abnormalities. The first documented fetal surgical procedure occurred in 1963 in Auckland, New Zealand when A. William Liley treated fetal hemolytic anemia, or Rh disease, with a blood transfusion. Three surgical techniques comprise many fetal surgeries: hysterotomy, or open abdominal surgery performed on the woman; fetoscopy, for which doctors use a fiber-optic endoscope to view and make repairs to abnormalities in the fetus; and percutaneous fetal theray, for which doctors use a catheter to drain excess fluid. As the sophistication of surgical and neonatal technology advanced in the late twentieth century, so too did the number of congenital disorders fetal surgeons treated, such as mylomeningeocele, blocked urinary tracts, twin-to-twin transfusion syndrome, polyhydramnios, diaphragmatic hernia, tracheal occlusion, and other anomalies. Many discuss the ethics of fetal surgery, as many consider it contentious, as fetal surgery risks both the developing fetus and the pregnant woman, and at times it only marginally improves patient outcomes. Some argue, however, that as more advanced diagnostic equipment and surgical methods improve, advanced clinical trials in a few conditions may demonstrate more benefits than risks to both pregnant women and fetuses.

Anencephaly is an open neural tube defect, meaning that part of the neural tube does not properly close or that it has reopened during early embryogenesis. An embryo with anencephaly develops without the top of the skull, but retains a partial skull, including the face. Anencephaly is one of the most common birth defects of the neural tube, occurring at a rate of approximately one in one thousand human pregnancies. The condition can be caused by environmental exposure to chemicals, dietary deficiencies, or genetic mutations.

Fetus in fetu is a rare variety of parasitic twins , where the developmentally abnormal parasitic twin is completely encapsulated within the torso of the otherwise normally developed host twin. In the late eighteenth century, German anatomist Johann Friedrich Meckel was the first to described fetus in fetu, which translates to “fetus within fetus.” Fetus in fetu is thought to result from the unequal division of the totipotent inner cell mass , the mass of cells that is the ancestral precursor to all cells in the body. The unequal division is thought to occur during the formation of the blastocyst, which can also result in parasitic and conjoined twins . Fetus in fetu represents a developmental anomaly that has prompted developmental biologists to further examine the mechanisms for how twins arise.

In 1616 in Padua, Italy, Fortunio Liceti, a professor of natural philosophy and medicine, wrote and published the first edition of De Monstruorum Causis, Natura et Differentiis (On the Reasons, Nature, and Differences of Monsters), hereafter De monstruorum. In De monstruorum, Liceti chronologically documented cases of human and animal monsters from antiquity to the seventeenth century. During the seventeenth century, many people considered such monsters as frightening signs of evil cursed by spiritual or supernatural entities. Liceti categorized monsters based on their potential causes, several of which he claimed were unrelated to the supernatural. Historians later noted that some documented monsters were infants with birth defects. In De monstruorum, Liceti elevated the status of monsters to potential subjects of scientific inquiry and provided an early model for the study of birth defects, a field later called teratology.

Roy John Britten studied DNA sequences in the US in the second
half of the twentieth century, and he helped discover repetitive
elements in DNA sequences. Additionally, Britten helped propose
models and concepts of gene regulatory networks. Britten studied the
organization of repetitive elements and, analyzing data from the
Human Genome Project, he found that the repetitive elements in DNA
segments do not code for proteins, enzymes, or cellular parts.
Britten hypothesized that repetitive elements helped cause cells to
differentiate into more specific cell kinds among different
organisms.

In the early 2000s, Manjong Han, Xiaodang Yang, Jennifer Farrington, and Ken Muneoka investigated how genes and proteins in fetal mice (Mus musculus) influenced those fetal mice to regenerate severed toes at Tulane University in New Orleans, Louisiana. The group used hind limbs from mice to show how the gene Msx1 (Homeobox 7) functions in regenerating amputated digits. The researchers showed that in the process of regenerating digit tips, Msx1 genes make products that regulate or influence other genes, such as the Bone Morphogenetic Protein 4 gene (BMP4 gene), to produce proteins, such as the BMP4 proteins. The researchers also showed that BMP4 proteins, which are produced from the BMP4 gene, function in tissues during the process of limb development. Furthermore, while Msx1 genes regulate other genes during the process of regeneration, they don't produce proteins otherwise needed to organize cells in the regeneration of digit tissues. The group published their results in 2003 as Digit Regeneration Is Regulated by Msx1 and BMP4 in Fetal Mice.