Understanding basic biological processes
Detailed knowledge of how each of our organ systems develops is far from complete. Many March of Dimes grantees are conducting research on basic biological processes of development. Grantees continue to probe how specific genes guide the development of each organ, and how environmental factors may influence the process. Better understanding of normal and abnormal development provides a much-needed basis for developing new strategies to prevent or treat specific birth defects.
Some grantees are exploring a remarkable process that occurs before fertilization that is crucial for normal development. Developing egg and sperm cells undergo a specialized form of cell division called meiosis that reduces the number of chromosomes by half so that the embryo ends up with the correct number of chromosomes (23 pairs of chromosomes, or 46 in all).
Sometimes during meiosis, egg or sperm cells end up with too many or too few chromosomes. When fertilization occurs, errors in chromosome number lead to miscarriage, stillbirth or birth of a baby with chromosomal birth defects, such as Down syndrome. These birth defects affect about 1 in 150 babies.
March of Dimes grantees are seeking to understand the cellular mechanisms that allow meiosis to run smoothly, in order to learn what can go wrong. For example, Kevin Charles Slep, PhD, of the University of North Carolina at Chapel Hill, is investigating how each chromosome becomes attached to a spindle fiber that pulls each member of a chromosome pair to the opposite end of the cell during division, helping to assure that each daughter cell receives the correct number of chromosomes. Others, such as Maitreya Dunham, PhD, of the University of Washington at Seattle, are seeking to determine how errors in chromosome number causes specific birth defects, as a step toward developing treatments.
Many other grantees are studying genes that regulate the development of various organ systems, including certain 'master genes' that guide embryonic cells to the appropriate sites to form the heart, limbs, eyes, kidney, spinal column and brain. One of the most complicated organ systems to build is the brain. Many genes take part in this complex process that starts in the earliest days of pregnancy and continues after birth. Errors can occur at any step along the way, sometimes resulting in intellectual disabilities, seizures or even death.
March of Dimes grantees are studying all stages of brain development. Some examine the early stages when the brain cleaves into the right and left hemispheres. Others look at what happens after the basic architecture necessary for normal brain function is in place. For example, during the third to fifth month, billions of nerve cells migrate from their birthplace in the brain to the cerebral cortex, the thinking part of the brain. Serious abnormalities in this migration can lead to lissencephaly ("smooth brain"), a severe brain malformation in which the surface folds of the brain are missing. Children with lissencephaly have severe intellectual disabilities and usually do not survive. David Joseph Solecki, PhD, of St. Jude Children's Research Hospital in Memphis, Tennessee, is examining the role of a gene family in regulating this migration for insight into its role in causing lissencephaly as well as more subtle learning problems and seizures. Other grantees study how nerve cells form connections and communicate with each other, which could help explain how miswiring of the brain may contribute to intellectual disabilities and autism.