The basic amount of cell migration that I have learned has led me to believe that it only happens in developing embryos. In fact, I am wrong. This article has taught me that it is very important in adult brains also. In fact this article is actually a blog about the work that this man, Dan, has done.
While cell migration is still mostly seen in fetuses, in terms of numbers of cells migrating in a small amount of time, migration as an adult is also critical. Migration of white blood cells helps the body to fight off disease and destroy pathogens that the body may have picked up. A continued expression of these fighters could result in inflammation though, so a solid balance is required between fight and retreat. I found it very interesting that this is actually the cause of asthma. If a person with asthma develops leukemia do they still have asthma? (Keep in mind that this question is NOT meant as a joke or harp on either of these diseases, but a serious question in terms of white blood cell counts. I mean no offense to anyone.)
From the beginning not only do the eggs and sperm have to travel to the meeting place but then the embryo has move to the uterus wall. The cells then divide and become differentiated. This also requires migration. There is especially coordinated migration in the young brain. The right connections need to be made in the right areas otherwise fatal or serious defects could occur. I would like to think of it as a dance or play of some sort where each person or nerve knows what it has to do and where it has to be at what part of the act. I know that many teachers and authors like to equate it to an orchestra.
It all just blows my mind that a human, or any organism, can develop from a single cell that has a mash of genes and develop into a fully functioning adult. Some times there are mistakes, but even then it is still on one in a couple hundred. It is a miracle! Another thing that I have learned about cell migration, not from this article, is that cells can know where they need to go based on the cells around them. Or they can differentiate into a certain cell based on their locations. The things that the brain can do, especially only days into development, are truly amazing and it's no wonder that most of it is still a mystery to the current generations.