The importance of maternal care during the early stages of life

Research Summary
Chelsea Maniscalco
Contributing writer for Baby Sleep News

We know that maternal care is important after a baby is born, but do you know the scientific reason why? There is still much more to be understood on this topic, but it is known that brain development is influenced by early life experiences. Scientists at the Salk Institute for Biological Studies in California recently published a study showing that maternal care actually alters the structure of genes. Stop and think about that for a minute. Genes are encoded in an individual’s DNA. How can they be changed? Well, early on in a baby’s life the brain is able to change in response to the environment. The brain is composed of billions of cells called neurons. Scientists noticed that neurons in the mouse brain carried different numbers of elements in their DNA. These elements, termed retrotransposons, are able to “jump” around the genome and cause changes in the DNA of the neurons.

What is a retrotransposon? A retrotransposon is a part of the DNA that can copy itself. These retrotransposons duplicate themselves by a “copy and paste” mechanism (see diagram). It makes a copy of itself and then is inserted back into its DNA at a new location. This is a way for a cell to make multiple copies of an element and paste the copy back into the DNA. While studying the impacts of maternal care in mice, scientists were able to observe changes in the number of retrotransposons found in a mouse’s DNA.

Scientists observed the interaction between mother mice and their babies for a two-week period. Maternal care, or nurturing, for rodents consists of licking, grooming, certain nesting patterns, contact with their baby, and a specific style of nursing. The more time the mother mouse focused on nurturing her babies, the fewer retrotransposons were detected in the brains of the baby mice. So, babies who have more attentive mothers have less gene movement! This inverse correlation was significant in the hippocampus, a major part of the brain. This part of the brain is extremely sensitive to changes in the environment, which makes it easy for the retrotransposons to “copy and paste” themselves. Early life stages were observed because during the first week of life, the hippocampus in rodents is multiplying the number of neuronal cells rapidly.

So why is this important to study? These results show that changes in DNA can be caused by differences in the environment. Depending on the quality of maternal care and how often it is provided, the baby mice have a range of differences in their neuronal DNA. Scientists have discovered that rodents experience different adult behavior depending on how much nurturing they received as babies. Adult mice that have low maternal care as babies exhibit more anxiety-like behavior.

Could the same be true in humans? We know that genes, which are inherited from our biological mother and father, are important for determining our eye and hair color, our height, our shoe size, but we also know that the environment during our early life, and the experiences that occur, can have an impact as well. During early stages of development the brain is still actively growing and maturing. It is during this time that the amount of nurturing from a mother mouse could be detected in the baby mouse’s DNA. This is an interesting observation in mice that could be similar in humans. Scientists have to be careful with this comparison though because mouse brains have more retrotransposons than human brains, making this an unequal comparison. There are huge differences between a mouse and human brain, but this finding is a good stepping-stone towards further characterizing the importance of maternal care during early stages of life. By understanding this process, scientists hope it will become possible to develop new treatments for disorders stemming from the brain, such as depression and schizophrenia, but much more research is still yet to come.

For more, check out the YouTube video from the primary investigator of the study: Early life experiences can cause genes to move around.