What if our genes were not the only ones we inherited from our parents? What if our genes could be turned on or off by inheritance?
This study, which was published in Nature Communications, has revealed these possibilities. Our study found that information other than our genes is passed from mother to child to influence how their skeletons develop. This is the “epigenetic information” that is normally reset between generations.
In our research, we studied mice. This was the first time in mammal history that an epigenetic effect derived from the mother’s egg has been passed on to the next generations. The health of the next generation is affected by this.
We cannot, however, be sure that humans will also inherit the same epigenetic changes. This includes the implications of how our skeleton is developed and the potential impact of diseases.
What is epigenetics?
Our genes (packages DNA) instruct our body to produce certain proteins. Our cells need instructions as well to determine whether a particular gene is being used (switched on) or not.
These instructions are in the form of small molecules (chemical or “epigenetic”) that are placed on top of DNA. These tags accumulate throughout your lifetime.
Consider how punctuation helps a reader to understand a sentence. Epigenetic tags help the cell understand DNA sequences.
These epigenetic tags are necessary to prevent the cell from making a protein when it shouldn’t or at all.
The timing is critical to the development of embryos. An embryo cannot develop properly if certain genes (which produce proteins) are switched on too early or late.
What did we discover?
We were interested to understand the function of SMCHD1, a protein found in mouse eggs.
We found that mice that were developed from eggs without SMCHD1 exhibited a skeleton with some vertebrae disrupted in the spine.
This can only be explained as an epigenetic shift due to the absence of SMCHD1 from the egg.
We focused on a group of genes called Hox. These genes encode a set of proteins that are known to regulate how the skeletons of mammals develop.
Hox are present in all mammals, including humans. They are essential for the formation of our spine. The timing of the Hox gene expression during embryonic development has been fine-tuned by evolution to ensure that the skeleton is correctly assembled.
The study found that the epigenetic tags created by SMCHD1 (the mother’s SMCHD1) in her eggs can influence how these and Hox gene expression in her offspring.
These findings are surprising because epigenetic markers in the egg are almost completely erased soon after conception. Imagine this as a sort of factory reset.
Epigenetic information from a mother’s ovum is rarely passed on to her children to influence their growth.
What does it mean to us?
Even genes that you do not inherit from your mother may still affect your development.
This could have implications for children of women who carry variants in the SMCHD1 genes. Human diseases, such as muscular dystrophy, are caused by variations in SMCHD1.
SMCHD1 could be a future target for new drugs to change the way the protein works and help patients who have diseases caused by variations of SMCHD1. It’s, therefore, important to know what the consequences of the disruption of the SMCHD1 gene in the egg could be for future generations.
How about other diseases?
Scientists now understand epigenetic tags, which are added to our genes to mark them as sensitive to environmental changes. It can be said that environmental factors, like our diet and level of activity, can influence how our genes are expressed. These changes do not alter DNA.
Due to “factory resets” between generations, epigenetic changes are most pronounced when the embryo is developing or very early in the development of the embryo. The embryo is, therefore, more susceptible to epigenetic changes, as well as environmental ones, during this developmental period.
In the future, as we learn more about epigenetic inheritance from mothers, the environment or diet of the mother could have an impact on the next generation.
We are now in a position to study the process of a single egg and determine what we might inherit.
