New research discovers why male and female embryos develop differently

Image credit: Izabelly Marques / Bonnie Kittle via Unsplash

New research has discovered why male and female embryos develop differently, a difference that has been found to occur as early as seven days after fertilisation. This new research has now opened the door to learning more about sex-based differences, which could aid scientists in understanding how to better treat illnesses that have impacted men and women differently.

According to Technology Networks, scientists have known that male and female embryos develop differently, with the male embryo to grow faster, since the 1990s. However, it was only in recent research, where scientists have discovered why this difference occurs.

The research, which was reported in a paper by Cornell University published in August this year on Cell & Bioscience, involved scientists growing cow embryos, that closely resemble human embryos, in a petri-dish to analyse their genetic sex and RNA sequencing. 

Through this they discovered that the male embryos were prioritising growth by focusing on genes associated with energy and metabolism, hence causing them to grow faster, whereas the female embryos focused on genes associated with the immune system and reproduction. These differences in development were identified as early as seven days after fertilisation.

The scientists behind the study have said that the results of this study can help us to understand more about sex-based differences which can be beneficial when understanding more about diseases that impact men and women differently. 

“Sex difference has been a factor ignored in a lot of studies and clinical trials. Until very recently, most mouse studies have used exclusively male mice. And most drug discovery is done with male mice,” said Jingyue “Ellie” Duan, co-author of the paper and assistant professor of functional genomics in the College of Agriculture and Life Sciences. “And yet, we see that onset and occurrence of many diseases are different in men and women: Alzheimer’s, autoimmune diseases, heart disease. In this basic study, we found that male and female embryos are different, even at this very early stage, on the basis of genome regulation.”

The insights in sex-based differences provided by the results of this research prove useful by the fact that sex-based hormones, like estrogen and testosterone, have not begun to influence the growth of the embryo at this stage of development.

“This could imply that there’s an intrinsic factor in our genome contributing to the sex-based differences we see, such as sex chromosomes (XX versus XY) or sex-linked genes, not just from hormonal change or environmental factors,” Duan said. 

“We’re born with this sex-specific genetic regulation that is contributing very differently to cellular behaviour, disease onset and immune system development, and continues through life all the way to health and aging. That’s a very important message for people in the clinical field and people developing drugs to understand.”

Further research into the developmental differences between male and female embryos is currently underway.

Sandra Parda of the Life Institute commented, saying: “This is a very interesting piece of research. On one hand it offers another form of window to the womb where we see the value of the embryo, where the gender, which is decided at the moment of fertilisation, is already playing a role in their development before one can be aware of their existence. The development of the human person is truly incredible.”

“On the other hand, such an insight being able to provide more information on how the medical world can provide more appropriate care to people, especially if this may need to be altered based on the gender of the person, is always a positive. Advances in science and medicine should always be used in ensuring that wider society can be treated with care and dignity.”