Tejal Somvanshi
Cornell researchers have discovered why male embryos grow faster than females – a mystery that has puzzled scientists since the 1990s. The answer lies in genetic differences that appear just days after fertilization. The study, published August 27 in Cell & Bioscience, reveals that male bovine embryos prioritize genes related to energy metabolism, giving them a growth advantage. Female embryos, meanwhile, focus on genes for sex differentiation, gonad development, and immune pathways that prepare them for later development.
“Male and female embryos are different, even at this very early stage, on the basis of genome regulation,” said Jingyue “Ellie” Duan, assistant professor of functional genomics at Cornell and study co-author.
What makes this finding remarkable is that these differences appear seven to eight days after fertilization – long before sex hormones like estrogen and testosterone begin influencing development. This suggests an intrinsic factor in the genome itself, likely related to sex chromosomes (XX versus XY) or sex-linked genes.
The discovery has significant implications for human health. Historically, most medical research and drug development has used male subjects, ignoring potential sex differences. Yet many diseases affect men and women differently, including Alzheimer’s, autoimmune conditions, and heart disease.
Similar Posts
“We’re born with this sex-specific genetic regulation that is contributing very differently to cellular behavior, disease onset and immune system development, and continues through life all the way to health and aging,” Duan explained.
The research also has practical applications for improving in vitro fertilization success rates in both humans and cattle. For the dairy industry, which relies heavily on cattle reproduction through IVF, understanding these differences could enhance breeding efficiency and sustainability.
This breakthrough was made possible through collaboration between Duan’s genomics lab and Soon Hon Cheong’s reproductive medicine group at Cornell’s College of Veterinary Medicine. The team is already expanding their research to study sex differences in embryos from fertilization through day eight of development.
The study was supported by the National Science Foundation and the Cornell Center for Vertebrate Genomics.
