Mitochondria, which produce energy for cellular functions, have their own genome — and we all inherit our mitochondrial DNA entirely from our mothers. Researchers theorize that if maternal and paternal mitochondrial DNA both ended up in a fertilized egg, they would compete in ways that are detrimental. However, the precise mechanisms behind the loss of paternal mitochondrial DNA have not been elucidated — until now.
Biochemist Dmitry Temiakov, PhD, and colleagues, used a sensitive method to detect DNA in sperm and showed that mature sperm do not carry any intact mitochondrial DNA. Dr. Temiakov’s team looked for clues by exploring molecular pathways involved in sperm maturation. They identified a specific protein called mitochondrial transcription factor A, or TFAM. In most other cells, TFAM serves as a helper molecule for mitochondrial DNA, but during sperm generation, the protein is modified and is unable to gain entry into mitochondria. Without TFAM, the genetic material in mitochondria is unprotected from degradation, and thus, mature sperm are left without any mitochondrial DNA.
“Nature ensures maternal mitochondrial DNA inheritance,” Dr. Temiakov says. “There are likely multiple pathways to prevent the transmission of paternal mitochondrial DNA. We have uncovered one of them.” While the discovery is exciting, he adds that there is much more to learn. Dr. Temiakov’s work earned the 2023 Michael and Melina Pellini Award for Innovation in the Biomedical Sciences.
