Epigenetic inheritance of diet-induced and sperm-borne mitochondrial RNAs

Abstract

Spermatozoa harbour a complex and environment-sensitive pool of small non-coding RNAs (sncRNAs)1, which influences offspring development and adult phenotypes1–7. Whether spermatozoa in the epididymis are directly susceptible to environmental cues is not fully understood8. Here we used two distinct paradigms of preconception acute high-fat diet to dissect epididymal versus testicular contributions to the sperm sncRNA pool and offspring health. We show that epididymal spermatozoa, but not developing germ cells, are sensitive to the environment and identify mitochondrial tRNAs (mt-tRNAs) and their fragments (mt-tsRNAs) as sperm-borne factors. In humans, mt-tsRNAs in spermatozoa correlate with body mass index, and paternal overweight at conception doubles offspring obesity risk and compromises metabolic health. Sperm sncRNA sequencing of mice mutant for genes involved in mitochondrial function, and metabolic phenotyping of their wild-type offspring, suggest that the upregulation of mt-tsRNAs is downstream of mitochondrial dysfunction. Single-embryo transcriptomics of genetically hybrid two-cell embryos demonstrated sperm-to-oocyte transfer of mt-tRNAs at fertilization and suggested their involvement in the control of early-embryo transcription. Our study supports the importance of paternal health at conception for offspring metabolism, shows that mt-tRNAs are diet-induced and sperm-borne and demonstrates, in a physiological setting, father-to-offspring transfer of sperm mitochondrial RNAs at fertilization.

Paternal epigenetic and genetic inheritance gets complicated: the conundrum of conceptus metabolism

“…A recent study from Tomar and colleagues adds a significant chapter to our understanding of both the breadth and impact epigenetic influences borne by sperm in mice and humans [1]. By tracking the origins and fate of mitochondrial tRNAs and their fragments (mt-tRNAs), this insightful and groundbreaking work links paternal health status at the time of conception to alterations in offspring metabolism via dietary inputs borne by sperm that materialize in an experimentally demonstrable fashion at the time of fertilization.…”