Thesis title: Systematic dissection of intergenerational epigenetic inheritance induced by paternal low protein diet
Diet plays a crucial role in human health and disease, with broad impact on multi-
ple aspects of modern societies. A healthy diet provides adequate macronutrients
(carbohydrates, proteins, fats) and micronutrients (i.e., vitamins and minerals), nec-
essary for correct development and physiology, with unbalanced dietary composition
promoting pathological states at multiple tissue levels, finally affecting quality of
life.
Furthermore, unhealthy dietary habits before conception or during gestation rep-
resent a risk factor for offspring metabolic disorder. Although maternal nutrition
has long been recognized as a critical factor, growing evidence demonstrates that
paternal nutrition has the potential to shape offspring metabolic physiology.
Experiments in isogenic model organisms, revealed how this occurs by transmis-
sion of epigenetic signals that modulate developmental trajectories in the progeny
through a process called intergenerational epigenetic inheritance. One of the classic
model of this phenomenon in mice is known as paternal Low Protein diet (LPD)
paradigm, where reduction of protein to carbohydrate ratio triggers multi-organ
reprogramming of lipid metabolism in their offspring, prominently affecting choles-
terol homeostasis. LPD consumption is coupled with alteration of sperm epigenome
including increased levels specific tRNA fragments (tRFs), which modulate early
embryonic transcriptomic trajectories. However, it remains unclear to what extent
LPD-induced intergenerational responses represent a universal mechanism conserved
across distinct genetic backgrounds, and mechanistically direct evidence connecting
sperm RNAs to postnatal metabolic outcomes in the progeny is still missing.
Here, I examined the hepatic molecular consequences in LPD fathers and their
progeny in FVB/NJ mice using two different models of LPD paradigms, to assess the
robustness of intergenerational responses in mice. My results show consistent, albeit
quantitatively variable, metabolic consequences across genetic backgrounds, char-
acterized by decreased lipid oxidation in fathers and enhanced cholesterogenesis in
their offspring. In contrast, altering the nutritional history preceding LPD exposure
leads to variable responses, indicating that ancestral nutrition can prime metabolism,
but the resulting phenotype depends on the combined influence of inherited dietary
information and the individual’s metabolic state.
To elucidate the molecular basis of this inheritance, I introduced synthetic 5’ tRNA-
Gly-GCC fragments (5’tRF-GG), a sperm RNA consistently elevated in response
to LPD, into control zygotes. The resulting progeny exhibited molecular features
reminiscent of paternal LPD offspring, including enhanced cholesterol biosynthesis
and reduced cholesteryl ester accumulation. These results indicate that 5’tRF-GG
can partially reproduce the LPD-induced metabolic phenotype, implicating it as a
carrier of paternal dietary signals.
Collectively, this work provides compelling evidence of sperm tRNA fragments acting
as molecular mediators of phenotypic responses to ancestral dietary conditions. At
the same time, it demonstrates that both genetic background and experimental
design critically influence the manifestation of intergenerational dietary effects,
underscoring the need for standardized paradigms to ensure reproducibility and
comparability across studies.