Epigenetic profiling of mouse uteri across reproductive aging
Advanced maternal age increases the risk of pregnancy complications because of a higher incidence of karyotypic imbalances in the oocyte. A very important yet much less explored contribution to this risk, however, is the declining capacity of the uterus to adapt to the hormonal stimulus of pregnancy. As such, it has remained unknown what drives the uterine aging phenotype on the molecular and cellular level. Here, we show in mice that maternal aging is associated with a progressive increase in transcriptional variation that is accompanied by a drastic accumulation of activating histone marks. Importantly, the transcriptional signatures associated with uterine aging differ substantially from those of organismal aging. Single-cell deconvolution analysis demonstrates that maternal age-induced effects originate in the epithelial compartment and specifically entail a dramatic up-regulation of the pioneer transcription factor FOXC1,  linked to an accumulation of H3K4me3 and H3K27ac across the locus. FOXC1 over-expression in human endometrial cells causes profound transcriptomic shifts and increases proliferation rates, recapitulating the aging phenotype. Using endometrial epithelial organoids of young and aged mice, we find that aging hallmarks including Foxc1 up-regulation and H3K27ac hyper-enrichment are conserved in vitro. In line with the epithelial hyperplasia phenotype seen in vivo, endometrial epithelial organoids from aged mice are larger and mis-express key factors critical for uterine gland maturity and function, most notably SOX9. Collectively, our data highlight the specific susceptibility of uterine epithelial cells to early-onset aging, with early changes manifesting in an increase in activating epigenetic marks that coalesce on the mis-regulation of FOXC1. Overall design: ChIP-seq of uterine tissue from mice at various ages. Samples are grouped into four age groups, Young (Y), Aged 1 (A1), Aged 2 (A2) and Aged 3 (A3). Two ChIP-seq libraries were prepared for each sample: H3K4me3 and H3K27ac.