PSAT091 The Impact of Pregnancy and Aging on the Female Mouse Adrenal Transcriptome

Abstract

Abstract Introduction Mouse adrenal glands contain a zona glomerulosa (mineralocorticoid production), zona fasciculata (glucocorticoid production), and a remnant of the fetal adrenal cortex (termed the x-zone). Instead of involuting at birth, as seen in humans, the x-zone expands postnatally and is predicted to function in the metabolism of progesterone and 11-deoxycorticosterone via its high expression of the enzyme, 20α-hydroxysteroid dehydrogenase (Akr1c18). Moreover, mouse adrenals have a clear x-zone sex-divergence at the time of puberty when the x-zone regresses in males. In females, the x-zone regresses during the first pregnancy and with aging. Sexual dimorphism unrelated to the x-zone has been documented in mouse adrenals, including differentially expressed sex-chromosome and sex-steroid driven genes, making the definition of x-zone specific transcripts more challenging. Objective Use RNA sequencing (RNAseq) to better define the x-zone transcriptome by comparing virgin mice to post-pregnant and aged females. Methods Adrenals from four 25-week-old (wk) virgin, four 25 wk post-pregnant, and four 50 wk female mice were used for RNAseq. Reads were aligned to the mm38 assembly with STAR. Expression was quantified with featureCounts. Normalization was performed with edgeR using the TMM method. Unwanted sources of variation were removed with sva. Statistical comparison was performed using limma. Statistically significant (FDR-adjusted, P<0.05) expression between groups allowed characterization of differentially expressed genes (DEGs). Results RNAseq allowed the analysis of adrenal gland RNA transcripts and identified 17,829 genes that met read count thresholds. 246 DEGs were found between virgin and post-pregnant females with 93 showing higher expression in virgin adrenals and 153 with higher expression in post-pregnant female adrenals. The most altered genes included Akr1c18 (fold change (FC) = 174.06; higher in virgin adrenals) and the proton transporter, Otop1 (FC = 20.82; higher in post-pregnant adrenals). When comparing 25 wk to 50 wk adrenals, 269 DEGs were found with 136 showing higher expression in 25 wk adrenals and 133 higher in the 50 wk adrenals. The most altered genes were Akr1c18 (FC = 34.17; higher in 25 wk adrenals) and the mouse mast cell protease, Mcpt2 (FC = 14.42; higher in 50 wk adrenals). The 25 wk virgin mice had 22 transcripts that were higher and 41 that were lower than found in both post-pregnant and 50 wk animals. Within this list are the established x-zone markers: Akr1c18 and the phosphoinositide 3-kinase, Pik3c2g. Discussion Clear differences in transcript levels were observed between virgin mice and those who had underwent pregnancy or aged to 50 wk. Both aged and post-pregnant mice showed lower expression of known x-zone transcripts and RNAseq analysis provided a tentative list of additional x-zone markers. Using female mice with differing x-zone status reduced the number of sexually dimorphic genes and allowed the characterization of genes related to the x-zone. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.