BackgroundIn Drosophila early post-meiotic spermatids, mitochondria undergo dramatic shaping into the Nebenkern, a spherical body with complex internal structure that contains two interwrapped giant mitochondrial derivatives. The purpose of this study was to elucidate genetic and molecular mechanisms underlying the shaping of this structure.ResultsThe knotted onions (knon) gene encodes an unconventionally large testis-specific paralog of ATP synthase subunit d and is required for internal structure of the Nebenkern as well as its subsequent disassembly and elongation. Knon localizes to spermatid mitochondria and, when exogenously expressed in flight muscle, alters the ratio of ATP synthase complex dimers to monomers. By RNAi knockdown we uncovered mitochondrial shaping roles for other testis-expressed ATP synthase subunits.ConclusionsWe demonstrate the first known instance of a tissue-specific ATP synthase subunit affecting tissue-specific mitochondrial morphogenesis. Since ATP synthase dimerization is known to affect the degree of inner mitochondrial membrane curvature in other systems, the effect of Knon and other testis-specific paralogs of ATP synthase subunits may be to mediate differential membrane curvature within the Nebenkern.

Background: Early life environmental exposures affect breast development and breast cancer risk in adulthood. The breast is particularly vulnerable during puberty when mammary epithelial cells proliferate exponentially. In overweight/obese (OB) women, inflammation increases breast aromatase expression and estrogen synthesis and promotes estrogen-receptor (ER)-positive breast cancer. In contrast, recent epidemiological studies suggest that obesity during childhood decreases future breast cancer risk. Studies on environmental exposures and breast cancer risk have thus far been limited to animal models. Here, we present the first interrogation of the human adolescent breast at the molecular level and investigate how obesity affects the immature breast. Methods: We performed RNA-seq in 62 breast tissue samples from adolescent girls/young women (ADOL; mean age 17.8 years) who underwent reduction mammoplasty. Thirty-one subjects were non-overweight/obese (NOB; mean BMI 23.4 kg/m 2) and 31 were overweight/obese (OB; BMI 32.1 kg/m 2). We also compared our data to published mammary transcriptome datasets from women (mean age 39 years) and young adult mice, rats, and macaques. Results: The ADOL breast transcriptome showed limited (30%) overlap with other species, but 88% overlap with adult women for the 500 most highly expressed genes in each dataset; only 43 genes were shared by all groups. In ADOL, there were 120 differentially expressed genes (DEG) in OB compared with NOB samples (p adj < 0.05). Based on these DEG, Ingenuity Pathway Analysis (IPA) identified the cytokines CSF1 and IL-10 and the chemokine receptor CCR2 as among the most highly activated upstream regulators, suggesting increased inflammation in the OB breast. Classical ER targets (e.g., PR, AREG) were not differentially expressed, yet IPA identified the ER and PR and growth factors/receptors (VEGF, HGF, HER3) and kinases (AKT1) involved in hormone-independent ER activation as activated upstream regulators in OB breast tissue.

Environmental exposures that occur early in life affect breast development and breast cancer (BC) risk in adulthood. Puberty is one such developmental ‘window of susceptibility’ when estrogen (E) stimulates breast adipocytes and stromal and epithelial cells to proliferate at an exponential rate, making them vulnerable to carcinogens. Excess adiposity during adulthood may increase BC risk through obesity-associated inflammation and/or aromatase activity, which increases local E levels. While obesity during puberty might be expected to also increase future BC risk, epidemiological studies suggest that pediatric obesity may actually be protective. The current studies investigated the gene expression profile of the normal adolescent breast and how early life factors such as obesity may influence these profiles. We performed RNA-seq in 62 histologically-normal breast tissue samples from adolescent girls and young women (mean age 17.8 yrs) who underwent breast reduction surgery. Twenty-nine patients were normal weight (NW; mean BMI 23.2 kg/m2) and 33 were overweight/obese (OB; BMI 31.7). Comparison of our adolescent dataset with published mammary RNAseq datasets from pubertal mice, rats, macaques, and adult women (mean age 38 yrs) revealed relatively poor (~ 30%) overlap with other species, but 88% overlap with adults for the 500 most highly expressed genes in each dataset. The small gene set (n=43) common to all groups was enriched for extracellular matrix components. We used DESeq2 to identify differentially-expressed (DE) genes in NW vs OB samples. To avoid confounding due to differences in the cellular composition of NW and OB samples, we first used CIBERSORT to computationally estimate the adipocyte fraction of each sample and included this estimate as a covariate. We identified 74 up-regulated and 73 down-regulated genes in NW vs. OB (padj &lt; 0.05). We used Ingenuity Pathway Analysis (IPA) to determine whether the DE genes might reflect activation or inhibition of upstream transcriptional regulators in OB samples. IPA identified the cytokines CSF1 and CSF2 and the chemokine receptor CCR2 as the most highly activated upstream regulators, suggesting a signature of increased inflammation in OB samples. While classical E receptor (ER) targets (e.g., PR, AREG) were not DE’d, IPA identified ESR1, 17-α-ethinyl estradiol, genistein, and PR, as well as growth factors/receptors (EGF, IGF-1, HGF, HER3) and kinases (AKT1, ERK) involved in hormone-independent ER activation, as activated upstream regulators in OB samples. These studies represent the first investigation of the human breast transcriptome during late puberty and demonstrate that in adolescents, as in adults, OB is associated with increased inflammation which may augment E action in the breast microenvironment.

No abstract