More than the SRY: The Non-Coding Landscape of the Y Chromosome and Its Importance in Human Disease.

Historically, the Y chromosome has presented challenges to classical methodology and philosophy of understanding the differences between males and females. A genetic unsolved puzzle, the Y chromosome was the last chromosome to be fully sequenced. With the advent of the Human Genome Project came a realization that the human genome is more than just genes encoding proteins, and an entire universe of RNA was discovered. This dark matter of biology and the black box surrounding the Y chromosome have collided over the last few years, as increasing numbers of non-coding RNAs have been identified across the length of the Y chromosome, many of which have played significant roles in disease. In this review, we will uncover what is known about the connections between the Y chromosome and the non-coding RNA universe that originates from it, particularly as it relates to long non-coding RNAs, microRNAs and circular RNAs.

Myeloid-Derived Suppressor Cells Gain Suppressive Function during Neonatal Bacterial Sepsis.

Neonates are at an increased risk of an infectious disease. This is consistent with an increased abundance of myeloid-derived suppressor cells (MDSCs) compared with older children and adults. Using a murine model of neonatal bacterial sepsis, we demonstrate that MDSCs modulate their activity during an infection to enhance immune suppressive functions. A gene expression analysis shows that MDSCs increased NOS2, Arg-1 and IL-27p28 expression in vitro and in vivo in response to Escherichia coli O1:K1:H7 and this is regulated at the level of the gene expression. Changes in the effector gene expression are consistent with increased enzymatic activity and cytokine secretion. The neonatal MDSCs express toll-like receptor (TLR) 2, 4 and 5 capable of recognizing pathogen-associated molecular patterns (PAMPS) on E. coli. However, a variable level of effector expression was achieved in response to LPS, peptidoglycan or flagellin. Individual bacterial PAMPs did not stimulate the expression of Arg-l and IL-27p28 equivalently to E. coli. However, the upregulation of NOS2 was achieved in response to LPS, peptidoglycan and flagella. The increased immune suppressive profile translated to an enhanced suppression of CD4+ T cell proliferation. Collectively, these findings increase our understanding of the dynamic nature of MDSC activity and suggest that these cells abundant in early life can acquire activity during an infection that suppresses protective immunity.

A Neonatal Imaging Model of Gram-Negative Bacterial Sepsis.

Neonates are at an increased risk of bacterial sepsis due to the unique immune profile they display in the first months of life. We have established a protocol for studying the pathogenesis of E. coli O1:K1:H7, a serotype responsible for high mortality rates in neonates. Our method utilizes intravital imaging of neonatal pups at different time points during the progression of infection. This imaging, paralleled by measurement of bacteria in the blood, inflammatory profiling, and tissue histopathology, signifies a rigorous approach to understanding infection dynamics during sepsis. In the current report, we model two infectious inoculums for comparison of bacterial burdens and severity of disease. We find that subscapular infection leads to disseminated infection by 10 h post-infection. By 24 h, infection of luminescent E. coli was abundant in the blood, lungs, and other peripheral tissues. Expression of inflammatory cytokines in the lungs is significant at 24 h, and this is followed by cellular infiltration and evidence of tissue damage that increases with infectious dose. Intravital imaging does have some limitations. This includes a luminescent signal threshold and some complications that can arise with neonates during anesthesia. Despite some limitations, we find that our infection model offers an insight for understanding longitudinal infection dynamics during neonatal murine sepsis, that has not been thoroughly examined to date. We expect this model can also be adapted to study other critical bacterial infections during early life.

Elevated Levels of Interleukin-27 in Early Life Compromise Protective Immunity in a Mouse Model of Gram-Negative Neonatal Sepsis.

Neonates are at increased risk for bacterial sepsis. We established that the immune-suppressive cytokine interleukin-27 (IL-27) is elevated in neonatal mice. Similarly, human cord blood-derived macrophages express IL-27 genes and secrete more cytokine than macrophages from adults. In the present work, we hypothesized that increased levels of IL-27 predispose neonatal mice to more severe infection during Gram-negative sepsis. Serum IL-27 levels continued to rise during infection. Peripheral tissue analysis revealed systemic IL-27 expression, while myeloid cell profiling identified Gr-1- and F4/80-expressing cells as the most abundant producers of IL-27 during infection. Increased IL-27 levels were consistent with increased mortality that was improved in IL-27 receptor α (IL-27Rα)-/- mice that lack a functional IL-27 receptor. Infected IL-27Rα-/- pups also exhibited improved weight gain and reduced morbidity. This was consistent with reduced bacterial burdens and more efficient bacterial killing by Ly6B.2+ myeloid cells and macrophages compared to WT neonates. Live animal imaging further supported a more severe and disseminated infection in WT neonates. This is the first report to describe the impact of elevated early-life IL-27 on the host response in a neonatal infection model while also defining the cell and tissue sources of cytokine. IL-27 is frequently associated with suppressed inflammation. In contrast, our findings demonstrate that IL-27 indirectly promotes an inflammatory cytokine response during neonatal sepsis by directly compromising control of bacteria that drive the inflammatory response. Collectively, our results suggest that IL-27 represents a therapeutic target to limit susceptibility and improve infectious outcomes in neonatal sepsis.

Murine myeloid-derived suppressor cells are a source of elevated levels of interleukin-27 in early life and compromise control of bacterial infection.

Microbial infections early in life remain a major cause of infant mortality worldwide. This is consistent with immune deficiencies in this population. Interleukin (IL)-27 is suppressive toward a variety of immune cell types, and we have shown that the production of IL-27 is elevated in humans and mice early in life. We hypothesize that elevated levels of IL-27 oppose protective responses to infection during the neonatal period. In this study, we extended previous findings in neonatal mice to identify a population of IL-27 producers that express Gr-1 and were further identified as myeloid-derived suppressor cells (MDSCs) based on the expression of surface markers and functional studies. In neonates, MDSCs are more abundant and contribute to the elevated pool of IL-27 in this population. Although the ability of MDSCs to regulate T lymphocyte activation has been well-studied, sparingly few studies have investigated the influence of MDSCs on innate immune function during bacterial infection. We demonstrate that macrophages are impaired in their ability to control growth of Escherichia coli when cocultured with MDSCs. This bacterium is a significant concern for neonates as a common cause of bacterial sepsis and meningitis. The suppressive effect of MDSCs on macrophage function is mediated by IL-27; inclusion of a reagent to neutralize IL-27 promotes improved control of bacterial growth. Taken together, these results suggest that the increased abundance of MDSCs may contribute to early life susceptibility to infection and further highlight production of IL-27 as a novel MDSC mechanism to suppress immunity.