Integrated Analysis of DNA Methylation and mRNA Expression Profiles to Identify Key Genes in Severe Oligozoospermia
FRONTIERS IN PHYSIOLOGY
Authors: Li, Zhiming; Zhuang, Xuan; Zeng, Jinxiong; Tzeng, Chi-Meng
Abstract
Severe oligozoospermia (SO) is a complex disorder, whose etiology is the combined effect of genetic factors and epigenetic conditions. In this study, we examined DNA methylation and mRNA expression status in a set of testicular tissues of SO patients (n = 3), and compared methylated data with those derived from obstructive azoospermia (OA) patients (n = 3) with normal spermatogenesis phenotype. We identified 1,960 differentially methylated CpG sites showing significant alterations in SO vs. OA using the Illumina Infinium HumanMethylation450 bead array. By integrating above DNA methylation data and mRNA expression results, we totally identified 72 methylated CpG sites located in 65 genes with anti-correlation between DNA methylation and mRNA expression. Integrated pathways analysis indicates that these genes are involved in response to hormone stimulus, activation of protein kinase activity, and apoptotic process, among others. We also observed some genes with inversely correlated difference is novel in male infertility field, including PTPRN2, EPHX1, SERPINB9, SLIT3, etc. Our results lay a groundwork for further biological study of SO. Moreover, we generated a workflow for integrated analysis of DNA methylation and mRNA expression, which is expandable to other study types.
The granzyme B-Serpinb9 axis controls the fate of lymphocytes after lysosomal stress
CELL DEATH AND DIFFERENTIATION
Authors: Bird, C. H.; Christensen, M. E.; Mangan, M. S. J.; Prakash, M. D.; Sedelies, K. A.; Smyth, M. J.; Harper, I.; Waterhouse, N. J.; Bird, P. I.
Abstract
Cytotoxic lymphocytes (CLs) contain lysosome-related organelles (LROs) that perform the normal degradative functions of the lysosome, in addition to storage and release of powerful cytotoxins employed to kill virally infected or abnormal cells. Among these cytotoxins is granzyme B (GrB), a protease that has also been implicated in activation (restimulation)-induced cell death of natural killer (NK) and T cells, but the underlying mechanism and its regulation are unclear. Here we show that restimulation of previously activated human or mouse lymphocytes induces lysosomal membrane permeabilisation (LMP), followed by GrB release from LROs into the CL cytosol. The model lysosomal stressors sphingosine and Leu-Leu-methyl-ester, and CLs from gene-targeted mice were used to show that LMP releases GrB in both a time-and concentration-dependent manner, and that the liberated GrB is responsible for cell death. The endogenous GrB inhibitor Serpinb9 (Sb9) protects CLs against LMP-induced death but is decreasingly effective as the extent of LMP increases. We also used these model stressors to show that GrB is the major effector of LMP-mediated death in T cells, but that in NK cells additional effectors are released, making GrB redundant. We found that limited LMP and GrB release occurs constitutively in proliferating lymphocytes and in NK cells engaged with targets in vitro. In Ectromelia virus-infected lymph nodes, working NK cells lacking Sb9 are more susceptible to GrB-mediated death. Taken together, these data show that a basal level of LMP occurs in proliferating and activated lymphocytes, and is increased on restimulation. LMP releases GrB from LROs into the lymphocyte cytoplasm and its ensuing interaction with Sb9 dictates whether or not the cell survives. The GrB-Sb9 nexus may therefore represent an additional mechanism of limiting lymphocyte lifespan and populations.