NAD+associated genes as potential biomarkers for predicting the prognosis of gastric cancer

Nicotinamide adenine dinucleotide(NAD+)plays an essential role in cellular metabolism,mitochondrial homeostasis,inflammation,and senescence.However,the role of NAD+-regulated genes,including coding and long non-coding genes in cancer development is poorly understood.We constructed a prediction model based on the expression level of NAD+metabolism-related genes(NMRGs).Furthermore,we validated the expression of NMRGs in gastric cancer(GC)tissues and cell lines;additionally,β-nicotinamide mononucleotide(NMN),a precursor of NAD+,was used to treat the GC cell lines to analyze its effects on the expression level of NMRGs lncRNAs and cellular proliferation,cell cycle,apoptosis,and senescence-associated secretory phenotype(SASP).A total of 13 NMRGs-related lncRNAs were selected to construct prognostic risk signatures,and patients with high-risk scores had a poor prognosis.Some immune checkpoint genes were upregulated in the high-risk group.In addition,cell cycle,epigenetics,and senescence were significantly downregulated in the high-risk group.Notably,we found that the levels of immune cell infiltration,including CD8 T cells,CD4 naïve T cells,CD4 memory-activated T cells,B memory cells,and naïve B cells,were significantly associated with risk scores.Furthermore,the treatment of NMN showed increased proliferation of AGS and MKN45 cells.In addition,the expression of SASP factors(IL6,IL8,IL10,TGF-β,and TNF-α)was significantly decreased after NMN treatment.We conclude that the lncRNAs associated with NAD+metabolism can potentially be used as biomarkers for predicting clinical outcomes of GC patients.

Blood-testis barrier and spermatogenesis： lessons From genetically-modified mice

The blood-testis barrier （BTB） is found between adjacent Sertoli cells in the testis where it creates a unique microenvironment for the development and maturation of meiotic and postmeiotic germ cells in seminiferous tubes. It is a compound proteinous structure, composed of several types of cell junctions including tight junctions （TJs）, adhesion junctions and gap junctions （GJs）. Some of the junctional proteins function as structural proteins of BTB and some have regulatory roles. The deletion or functional silencing of genes encoding these proteins may disrupt the BTB, which may cause immunological or other damages to meiotic and postmeiotic cells and ultimately lead to spermatogenic arrest and infertility. In this review, we will summarize the findings on the BTB structure and function from genetically-modified mouse models and discuss the future perspectives.

cGAS regulates the DNA damage response to maintain proliferative signaling in gastric cancer cells

The activation of some oncogenes promote cancer cell proliferation and growth,facilitate cancer progression and metastasis by induce DNA replication stress,even genome instability.Activation of the cyclic GMP-AMP synthase(cGAS)mediates classical DNA sensing,is involved in genome instability,and is linked to various tumor development or therapy.However,the function of cGAS in gastric cancer remains elusive.In this study,the TCGA database and retrospective immunohistochemical analyses revealed substantially high cGAS expression in gastric cancer tissues and cell lines.By employing cGAS high-expression gastric cancer cell lines,including AGS and MKN45,ectopic silencing of cGAS caused a significant reduction in the proliferation of the cells,tumor growth,and mass in xenograft mice.Mechanistically,database analysis predicted a possible involvement of cGAS in the DNA damage response(DDR),further data through cells revealed protein interactions of the cGAS and MRE11-RAD50-NBN(MRN)complex,which activated cell cycle checkpoints,even increased genome instability in gastric cancer cells,thereby contributing to gastric cancer progression and sensitivity to treatment with DNA damaging agents.Furthermore,the upregulation of cGAS significantly exacerbated the prognosis of gastric cancer patients while improving radiotherapeutic outcomes.Therefore,we concluded that cGAS is involved in gastric cancer progression by fueling genome instability,implying that intervening in the cGAS pathway could be a practicable therapeutic approach for gastric cancer.

A TOP6BL mutation abolishes meiotic DNA double-strand break formation and causes human infertility

Meiosis is pivotal for sexual reproduction and fertility. Meiotic programmed DNA double-strand breaks(DSBs) initiate homologous recombination, ensuring faithful chromosome segregation and generation of gametes. However, few studies have focused on meiotic DSB formation in human reproduction.Here, we report four infertile siblings born to a consanguineous marriage, with three brothers suffering from non-obstructive azoospermia and one sister suffering from unexplained infertility with normal menstrual cycles and normal ovary sizes with follicular activity. An autosomal recessive mutation in TOP6BL was found co-segregating with infertility in this family. Investigation of one male patient revealed failure in programmed meiotic DSB formation and meiotic arrest prior to pachytene stage of prophase I.Mouse models carrying similar mutations to that in patients recapitulated the spermatogenic abnormalities of the patient. Pathogenicity of the mutation in the female patient was supported by observations in mice that meiotic programmed DSBs failed to form in mutant oocytes and oocyte maturation failure due to absence of meiotic recombination. Our study thus illustrates the phenotypical characteristics and the genotype-phenotype correlations of meiotic DSB formation failure in humans.