Spermatogenesis Nishimura, Hitoshi; L’Hernault, Steven W.
Current biology,
09/2017, Letnik:
27, Številka:
18
Journal Article
Recenzirano
Odprti dostop
Most organisms consist of two cell lineages — somatic cells and germ cells. The former are required for the current generation, and the latter create offspring. Male and female germ cells are usually ...produced during spermatogenesis and oogenesis, which take place in the testis and the ovary, respectively.
Spermatogenesis involves the differentiation of spermatogonial stem cells into spermatocytes via mitotic cell division and the production of haploid spermatids from the tetraploid primary spermatocytes via meiotic cell division. Spermatids subsequently give rise to spermatozoa in the final phase of spermatogenesis, called spermiogenesis. These fundamental steps, where mitotic proliferation precedes meiosis during spermatogenesis, are observed in a wide variety of organisms. However, developing a comprehensive understanding of the cell biology and genetics of spermatogenesis is difficult for most species because it occurs within a complex testicular environment characterized by the intimate association of developing sperm with accessory cells. In this Primer, we summarize the processes of spermatogenesis occurring in two pivotal model animals — mouse and Caenorhabditis elegans — and compare them to consider which important features might be evolutionarily conserved.
In this Primer, Nishimura and L’Hernault describe and compare the processes of spermatogenesis in mice and Caenorhabditis elegans.
A rare subset of HIV-infected individuals, designated viremic non-progressors (VNP), remain asymptomatic and maintain normal levels of CD4+ T-cells despite persistently high viremia. To identify ...mechanisms potentially responsible for the VNP phenotype, we compared VNPs (average >9 years of HIV infection) to HIV-infected individuals who have similar CD4+ T-cell counts and viral load, but who are likely to progress if left untreated ("putative progressors", PP), thus avoiding the confounding effect of differences related to substantial CD4+ T cell depletion. We found that VNPs, compared to PPs, had preserved levels of CD4+ stem cell memory cells (TSCM (p<0.0001), which was associated with decreased HIV infection of these cells in VNPs (r = -0.649, p = 0.019). In addition, VNPs had decreased HIV infection in CD4+ central memory (TCM) cells (p = 0.035), and the total number of TCM cells was associated with increased proliferation of memory CD4+ T cells (r = 0.733, p = 0.01). Our results suggest that, in HIV-infected VNPs, decreased infection of CD4+ TCM and TSCM, cells are involved in preservation of CD4+ T cell homeostasis and lack of disease progression despite high viremia.
Facilities involved in the manufacture of pharmaceutical products are an under-investigated source of pharmaceuticals to the environment. Between 2004 and 2009, 35 to 38 effluent samples were ...collected from each of three wastewater treatment plants (WWTPs) in New York and analyzed for seven pharmaceuticals including opioids and muscle relaxants. Two WWTPs (NY2 and NY3) receive substantial flows (>20% of plant flow) from pharmaceutical formulation facilities (PFF) and one (NY1) receives no PFF flow. Samples of effluents from 23 WWTPs across the United States were analyzed once for these pharmaceuticals as part of a national survey. Maximum pharmaceutical effluent concentrations for the national survey and NY1 effluent samples were generally <1 μg/L. Four pharmaceuticals (methadone, oxycodone, butalbital, and metaxalone) in samples of NY3 effluent had median concentrations ranging from 3.4 to >400 μg/L. Maximum concentrations of oxycodone (1700 μg/L) and metaxalone (3800 μg/L) in samples from NY3 effluent exceeded 1000 μg/L. Three pharmaceuticals (butalbital, carisoprodol, and oxycodone) in samples of NY2 effluent had median concentrations ranging from 2 to 11 μg/L. These findings suggest that current manufacturing practices at these PFFs can result in pharmaceuticals concentrations from 10 to 1000 times higher than those typically found in WWTP effluents.
Microbial genome mining is a rapidly developing approach to discover new and novel secondary metabolites for drug discovery. Many advances have been made in the past decade to facilitate genome ...mining, and these are reviewed in this Special Issue of the Journal of Industrial Microbiology and Biotechnology. In this Introductory Review, we discuss the concept of genome mining and why it is important for the revitalization of natural product discovery; what microbes show the most promise for focused genome mining; how microbial genomes can be mined; how genome mining can be leveraged with other technologies; how progress on genome mining can be accelerated; and who should fund future progress in this promising field. We direct interested readers to more focused reviews on the individual topics in this Special Issue for more detailed summaries on the current state-of-the-art.
Although a variety of studies have examined the predictors or outcomes of adolescents’ social networking site use, these studies did not incorporate (1) an integrated, longitudinal approach to ...examine these relationships longitudinally in a single comprehensive model or (2) a differential approach to distinguish between different types of social networking site use. Therefore, this two-wave panel study (N = 1,612) developed an integrated and differential model to provide a deeper understanding of the relationships among loneliness, specific types of Facebook use, and adolescents’ depressed mood. Using structural equation modeling, the results point to the presence of a poor-get-richer effect regarding active public Facebook use but reveal a poor-get-poorer effect regarding passive Facebook use. The discussion focuses on the explanation and understanding of these findings.
This article contributes to the literature concerning the construction of working-class masculine identity in a context of unprecedented social transformation. Drawing on qualitative interviews with ...24 young men currently employed in the retail sector, this study finds that contrary to much research on masculinities young working-class men are able to resist dominant and hegemonic cultural ideals. The respondents demonstrate a very different attitude towards the 'emotional labour' required in the service sector than is often documented, while also rejecting notions of traditional gendered domestic responsibilities in respect of their futures as potential partners and parents. Congruent with other emerging research in this area, the reference point for an 'acceptable' masculine identity appears to have shifted, with some young working-class men's lives, at least, illustrating an attenuated or softened version of masculinity.
Myofibroblasts are alpha-smooth muscle actin (SMA)+ cells that have a critical role in the corneal stromal response to infections, injuries, and surgeries, and which produce corneal scarring fibrosis ...when they develop in excess. These contractile and opaque cells—produce large amounts of disordered extracellular matrix (ECM)—and develop from keratocyte-derived corneal fibroblasts or bone marrow-derived fibrocytes, and possibly other cell types, in response to TGFβ1, TGFβ2 and PDGF from the epithelium, tears, endothelium, and other stromal cells. Recent proteomic analyses have revealed that the myofibroblasts that develop from different progenitors aren't interchangeable, but have major differences in protein expression and functions. Absence or defective regeneration of the epithelial basement membrane (EBM) and/or Descemet's basement membrane (DBM) results in development and persistence of myofibroblasts in the corneal stroma. The functions of myofibroblasts in the cornea include production of volume-additive ECM, tissue contraction, production of various growth factors, cytokines and chemokines that regulate stromal cells, including other myofibroblasts, production of collagenases and metalloproteinases involved in tissue remodeling, and the expression of toll-like receptors that likely have critical roles in the clearance of bacteria and viruses causing corneal infections.
•Myofibroblasts are the major contributor to corneal fibrosis after injury or infection.•Myofibroblasts are dependent on TGF beta-1 or-2 for development and survival.•Corneal myofibroblasts are derived from keratocyte- and fibrocyte-derived precursors.•Myofibroblasts derived from different precursors have differential gene expression.
The metazoan mitochondrial translation machinery is unusual in having a single tRNAMet that fulfills the dual role of the initiator and elongator tRNAMet. A portion of the Met-tRNAMet pool is ...formylated by mitochondrial methionyl-tRNA formyltransferase (MTFMT) to generate N-formylmethionine-tRNAMet (fMet-tRNAmet), which is used for translation initiation; however, the requirement of formylation for initiation in human mitochondria is still under debate. Using targeted sequencing of the mtDNA and nuclear exons encoding the mitochondrial proteome (MitoExome), we identified compound heterozygous mutations in MTFMT in two unrelated children presenting with Leigh syndrome and combined OXPHOS deficiency. Patient fibroblasts exhibit severe defects in mitochondrial translation that can be rescued by exogenous expression of MTFMT. Furthermore, patient fibroblasts have dramatically reduced fMet-tRNAMet levels and an abnormal formylation profile of mitochondrially translated COX1. Our findings demonstrate that MTFMT is critical for efficient human mitochondrial translation and reveal a human disorder of Met-tRNAMet formylation.
► Mutations in MTFMT cause Leigh syndrome and combined OXPHOS deficiency ► Fibroblasts from patients with mutations in MTFMT have abnormal tRNAMet pools ► Met-tRNAMet formylation is critical for efficient human mitochondrial translation
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