Mfc1 is a novel copper transporter during meiosis

Molecular Regulation of Copper Homeostasis in the Male Gonad during the Process of Spermatogenesis

Owing to its redox properties, copper is a cofactor of enzymes that catalyze reactions in fundamental metabolic processes. However, copper-oxygen interaction, which is a source of toxic oxygen radicals generated by the Fenton reaction, makes copper a doubled-edged-sword in an oxygen environment. Among the microelements influencing male fertility, copper plays a special role because both copper deficiency and overload in the gonads worsen spermatozoa quality and disturb reproductive function in mammals. Male gametes are produced during spermatogenesis, a multi-step process that consumes large amounts of oxygen. Germ cells containing a high amount of unsaturated fatty acids in their membranes are particularly vulnerable to excess copper-mediated oxidative stress. In addition, an appropriate copper level is necessary to initiate meiosis in premeiotic germ cells. The balance between essential and toxic copper concentrations in germ cells at different stages of spermatogenesis and in Sertoli cells that support their development is handled by a network of copper importers, chaperones, recipient proteins, and exporters. Here, we describe coordinated regulation/functioning of copper-binding proteins expressed in germ and Sertoli cells with special emphasis on copper transporters, copper transporting ATPases, and SOD1, a copper-dependent antioxidant enzyme. These and other proteins assure copper bioavailability in germ cells and protection against copper toxicity.

Molecular machinery providing copper bioavailability for spermatozoa along the epididymial tubule in mouse

Progressive functional maturation of spermatozoa is completed during the transit of these cells through the epididymis, a tubule structure connecting a testicle to a vas deferens. Epididymal epithelial cells by means of their secretory and absorptive functions determine a highly specialized luminal microenvironment containing multiple organic and inorganic components. The latter include copper ions, which due to their redox properties are indispensable for critical homeostatic processes occurring in spermatozoa floating in different part of epididymis but can be potentially toxic. Main purpose of our study was to determine epididymal region-dependent expression and localization of copper transporters ensuring a tight control of copper concentration in epididymal fluid. We also aimed at identifying proteins responsible for copper uptake by spermatozoa and verifying whether this process is coordinated with copper supply to superoxide dismutase 1 (SOD1), a copper-dependent antioxidant enzyme. Our study identifies two ATPases-ATP7A, ATP7B and Slc31a1, major copper importers/exporters depending on their differential expression on epididymal polarized epithelial cells of the caput, corpus, and cauda. Next, ceruloplasmin seems to be a chief protein transporting copper in the epididymal fluid and providing this biometal to spermatozoa. The entry of copper to germ cells is mediated by Slc31a1 and is correlated with both expressions of copper chaperone for superoxide dismutase (CCS), copper chaperone directly providing copper ions to SOD1 and with the expression and activity of the latter. Our results outline a network of cooperating copper binding proteins expressed in epididymal epithelium and in spermatozoa that orchestrate bioavailability of this microelement for gametes and protect them against copper toxicity.

Bivariate genome-wide association study of the growth plasticity of Staphylococcus aureus in coculture with Escherichia coli

Phenotypic plasticity is the capacity to change the phenotype in response to different environments without alteration of the genotype. Despite sufficient evidence that microorganisms have a major role in the fitness and sickness of eukaryotes, there has been little research regarding microbial phenotypic plasticity. In this study, 45 strains of Staphylococcus aureus were grown for 12 days in both monoculture and in coculture with the same strain of Escherichia coli to create a competitive environment. Cell abundance was determined by quantitative PCR every 24 h, and growth curves of each S. aureus strain under the two sets of conditions were generated. Combined with whole-genome resequencing data, bivariate genome-wide association study (GWAS) was performed to analyze the growth plasticity of S. aureus in coculture. Finally, 20 significant single-nucleotide polymorphisms (eight annotated, seven unannotated, and five non-coding regions) were obtained, which may affect the competitive growth of S. aureus. This study advances genome-wide bacterial growth plasticity research and demonstrates the potential of bivariate GWAS for bacterial phenotypic plasticity research. KEY POINTS: • Growth plasticity of S. aureus was analyzed by bivariate GWAS. • Twenty significant SNPs may affect the growth plasticity of S. aureus.

Atp7a and Atp7b regulate copper homeostasis in developing male germ cells in mice

The maintenance of copper homeostasis is critical for all cells. As learned from mice with disturbed copper metabolism, this trace element is also important for spermatogenesis. The experiments conducted in yeasts have demonstrated that appropriate copper level must be preserved to enable meiosis progression; however, increased copper level is toxic for cells. This study aims to analyze the expression profile of Atp7a and Atp7b and other genes encoding copper-related proteins during spermatogenesis in mice. Using the transcripts and protein detection techniques, we demonstrate that within seminiferous tubuli, ATP7A is mainly present in early meiotic germ cells (leptotene to pachytene spermatocytes) and in Sertoli cells (SCs). During spermatogenesis, the progression Atp7a expression profile corresponds to Slc31a1 (encoding copper importer CTR1) and Atox1 (encoding chaperon protein, which delivers copper from CTR1 to ATP7A and ATP7B) expression, suggesting that male germ cells retrieve copper and ATP7A protects them from copper overdose. In contrast, ATP7B protein is observed in SCs and near elongated spermatids; thus, its function seems to be related to copper extraction during spermiogenesis. This is the first study to give a comprehensive view on the activity of copper-related genes during spermatogenesis in mice.

Transcriptomic analysis of basidiocarp development in Ustilago maydis (DC) Cda

Previously, we demonstrated that when Ustilago maydis (DC) Cda., a phytopathogenic basidiomycete and the causal agent of corn smut, is grown in the vicinity of maize embryogenic calli in a medium supplemented with the herbicide Dicamba, it developed gastroid-like basidiocarps. To elucidate the molecular mechanisms involved in the basidiocarp development by the fungus, we proceeded to analyze the transcriptome of the process, identifying a total of 2002 and 1064 differentially expressed genes at two developmental stages, young and mature basidiocarps, respectively. Function of these genes was analyzed with the use of different databases. MIPS analysis revealed that in the stage of young basidiocarp, among the ca. two thousand differentially expressed genes, there were some previously described for basidiocarp development in other fungal species. Additional elements that operated at this stage included, among others, genes encoding the transcription factors FOXO3, MIG3, PRO1, TEC1, copper and MFS transporters, and cytochromes P450. During mature basidiocarp development, important up-regulated genes included those encoding hydrophobins, laccases, and ferric reductase (FRE/NOX). The demonstration that a mapkk mutant was unable to form basidiocarps, indicated the importance of the MAPK signaling pathway in this developmental process.