Characterization of Schistosome Sox Genes and Identification of a Flatworm Class of Sox Regulators.

Schistosome helminths infect over 200 million people across 78 countries and are responsible for nearly 300,000 deaths annually. However, our understanding of basic genetic pathways crucial for schistosome development is limited. The sex determining region Y-box 2 (Sox2) protein is a Sox B type transcriptional activator that is expressed prior to blastulation in mammals and is necessary for embryogenesis. Sox expression is associated with pluripotency and stem cells, neuronal differentiation, gut development, and cancer. Schistosomes express a Sox-like gene expressed in the schistosomula after infecting a mammalian host when schistosomes have about 900 cells. Here, we characterized and named this Sox-like gene SmSOXS1. SmSoxS1 protein is a developmentally regulated activator that localizes to the anterior and posterior ends of the schistosomula and binds to Sox-specific DNA elements. In addition to SmSoxS1, we have also identified an additional six Sox genes in schistosomes, two Sox B, one SoxC, and three Sox genes that may establish a flatworm-specific class of Sox genes with planarians. These data identify novel Sox genes in schistosomes to expand the potential functional roles for Sox2 and may provide interesting insights into early multicellular development of flatworms.

Demonstration of N,N-Dimethyldithiocarbamate as a Copper-Dependent Antibiotic against Multiple Upper Respiratory Tract Pathogens.

Transition metals are necessary cofactors and structural elements in living systems. Exposure to high concentrations of biologically important transition metals, such as zinc and copper, results in cell toxicity. At the infection site, the immune system deploys metal sorbent proteins (e.g., lactoferrin and calprotectin) to starve pathogens of necessary metals (such as iron), while phagocytes expose engulfed pathogens to high levels of other metals, such as copper and zinc. The opportunistic pathogen Streptococcus pneumoniae (the pneumococcus) encounters macrophages during initial and protracted infections. The pneumococcus employs a copper export pathway, which improves colonization and persistent infection of the nasopharynx and the upper respiratory tract. Because copper is tightly regulated in the host, we instead sought to leverage the localized power of nutritional immunity by identifying small molecules with copper-dependent toxicity (CDT) through a targeted screen of compounds for antibiotic efficacy. We chose to include dithiocarbamates, based on the copper synergy observed in other organisms with 1-(diethylthiocarbamoyldisulfanyl)-N,N-diethyl-methanethioamide (tetraethylthiuram disulfide, disulfiram). We observed CDT of some dithiocarbamates in S. pneumoniae. Only N,N-dimethyldithiocarbamate (DMDC) was consistently toxic across a range of concentrations with copper both in vitro and in vivo against the pneumococcus. We also observed various degrees of CDT in vitro using DMDC in Staphylococcus aureus, Coccidioides posadasii, and Schistosoma mansoni. Collectively, we demonstrate that the compound DMDC is a potent bactericidal compound against S. pneumoniae with antimicrobial efficacy against bacterial and fungal pathogens. IMPORTANCE With the rise of antibiotic resistance, approaches that add new antimicrobials to the current repertoire are vital. Here, we investigate putative and known copper ionophores in an attempt to intoxicate bacteria and use ionophore/copper synergy, and we ultimately find success with N,N-dimethyldithiocarbamate (DMDC). We show that DMDC has in vitro efficacy in a copper-dependent manner and kills pathogens across three different kingdoms, Streptococcus pneumoniae, Coccidioides posadasii, and Schistosoma mansoni, and in vivo efficacy against S. pneumoniae. As such, dithiocarbamates represent a new potential class of antimicrobials and thus warrant further mechanistic investigation.

Multiomic analysis of Schistosoma mansoni reveals unique expression profiles in cercarial heads and tails.

Schistosomes require both molluscan and mammalian hosts for development. The larval cercaria exits the snail host and swims to identify and invade the mammalian host. The cercaria has two macrostructures, the head and the tail. The head invades the host, where it matures into an adult worm. The tail is lost after host invasion. Translation in the cercaria differs in each macrostructure, with higher levels of translation in the cercarial tail and little to no translational activity in the cercarial head. We compared the transcriptome and proteome of the cercarial head and tail and observed stark differences between the two macrostructures. We identified unique and differentially expressed transcripts and proteins, including ribosomal components expressed in higher levels in tails than in heads, which may explain the differences in translation levels between heads and tails. We also characterized the weak correlation between transcription and translation in infectious cercarial heads and tails.

Heads or tails? Differential translational regulation in cercarial heads and tails of schistosome worms.

Schistosomes are obligate helminths responsible for over 218 million cases of human schistosomiasis in 78 countries around the world. Infection occurs when free-swimming cercariae penetrate human skin and initiate developmental progression into parasitic obligate worms that consume red blood cells. Transcriptomic studies of infectious cercariae reveal abundant mRNAs associated with energy metabolism and host invasion. However, the cercaria is mostly transcriptionally quiescent, suggesting that most mRNAs are primed prior to cercarial escape from the snail host. The use of transcriptomics to understand protein expression presumes that transcription and translation are functionally coupled and the cercarial stage has categorically been treated as a single unit for -omic analysis. Per contra, the relationship between transcription and translation in infectious cercariae has not been described. To understand the correlation between transcription and translation in cercariae, we separately measured nascent translation levels in cercarial heads, cercarial tails and in the developing schistosomula, the next stage of its life cycle. The loss of the cercarial tail is essential for the transformation from a cercaria to a schistosomulum. We observed that translation was initially limited and the translation rate accelerated during the first 72-hours after tail loss. When we tested nascent translation in cercarial heads, cercarial tails, whole cercariae, and 4-hour schistosomula, we found that translation is significantly upregulated in the cercarial tail when compared to the cercarial head and that translation was undetectable in heads using immunofluorescent image quantification (p = .0005). These data represent a major shift in how we understand the cercarial stage. The cercarial head is mostly transcriptionally and translationally quiescent while being sufficient for progression into a schistosomulum. In addition, transcription and translation are not linked in Schistosoma mansoni cercaria. Thus, our current conceptual approach of treating the cercaria as a single functional unit for -omic studies may be insufficient to understand cercarial development.