Spatially resolved transcriptomics and the kidney: many opportunities.

Defining changes in gene expression during health and disease is critical for the understanding of human physiology. In recent years, single-cell/nuclei RNA sequencing (sc/snRNAseq) has revolutionized the definition and discovery of cell types and states as well as the interpretation of organ- and cell-type-specific signaling pathways. However, these advances require tissue dissociation to the level of the single cell or single nuclei level. Spatially resolved transcriptomics (SrT) now provides a platform to overcome this barrier in understanding the physiological contexts of gene expression and cellular microenvironment changes in development and disease. Some of these transcriptomic tools allow for high-resolution mapping of hundreds of genes simultaneously in cellular and subcellular compartments. Other tools offer genome depth mapping but at lower resolution. We review advances in SrT, considerations for using SrT in your own research, and applications for kidney biology.

A Trigger Phosphodiesterase Modulates the Global c-di-GMP Pool, Motility, and Biofilm Formation in Vibrio parahaemolyticus.

Vibrio parahaemolyticus cells transit from free-swimming to surface adapted lifestyles, such as swarming colonies and three-dimensional biofilms. These transitions are regulated by sensory modules and regulatory networks that involve the second messenger cyclic diguanylate monophosphate (c-di-GMP). In this work, we show that a previously uncharacterized c-di-GMP phosphodiesterase (VP1881) from V. parahaemolyticus plays an important role in modulating the c-di-GMP pool. We found that the product of VP1881 promotes its own expression when the levels of c-di-GMP are low or when the phosphodiesterase (PDE) is catalytically inactive. This behavior has been observed in a class of c-di-GMP receptors called trigger phosphodiesterases, and hence we named the product of VP1881 TpdA, for trigger phosphodiesterase A. The absence of tpdA showed a negative effect on swimming motility while, its overexpression from an isopropyl-ß-d-thiogalactopyranoside (IPTG)-inducible promoter showed a positive effect on both swimming and swarming motility and a negative effect on biofilm formation. Changes in TpdA abundance altered the expression of representative polar and lateral flagellar genes, as well as that of the biofilm-related gene cpsA. Our results also revealed that autoactivation of the native PtpdA promoter is sufficient to alter c-di-GMP signaling responses such as swarming and biofilm formation in V. parahaemolyticus, an observation that could have important implications in the dynamics of these social behaviors. IMPORTANCE c-di-GMP trigger phosphodiesterases (PDEs) could play a key role in controlling the heterogeneity of biofilm matrix composition, a property that endows characteristics that are potentially relevant for sustaining integrity and functionality of biofilms in a variety of natural environments. Trigger PDEs are not always easy to identify based on their sequence, and hence not many examples of these type of signaling proteins have been reported in the literature. Here, we report on the identification of a novel trigger PDE in V. parahaemolyticus and provide evidence suggesting that its autoactivation could play an important role in the progression of swarming motility and biofilm formation, multicellular behaviors that are important for the survival and dissemination of this environmental pathogen.