Menshikh, A. | bioRxiv Science

bioRxiv2024

Partial repair causes permanent defects in papillary structure and function after reversal of urinary obstruction

Urinary obstruction causes injury to the renal papilla and leads to defects in the ability to concentrate urine which predisposes to progressive kidney injury. However, the regenerative capacity of the papilla after reversal of obstruction is poorly understood. To address this, we developed a mouse model of reversible urinary obstruction which is characterized by extensive papillary injury, followed by a robust regeneration response and complete histological recovery over a 3- month period. However, these mice have a pronounced defect in urinary concentrating capacity. We now show that this is due to permanent changes in the composition, organization, and transcriptional signatures of epithelial, endothelial, and interstitial cell lineages in the papilla. There are persistent inflammatory responses that are also seen in patients with renal stone disease but are associated with cell-specific adaptive responses to the increasingly hypoxic environment of the papilla after reversal of obstruction. Taken together, our analysis of a new model of reversible urinary obstruction reveals that partial repair leads to permanent changes in the structure and function of all of the major cellular compartments in the papilla that include both shared and distinct responses to different types of renal papillary injury in humans and mice. SummaryPartial repair after reversal of urinary obstruction leads to permanent changes in structure and function of all major cellular compartments in the renal papilla O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/612436v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@1438af5org.highwire.dtl.DTLVardef@157ff60org.highwire.dtl.DTLVardef@3f09c0org.highwire.dtl.DTLVardef@9950b1_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2022

Transposase N-terminal phosphorylation and asymmetric transposon ends inhibit piggyBac transposition in mammalian cells

Mechanistic regulation of DNA transposon systems in mammalian cells remains poorly understood. Using modeling, biochemical, and cell-based assays, we sought to extend the recent cryoEM structural insight into the piggyBac transpososome to evaluate the previously unexplained role of the transposase N-terminus, the need for asymmetric transposon ends, and the complexity of transposase tetramer formation for transposition in mammalian cells. We found that N-terminal phosphorylation by casein kinase II inhibits transposase-DNA interaction and designed deletion of this phosphorylated domain releases inhibition thereby enhancing activity. We also found that the N-terminal domain promotes transposase dimerization in the absence of transposon DNA. N-terminal deletion enables transposition of symmetric transposon ends that was previously not achievable with piggyBac. The complex transposase tetramer needed for transposition of asymmetric transposon ends can be overcome via appending a second transposase C-terminal domain in combination with symmetric transposon ends overcoming the negative regulation by asymmetric ends. Our results demonstrate that N-terminal transposase phosphorylation and the requirement for asymmetric transposon ends both negatively regulate piggyBac transposons in mammalian cells. These novel insights into mechanism and structure of the piggyBac transposase expand its potential use for genomic applications.

molecular biology↗