The kidney proximal tubule is the primary site in the nephron for excretion of waste products through a combination of active uptake and secretory processes, and is also a primary target of drug-induced nephrotoxicity. Here, we describe the development and functional characterization of a 3-dimensional flow-directed human kidney proximal tubule microphysiological system. The system replicates the polarity of the proximal tubule, expresses appropriate marker proteins, exhibits biochemical and synthetic activities, as well as secretory and reabsorptive processes associated with proximal tubule function in vivo. This microphysiological system can serve as an ideal platform for ex vivo modeling of renal drug clearance and drug-induced nephrotoxicity. Additionally, this novel system can be used for preclinical screening of new chemical compounds prior to initiating human clinical trials.

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Post-translational methylation of the non-histone, actin-binding protein EF1α1 is essential for neural crest migration.

Background: The kidneys efficiently filter waste products while retaining serum proteins in the circulation. However, numerous diseases compromise this barrier function, resulting in spillage of serum proteins into the urine (proteinuria). Some studies of glomerular filtration suggest that tubules may be physiologically exposed to nephrotic-range protein levels. Therefore, whether serum components can directly injure the downstream tubular portions of the kidney, which in turn can lead to inflammation and fibrosis, remains controversial. Methods: We tested the effects of serum protein exposure in human kidney tubule microphysiologic systems (MPS) and with orthogonal epigenomic approaches. Animal models cannot directly assess the effect of serum components on tubules. Results: Serum, but not its major protein component albumin, induced tubular injury and secretion of proinflammatory cytokines. Epigenomic comparison of serum-injured tubules and intact kidney tissue revealed canonical stress-inducible regulation of injury-induced genes. Concordant transcriptional changes in microdissected tubulointerstitium were also observed in an independent cohort of patients with proteinuric kidney disease. Conclusions: Our results demonstrate a causal role for serum proteins in tubular injury and identify regulatory mechanisms and novel pathways for intervention.

Background Neural crest cells are multipotent cells that migrate extensively throughout vertebrate embryos to form diverse lineages. Cell migration requires polarized, organized actin networks that provide the driving force for motility. Actin-binding proteins that regulate neural crest cell migration are just beginning to be defined. Results We recently identified a number of actin-associated factors through proteomic profiling of methylated proteins in migratory neural crest cells. Here, we report the previously undocumented expression pattern of three of these proteins in chick early neural crest development: doublecortin (DCX), tropomyosin-1 (TPM-1), and actin depolymerizing factor (ADF). All three genes are expressed with varying degrees of specificity and intensity in premigratory and migratory neural crest cells, and their resulting proteins exhibit distinct subcellular localization in migratory neural crest cells. Morpholino knock down of ADF reveals it is required for Sox10 gene expression, but minimally important during neural crest migration. Conclusions Neural crest cells express DCX, TPM-1 and ADF. ADF is necessary during neural crest specification, but largely dispensable for migration.