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Hepatocyte nuclear factor 1B(HNF1B) encodes a transcription factor expressed in developing human kidney epithelia. HeterozygousHNF1Bmutations are the commonest monogenic cause of dysplastic kidney malformations (DKMs). To understand their pathobiology, we generated heterozygousHNF1Bmutant kidney organoids from CRISPR-Cas9 gene-edited human ESCs and iPSCs reprogrammed from a family withHNF1B-asscociated DKMs. Mutant organoids contained enlarged malformed tubules and displayed deregulated cell turnover. Numerous genes implicated in Mendelian kidney tubulopathies were downregulated, and mutant tubules resisted the cAMP-mediated dilatation seen in controls. Bioinformatic analyses indicated abnormal WNT, calcium, and glutamatergic pathways, the latter hitherto unstudied in developing kidneys. Glutamate ionotropic receptor kainate type subunit 3 was upregulated in mutant organoids and was detected in their tubules and in fetal human DKM dysplastic epithelia. These results reveal morphological, molecular, and physiological roles for HNF1B in human kidney tubule morphogenesis and functional differentiation. They additionally suggest druggable targets to ameliorate disease.

Background: Kidney disease causes major suffering and premature mortality worldwide. With no cure for kidney failure currently available, and with limited options for treatment, there is an urgent need to develop effective pharmaceutical interventions to slow or prevent kidney disease progression. Summary: In this review, we consider the feasibility of using human pluripotent stem cell-derived kidney tissues, or organoids, to model genetic kidney disease. Notable successes have been made in modelling genetic tubular diseases (e.g., cystinosis), polycystic kidney disease, and medullary cystic kidney disease. Organoid models have also been used to test novel therapies that ameliorate aberrant cell biology. Some progress has been made in modelling congenital glomerular disease, even though glomeruli within organoids are developmentally immature. Less progress has been made in modelling structural kidney malformations, perhaps because sufficiently mature metanephric mesenchyme-derived nephrons, ureteric bud-derived branching collecting ducts, and a prominent stromal cell population are not generated together within a single protocol. Key Messages: We predict that the field will advance significantly if organoids can be generated with a full complement of cell lineages and with kidney components displaying key physiological functions, such as glomerular filtration. The future economic upscaling of reproducible organoid generation will facilitate more widespread research applications, including the potential therapeutic application of these stem cell-based technologies.

Summary MicroRNAs (miRNAs) are gene expression regulators and they have been implicated in acquired kidney diseases and in renal development, mostly through animal studies. We hypothesized that the miR-199a/214 cluster regulates human kidney development. We detected its expression in human embryonic kidneys by in situ hybridization. To mechanistically study the cluster, we used 2D and 3D human embryonic stem cell (hESC) models of kidney development. After confirming expression in each model, we inhibited the miRNAs using lentivirally transduced miRNA sponges. This reduced the WT1+ metanephric mesenchyme domain in 2D cultures. Sponges did not prevent the formation of 3D kidney-like organoids. These organoids, however, contained dysmorphic glomeruli, downregulated WT1, aberrant proximal tubules, and increased interstitial capillaries. Thus, the miR-199a/214 cluster fine-tunes differentiation of both metanephric mesenchymal-derived nephrons and kidney endothelia. While clinical implications require further study, it is noted that patients with heterozygous deletions encompassing this miRNA locus can have malformed kidneys., Graphical Abstract, Highlights • miR-199a/214 is expressed in the developing human kidney • Its function can be modeled using hESC-derived kidney organoids • Inhibiting these miRNAs results in dysmorphic glomeruli and proximal tubules • Their inhibition also leads to a denser vascular network between tubules, Bantounas and colleagues studied the role of the miR-199a/214 cluster in hESC-kidney development because they found it was expressed in native embryonic human kidneys. Using hESC-derived 3D kidney organoids, they found that blocking the miRNAs' function resulted in aberrations in glomeruli and proximal tubules and increased vascular density between tubules. Thus, the cluster fine-tunes kidney differentiation.

Voltage-gated sodium channels (Nav) are crucial to the initiation and propagation of action potentials in electrically excitable cells. Inhibitors of such ion channels have been developed and approved as drugs to treat a variety of indications. In contrast, sodium channel activators have not been considered relevant and safe in a therapeutic setting because of their high risk of toxicity and side effects. Nevertheless, there is a recent interest in activators of e.g. Nav1.1 (SCN1A) for the treatment of neurological indications, i.e. that selective positive modulation of the Nav1.1 sodium channel may hold therapeutic potential for epilepsy, schizophrenia, and Alzheimer's disease (Jensen et al., 2014). Research aimed at the identification of novel, selective Nav positive modulators, however, appears to be hampered by a deficit in suitable tool compounds with certain modulating features to initiate and validate screening assays. Although sodium channel modifying pyrethroids have been in use as important pest management tools in agriculture, public health, and a variety of household applications, their action on human Nav has not been studied in detail. Therefore we tested a set of Type 1 pyrethroids that have been described to have positive modulatory effects on insect and rodent sodium channels. Utilizing the Syncropatch 96 automated patch clamp system we were able to identify several pyrethroids activating human Nav 1.1 and/or Nav1.5. Confirmation and characterization by manual patch-clamp revealed pyrethroids with different types of positive modulation. Both, compounds acting via a delay of the inactivation time constant (similar to those published recently by Crestey et al., 2015) as well as such promoting a sustained channel opening (Veratridine-like) were identified for Nav1.1 and Nav1.5, respectively.