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Andrew McMahon (PI)
University of Southern California
We will extend our hGUDMAP studies of the human fetal kidney to generate new resources for the RBK consortium. In a collaboration with ABCAM, we will characterize rabbit monoclonal antibodies for cross species (mouse and human) cell-type specificity in identifying key cell types of the developing kidney. We will validate MARIS (Method for Analyzing RNA following Intracellular Sorting) as a broadly applicable approach for acquiring transcriptional signatures from specific cell types in the developing kidneys. Finally, recognizing the importance of Six2 in regulating nephron progenitors, we will compare the Six2 regulatory landscape in the embryonic kidney with that of pluripotent stem cell derived Six2+ nephron progenitors generated in cell culture.
Tran, Tracy; Lindstrom, Nils O.; Ransick, Andrew; De Sena Brandine, Guilherme; Guo, Qiuyu; Kim, Albert D.; Der, Balint; Peti-Peterdi, Janos; Smith, Andrew D.; Thornton, Matthew; Grubbs, Brendan; McMahon, Jill A.; McMahon, Andrew P. Dev Cell. 50(1):102–116.e6. July 2019.
The renal corpuscle of the kidney comprises a glomerular vasculature embraced by podocytes and supported by mesangial myofibroblasts, which ensure plasma filtration at the podocyte-generated slit diaphragm. With a spectrum of podocyte-expressed gene mutations causing chronic disease, an enhanced understanding of podocyte development and function to create relevant in vitro podocyte models is a clinical imperative. To characterize podocyte development, scRNA-seq was performed on human fetal kidneys, identifying distinct transcriptional signatures accompanying the differentiation of functional podocytes from progenitors. Interestingly, organoid-generated podocytes exhibited highly similar, progressive transcriptional profiles despite an absence of the vasculature, although abnormal gene expression was pinpointed in late podocytes. On transplantation into mice, organoid-derived podocytes recruited the host vasculature and partially corrected transcriptional profiles. Thus, human podocyte development is mostly intrinsically regulated and vascular interactions refine maturation. These studies support the application of organoid-derived podocytes to model disease and to restore or replace normal kidney functions.
Lindström, NO; McMahon, JA; Guo, J; Tran, T; Guo, Q; Rutledge, E; Parvez, RK; Saribekyan, G; Schuler, RE; Liao, C; Kim, AD; Abdelhalim, A; Ruffins, SW; Thornton, ME; Basking, L; Grubbs, B; Kesselman, C; McMahon, AP. J Am Soc Nephrol. February 2018.
Human kidney function is underpinned by approximately 1,000,000 nephrons, although the number varies substantially, and low nephron number is linked to disease. Human kidney development initiates around 4 weeks of gestation and ends around 34-37 weeks of gestation. Over this period, a reiterative inductive process establishes the nephron complement. Studies have provided insightful anatomic descriptions of human kidney development, but the limited histologic views are not readily accessible to a broad audience. In this first paper in a series providing comprehensive insight into human kidney formation, we examined human kidney development in 135 anonymously donated human kidney specimens. We documented kidney development at a macroscopic and cellular level through histologic analysis, RNA in situ hybridization, immunofluorescence studies, and transcriptional profiling, contrasting human development (4-23 weeks) with mouse development at selected stages (embryonic day 15.5 and postnatal day 2). The high-resolution histologic interactive atlas of human kidney organogenesis generated can be viewed at the GUDMAP database (www.gudmap.org) together with three-dimensional reconstructions of key components of the data herein. At the anatomic level, human and mouse kidney development differ in timing, scale, and global features such as lobe formation and progenitor niche organization. The data also highlight differences in molecular and cellular features, including the expression and cellular distribution of anchor gene markers used to identify key cell types in mouse kidney studies. These data will facilitate and inform in vitro efforts to generate human kidney structures and comparative functional analyses across mammalian species.
Oxburgh, L; Carroll, TJ; Cleaver, O; Gossett, DR; Hoshizaki, DK; Hubbell, JA; Humphreys, BD; Jain, S; Jensen, J; Kaplan, DL; Kesselman, C; Ketchum, CJ; Little, MH; McMahon, AP; Shankland, SJ; Spence, JR; Valerius, MT; Wertheim, JA; Wessely, O; Zheng, Y; Drummond, IA. J Am Soc Nephrol. 28(5):1370–1378. May 2017.
(Re)Building a Kidney is a National Institute of Diabetes and Digestive and Kidney Diseases-led consortium to optimize approaches for the isolation, expansion, and differentiation of appropriate kidney cell types and the integration of these cells into complex structures that replicate human kidney function. The ultimate goals of the consortium are two-fold: to develop and implement strategies for in vitro engineering of replacement kidney tissue, and to devise strategies to stimulate regeneration of nephrons in situ to restore failing kidney function. Projects within the consortium will answer fundamental questions regarding human gene expression in the developing kidney, essential signaling crosstalk between distinct cell types of the developing kidney, how to derive the many cell types of the kidney through directed differentiation of human pluripotent stem cells, which bioengineering or scaffolding strategies have the most potential for kidney tissue formation, and basic parameters of the regenerative response to injury. As these projects progress, the consortium will incorporate systematic investigations in physiologic function of in vitro and in vivo differentiated kidney tissue, strategies for engraftment in experimental animals, and development of therapeutic approaches to activate innate reparative responses.