Conditional Myh9 and Myh10 inactivation in adult mouse renal epithelium results in progressive kidney disease
Karla L. Otterpohl, … , Kameswaran Surendran, Indra Chandrasekar
Karla L. Otterpohl, … , Kameswaran Surendran, Indra Chandrasekar
Published October 1, 2020
Citation Information: JCI Insight. 2020;5(21):e138530. https://doi.org/10.1172/jci.insight.138530.
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Research Article Cell biology Nephrology

Conditional Myh9 and Myh10 inactivation in adult mouse renal epithelium results in progressive kidney disease

Abstract

Actin-associated nonmuscle myosin II (NM2) motor proteins play critical roles in a myriad of cellular functions, including endocytosis and organelle transport pathways. Cell type–specific expression and unique subcellular localization of the NM2 proteins, encoded by the Myh9 and Myh10 genes, in the mouse kidney tubules led us to hypothesize that these proteins have specialized functional roles within the renal epithelium. Inducible conditional knockout (cKO) of Myh9 and Myh10 in the renal tubules of adult mice resulted in progressive kidney disease. Prior to overt renal tubular injury, we observed intracellular accumulation of the glycosylphosphatidylinositol-anchored protein uromodulin (UMOD) and gradual loss of Na+ K+ 2Cl– cotransporter from the apical membrane of the thick ascending limb epithelia. The UMOD accumulation coincided with expansion of endoplasmic reticulum (ER) tubules and activation of ER stress and unfolded protein response pathways in Myh9&10-cKO kidneys. We conclude that NM2 proteins are required for localization and transport of UMOD and loss of function results in accumulation of UMOD and ER stress–mediated progressive renal tubulointerstitial disease. These observations establish cell type–specific role(s) for NM2 proteins in regulation of specialized renal epithelial transport pathways and reveal the possibility that human kidney disease associated with MYH9 mutations could be of renal epithelial origin.

Authors

Karla L. Otterpohl, Brook W. Busselman, Ishara Ratnayake, Ryan G. Hart, Kimberly R. Hart, Claire M. Evans, Carrie L. Phillips, Jordan R. Beach, Phil Ahrenkiel, Bruce A. Molitoris, Kameswaran Surendran, Indra Chandrasekar

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Figure 7

TEM confirms ER expansion in Myh9&10-cKO mouse TAL tubules.

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TEM confirms ER expansion in Myh9&10-cKO mouse TAL tubules. (A–F) Ni...
(A–F) Nine-week-old control and cKO mouse kidneys were subjected to TEM to analyze the ultrastructure of the TAL tubules. (A–C) Representative TEM image from the control mouse kidney showing the ultrastructure of the TAL epithelial cells. Black boxes represent the selective regions of the TAL epithelium in A for visualization of ER tubules shown in B and C (arrowheads). The representative ER tubules in the control kidney have ribosomes, are short in length, and have a small ER lumen (black arrowheads). (D–F) Representative TEM images showing a TAL tubule from the cKO mouse kidney. Black boxes represent the selective regions of the TAL epithelium in D for visualization of ER tubules shown in E and F. ER tubules have increased length and lumen diameter (luminal space) in the cKO TAL tubules (black arrowheads). Some ER tubules appear to be disintegrating and no longer maintain normal structure (black arrows). Scale bars: 2 μm (A and D), 1 μm (B, C, E, and F). (G–I) Graphs show the relationship between ER perimeter, ER area, and total TAL tubule area from 3 tubules (17 TAL cells, 181 ER tubules) from the control kidney and 4 tubules (28 TAL cells, 358 ER tubules) from the cKO kidney. (G) cKO kidneys have a statistically significant (*) increase in the ratio of ER perimeter to the total area of the TAL tubules compared with the controls (P value = 0.003). (H) The ratio of total ER area to TAL tubule area varied between the cKO tubules, ranging from 5- to 20-fold increase in the ratio compared with the control tubules and was significantly (*) different (P value = 0.031). (I) Scatter plot showing the relationship between ER perimeter and ER area in the TAL tubules of control and cKO kidneys with a linear relationship between perimeter size and ER area. Statistics were done using unpaired t test, 2-tailed. Error bars depict standard deviation.