Coordinated contractions of the smooth muscle coat surrounding the kidney outflow tract (OT), including the renal calyces, pelvis and ureter, are essential for draining urine out of the kidney. Congenital defects that impair this peristaltic process are common, and the leading cause of renal failure in children. However, the signaling pathways that control the differentiation of the cell types mediating urinary tract peristalsis remain poorly understood. In the previous funding period we showed that Bone Morphogenetic Protein signaling during the early stages of development is essential for the formation of the OT smooth muscle coat. In this project we will study the differentiated cell types that coordinate contraction in this musculature. We recently discovered that the normal initiation and coordination of OT smooth muscle contraction is dependent on Hyperpolarizing Cation Channel (HCN) activity.
In Aim 1, we will determine if HCN expressing OT cells exhibit the electrophysiological and structural properties required for triggering smooth muscle contraction using our recently developed high resolution video-microscopic and optical mapping protocols and electron-microscopic techniques. Moreover, we will determine if HCN channel activity is essential for the efficient flow of urine from the kidney to the bladder by analyzing OT structure, smooth muscle contractile and electrical activity in mice with targeted HCN gene deletions. We have also uncovered a role for the tyrosine kinase receptor C-kit in controlling OT contractile activity.
In Aim 2 we will analyze OT architecture and smooth muscle function in mice with loss-of-function mutant C-Kit alleles using morphological and functional assays.
Aim 3 is based on our preliminary data demonstrating that mice harboring a constitutively active C-kit allele develop fetal hydronephrosis. We will determine if this defect due to C-kit gain-of-function is caused by a structural occlusion of the OT tract or as we predict, a defect in coordinated peristalsis. Collectively, the results of proposed experiments identifying the cell types required for triggering coordinated OT peristalsis will open up a new area of investigation focused on the signaling pathways controlling the differentiation of these pacemaker cells. Ultimately, our studies will reveal drug targets for the modification of ureter peristalsis and may reveal unappreciated causes of hydronephrosis.

Public Health Relevance

In this project we will identify ion channels and signaling molecules that control coordinated ureter peristalsis, a process essential for propelling urine from the kidney to the bladder. Furthermore, we determine if defects in the function of these proteins cause pressure induced dilations of the renal pelvis in mice using murine genetics. Results of proposed experiments using optical mapping, video-microscopic and morphological techniques to detect alterations in ureter structure and function in wild type and mutant mice will reveal drug targets to modify urinary tract peristalsis and may uncover unappreciated causes of pathological renal pelvis dilations or hydronephrosis, the leading cause of renal failure in infants and children.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Urologic and Kidney Development and Genitourinary Diseases Study Section (UKGD)
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Hoshizaki, Deborah K
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Weill Medical College of Cornell University
Schools of Medicine
New York
United States
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Hurtado, Romulo; Smith, Carl S (2016) Hyperpolarization-activated cation and T-type calcium ion channel expression in porcine and human renal pacemaker tissues. J Anat 228:812-25
Hurtado, Romulo; Zewdu, Rediet; Mtui, James et al. (2015) Pbx1-dependent control of VMC differentiation kinetics underlies gross renal vascular patterning. Development 142:2653-64
Herzlinger, Doris; Hurtado, Romulo (2014) Patterning the renal vascular bed. Semin Cell Dev Biol 36:50-6
Hurtado, Romulo; Bub, Gil; Herzlinger, Doris (2014) A molecular signature of tissues with pacemaker activity in the heart and upper urinary tract involves coexpressed hyperpolarization-activated cation and T-type Ca2+ channels. FASEB J 28:730-9
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Herzlinger, Doris (2011) Upper urinary tract pacemaker cells join the GLI club. J Clin Invest 121:836-8
Hurtado, Romulo; Bub, Gil; Herzlinger, Doris (2010) The pelvis-kidney junction contains HCN3, a hyperpolarization-activated cation channel that triggers ureter peristalsis. Kidney Int 77:500-8
Wang, Gerald J; Brenner-Anantharam, Andrea; Vaughan, E Darracott et al. (2009) Antagonism of BMP4 signaling disrupts smooth muscle investment of the ureter and ureteropelvic junction. J Urol 181:401-7
Guillaume, Richard; Bressan, Michel; Herzlinger, Doris (2009) Paraxial mesoderm contributes stromal cells to the developing kidney. Dev Biol 329:169-75
Brenner-Anantharam, Andrea; Cebrian, Cristina; Guillaume, Richard et al. (2007) Tailbud-derived mesenchyme promotes urinary tract segmentation via BMP4 signaling. Development 134:1967-75

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