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Published on: October 12, 2017
Novel mechanisms of early upper and lower urinary tract patterning regulated by RetY1015 docking tyrosine in mice
Masato Hoshi1, Ekatherina Batourina, Cathy Mendelsohn
1Department of Internal Medicine (Renal division), Washington University School ofMedicine, St Louis, MO 63110, USA.
Abstract:
Mutations in the receptor tyrosine kinase RET are associated with congenital anomalies of kidneys or urinary tract (CAKUT). RET tyrosine Y1015 is the docking site for PLCγ, a major regulator of RET signaling. Abrogating signaling via Y1015 causes CAKUT that are markedly different than renal agenesis in Ret-null or RetY1062F mutant mice. We performed analysis of Y1015F mutant upper and lower urinary tracts in mice to delineate its molecular and developmental roles during early urinary tract formation. We found that the degeneration of the common nephric ducts (CND), the caudal-most Wolffian duct (WD) segment, depends on Y1015 signals. The CNDs in Y1015F mutants persist owing to increased proliferation and reduced apoptosis, and showed abundance of phospho-ERK-positive cells. In the upper urinary tract, the Y1015 signals are required for proper patterning of the mesonephros and metanephros. Timely regression of mesonephric mesenchyme and proper demarcation of mesonephric and metanephric mesenchyme from the WD depends on RetY1015 signaling. We show that the mechanism of de novo ectopic budding is via increased ERK activity due to abnormal mesenchymal GDNF expression. Although reduction in GDNF dosage improved CAKUT it did not affect delayed mesenchyme regression. Experiments using whole-mount immunofluorescence confocal microscopy and explants cultures of early embryos with ERK-specific inhibitors suggest an imbalance between increased proliferation, decreased apoptosis and increased ERK activity as a mechanism for WD defects in RetY1015F mice. Our work demonstrates novel inhibitory roles of RetY1015 and provides a possible mechanistic explanation for some of the confounding broad range phenotypes in individuals with CAKUT.
Insights
Ret tyrosine Y1015 signaling is crucial for normal kidney and urinary tract development. Disrupting this signaling leads to congenital anomalies of kidneys or urinary tract (CAKUT) by affecting cell proliferation and apoptosis.
Area of Science:
- Developmental Biology
- Molecular Biology
- Genetics
Background:
- Mutations in the receptor tyrosine kinase RET are linked to congenital anomalies of kidneys or urinary tract (CAKUT).
- The RET tyrosine Y1015 residue serves as a critical docking site for PLCγ, a key regulator of RET signaling pathways.
- Altering RET signaling at Y1015 results in CAKUT phenotypes distinct from those observed in Ret-null or RetY1062F mutant mice.
Purpose of the Study:
- To investigate the molecular and developmental functions of RET tyrosine Y1015 during early urinary tract formation.
- To elucidate the role of Y1015 signaling in the degeneration of common nephric ducts (CNDs) and upper urinary tract patterning.
- To understand the mechanisms underlying CAKUT phenotypes associated with Y1015 mutations.
Main Methods:
- Analysis of Y1015F mutant mouse models.
- Whole-mount immunofluorescence confocal microscopy.
- Explant cultures of early embryos treated with ERK-specific inhibitors.
Main Results:
- Y1015 signaling is essential for the regression of common nephric ducts (CNDs); Y1015F mutants exhibit persistent CNDs due to increased proliferation and reduced apoptosis.
- Y1015 signaling is required for proper mesonephros and metanephros patterning and timely regression of mesonephric mesenchyme.
- Increased ERK activity, driven by abnormal mesenchymal GDNF expression, contributes to de novo ectopic budding and WD defects in Y1015F mutants.
Conclusions:
- RET Y1015 signaling plays a novel inhibitory role in urinary tract development.
- Dysregulation of Y1015 signaling, leading to increased proliferation, decreased apoptosis, and elevated ERK activity, explains CAKUT phenotypes.
- This study provides mechanistic insights into the diverse CAKUT phenotypes observed in individuals with RET mutations.
