Robo2 and Gen1 Coregulate Ureteric Budding by Activating the MAPK/ERK Signaling Pathway in Mice.

Yaxin Li,Xiaohui Wu,Xuanjin Du,Hong Xu,Qian Shen,Minghui Yu,Lihong Tan,Shanshan Xue

doi:10.3389/fmed.2021.807898

Abstract

Congenital anomalies of the kidney and urinary tract (CAKUT) are some of the most common developmental defects and have a complicated etiology, indicating an interaction of (epi-) genetic and environmental factors. Single gene mutations and copy number variations (CNVs) do not explain most cases of CAKUT, and simultaneous contributions of more than one gene (di-, oligo-, or polygenic effects; i.e., complex genetics) may lead to the pathogenesis of CAKUT. Robo2 plays a key role in regulating ureteric bud (UB) formation in the embryo, with mutations leading to supernumerary kidneys. Gen1 is a candidate gene associated with CAKUT because of its important role in early metanephric development in mice. We established a mouse model with double disruption of Robo2 and Gen1 using a piggyBac transposon and found that double gene mutation led to significantly increased CAKUT phenotypes in Robo2PB/+Gen1PB/+ mouse offspring, especially a duplicated collecting system. Increased ectopic UB formation was observed in the Robo2PB/+Gen1PB/+ mice during the embryonic period. Robo2 and Gen1 exert synergistic effects on mouse kidney development, promoting cell proliferation by activating the GDNF/RET pathway and downstream MAPK/ERK signaling. Our findings provide a disease model for CAKUT as an oligogenic disorder.

Highlights

Congenital anomalies of the kidney and urinary tract (CAKUT) collectively represent a diverse group of structural malformations that occur during embryonic kidney development, including renal hypoplasia/dysplasia, agenesis, multicystic dysplasia, duplex kidney, hydroureters and ureteropelvic junction obstructions [1]
We analyzed the expression of Robo2 and Gen1 in the control and mutant mice on E12.5 using RT-PCR
We showed that double heterozygous mutation for Robo2 and Gen1 led to significantly increased CAKUT phenotypes, a duplicated collecting system, indicating a genetic interaction between the two genes

Summary

Introduction

Congenital anomalies of the kidney and urinary tract (CAKUT) collectively represent a diverse group of structural malformations that occur during embryonic kidney development, including renal hypoplasia/dysplasia, agenesis, multicystic dysplasia, duplex kidney, hydroureters and ureteropelvic junction obstructions [1]. The development of the kidney and urinary tract is tightly regulated by multiple genes. Single gene mutations and copy number variations (CNVs) do not explain the majority of sporadic cases of CAKUT, while complex interactions of multiple genetic and environmental factors may explain a substantial proportion of cases [7]. Even in mouse models, the phenotypes resulting from genetic deletion vary substantially, suggesting that gene-gene and gene-environment interactions contribute to CAKUT [8]. Some mouse polygenic models of CAKUT, such as Pax2+/−Pax8+/− [8], Hnf1b+/−Pax2+/− [9], and Foxc1+/−Foxc2+/− [10] double heterozygous mice, have been established, suggesting that a haploinsufficient genetic combination will result in the CAKUT phenotype.

Methods

Results

Conclusion