Kidney Week

Abstract: FR-PO289

Mechanisms of Cystogenesis by Cd79a-Driven, Conditional mTOR Activation in Mouse Developing Nephron

Session Information

• Genetic Diseases of the Kidneys: Cystic - II
  November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1101 Genetic Diseases of the Kidneys: Cystic

Authors

• Tran, Linh Nguyen Truc, Kansai Ika Daigaku Fuzoku Hirakata Byoin, Hirakata, Osaka, Japan

Linh Nguyen Truc Tran,

• Matsuda, Satoshi, Kansai Ika Daigaku Fuzoku Hirakata Byoin, Hirakata, Osaka, Japan

Satoshi Matsuda,

• Tran Thuy, Huong Quynh, Kansai Ika Daigaku Fuzoku Hirakata Byoin, Hirakata, Osaka, Japan

Huong Quynh Tran Thuy,

• Yoshizawa, Katsuhiko, Mukogawa Joshi Daigaku, Nishinomiya, Hyogo, Japan

Katsuhiko Yoshizawa,

• Tsukaguchi, Hiroyasu, Kansai Ika Daigaku Fuzoku Hirakata Byoin, Hirakata, Osaka, Japan

Hiroyasu Tsukaguchi,

Background

Polycystic kidney diseases (PKD) are a common genetic disorder arising from developmental and/or postnatal processes. Defects of primary cilia and/or their signaling pathways, e.g., mTOR pathways, underlie the pathogenesis. However, how mTOR regulates tubular integrity remains unclear. To define the role of mTOR pathway in cyst formation, we studied phenotypes of in-house PKD mouse model (Cd79a-Cre;Tsc1^ff, thereafter Cd79a-Tsc1 KO). The Cre mediated-Tsc1 depletion driven by Cd79a, the known B cell receptors, allowed a unique conditional mTORC1 activation along the distal nephron after embryonic E16.

Methods

Paraffin kidney sections were stained with PCNA and TUNEL, a marker of proliferation and apoptosis, respectively. The activation of mTORC1 and mTORC2 was evaluated by the phosphorylation of ribosomal protein S6^S240/244 and Akt^S473, respectively.

Results

Cd79a-Tsc1 KO kidney recapitulated human ADPKD pathology. Cysts appeared initially from the distal nephron by postnatal 2 weeks and developed global PKD by 4 weeks. Early cysts were of several cell types, either lined by cuboidal, hypertrophic cells with karyocytomegaly, or flattened, dedifferentiated epithelium with luminal cell exfoliation.
In Cd79a-Tsc1 KO tubules, epithelial cells continued to proliferate even after physiological nephrogenesis of postnatal 2 weeks, while apoptosis was hardly seen until later tumorigenic stage after 9 weeks. Overactivation of mTORC1 was found in part but not all cyst-lining cells and occasionally regardless of Tsc1 depletion, suggesting the non-autonomous mechanisms of the cystogenesis. Elongation of cilia and disorientation of cell intercalation as well as oriented cell division were seen in pre-cystic, developing tubules, indicating the defective cilia-related planar polarity.

Conclusion

Our results indicate that PKD phenotypes arising from overactivation of mTORC1 in early developing nephron closely resemble those of the primary cilia disorder ADPKD, suggesting two conditions share the common mechanisms. Cystogenesis are likely triggered at early developmental stage of tubulogenesis shaping the optimal tubule diameter through coordinated proliferation with polarity.

Funding

• Government Support – Non-U.S.