Glis3 Is Associated with Primary Cilia and Wwtr1/TAZ and Implicated in Polycystic Kidney Disease

Abstract

In this study, we describe the generation and partial characterization of Krüppel-like zinc finger protein Glis3 mutant (Glis3 zf/zf ) mice. These mice display abnormalities very similar to those of patients with neonatal diabetes and hypothyroidism syndrome, including the development of diabetes and polycystic kidney disease. We demonstrate that Glis3 localizes to the primary cilium, suggesting that Glis3 is part of a cilium-associated signaling pathway. Although Glis3 zf/zf mice form normal primary cilia, renal cysts contain relatively fewer cells with a primary cilium. We further show that Glis3 interacts with the transcriptional modulator Wwtr1/TAZ, which itself has been implicated in glomerulocystic kidney disease. Wwtr1 recognizes a P/LPXY motif in the C terminus of Glis3 and enhances Glis3-mediated transcriptional activation, indicating that Wwtr1 functions as a coactivator of Glis3. Mutations in the P/LPXY motif abrogate the interaction with Wwtr1 and the transcriptional activity of Glis3, indicating that this motif is part of the transcription activation domain of Glis3. Our study demonstrates that dysfunction of Glis3 leads to the development of cystic renal disease, suggesting that Glis3 plays a critical role in maintaining normal renal functions. We propose that localization to the primary cilium and interaction with Wwtr1 are key elements of the Glis3 signaling pathway.

Modulation of the Transactivation Function and Stability of Krüppel-like Zinc Finger Protein Gli-similar 3 (Glis3) by Suppressor of Fused

“…SUFU has been shown to co-localize to the primary cilium with Gli proteins, and although the functional consequence of their co-localization is still far from being understood, both primary cilium-dependent and -independent regulation of Gli proteins by SUFU have been reported (32,33,41,42). In this context it is interesting to note that Glis2 and Glis3 have also been localized to the primary cilium (7,10,44). One might speculate that SUFU-Glis3 interaction might be linked functionally to the primary cilium and possibly involved in the regulation of Glis3 activity.…”

“…We reported previously that Glis3 robustly activates transcription of murine Ins2 via its proximal promoter, which contains two functional Glis-responsive elements (7,8). To assess the potential role of the Glis3 N terminus in modulating Glis3 transcriptional activity, we examined the effect of various N-terminal deletions on the activation of the Ins2 promoter.…”

“…The most notable elements within the insulin promoter are the A-, E-, and C-boxes, which bind Pdx1, ␤2/NeuroD1, and MafA, respectively. Glis3 induces insulin gene expression through two GlisBS within the proximal promoter region (7,8). Thus far, little is known about the precise mechanisms that control Glis3 activation and Glis3-induced transcription.…”

“…Mice with a disrupted Glis3 function develop neonatal diabetes, hypothyroidism, and polycystic kidney disease (6,7,17). Recently, Glis3 has been shown to positively regulate transcription of the human proinsulin (INS) and rodent insulin 2 (Ins2) genes in pancreatic ␤-cells (7,8). Transcriptional regulation and ␤-cellspecific expression of the insulin gene occurs via an ϳ600-bp upstream regulatory region (18,19).…”

“…Genetic aberrations in the GLIS3 gene have been linked to the development of neonatal diabetes and congenital hypothyroidism, polycystic kidney disease, and liver fibrosis, as well as type 1 and type 2 diabetes (11)(12)(13)(14)(15)(16). Mice with a disrupted Glis3 function develop neonatal diabetes, hypothyroidism, and polycystic kidney disease (6,7,17). Recently, Glis3 has been shown to positively regulate transcription of the human proinsulin (INS) and rodent insulin 2 (Ins2) genes in pancreatic ␤-cells (7,8).…”