Eun Young Park‡,1, Young Hoon Sung§,1, Moon Hee Yang‡,1, Ji Yeun Noh‡, So Young Park‡, Tae Young Lee‡, Yeon Joo Yook‡, Kyung Hyun Yoo‡, Kyung Jin Roh¶, Ingyu Kim∥, Young-Hwan Hwang**, Goo Taeg Oh‡‡, Je Kyung Seong¶, Curie Ahn§§, Han-Woong Lee§,2 and Jong Hoon Park‡,3
‡Department of Biological Science, Sookmyung Women's University, Seoul 140-742, Republic of Korea, the §Department of Biochemistry, Yonsei University, Seoul 120-749, Republic of Korea, the ¶Laboratory of Developmental Biology and Genomics, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Republic of Korea, the ∥Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, the **Department of Internal Medicine, Eulji Medical Center, Seoul 139-711, Republic of Korea, the ‡‡Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, Seoul 120-750, Republic of Korea, and the §§Department of Internal Medicine, Seoul National University College of Medicine, Seoul 110-744, Republic of Korea
2 To whom correspondence may be addressed.
3 To whom correspondence may be addressed.
The pathogenic mechanisms of human autosomal dominant polycystic kidney disease (ADPKD) have been well known to include the mutational inactivation of PKD2. Although haploinsufficiency and loss of heterozygosity at the Pkd2 locus can cause cyst formation in mice, polycystin-2 is frequently expressed in the renal cyst of human ADPKD, raising the possibility that deregulated activation of PKD2 may be associated with the cystogenesis of human ADPKD. To determine whether increased PKD2 expression is physiologically pathogenic, we generated PKD2-overexpressing transgenic mice. These mice developed typical renal cysts and an increase of proliferation and apoptosis, which are reflective of the human ADPKD phenotype. These manifestations were first observed at six months, and progressed with age. In addition, we found that ERK activation was induced by PKD2 overexpression via B-Raf signaling, providing a possible molecular mechanism of cystogenesis. In PKD2 transgenic mice, B-Raf/MEK/ERK sequential signaling was up-regulated. Additionally, the transgenic human polycystin-2 partially rescues the lethality of Pkd2 knock-out mice and therefore demonstrates that the transgene generated a functional product. Functional strengthening or deregulated activation of PKD2 may be a direct cause of ADPKD. The present study provides evidence for an in vivo role of overexpressed PKD2 in cyst formation. This transgenic mouse model should provide new insights into the pathogenic mechanism of human ADPKD.
1 These authors contributed equally to this work.