Cancer susceptibility and embryonic lethality in Mob1a/1b double-mutant mice
Miki Nishio, … , Satoshi Itami, Akira Suzuki
Miki Nishio, … , Satoshi Itami, Akira Suzuki
Published November 12, 2012
Citation Information: J Clin Invest. 2012;122(12):4505-4518. https://doi.org/10.1172/JCI63735.
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Cancer susceptibility and embryonic lethality in Mob1a/1b double-mutant mice

Abstract

Mps one binder 1a (MOB1A) and MOB1B are key components of the Hippo signaling pathway and are mutated or inactivated in many human cancers. Here we show that intact Mob1a or Mob1b is essential for murine embryogenesis and that loss of the remaining WT Mob1 allele in Mob1aΔ/Δ1btr/+ or Mob1aΔ/+1btr/tr mice results in tumor development. Because most of these cancers resembled trichilemmal carcinomas, we generated double-mutant mice bearing tamoxifen-inducible, keratinocyte-specific homozygous-null mutations of Mob1a and Mob1b (kDKO mice). kDKO mice showed hyperplastic keratinocyte progenitors and defective keratinocyte terminal differentiation and soon died of malnutrition. kDKO keratinocytes exhibited hyperproliferation, apoptotic resistance, impaired contact inhibition, enhanced progenitor self renewal, and increased centrosomes. Examination of Hippo pathway signaling in kDKO keratinocytes revealed that loss of Mob1a/b altered the activities of the downstream Hippo mediators LATS and YAP1. Similarly, YAP1 was activated in some human trichilemmal carcinomas, and some of these also exhibited MOB1A/1B inactivation. Our results clearly demonstrate that MOB1A and MOB1B have overlapping functions in skin homeostasis, and exert their roles as tumor suppressors by regulating downstream elements of the Hippo pathway.

Authors

Miki Nishio, Koichi Hamada, Kohichi Kawahara, Masato Sasaki, Fumihito Noguchi, Shuhei Chiba, Kensaku Mizuno, Satoshi O. Suzuki, Youyi Dong, Masaaki Tokuda, Takumi Morikawa, Hiroki Hikasa, Jonathan Eggenschwiler, Norikazu Yabuta, Hiroshi Nojima, Kentaro Nakagawa, Yutaka Hata, Hiroshi Nishina, Koshi Mimori, Masaki Mori, Takehiko Sasaki, Tak W. Mak, Toru Nakano, Satoshi Itami, Akira Suzuki

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Figure 4

Tumorigenic anomalies in Mob1a/1b double-homozygous mutant keratinocytes.

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Tumorigenic anomalies in Mob1a/1b double-homozygous mutant keratinocytes...
(A) Anti-Ki67 immunostaining of IFE (left) and HF (middle) of control and kDKO(P1) mice at P13. Scale bars: 50 μm. Quantitation of Ki67+ cells (right); *P < 0.01. (B) Histology (left) and quantitation (right) of TUNEL-stained cells in epidermis from control and kDKO(P1) mice at P16. Scale bar: 50 μm; *P < 0.01. (C) Keratinocytes from control and kDKO(P1) mice at P4 were cultured for the indicated number of days, and total cell numbers were counted. kDKO(P1) keratinocytes achieved higher saturation plating density; *P < 0.01. (D) Left: H&E-stained epidermal basal layer of control and kDKO(P1) mice at P19. Scale bar: 20 μm. Right: quantitation (cell number/50 εm BM); n = 5/group; *P < 0.05. (E–G) Immunostaining to detect γ-Tubulin (green) and α-Tubulin (red) in control and kDKO(P1) keratinocytes. DAPI, nuclei. Mutant keratinocytes showed excess centrosomes (E), multi-polar spindles (F), and micronuclei (G). Scale bars: 20 μm; *P < 0.05. (H) Identification of keratinocyte stem cells in HFs of control and kDKO(P1) mice at P19 (n = 4/group) using quantitative RT-PCR (left), *P < 0.01; flow cytometry (middle) to detect CD34; immunostaining (right) to detect SOX9. Scale bar: 100 μm. (I) Freshly isolated control and kDKO(P1) keratinocytes were plated to generate primary colonies (left) and secondary colonies (right). Giemsa staining (top) and colony counts (bottom) were performed on day 14 after plating; n = 4/group;*P < 0.02. Results shown are representative of at least 3 independent trials and at least 3 mice/group. Data are presented as the mean ± SEM, and P values were determined using the 2-tailed Student’s t test.