Taspase1-dependent TFIIA cleavage coordinates head morphogenesis by limiting Cdkn2a locus transcription
Shugaku Takeda, … , Emily H. Cheng, James J. Hsieh
Shugaku Takeda, … , Emily H. Cheng, James J. Hsieh
Published February 9, 2015
Citation Information: J Clin Invest. 2015;125(3):1203-1214. https://doi.org/10.1172/JCI77075.
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Taspase1-dependent TFIIA cleavage coordinates head morphogenesis by limiting Cdkn2a locus transcription

Abstract

Head morphogenesis requires complex signal relays to enable precisely coordinated proliferation, migration, and patterning. Here, we demonstrate that, during mouse head formation, taspase1-mediated (TASP1-mediated) cleavage of the general transcription factor TFIIA ensures proper coordination of rapid cell proliferation and morphogenesis by maintaining limited transcription of the negative cell cycle regulators p16Ink4a and p19Arf from the Cdkn2a locus. In mice, loss of TASP1 function led to catastrophic craniofacial malformations that were associated with inadequate cell proliferation. Compound deficiency of Cdkn2a, especially p16Ink4a deficiency, markedly reduced the craniofacial anomalies of TASP1-deficent mice. Furthermore, evaluation of mice expressing noncleavable TASP1 targets revealed that TFIIA is the principal TASP1 substrate that orchestrates craniofacial morphogenesis. ChIP analyses determined that noncleaved TFIIA accumulates at the p16Ink4a and p19Arf promoters to drive transcription of these negative regulators. In summary, our study elucidates a regulatory circuit comprising proteolysis, transcription, and proliferation that is pivotal for construction of the mammalian head.

Authors

Shugaku Takeda, Satoru Sasagawa, Toshinao Oyama, Adam C. Searleman, Todd D. Westergard, Emily H. Cheng, James J. Hsieh

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Figure 2

Disruption of brain architecture in Tasp1–/– embryos.

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Disruption of brain architecture in Tasp1–/– embryos. (A) Lateral views ...
(A) Lateral views of representative WT and Tasp1–/– embryos at different developmental stages (E8.5–E14.5). Tasp1–/– embryos at E9.5 and older show truncations of head structures (93.8% at E9.5, n = 16; 93.0% at E10.5, n = 41; 100% at E12.5, n = 12; 94.3% at E14.5, n = 175). Scale bar: 1.0 mm. (B) Hematoxylin and eosin–stained sagittal sections of WT and Tasp1–/– heads at the indicated developmental stages. Skull structures are identified where indicated. Note the hypoplasia of prosencephalic derivatives in Tasp1–/– embryos. cp, choroid plexus; cx, cerebral cortex; di, diencephalon; mes, mesencephalon; np, nasal process; oe, olfactory epithelium; os, optic stalk; p, pons; pa, first pharyngeal arch; rh, rhombencephalon; str, striatum; t, tongue; tel, telencephalon. Scale bar: 1.0 mm. (C) Whole-mount anti-CD31 IHC of E10.5 WT and Tasp1–/– embryos showing spreading of cranial vessels throughout entire heads. At least 3 embryos were tested for each group. Scale bar: 0.5 mm. (D) Hematoxylin and eosin–stained sagittal sections of WT and Tasp1–/– E10.5 embryos. Tasp1–/– hearts are smaller but exhibit normal development. at, atrium; ec, endocardial cushion; tr, myocardial trabeculae; vn, ventricle. At least 3 embryos were tested for each group. Scale bar: 0.5 mm. (E) Whole-mount in situ hybridization with Tasp1 antisense and sense (negative control) probes on E10.5 WT embryos. Tasp1 mRNA was detected at brain ventricles, pharyngeal arches, and limb buds. At least 3 embryos were tested for each probe. Scale bar: 1.0 mm.