Department of Oral Biology, School of Dental Medicine, University at Buffalo, State University of New York, Buffalo, NY, USA.
Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
J Dent Res. 2022 Jul;101(7):832-839. doi: 10.1177/00220345211070583. Epub 2022 Feb 3.
Tooth agenesis is a common structural birth defect in humans that results from failure of morphogenesis during early tooth development. The homeobox transcription factor Msx1 and the canonical Wnt signaling pathway are essential for "bud to cap" morphogenesis and are causal factors for tooth agenesis. Our recent study suggested that Msx1 regulates Wnt signaling during early tooth development by suppressing the expression of and in the tooth bud mesenchyme, and it demonstrated partial rescue of -deficient molar teeth by a combination of DKK inhibition and genetic inactivation of SFRPs. In this study, we found that Sostdc1/Wise, another secreted Wnt antagonist, is involved in regulating the odontogenic pathway downstream of Msx1. Whereas expression in the developing tooth germ was not increased in embryos, genetic inactivation of rescued maxillary molar, but not mandibular molar, morphogenesis in mice with full penetrance. Since the ; embryos exhibited ectopic expression in the developing dental mesenchyme, similar to embryos, we generated and analyzed tooth development in ; double and ;; triple mutant mice. The ; double mutants showed rescued maxillary molar morphogenesis at high penetrance, with a small percentage also exhibiting mandibular molars that transitioned to the cap stage. Furthermore, tooth development was rescued in the maxillary and mandibular molars, with full penetrance, in the ;; mice. Together, these data reveal 1) that a key role of Msx1 in driving tooth development through the bud-to-cap transition is to control the expression of and 2) that modulation of Wnt signaling activity by Dkk2 and Sostdc1 plays a crucial role in the Msx1-dependent odontogenic pathway during early tooth morphogenesis.
牙齿缺失是人类常见的结构出生缺陷,是由于牙齿发育早期形态发生失败导致的。同源盒转录因子 Msx1 和经典 Wnt 信号通路对于“芽帽”形态发生是必需的,也是牙齿缺失的因果因素。我们最近的研究表明,Msx1 通过抑制牙芽间质中 和 的表达来调节早期牙齿发育中的 Wnt 信号,并且通过 DKK 抑制和 SFRP 的遗传失活的组合,对 - 缺陷的磨牙进行了部分挽救。在这项研究中,我们发现另一种分泌型 Wnt 拮抗剂 Sostdc1/Wise 参与调节 Msx1 下游的牙源性途径。虽然在 胚胎中发育中的牙胚中 的表达没有增加,但是 的遗传失活挽救了上颌磨牙,但下颌磨牙的形态发生没有挽救,具有完全的外显率。由于 ; 胚胎在发育中的牙间质中表现出异位 的表达,类似于 胚胎,因此我们生成并分析了 ; 双和 ;; 三重突变小鼠的牙齿发育。 ; 双突变体在高外显率下表现出上颌磨牙形态发生的挽救,一小部分也表现出下颌磨牙向帽状期的转变。此外, ; 小鼠的上颌和下颌磨牙的牙齿发育在完全外显率下得到挽救。总之,这些数据揭示了 1)Msx1 通过向帽状期的转变来驱动牙齿发育的关键作用是控制 和 的表达,2)Dkk2 和 Sostdc1 对 Wnt 信号活性的调节在早期牙齿形态发生中 Msx1 依赖性牙源性途径中起着至关重要的作用。
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