Rifas L, Towler D A, Avioli L V
Department of Internal Medicine, Divisions of Bone and Mineral Diseases and Molecular Pharmacology, Washington University School of Medicine and Barnes-Jewish Hospital North, St. Louis, MO 63110, USA.
Proc Natl Acad Sci U S A. 1997 Jul 8;94(14):7549-54. doi: 10.1073/pnas.94.14.7549.
Ethanol acts as a teratogen in developing fetuses causing abnormalities of the brain, heart, craniofacial bones, and limb skeletal elements. To assess whether some teratogenic actions of ethanol might occur via dysregulation of msx2 expression, we examined msx2 expression in developing mouse embryos exposed to ethanol on embryonic day (E) 8 of gestation and subjected to whole mount in situ hybridization on E11-11.5 using a riboprobe for mouse msx2. Control mice exhibited expression of msx2 in developing brain, the developing limb buds and apical ectodermal ridge, the lateral and nasal processes, olfactory pit, palatal shelf of the maxilla, the eye, the lens of the eye, otic vesicle, prevertebral bodies (notochord), and endocardial cushion. Embryos exposed to ethanol in utero were significantly smaller than their normal counterparts and did not exhibit expression of msx2 in any structures. Similarly, msx2 expression, as determined by reverse transcription-PCR and Northern blot hybridization, was reduced approximately 40-50% in fetal mouse calvarial osteoblastic cells exposed to 1% ethanol for 48 hr while alkaline phosphatase was increased by 2-fold and bone morphogenetic protein showed essentially no change. Transcriptional activity of the msx2 promoter was specifically suppressed by alcohol in MC3T3-E1 osteoblasts. Taken together, these data demonstrate that fetal alcohol exposure decreases msx2 expression, a known regulator of osteoblast and myoblast differentiation, and suggest that one of the "putative" mechanisms for fetal alcohol syndrome is the inhibition of msx2 expression during key developmental periods leading to developmental retardation, altered craniofacial morphogenesis, and cardiac defects.
乙醇在发育中的胎儿体内可作为致畸剂，导致大脑、心脏、颅面骨和四肢骨骼元素出现异常。为了评估乙醇的某些致畸作用是否可能通过msx2表达失调而发生，我们检测了妊娠第8天（E8）暴露于乙醇的发育中小鼠胚胎的msx2表达，并在E11 - 11.5使用小鼠msx2的核糖探针进行全胚胎原位杂交。对照小鼠在发育中的脑、发育中的肢芽和顶端外胚层嵴、外侧和鼻突、嗅窝、上颌的腭板、眼睛、晶状体、耳泡、椎前体（脊索）和心内膜垫中均表现出msx2的表达。子宫内暴露于乙醇的胚胎明显小于其正常对照胚胎，并且在任何结构中均未表现出msx2的表达。同样，通过逆转录 - PCR和Northern印迹杂交测定，暴露于1%乙醇48小时的胎鼠颅骨成骨细胞中msx2表达降低了约40 - 50%，而碱性磷酸酶增加了2倍，骨形态发生蛋白基本没有变化。在MC3T3 - E1成骨细胞中，msx2启动子的转录活性被酒精特异性抑制。综上所述，这些数据表明胎儿酒精暴露会降低msx2的表达，msx2是成骨细胞和成肌细胞分化的已知调节因子，并提示胎儿酒精综合征的一种“假定”机制是在关键发育时期抑制msx2表达，导致发育迟缓、颅面形态发生改变和心脏缺陷。
