Couwenhoven R I, Snead M L
Center for Craniofacial Molecular Biology, University of Southern California School of Dentistry, Los Angeles 90033.
Dev Biol. 1994 Jul;164(1):290-9. doi: 10.1006/dbio.1994.1199.
The expression of tissue-specific enamel matrix genes is believed to require both instructive and permissive interactions of enamel organ epithelium with dental papilla mesenchyme and/or extracellular matrix during a restricted period of development. Biosynthesis of amelogenin gene products has been found to be associated with the terminal differentiation of inner enamel organ epithelium. The developing mouse first mandibular molar was used for a detailed examination of the temporal initiation and developmental pattern of amelogenin transcription. These studies define temporally instructive versus permissive influences on amelogenin transcription. During in vivo development, amelogenin transcripts were detected in late cap (15 days in utero; E15) through bell stage (E16 through E19) mouse molar tooth formation utilizing reverse transcription coupled to polymerase chain reaction amplification. Alternatively spliced amelogenin transcripts were detected in late bell stage (E18) molars. Amelogenin transcripts were also detected in isolated late cap stage (E15) enamel organ epithelium dissected free of dental papilla mesenchyme and cultured within a substitute basement membrane gel, but not in identical cap stage enamel organ epithelium cultured on plastic or a laminin-coated filter. Amelogenin transcripts were also found in early cap stage (E14) isolated enamel organ epithelium cultured within a basement membrane gel, but were not detected in enamel organ epithelium isolated from earlier stages of odontogenesis and cultured within a basement membrane gel. The results of these experiments indicate that a basement membrane gel is a useful extracellular substrate which provides permissive interactions required for the expression of amelogenin transcripts by enamel organ epithelium and that instructive interactions which determine enamel organ epithelium to become committed to amelogenin transcription occur prior to the early cap stage (E14) of odontogenesis. The results also suggest that continued interactions of enamel organ epithelium with dental papilla mesenchyme serve to regulate amelogenin transcription and post-transcriptional amelogenin RNA splicing in a complex manner during odontogenesis.
组织特异性釉基质基因的表达被认为在发育的特定时期需要釉器上皮与牙乳头间充质和/或细胞外基质之间的诱导性和允许性相互作用。已发现釉原蛋白基因产物的生物合成与内釉器上皮的终末分化有关。发育中的小鼠第一下颌磨牙被用于详细研究釉原蛋白转录的时间起始和发育模式。这些研究确定了对釉原蛋白转录的时间诱导性和允许性影响。在体内发育过程中，利用逆转录-聚合酶链反应扩增技术，在帽状晚期（子宫内15天；E15）至钟状期（E16至E19）的小鼠磨牙形成过程中检测到了釉原蛋白转录本。在钟状晚期（E18）磨牙中检测到了选择性剪接的釉原蛋白转录本。在分离的帽状晚期（E15）釉器上皮中也检测到了釉原蛋白转录本，该上皮已从牙乳头间充质中分离出来，并在替代基底膜凝胶中培养，但在塑料或层粘连蛋白包被的滤膜上培养的相同帽状期釉器上皮中未检测到。在基底膜凝胶中培养的帽状早期（E14）分离的釉器上皮中也发现了釉原蛋白转录本，但在牙胚发生早期阶段分离并在基底膜凝胶中培养的釉器上皮中未检测到。这些实验结果表明，基底膜凝胶是一种有用的细胞外基质，它提供了釉器上皮表达釉原蛋白转录本所需的允许性相互作用，并且决定釉器上皮致力于釉原蛋白转录的诱导性相互作用发生在牙胚发生的帽状早期（E14）之前。结果还表明，在牙胚发生过程中，釉器上皮与牙乳头间充质的持续相互作用以复杂的方式调节釉原蛋白转录和转录后釉原蛋白RNA剪接。
