[Show abstract][Hide abstract] ABSTRACT: Gap junctions are composed of transmembrane proteins belonging to the connexin family. These proteins permit the exchange of mall regulatory molecules directly between cells for the control of growth, development and differentiation. Although the presence of gap junctions in teeth has been already evidenced, the involved connexins have not yet been identified in human species. Here, we examined the distribution of connexin 43 (Cx43) in embryonic and permanent intact and carious human teeth. During tooth development, Cx43 localized both in epithelial and mesenchymal dental cells, correlated with cytodifferentiation gradients. In adult intact teeth, Cx43 was distributed in odontoblast processes. While Cx43 expression was downregulated in mature intact teeth, Cx43 appeared to be upregulated in odontoblasts facing carious lesions. In cultured pulp cells, Cx43 expression was related to the formation of mineralized nodules. These results indicate that Cx43 expression is developmentally regulated in human dental tissues, and suggest that Cx43 may participate in the processes of dentin formation and pathology.
Full-text · Article · Feb 2002 · Connective Tissue Research
[Show abstract][Hide abstract] ABSTRACT: The molecular mechanisms governing the decision between molariform and incisiform patterns of rodent dentition are not yet known. Transcription factors are regulators of regionally specific morphogenesis and key co-ordinators of gene activity during developmental processes. Here, we analysed the expression of several transcription factors during mouse tooth development. Otlx2/Rieg is a homeobox gene involved in Rieger syndrome, a human disorder characterized by dental hypoplasia. Otlx2/Rieg expression distinguishes stomatodeal epithelium well before tooth initiation, and thereafter its expression becomes restricted to the epithelia of both molar and incisor primordia. The recently identified homeodomain transcription factor Barx1 is first expressed in mesenchyme of the first branchial arch, but during advanced developmental stages the gene is exclusively expressed in the mesenchyme of molar primordia. Finally, the Sry-related transcription factor Sox9 is expressed in epithelial components and to a lesser degree in condensed mesenchyme of the developing teeth. These results suggest that Otlx2/Rieg, Barx1, and Sox9 participate in the hierarchical cascade of factors involved in the regulation of tooth morphogenesis.
Full-text · Article · Feb 1998 · European Journal Of Oral Sciences
[Show abstract][Hide abstract] ABSTRACT: The mouse Otlx2 gene is a new member of the paired-like family of homeobox genes whose human homologue, RIEG, is involved in Rieger syndrome, an autosomal-dominant disorder. One of the cardinal features of Rieger syndrome is dental hypoplasia, indicating that Otlx2/RIEG activity is essential for normal tooth development. Here, we analyzed the expression of Otlx2 during mouse tooth development and studied its regulation in dental explants. Otlx2 expression distinguishes stomatodeal from other ectoderm as early as Embryonic Day 8.5, well before tooth initiation. Thereafter, its craniofacial expression becomes restricted to the tooth-forming areas and to the epithelial components of molar and incisor primordia. Although Otlx2 induction precedes the specification of odontogenic mesenchyme, tissue recombination experiments show that the maintenance of its expression requires signals from the mesenchyme and that dental mesenchyme has the capacity to induce ectopic expression of Otlx2 in nondental epithelium. Finally, we compare Otlx2 expression with that of the recently identified homeodomain transcription factor Barx1 expressed in molar mesenchyme. Their strictly complementary expression patterns in the epithelial and mesenchymal components suggest that both genes participate in the reciprocal tissue interactions which are a hallmark of odontogenesis.
Full-text · Article · Oct 1997 · Developmental Biology