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Abstract
Dlx (distal-less gene) homeogenes encode transcription factors that are involved in
the patterning of orofacial skeleton derived from cephalic neural crest cells. In
order to study the role of DLX genes during embryonic development in human, DLX5 expression
pattern was investigated in 6- to 11-week-old human embryos. A DLX5 PCR fragment was
amplified from a human dental cDNA library subcloned and used for in situ hybridization
investigations. DLX5 gene expression was primarily detected in the mandible at 6 weeks
and then, after in the maxilla. DLX5 gene expression became restricted to progenitor
cells of developing tooth germs, bones and cartilages of mandible and maxilla. During
odontogenesis from bud to late cap stages, DLX5 transcripts were present in both dental
epithelium and mesenchyme tissues. DLX5 expression was restricted to few cells in
the vestibular aspect of the dental epithelium, while DLX5 mRNA signal was more widely
distributed in dental mesenchyme. The observed expression pattern of DLX5 homeogene
extends the proposed site-specific combination of homeogene expression in neural crest
derived cells to human specific dentition. Furthermore, during the bud and cap stages
of tooth morphogenesis, the asymmetric expression of DLX5 in the dental epithelium
and dental mesenchyme may contribute to the complex patterning of human tooth shape.