Expression of DLX5 during human embryonic craniofacial development

Dlx (distal-less gene) homeogenes encode transcription factors that are inv olved in the patterning of orofacial skeleton derived from cephalic neural crest cells. In order to study the role of DLX genes during embryonic devel opment 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 cD NA library subcloned and used for in situ hybridization investigations. DLX 5 gene expression was primarily detected in the mandible at 6 weeks and the n, after in the maxilla. DLX5 gene expression became restricted to progenit or cells of developing tooth germs, bones and cartilages of mandible and ma xilla. During odontogenesis from bud to late cap stages, DLX5 transcripts w ere present in both dental epithelium and mesenchyme tissues. DLX5 expressi on was restricted to few cells in the vestibular aspect of the dental epith elium, while DLX5 mRNA signal was more widely distributed in dental mesench yme. 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 stag es of tooth morphogenesis, the asymmetric expression of DLX5 in the dental epithelium and dental mesenchyme may contribute to the complex patterning o f human tooth shape. (C) 1999 Elsevier Science Ireland Ltd. All rights rese rved.