Ameloblastin Mutations in Dental Oral Tumors

Ameloblastomas are benign tumors arising from odontogenic epithelium. They are locally aggressive and have a high rate of recurrence. In efforts to understand ameloblastomas, investigators have studied the ameloblast-derived enamel protein ameloblastin (AMBN) based on its essential role in maintaining ameloblast differentiation and epithelial-mesenchymal signaling. Perdigao et al. (2004) studied three ameloblastoma types and found AMBN mutations that may have an important role in tumor formation. However, Chun-Hua et al. (2006) found no AMBN mutations in 11 ameloblastomas tested. Objective: To investigate potential AMBN gene mutations in two dental epithelial oral tumors. Methods: Total genomic DNA was extracted from fresh tumor samples: an ameloblastoma and an odontogenic keratocyst. Sixteen overlapped fragments of the AMBN gene coding regions and exon-intron boundaries were amplified using specific primer sets. PCR products were enzymatically purified and bidirectional DNA sequence performed. Sequencing results were compared against reference sequences by SeqScape software 2.5. In silico predictions were applied to forecast the potential functional significance of any alterations. Results: A synonymous alteration (c.234T>C, Gly78Gly) was found only in the ameloblastoma while a non-synonymous alteration (c.305C>A, Ser102Tyr) was detected in both tumor samples. Ser102 is located near the 5'end of the potential AMBN SH3 binding domain and is highly conserved among the four species (Human, chimpanzee, dog and Rattus) examined. The software program Polyphen predicted this change may cause possible damage. Grantham score classified the missense alteration as enriched deleterious (score 143). These data support the alteration Ser102Tyr could potentially correlate with the pathogenic development of these tumors. Conclusions: Our data supports previous studies describing AMBN mutations associated with formation of ameloblastomas. However, we have identified a novel AMBN alteration that could potentially correlate with the pathogenic development of amelobastoma in the two tumors tested. Supported by T35-HL007473; IOHR/ UAB-SOD.