| Tooth agenesis is a common tooth dysplasia. Except for wisdom tooth, the congenital deficiency rate is about 1.6%-9.6%. Tooth agenesis also named teeth number deficiency. It happens in tooth forming process or earlier period of tooth germ development. Congenital missing tooth can be divided into hypodontia, oligodontia and anodontia. Oligodontia is defined as absence of six or more teeth. It has two types: syndromic oligodontia and non-syndromic oligodontia. The condition can be inherited as an autosome-dominant , autosome-recessive, or X-linked trait, some of which happens individually, some has familial heredity background.Any tissue or organ's development is controlled by genes, and any tissue or organ's displasia is related togene' s mutation as well. There are more than 200 genes controlling and adjusting teeth development. They decide tooth position, number, size and shape, etc. In the period of tooth germ development, complicated molecule networks are established between epithelial cells and mesenchymal cells. The signal molecules of the networks are responsible for the tooth development alone or coordinated with other molecules. However, the research about the relationship between these signal molecules and transcription factors with diseases got few achievement. For example, what is the molecule mechanism of oligodontia? No scientificanswerers are got up to now.The research found that oligodontia is intimately related to PAX9, and hypodontia is mainly related to MSX1. PAX9 is a newly discovered member of Pax family, existing in all vertebrates, which is a transcription factor that takes a key responsibility in tooth development. MSX1 expressed in many tissues of teeth in each period of tooth growth, and is an important controlling molecule in FGFs> BMPs signal networks.Most of researchers suggested that PAX9 is a chief pathogenic gene that causes oligodontia, but the ways and positions of mutation are disputable , that is related to the number, position of missing tooth and patient's genetic background(races, nationalities, et al). To study the pathogenic genes of oligodontia further, this article select PAX9 and MSX1 as candidate pathogenic genes of oligodontia for further study by PCR, sequencing and SNPdetection using TaqMan-MGB probe, based on analyzing the clinical data of 4 different cases of oligodontia and 1 case of hypodontia accompanied with lip cleft palate. As follows:1 The clinical study on oligodontiaWe studyed the clinical character of 4 different types of cases on. oligodontia and one case on hypodontia accompanied with lip cleft palate by common oral examination, pantomoagram radiographs of dentition, laboratory examination and pedigree analysis. The results were as following: (1) The number and positions of missing teeth are different, and oligodontia patients have varieties heredity styles, but clinical laboratory examinations have no obvious abnormorlity. (2)In the same environmental condition, One of twins manifests Ectodermal dysplasia syndrome, another don't have the similar abnormality, so genetic materials are important factors in case 1. (3)In case 2 the proband and his father have oligodontia, and the female of the family are normal, it suggest that oligodontia may be Y-linked hereditary disease. (4)In case 3 the patient and his mother have different clinical situations, and it suggest that environmental factors may determine the phenotype diversity of oligodontia. (5) In case 5 drug taking of the patient's mother in gestational period resulted in children's oligodontia, suggest that drug taking may be a factor causing oligodontia. All of above results suggest that Environmental factors and geneticmaterials are determinative factors, which result in phenotype diversity of congenital missing tooth.2 The detection of PAX9 gene mutation in patients of oligodontiaTo study whether PAX9 is the pathogenic gene causing oligodontia, as well as mutation sites and styles, we got out DNA from the venous blood of 14 persons composed of all 5 patients above, as well...
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