Ziedonis Skobe, PhD

Tooth formation is the result of a complicated series of steps in which different cell types interact to produce the final durable structure. Unfortunately, the actions of certain bacteria that reside in the mouth can undermine the processes needed to maintain healthy teeth. Research in the Skobe laboratory aims to uncover the complex machinery required for tooth development and to understand how bacteria have such a destructive impact on these otherwise durable and long-lasting structures.

During tooth formation the epithelial cell layers proceed through a five-stage life cycle to produce dental enamel. Enamel is composed of rod-like structures that are woven into a characteristic pattern. Members of the Skobe laboratory use a variety of cytological and immunohistochemical techniques to examine the developing tooth to determine how these rod patterns are formed and then mineralize to become 99% inorganic. We are using similar approaches to investigate mechanisms of tooth destruction by pathogenic oral bacteria.

Molecular Mechanisms in Tooth Formation

Continuously erupting rat incisors provide an excellent model for studying amelogenesis because all stages of the ameloblast life cycle are manifested in these teeth throughout the lifetime of the rat. Recently, we have used this model to obtain important information about several molecules that appear to function in concert during enamel formation. The E-cadherin/catenin complex mediates attachment of ameloblasts to each other. We believe this complex also participates in the alignment of enamel structure during tooth formation. Adenomatous polyposis coli (APC) protein, which controls function of the cadherin-catenin complex, is a tumor suppressor protein abundantly expressed in enamel organ cells during amelogenesis. Mutations in APC are associated with familial polyposis and also sporadic colon adenomas, both predisposing conditions for cancer development. Some familial polyposis patients also develop Gardner’s Syndrome, a condition characterized by supernumerary teeth, mandibular osteomas, and other abnormalaties. Our studies in the rat incisor model indicate that APC expression is upregulated and downregulated twice during the normal life cycle of ameloblasts. Thus, APC is important in the normal function of both intestinal and odontogenic epithelium. We are also investigating the possible role of APC interacting with b-catenin in the Wnt signaling pathway in amelogenesis. This pathway is commonly present in developing organ systems. Furthermore, it is known that APC associates with the tubulin and the actin cytoskeleton. We postulate that the cytoskeleton participates in ameloblast motility and directs the orientation of enamel rods. The study of these proteins is one facet of the multidisciplinary approach of the Biomineralization Department in studying molecular mechanisms of mineralizing tissues.

Recently we discovered that administration of high fluoride doses in the drinking water of rats alters the cadherin/catenin complex in the enamel organ of incisor teeth. We are now investigating this observation more closely in order to determine if these alterations are due to either protein or gene alterations. It is well known that fluoride inhibits many enzymes, and such inhibition may be the basis of altered complex localization. The other possibility is that gene expression is affected which would be revealed by microarray analysis.

Processes Leading to Tooth Destruction

We are collaborating with laboratories at Boston University and Harvard School of Dental Medicine on projects to use Laser Dissection Microscopy in conjunction with DNA-DNA hybridization and immunohistochemistry in order to identify bacteria that destroy both hard and soft tooth tissues. A team of clinicians, microbiologists, and structural biologists have joined efforts to answer a series of important questions. Which bacteria destroy cementum and dentin below the gingival margin? Which bacteria are responsible for endodontic pathology? Which bacteria are present in the teeth of patients who do not respond to conventional endodontic therapy? Are bacteria present in periapical lesions or is a host response soley responsible for the damage? The answers to these questions will lead us to find ways of improving current therapies and result in more effective treatments of patients.

Selected Publications

Bartlett JD, Skobe Z, Lee DH, Wright JT, Li Y, Kulkarni AB, Gibson CW. (2006) A developmental comparison of matrix metalloproteinase-20 and amelogenin null mouse enamel. Eur. J. Oral Sci. 114(Suppl. 1):18-23.

Beniash E, Skobe Z, Bartlett JD. (2006) Formation of the dentino-enamel interface in enamelysin (MMP-20)-deficient mouse incisors. Eur. J. Oral Sci. 114(Suppl. 1):24-29.

Skobe Z. (2006) SEM evidence that one ameloblast secretes one keyhole-shaped enamel rod in monkey key teeth. Eur. J. Oral Sci. 114(Suppl. 1):338-342.

Staff

Postdoctoral Fellows

Matthew Saper, Ph.D.

Staff Associate

Justine M. Dobeck, M.S.