Genetic Studies of Human Craniofacial Diseases

Dental & Craniofacial Research

Investigators

Linked publications, trials & patents

Abstract

The Human Craniofacial Genetics Section laboratory was established in April 2004 to study the genetic basis of oral and craniofacial diseases. The goal of the section is to understand the genetic basis of human dental and craniofacial diseases so that we may identify specific etiologic components of disease that permit development of better diagnostic and treatment strategies. The laboratory is aligned along three general anatomical themes bone, teeth and skin. Investigators have been recruited whose interests and areas of expertise can be applied to each theme, with specific expertise in cell culture, immunohistochemistry and imaging, molecular biology, expression profiling of oral microbes and proteomics. [unreadable] [unreadable] The working paradigm of the section is that there is a genetic basis to human disease and that understanding the genetic basis of disease will foster development of better diagnostic and treatment strategies. Studies of genetic diseases can provide significant insight into normal as well as abnormal development. In terms of genetics, diseases can be divided into two broad types, those for which single genes are deterministic of disease, and those for which genetic factors contribute to risk, but are not individually deterministic. We are studying both simple Mendelian diseases (amelogenesis imperfecta, tricho-dento-osseous syndrome, Papillon Lefevre and hereditary gingival overgrowth), as well as complex diseases (oral facial clefting, periodontitis, Sjogrens syndrome). Gene-environment interactions are also important determinants of disease etiology. We are investigating microbial-protein interactions in the oral cavity in several diseases including dental caries, and in several conditions including pre and post bone marrow transplant and critical care patients.[unreadable] [unreadable] Previously we determined that a DLX3 truncation mutation is responsible for tricho-dento-osseous syndrome (TDO) in humans. One feature of the condition is increased bone thickness and density. Our goal is to understand how this mutation results in these favorable osseous findings. We have generated . transgenic (TG) mice that carry the same deletion mutation responsible for TDO in humans. The mice have phenotypic features including taurodontism, enhanced bone density and thickness. These TG mice show defects in odontoblasts and cementoblasts resulting in reduced dentin formation. Bone density and thickness are markedly enhanced in TG mice. Further analysis will provide the mechanisms and roles of MT-DLX3 in the tooth and bone development, that leads to clinical findings observed in humans. [unreadable] [unreadable] Human linkage and association studies support a gene(s) for nonsyndromic cleft lip with or without cleft palate (CL/P) on chromosome 4q31-q32 at or near the PDGFC gene locus. PDGF-C is necessary for palate formation in mice, and pdgfc-/- is associated with a complete cleft of the secondary palate. We sequenced the PDGFC gene in CL/P cases and controls and identified a regulatory region genetic polymorphism associated with CL/P. Transfection assays of PDGFC promoter reporter constructs indicate that this polymorphism is associated with a significant decrease (~ 50%) of PDGFC gene promoter activity. Therefore we have study the roles of PDGF-C on hard tissue development such as osteoblastic bone formation and osteoclastic bone resorption. [unreadable] [unreadable] We have previously identified a mutation of the son of sevenless 1 (SOS1) gene in hereditary gingival fibromatosis (HGF). We have characterized phenotypic and morphological characteristics of gingival fibroblasts with and have begun to identify key downfield targets of the mutant SOS1 protein responsible for HGF. We have demonstrated in vivo and in vitro that fibroblasts with the SOS1 mutation have higher proliferation rates, resulting in increased cell numbers and amounts of collagen. In addition, we have studied the difference in cell cycle profiling and cell attachment on different extracellular matrices between normal control and HGF fibroblasts. We are continuing studies to elucidate the molecular mechanism of gingival overgrowth. We are also studying other cases of HGF, and have determined that other genes are responsible for this condition in different families. We are in the process of identifying these additional genes.[unreadable] [unreadable] We have identified the genetic mutation in DSPP responsible for Dentinogenesis imperfecta in the Brandywine population from Maryland. Through work performed for 5 different forms of DI due to DSPP mutation, we have determined the mutation responsible for most of these forms of DI results from an endoplasmic reticulum storage type disease. Form previous work with genetic forms of kidney disease, we have also determined that molecular chaperones can increase release of the mutant protein from the endoplasmic reticulum. We are in the process of evaluating biocompatible chaperones that may permit treatment of dentinogenesis imperfecta. [unreadable] [unreadable] Last year we identified several novel gene mutations in genes for amelogenesis imperfecta (AI) and we were the first to identify gene mutations in 2 other genes (KLK4, MMP20) that cause AI. We are continuing studies to identify genetic mutations responsible for AI in other families. Additionally, we continue to follow up on linkage of AI to chromosome 8q. We have sequenced ~ 40 genes but have not found mutation. [unreadable] [unreadable] We have performed studies to evaluate changes in saliva proteins in individuals with Sjogren?s syndrome. We have characterized proteins present (quantitative and qualitative) in patients and controls to identify disease biomarkers using SELDI and 2D-DIGE combined mass spectrometry. [unreadable] We have also performed protein profiling of temporomandibular joint fluid to understand the pathophysiology of TMD. Using liquid chromatography based tandem mass spectrometry we have identified a protein catalogue on the composition of temporomandibular joint fluid. A number of proteins were expressed in TMD fluids that may serve as biomarkers. We have also studied saliva composition Salivary samples were isolated for pre and post bone marrow transplant patients (n = 40) and evaluated by SELDI and 2D-DIGE combined mass spectrometry. We were able to identify several differentially expressed proteins that were altered in pre and post transplant cases. These findings have been submitted to the Journal ?Experimental Hematology? in July 2006.[unreadable] [unreadable] Ventilator-associated pneumonia (VAP) is associated with significant morbidity, mortality, health care utilization and costs. The oral flora undergoes major shift during ICU stay and a causative pathway of VAP may be aspiration of oropharyngeal pathogens. More than 700 bacterial species have been detected in the oral cavity, but over 50% are not cultivatable, limiting identification. We are using genetic approaches to longitudinally characterize the oral flora changes in ventilated ICU patients. We are studying changes in the oral flora of intubated patients to characterize changes in the flora. Additionally, we are evaluating the effects of simple treatments to determine if they can provide a beneficial effect in intubated ICU patients.