OUTLINE 1. Cherubism: A Definition 2. Clinical Phenotype A. Physical Description B. Familial Analysis C. Radiological Analysis D. Histopathological Analysis 3. Associated Complications 4. The Quest to Identify the Cherubism Mutation A. Study Participants B. Positional Cloning C. Overall Results D. The Role of SH3BP2 5. Molecular Diagnosis and Treatment
CHERUBISM: A Definition DEFINITION: Cherubism is the hereditary form of polyostotic fibrous dysplasia that causes characteristic deformity in the lower half of the face due to the degeneration of maxilla and mandible bone tissue and its replacement with excessive amounts of fibrous tissue. Jones: 1933 Maxilla and mandible http://www.toddthomsen.com/powerpoints/Dental Emergencies_files/frame.htm#slide0026.htm
CLINICAL PHENOTYPE: Physical Description Bilateral swelling of the jaw Painless Premature loss of primary teeth Impaired development and eruption of permanent teeth Onset: 4-10 years Stabilizes after puberty Spontaneous regression ~25-30 years
CLINICAL PHENOTYPE: Radiological Analysis Multilocular radiolucencies Note absence of solid bone structure and enlarged jaw region Tiziani, V., et al. 1999. Figure 3.Ueki, Y., V. Tiziani, et al. 2001. Figure 1b.
CLINICAL PHENOTYPE: Histopathological Analysis Multinucleated giant cells: osteoclasts Note fibrous tissue and bone formation http://www.dental.mu.edu/oralpath/spresent/cherubism/sld001.htm EARLY STAGE:LATE STAGE:
ASSOCIATED COMPLICATIONS Complications resulting from Cherubism: –Delayed dentition –Dental root reabsoprtion –Malalignment of teeth –Impacted teeth –Displacement of orbital contents
THE QUEST TO IDENTIFY THE CHERUBISM MUTATION Initial Research: –J. Mangion, et al., 1999 –V. Tiziani, et al., 1999 Subsequent Research: –Y. Ueki, V. Tiziani, et al., 2001
STUDY PARTICIPANTS 15 patients (10♂, 5♀) from 4 families Focus: Family A –3 generation family, 8 affected members Collected blood samples and isolated DNA Identification Process: POSITIONAL CLONING Tiziani, V., et al. 1999. Figure 1.
STEP #1: GENOTYPING Used polymorphic microsatellite markers (SSRPs) PCR amplified genome DNA using γ -[ 32 P]-ATP end-labeled primers Separated DNA via denaturing polyacrylamide gels Performed autoradiography
STEP #1: GENOTYPING Linkage Analysis –Pairwise linkage analysis –Used MLINK program of LINKAGE package computer software –Excluded several potential candidate gene loci –Switched to random mapping of entire genome (360 polymorphic microsatellite markers)
STEP #1: GENOTYPING Linkage Analysis Results –Haplotype analysis showed no recombination on chromosome 4p LOD Scores: –Combined LOD score: 4.21, ~22cM –Family A: Z MAX = 3.31 –Family B: Z MAX = 0.60 –Family C: Z MAX = 0.30 –Family D: Z MAX = 0.30
STEP #2: LOCATION IDENTIFICATION Linkage assigned to chromosome 4p16 Between markers D4S2936 & D4S2949 According to physical map, interval spans ~22 cM unit Note: Candidate Genes Summary: “The disease develops in a time frame coinciding with many different events of tooth development…”
STEP #3: IDENTIFYING THE GENE – SH3BP2 Study participants: –66 individuals –15 families Linkage and haplotype analysis –Results coincide with initial study Sequenced cDNA and genomic DNA Overall results: –Point mutations –SH3-binding domain –SH3BP2
OVERALL RESULTS Tiziani, V., Y. Ueki, et al. 2001. Figure 1d.
THE ROLE OF SH3BP2 Tiziani, V., Y. Ueki, et al. 2001. Figure 1c.
THE ROLE OF SH3BP2 SH3BP2: Src Homology 3 Binding Protein 2 Small protein domain, including: –SH3 Binding Domain –SH2 Binding Domain –Pleckstrin Homology Domain Mediate: –Protein-protein associations –Regulate cytoplasmic signaling
MOLECULAR DIAGNOSIS AND TREATMENT Diagnosis: DNA sequencing Treatment: –Usually unnecessary –Reasons: Pain Associated complications Cosmetic reasons
REFERENCES Cong, M., and T. Ton. Cherubism. Found at: http://www.dental.mu.edu/oralpath/spresent/cherubism/sld001.htm. http://www.dental.mu.edu/oralpath/spresent/cherubism/sld001.htm Henry, F., et al. Cherubism: the value of imaging and preoperative embolization. J. Radiol. 2003 (Nov.); 84: 1774-1778. Lewis, C. R. Cherubism. Found at: http://clearinghouse.mwsc.edu/manuscripts/163.asp.http://clearinghouse.mwsc.edu/manuscripts/163.asp Lo, B., et al. Novel mutation in the gene encoding c-Abl-binding protein SH3BP2 causes cherubism. Am. J. Med. Genet.. 2003 (Aug.); 121A(1): 37-40. Mangion, J., et al. The gene for cherubism maps to chromosome 4p16.3. Am. J. Hum. Genet. 1999; 65: 151-157. Medterms Website. Cherubism. Found at: http://www.medterms.com/script/main/art.asp?articlekey=9508. http://www.medterms.com/script/main/art.asp?articlekey=9508 Online Mendelian Inheritance in Man (OMIM). Found at: http://www.ncbi.nlm.nih.gov/Omim, for Cherubism [MIM 118400], FGFR3 [MIM 134934], MSX1 [MIM 142983], and SH3BP2 [MIM602104]. http://www.ncbi.nlm.nih.gov/Omim Schultze-Mosgali, S., L. M. Holbach, and J. Wiltfang. Cherubism: clinical evidence and therapy. J. Craniofac. Surg. 2003 (March); 14(2): 201-206 Tiziani, V., et al. The gene for cherubism maps to chromosome 4p16. Am. J. Hum. Genet. 1999; 65: 158-166. Ueki, Y., V. Tiziani, et al. Mutations in the gene encoding c-Abl binding protein SH3BP2 cause cherubism. Nature Genet. 2001; 28: 125-126.