CHERUBISMCynthia Kerska – Fall, 2004

OUTLINE1. Cherubism: A Definition2. Clinical Phenotype

A. Physical DescriptionB. Familial AnalysisC. Radiological AnalysisD. Histopathological Analysis

3. Associated Complications4. The Quest to Identify the Cherubism Mutation

A. Study ParticipantsB. Positional CloningC. Overall ResultsD. 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: Familial Analysis

• Hereditary

• Autosomal dominant

Tiziani, V., et al. 1999. Figure 1.

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-[32P]-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: ZMAX = 3.31

– Family B: ZMAX = 0.60

– Family C: ZMAX = 0.30

– Family D: ZMAX = 0.30

Tiziani, V., et al. 1999. Table 2.

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.

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.

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.

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].

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.