The use of DNA from paraffin wax preserved tissue for predictive diagnosis in familial adenomatous polyposis

Diagnosis of DiGeorge syndrome in nuclei released from archival autoptic heart specimens using fluorescence in situ hybridization

Seven formalin-fixed, paraffin-embedded heart specimens set up at autopsy performed from 3 to 18 years before analysis of newborns in which DiGeorge syndrome (DGS) was suspected were evaluated by fluorescence in situ hybridization (FISH) using a DGS region-specific probe and a control probe on nuclei released from thick sections. The diagnosis was confirmed in four of the six specimens, which provided valuable results, and in none of the controls. This study supports the feasibility and usefulness of FISH genotyping of archival autoptic material, which improves and assists the counselling procedures.

Combined use of molecular and biomarkers for presymptomatic carrier risk assessment in familial adenomatous polyposis: implications for screening guidelines

Predictive carrier testing for the inherited disorder of familial adenomatous polyposis (FAP) can be conducted using DNA markers linked to the FAP locus. The presence of characteristic hypertrophic retinal lesions has been advocated as useful biomarkers for FAP. We have compared molecular linkage and retinal screening techniques by evaluating the presymptomatic carrier risk of 40 at-risk individuals from 15 FAP families. Linkage analysis was informative in all and retinal lesion analysis in 25 cases. For informative at-risk population, predictive diagnosis by both techniques was completely concordant and identified 15 members at "high" and 10 at "low" risk of inheriting FAP. Because of the unique advantages offered by each technique, a strategy integrating both techniques will increase the number of FAP families that can be screened presymptomatically. Identification of individuals at high risk of polyposis will improve their clinical surveillance and further reduce the incidence of colorectal cancer in FAP families.

Improved predictive carrier testing for familial adenomatous polyposis using DNA from a single archival specimen and polymorphic markers with multiple alleles

Familial adenomatous polyposis (FAP) is an autosomal dominant inherited condition caused by mutations in a candidate tumor suppressor gene, adenomatous polyposis coli. Predictive carrier testing for FAP can be accomplished by DNA linkage or mutation detection analysis. In many FAP families all affected individuals are deceased. Archival tissue specimens, if available from such patients, are a useful source of DNA for molecular analysis. We investigated the carrier risk of a presymptomatic 5-year-old girl with a family history of FAP. An archival specimen of normal colonic tissue was only available from the proband's affected deceased father. We screened DNA extracted from this specimen with dinucleotide repeat (CA/GT)n polymorphic marker (D5S346) linked to the adenomatous polyposis coli gene and established that the proband is at more than 99% risk of developing FAP. The proband's increased risk status was subsequently confirmed by identification of a germline adenomatous polyposis coli gene mutation consisting of a 5 base pair deletion at codon 1061. This strategy of using DNA from archival specimens of affected, unavailable FAP patients will increase the number of at-risk individuals that can be diagnosed presymptomatically.