A gene dosage map of Chromosome 18: a map with clinical utility.

Purpose: Microarray technology has revolutionized the field of clinical genetics with the ability to detect very small copy number changes. However, challenges remain in linking genotype with phenotype. Our goal is to enable a clinical geneticist to align the molecular karyotype information from an individual patient with the annotated genomic content, so as to provide a clinical prognosis.

High resolution genomic analysis of 18q- using oligo-microarray comparative genomic hybridization (aCGH).

The advent of oligonucleotide array comparative genomic hybridization (aCGH) has revolutionized diagnosis of chromosome abnormalities in the genetics clinic. This new technology also has valuable potential as a research tool to investigate larger genomic rearrangements that are typically diagnosed via routine karyotype. aCGH was used as a tool for the high-resolution analysis of chromosome content in individuals with known deletions of chromosome 18.

Narrowing critical regions and determining penetrance for selected 18q- phenotypes.

One of our primary goals is to help families who have a child with an 18q deletion anticipate medical issues in order to optimize their child's medical care. To this end we have narrowed the critical regions for four phenotypic features and determined the penetrance for each of those phenotypes when the critical region for that feature is hemizygous. We completed molecular analysis using oligo-array CGH and clinical assessments on 151 individuals with deletions of 18q and made genotype-phenotype correlations defining or narrowing critical regions.

Molecular and clinical characterization of a recurrent cryptic unbalanced t(4q;18q) resulting in an 18q deletion and 4q duplication.

Recurrent constitutional non-Robertsonian translocations are very rare. We present the third instance of cryptic, unbalanced translocation between 4q and 18q. This individual had an apparently normal karyotype; however, after subtelomere fluorescence in situ hybridization (FISH), he was found to have a cryptic unbalanced translocation between 4q and 18q [ish der(18)t(4;18)(q35;q23)(4qtel+,18qtel-)].