Chromosomal anomalies on 6p25 in iris hypoplasia and Axenfeld-Rieger syndrome patients defined on a purpose-built genomic microarray.

In many inherited diseases, the same phenotype can be produced both by single-base changes and by large deletions, or in some cases by duplications. Routine high-throughput sequencing can now detect small mutations relatively easily in a diagnostic setting, but deletions and duplications in the 50-500-kb region remain a more difficult problem. We have explored the application of array-CGH to the detection of such changes on a set of 20 samples consisting of patients with eye diseases associated with changes on chromosome 6p25 together with unaffected individuals, as well as two samples from tuberous sclerosis 2 (TSC2)-affected patients. We developed a microarray consisting of degenerate oligonucleotide primer (DOP)-PCR products from 260 human genomic clones, including BACs, PACs, and cosmids. In a masked study, chromosome changes in patients with iris hypoplasia (duplication) and Axenfeld-Rieger syndrome (deletion) were unequivocally distinguished from controls. Of the 20 6p25 samples analyzed, 19 were analyzed correctly (10 duplication cases, two deletions, and seven normals), while one individual failed to give a result because of poor hybridization. The extent of the duplication or deletion estimated was similar to that obtained by independent and much more time-consuming FISH experiments. On the other hand, deletions in the two TSC2-affected samples, previously mapped by DNA molecular combing, were not detected on the array, possibly due to the repeat content of that region. Excluding the 16p13 cosmids, consistent results were obtained from all other cosmid clones; the potential for producing affordable disease-specific diagnostic microarray as an adjunct to diagnosis is discussed.