New tetranucleotide STRP markers for detecting the 22q11.2 deletion.

The 22q11.2 deletion syndrome is the most common microdeletion syndrome mainly characterized by hemizygous deletions and congenital heart defect (CHD). By using polymerase chain reaction (PCR), genotyping of short tandem repeat polymorphic (STRP) markers is a common and powerful means of detecting microdeletion. We have developed five new tetranucleotide repeat markers, 22D_4_1, 22D_4_2, 22D_4_3, 22D_4_4 and D22S873 in the proximal region of 22q11.2 deletion. To ascertain whether these markers could be used reliably in genotyping, we performed genotyping analysis on 200 unrelated individuals from a Chinese Han population and 67 CHD patients and their unaffected parents. Population data showed that the five markers met Hardy-Weinberg expectations and were highly polymorphic. By using the five markers, six of 67 CHD patients were determined to have a deletion within chromosome 22q11.2. Compared with dinucleotide markers, tetranucleotide markers produce weaker stutter bands and have no artificial multiband patterns. PCR amplification results from the five new tetranucleotide STRP markers were unambiguous and easier to interpret in genotyping. This study demonstrated that the five markers were efficient and reliable suggesting that genotyping using tetranucleotide STRP markers is an alterative approach to detect the deletion on chromosome 22q11.2 in clinical diagnosis and for genetic consultation.