Application of molecular genetics techniques for detecting deleted segmental aneuploidy in Williams Syndrome

Abstract

BackgroundWilliam’s Syndrome (WS) is one of the most powerfulmodels of human cognition and rare genetic disorder, theincidence of WS range between 1/7500 and 50,000 and isconsidered to be a segmental aneuploidy due to heterozy-gous deletion of a contiguous gene at the long arm ofchromosome7atq11.23[1].The deletion size usuallyranges between 1.5-1.8 Mb. At least 26 genes have beendetected in the deletion region in WS patients [2,3]. Theaim of this study was to determine the efficient methodfor detection of the microdeletion at chromosome 7q11.23in patients with WS. This comparative study will help todetermine the effective methods to detect the microdele-tion at chromosome 7q11.23 in William’ssyndrome.Materials and methodsThe study included 29 patients referred to the DGMU withthe provisional diagnosis of WS. Peripheral blood sampleswere taken after obtaining informative consent from theparents or patients’ guardian. We applied conventionalCytogenetic (G-banding technique), Molecular Cytogenetic(Fluorescent In-Situ Hybridization) and Real time PCRTechniques for detection of segmental Aneuploidy inWilliams-Beuren Syndrome.ResultsNo deletions were detected by Karyotyping, however onepatient had translocation chromosomes (18; 19)(q11.1;p13.3). FISH technique could detect microdeletion inchromosome 7q11.23 in 6/23 patients. However, qPCRcould detect deletion in 9/23 samples. Furthermore, thesize of deletion could be detected accurately using theqPCR technique.ConclusionsReal time PCR could be used to confirm the FISH resultsand to detect small deletions or duplications that couldnot be detected by FISH.