Identification of 54 large deletions/duplications in TSC1 and TSC2 using MLPA, and genotype-phenotype correlations |
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Authors: | Piotr Kozlowski Penelope Roberts Sandra Dabora David Franz John Bissler Hope Northrup Kit Sing Au Ross Lazarus Dorota Domanska-Pakiela Katarzyna Kotulska Sergiusz Jozwiak David J. Kwiatkowski |
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Affiliation: | (1) Genetics Laboratory, Division of Translational Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, One Blackfan Circle, 6th flr, Rm 216, Boston, MA 02115, USA;(2) Deparment of Pediatrics and Neurology, Children’s Hospital Medical Center, Cincinnati, OH, USA;(3) Division of Medical Genetics, Department of Pediatrics, UT Medical School at Houston, Houston, TX, USA;(4) Channing Laboratory, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA;(5) The Children’s Memorial Health Institute, Warsaw, Poland |
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Abstract: | Tuberous sclerosis (TSC) is an autosomal dominant disorder caused by mutations in either of two genes, TSC1 and TSC2. Point mutations and small indels account for most TSC1 and TSC2 mutations. We examined 261 TSC DNA samples (209 small-mutation-negative and 52 unscreened) for large deletion/duplication mutations using multiplex ligation-dependent probe amplification (MLPA) probe sets designed to permit interrogation of all TSC1/2 exons, as well as 15–50 kb of flanking sequence. Large deletion/duplication mutations in TSC1 and TSC2 were identified in 54 patients, of which 50 were in TSC2, and 4 were in TSC1. All but two mutations were deletions. Only 13 deletions were intragenic in TSC2, and one in TSC1, so that 39 (73%) deletions extended beyond the 5′, 3′ or both ends of TSC1 or TSC2. Mutations were identified in 24% of small-mutation-negative and 8% of unscreened samples. Eight of 54 (15%) mutations were mosaic, affecting 34–62% of cells. All intragenic mutations were confirmed by LR-PCR. Genotype/phenotype analysis showed that all (21 of 21) patients with TSC2 deletions extending 3′ into the PKD1 gene had kidney cysts. Breakpoints of intragenic deletions were randomly distributed along the TSC2 sequence, and did not preferentially involve repeat sequence elements. Our own 20-plex probe sets gave more robust performance than the 40-plex probe sets from MRC-Holland. We conclude that large deletions in TSC1 and TSC2 account for about 0.5 and 6% of mutations seen in TSC patients, respectively, and MLPA is a highly sensitive and accurate detection method, including for mosaicism. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | TSC1 TSC2 PKD1 Large deletions MLPA Mosaic mutations |
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