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|Title: ||Alu-Alu recombination underlying the first large genomic deletion in GlcNAc-phosphotransferase α/β (GNPTAB) gene in a MLII α/β patient [Poster]|
|Authors: ||Coutinho, Maria Francisca|
da Silva Santos, Liliana
Lund, Allan M
Johansen, Klaus B
Prata, Maria João
|Keywords: ||Doenças Genéticas|
|Issue Date: ||Sep-2011|
|Publisher: ||Instituto Nacional de Saúde Doutor Ricardo Jorge, IP|
|Abstract: ||Mucolipidosis type II α/β is a severe, autosomal recessive lysosomal storage disorder, caused by a defect in the GNPTAB gene that codes for the α/β subunits of the GlcNAc-phosphotransferase. To date, over 100 different mutations have been identified in MLII α/β patients including missense, nonsense, small deletions, small insertions and splice site mutations (Human Gene Mutation Database website [http://www.hgmd.org] and references therein). Large genomic rearrangements were rarely reported (1,6%) with only two large insertions having been described up to now (Tappino et al., 2008; Otomo et al., 2009) but no known large deletions.
Results: In this work, through long range PCR and sequencing methodologies we identified a large homozygous intragenic GNPTAB gene deletion, encompassing exon 19, in a ML II α/β patient and refined the characterization of this rearrangement. As a result, it was possible to identify the deletion breakpoints and determine the deletion extension which was 897 bp and included the last 386 nucleotides of intron 18, exon 19, and the first 343 bp of intron 19. A 21bp repetitive motif in introns 18 and 19 was observed at both deletion breakpoints. Further analysis revealed that both the 5’ and 3’ breakpoints were located within highly homologous Alu elements (Alu-Sz in intron 18 and Alu-Sq2, in intron 19), suggesting that this deletion has probably resulted from Alu-Alu unequal homologous recombination.
RT-PCR methods were used to further evaluate the consequences of the alteration for the processing of the mutant pre mRNA GNPTAB, revealing the production of three abnormal transcripts: one without exon 19; another with an additional loss of exon 20, and a third in which exon 19 was substituted by a pseudoexon inclusion consisting of a 62 bp fragment from intron 18. Interestingly, this 62 bp fragment corresponds to the Alu-Sz element integrated in intron 18.
Conclusion: To the best of our knowledge, this represents the first description of a large deletion identified in the GNPTAB gene. Furthermore, the work adds on the knowledge of the molecular mechanisms underlying causative mutations in ML II and highlights the importance of cDNA analysis on the prediction of the impact of large deletions at protein levels, since a simple gDNA analysis might be misleading.|
|Peer Reviewed: ||yes|
|Appears in Collections:||DGH - Posters/abstracts em congressos internacionais|
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