Abstract
We report the molecular characterization of 12 unrelated Italian patients affected with Sandhoff disease (SD), a recessively inherited disorder caused by mutations in HEXB gene. We identified 11 different mutations of which six are novel: one large deletion of 2,406 nt, (c.299+1471_408del2406), one frameshift mutation c.965delT (p.I322fsX32), one nonsense c.1372C>T (p.Q458X), and three splicing mutations (c.299G>T, c.300-2A>G and c.512-1G>T). One allele was only characterized at the messenger RNA (mRNA) level (r = 1170_1242del). Real-time polymerase chain reaction analysis of the HEXB mRNA from fibroblasts derived from patients carrying the novel point mutations showed that the presence of the premature termination codon in the transcript bearing the mutation c.965delT triggers the nonsense-mediated decay (NMD) pathway, which results in the degradation of the aberrant mRNA. The presence of the c.299G>T mutation leads to the degradation of the mutated mRNA by a mechanism other than NMD, while mutations c.300-2A>G and c.512-1G>T cause the expression of aberrant transcripts. In our group, the most frequent mutation was c.850C>T (p.R284X) representing 29% of the alleles. Haplotype analysis suggested that this mutation did not originate from a single genetic event. Interestingly, the common 16-kb deletion mutation was absent. This work provides valuable information regarding the molecular genetics of SD in Italy and provides new insights into the molecular basis of the disease.
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Acknowledgments
The authors would like to thank Dr. Gomez-Lira M for providing the DNA sample used as a positive control for the 16 Kb HEXB deletion. This work was supported by a grant from Actelion Co, Basel. The samples were obtained from the “Cell Line and DNA Bank from Patients affected by Genetic Diseases” collection (http://www.gaslini.org/labdppm.htm) supported by Italian Telethon grants. EB is supported by Telethon Onlus Foundation and EURASnet. All the experiments performed in this work comply with the current Italian laws.
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Zampieri, S., Filocamo, M., Buratti, E. et al. Molecular and functional analysis of the HEXB gene in Italian patients affected with Sandhoff disease: identification of six novel alleles. Neurogenetics 10, 49–58 (2009). https://doi.org/10.1007/s10048-008-0145-1
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DOI: https://doi.org/10.1007/s10048-008-0145-1