Nonsense-mediated mRNA decay in the ADAMTS13 gene caused by a 29-nucleotide deletion.
BACKGROUND
In mammalian cells a regulatory mechanism, known as nonsense-mediated mRNA decay, degrades mRNA harboring premature termination codons. This mechanism is intron-dependent and functions as a quality control mechanism to eliminate abnormal transcripts and modulates the levels of a variety of naturally occurring transcripts.


METHODS
In this study, we explored the molecular mechanism of ADAMTS13 deficiency in two compound heterozygous siblings carrying a 29-nucleotide deletion mutation located in exon 3 (c.291_319delGGAGGACACAGAGCGCTATGTGCTCACCA) in one allele and a single base (A) insertion mutation (c.4143_4144insA) in the second CUB domain previously reported in the other allele. Real-time quantitative reverse transcriptase polymerase chain reaction was used to explore whether the premature termination codons introduced by the deletion of the 29 nucleotides triggered the nonsense-mediated mRNA decay.


RESULTS
In vitro-expression studies demonstrated that the premature termination codons inserted by the 29 bp deletion probably lead to a reduction of ADAMTS13 mRNA levels through the regulatory mechanisms of nonsense-mRNA decay. Furthermore, the 4143_4144insA mutation causes an impairment of secretion that leads to retention of the mutant protein in the endoplasmic reticulum, as observed in immunofluorescence studies.


CONCLUSIONS
In conclusion, this work reports how two different ADAMTS13 gene defects acting at two different levels, i.e, impairment of steady-state mRNA level caused by the premature termination codon mediated decay mechanism induced by the 29 bp deletion mutation and alteration of the secretion pathway due to 4143_4144insA, lead to a severe deficiency of ADAMTS13.
Angelo Bianchi, Bonomi Hemophilia and Thrombosis, Centre, University of Milan, Department of Medicine and Medical Specialities, IRCCS Maggiore Hospital, Mangiagalli and Regina Elena Foundation, Luigi Villa Foundation, Milan, Italy.
Isabella
I
Garagiola
Carla
C
Valsecchi
Silvia
S
Lavoretano
Hale
H
Oren
Martina
M
Bohm
Flora
F
Peyvandi
D051722:ADAM Proteins / Q000235:genetics* / Q000276:immunology; D000071120:ADAMTS13 Protein; D000743:Anemia, Hemolytic / Q000235:genetics*; D001483:Base Sequence; D002460:Cell Line; D018389:Codon, Nonsense / Q000235:genetics; D005091:Exons; D005822:Genetic Vectors; D016678:Genome; D006801:Humans; D007668:Kidney / Q000196:embryology; D008297:Male; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D013489:Suppression, Genetic; D014162:Transfection; D014421:Turkey
D018389:Codon, Nonsense; D012333:RNA, Messenger; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human