Wg. Liu et al., MUTANT FIBRILLIN-1 MONOMERS LACKING EGF-LIKE DOMAINS DISRUPT MICROFIBRIL ASSEMBLY AND CAUSE SEVERE MARFAN-SYNDROME, Human molecular genetics, 5(10), 1996, pp. 1581-1587
Marfan syndrome (MFS), a heritable connective tissue disorder, is caus
ed by mutations in the gene coding for fibrillin-1 (FBN1), an extracel
lular matrix protein, One of the three major categories of FBN1 mutati
ons involves exon-skipping, To rapidly detect such mutations, we devel
oped a long RT-PCR method, Either three segments covering the entire F
BN1 coding sequence or a single 8.9 kb FBN1 coding segment were amplif
ied from reverse-transcribed total fibroblast RNA, Restriction fragmen
t patterns of these RT-PCR products were compared and abnormal fragmen
ts were directly sequenced, Six exon-skipping mutations were identifie
d in a panel of 60 MFS probands, All skipped exons encode calcium bind
ing epidermal growth factor (EGF)-like domains and maintain the readin
g frame, In five probands, exon-skipping was due to point mutations in
splice site sequences, and one had a 6 bp deletion in a donor splice
site, Pulse-chase analysis of labelled fibrillin protein revealed norm
al levels of synthesis but significantly reduced matrix deposition, Th
is dominant-negative effect of the mutant monomers is considered in th
e light of current models of fibrillin assembly, Probands with this ty
pe of FBN1 mutation include the most severe forms of MFS, such as neon
atally lethal presentations.