A novel missense mutation in the COL7A1 gene underlies epidermolysis bullosa pruriginosa.
ABSTRACT Epidermolysis bullosa (EB) pruriginosa is a subtype of dominant dystrophic EB (DDEB), characterized by severe pruritus and blistering localized to the extensor surface of the extremities. EB pruriginosa exhibits extensive clinical heterogeneity with variable expression and delayed age of onset. Mutations in the COL7A1 gene, especially in glycine residues within Gly-X-Y repeats, have been shown to cause this form of DDEB. Here, we report a novel COL7A1 mutation in a Taiwanese pedigree with EB pruriginosa. Using PCR and direct sequence analysis we have identified a G-->T transversion at nucleotide 7097 in exon 92 of COL7A1, converting a glycine residue to valine (G2366V). The mutation resides within a consecutive, uninterrupted stretch of 17 Gly-X-Y residues in the triple-helical domain of type VII collagen. Interestingly, an affected member of this family also displayed elevated IgE levels, previously reported in some patients with this disorder. Our finding further implicates COL7A1 mutation in the pathogenesis of EB pruriginosa and underscores the heterogeneous clinical symptoms of glycine mutations in DDEB.
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ABSTRACT: The human type VII collagen (COL7A1) gene is the locus for mutations in at least some cases of dystrophic epidermolysis bullosa. Here we describe the entire intron/exon organization of COL7A1, which is shown to have 118 exons, more than any previously described gene. Despite this complexity, COL7A1 is compact. Consisting of 31,132 bp from transcription start site to polyadenylation site, it is only about three times the size of type VII collagen mRNA. Thus, COL7A1 introns are small. A 71-nucleotide COL7A1 intron is the smallest intron yet reported in a collagen gene, and only one COL7A1 intron is greater than 1 kb in length. All exons in the COL7A1 triple helix coding region that do not begin with sequences corresponding to imperfections of the triple helix begin with intact codons for Gly residues of Gly-X-Y repeats. This is reminiscent of the structure of fibrillar rather than other nonfibrillar collagen genes. In addition, the COL7A1 triple helix coding region contains many exons of recurring sizes (e.g., 25 exons are 36 bp, 12 exons are 45 bp, 8 exons are 63 bp), suggesting an evolutionary origin distinct from those of other nonfibrillar collagen genes. Sequences from the 5' portion of COL7A1 are presented along with the 3766-bp intergenic sequence, which separates COL7A1 from the upstream gene encoding the core I protein of the cytochrome bc1 complex. The COL7A1 promoter region is found to lack extensive homologies with promoter regions of other genes expressed primarily in skin.Genomics 06/1994; 21(1):169-79. · 3.01 Impact Factor
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ABSTRACT: To identify gene mutation of a epidermolysis bullosa pruriginosa family. Polymerase chain reaction (PCR), DNA sequencing, multiplex PCR using allele-specific oligonucleotide primers. A G6100A transition of COL7A1 was found in patients, resulting in G2034R substitution in type VII collagen. The mutation was not found in control normal individuals. The mutation of G2034R is the underlying cause of epidermolysis bullosa pruriginosa in this family, not common polymorphism.Zhonghua yi xue za zhi 12/2000; 80(11):869-71.
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ABSTRACT: Dystrophic epidermolysis bullosa pruriginosa, a subtype of epidermolysis bullosa dystrophica and a heterogeneous inherited disease, is characterized by pruritus, excoriated nodular prurigo-like lesions, skin fragility, altered anchoring fibrils and loss of dermal-epidermal adhesion. Mutation in type VII collagen gene (COL7A1) is thought to be implicated in the underlying change for dystrophic epidermolysis bullosa pruriginosa. We report here a large family of dominant dystrophic epidermolysis bullosa pruriginosa. Mutation analysis using polymerase chain reaction and direct sequencing demonstrated a novel nucleotide substitution of 6899A-->G in exon 87 in one COL7A1 allele of the proband and 18 affected family members. This substitution was not found in 100 normal alleles. Polymerase chain reaction and sequencing of the cDNA, reverse transcribed from the proband's peripheral lymphocyte RNA, suggest that this mutation causes aberrant COL7A1 mRNA splicing of exon 87 skipping. Clinical features and pedigree analysis suggest that 6899A-->G substitution is a mutation with full penetrance and variable expressivity.Acta Dermato Venereologica 02/2002; 82(3):187-91. · 3.49 Impact Factor
A novel missense mutation in the COL7A1 gene underlies epidermolysis
Gary S. Chuang, Amalia Martinez-Mir, Hsin-Su Yu,* Feng-Yi Sung, § Rita Y. Chuang,
Peter B. Cserhalmi-Friedman and Angela M. Christiano†
Departments of Dermatology and †Genetics & Development, Columbia University,
College of Physicians and Surgeons, New York, USA; *Department of Dermatology,
National Taiwan University, Taipei, Taiwan; §Department of Dermatology Jen-Ai
Municipal Hospital, Taipei, Taiwan.
Short Title: COL7A1 mutation in Epidermolysis Bullosa Pruriginosa
Angela M. Christiano, Ph.D.
Department of Dermatology
Columbia University, College of Physicians and Surgeons
630 West 168th Street VC-1526
New York, NY 10032, USA
Tel. : 212 305 9565
Fax: 212 305 7391
Abbreviations: COL7A1, COL7A1 gene; DEB, dystrophic epidermolysis bullosa;
DDEB, dominant dystrophic epidermolysis bullosa; EB, epidermolysis bullosa; PCR,
polymerase chain reaction.
Keywords: COL7A1 gene, epidermolysis bullosa pruriginosa, mutation
Epidermolysis bullosa (EB) pruriginosa is a subtype of dominant dystrophic epidermolysis
bullosa (DDEB), characterized by severe pruritus and blistering localized to the extensor
surface of the extremities. EB pruriginosa exhibits extensive clinical heterogeneity with
variable expressivity and delayed age of onset. Mutations in the COL7A1 gene, especially
in glycine residues within of Gly-X-Y repeats, have been shown to cause this form of
DDEB. Here, we report a novel COL7A1 mutation in a Taiwanese pedigree with EB
pruriginosa. Using polymerase chain reaction amplification and direct sequence analysis,
we have identified a G-to-T transversion at nucleotide 7097 within exon 92 of COL7A1,
converting a glycine residue to valine (G2366V). The mutation resides within a
consecutive, uninterrupted 17 Gly-X-Y of the triple-helical domain of type VII collagen.
Interestingly, the proband in our family also displayed elevated IgE levels, previously
reported in some patients with this disorder. Our finding further implicates COL7A1
mutation in the pathogenesis of EB pruriginosa and underscores the heterogeneous clinical
symptoms of glycine mutations in DDEB.
Dystrophic epidermolysis bullosa (DEB) is a collection of hereditary bullous
disorders characterized by blistering, scarring, and nail dystrophy.1 The fragility is
attributed to scarcity, or even the complete absence of anchoring fibrils composed mainly of
type VII collagen.1 Autosomal dominant and recessive inheritance patterns, as well as
sporadic cases of DEB have all been described.2-4 To date, several hundred pathogenetic
mutations within the collagenous and noncollagenous domains of type VII collagen gene
(COL7A1) have been identified in different forms of DEB.5-12 One subtype of dominant
dystrophic epidermolysis bullosa (DDEB) is EB pruriginosa associated with intense
pruritus and nodular prurigo-like lichenified lesions localized mostly in the lower
extremities and extensor forearms.2 Specifically in EB pruriginosa, 13 mutations, 9 of
which involve glycine substitution, have been reported in literature (Fig. 2).
Here, we have identified a two-generation EB pruriginosa kindred of Taiwanese
descent (Fig. 1a). The proband is a 52-year old woman (II-8) who developed intense
pruritic blisters in her lower extremities and extensor surface of both arms in her twenties.
A detailed clinical description of her symptoms was reported previously in the Chinese
literature.13 Briefly, histology of biopsy showed a subepidermal cleft and mild
perivascular mononuclear infiltration in the upper dermis. Upon electron microscopic
examination, the anchoring fibrils were found to be decreased in number and thinner than in
normal control skin. Neither the parents nor the six other siblings of the index case
developed any similar symptoms. Recently, at the age of 25 years, the son (III-1) of the
proband developed similar pruritic blisters on both shins and extensor arms (Fig. 2b).
Although the 22 year-old daughter of the proband (III-2) lacked blistering lesions, nail
dystrophy, and other symptoms of the disease, she had reported localized pruritus on
pretibial skin and not yet reached the age of onset of her mother and brother.
After obtaining informed consent, DNA was isolated from peripheral blood
lymphocytes in individuals II-7, II-8, and III-1 and from buccal cells in individual III-2,
using PureGene DNA Isolation Kit (Minneapolis, MN). PCR amplification of the
genomic sequence of COL7A1 gene was performed with oligonucleotide primers and
conditions described previously.6 The PCR products were directly sequenced using ABI
Prism Big Dye Terminator Cycle Sequencing Ready Reaction kit (Applied Biosystems)
and the ABI Prism 310 automated sequencing system. Sequencing of affected individuals
(II-8 and III-1) revealed a heterozygous GT transversion in exon 92 of the COL7A1 gene at
nucleotide position 7097 (Fig. 1c), leading to the conversion of a glycine residue (GGT) to
a valine residue (GTT), designated G2366V. Although individual III-2 has not yet
developed the blistering symptoms of EB pruriginosa, sequence analysis confirmed that she
is a carrier of the missense mutation and thus predisposed to developing symptoms in the
future. Mismatched PCR with a forward primer (5’-GAGCTC CTG TGA GCC AAT
TC-3’) and a reverse mismatch primer (5’-CTG GGT ACA CAT ACC TTG TAA-3’) was
used to create a new recognition site for the restriction enzyme MaeIII. Restriction digest
of the mismatched PCR product confirmed the mutation in affected and carrier family
members, and excluded the mutation from 33 unrelated, unaffected control individuals, thus
arguing against it being a common polymorphism.
To date, the etiology of severe pruritus in EB pruriginosa is unknown. Several
studies had implicated an elevated IgE level and immune predisposition to atopy in the
pathogenesis of the pruriginosa phenotype.4,15 Interestingly, with no prior personal or
family history of atopy, patient III-1 reported an episode of idiopathic atopic dermatitis in
the extensor arms, waist, buttock, and pretibial areas immediately before the appearance of
blisters on his pretibia. In accounting for pruritus in the family reported here, available
blood chemistry of patient III-1 showed an elevated level of serum IgE (222 IU/milliliter;
normal range 0-59 IU/milliliter), over three times the upper limit of normal range. Other
causes of itching in III-1 have been ruled out, including thyroid dysfunction, uremia, and
low ferritin levels. Our study supports the earlier observation by Mellerio et al4 which
found serum IgE levels to be elevated in seven out of nine EB pruriginosa patients. The
pathogenesis of pruriginosa phenotype is poorly understood and how the immune response
may participate in the development of the phenotype remains to be elucidated.
The mutation in residue G2366 occurs in the midst of 17 consecutive uninterrupted
Gly-X-Y repeats in the triple helical domain of COL7A1. The missense mutation
G2366V would likely destabilize the essential triple-helix formation of the collagenous
domain. Glycine substitution mutations have been previously reported in various subtypes