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Two novel mutations on exon 8 and intron 65 of COL7A1 gene in two Chinese brothers result in recessive dystrophic epidermolysis bullosa.
[dystrophic epidermolysis bullosa]
Dystrophic
epidermolysis
bullosa
is
an
inherited
bullous
dermatosis
caused
by
the
COL
7
A
1
gene
mutation
in
autosomal
dominant
or
recessive
mode
.
COL
7
A
1
gene
encodes
type
VII
collagen
-
the
main
component
of
the
anchoring
fibrils
at
the
dermal-epidermal
junction
.
Besides
the
730
mutations
reported
,
we
identified
two
novel
COL
7
A
1
gene
mutations
in
a
Chinese
family
,
which
caused
recessive
dystrophic
epidermolysis
bullosa
(
RDEB
)
.
The
diagnosis
was
established
histopathologically
and
ultrastructurally
.
After
genomic
DNA
extraction
from
the
peripheral
blood
sample
of
all
subjects
(
5
pedigree
members
and
136
unrelated
control
individuals
)
,
COL
7
A
1
gene
screening
was
performed
by
polymerase
chain
reaction
amplification
and
direct
DNA
sequencing
of
the
whole
coding
exons
and
flanking
intronic
regions
.
Genetic
analysis
of
the
COL
7
A
1
gene
in
affected
individuals
revealed
compound
heterozygotes
with
identical
novel
mutations
.
The
maternal
mutation
is
a
2
-
bp
deletion
at
exon
8
(
c
.
1006
_
1007
delCA
)
,
leading
to
a
subsequent
reading
frame-shift
and
producing
a
premature
termination
codon
located
48
amino
acids
downstream
in
exon
9
(
p
.
Q
336
EfsX
48
)
,
consequently
resulting
in
the
truncation
of
2561
amino
acids
downstream
.
This
was
only
present
in
two
affected
brothers
,
but
not
in
the
other
unaffected
family
members
.
The
paternal
mutation
is
a
1
-
bp
deletion
occurring
at
the
first
base
of
intron
65
(
c
.
IVS
5568
+
1
delG
)
that
deductively
changes
the
strongly
conserved
GT
dinucleotide
at
the
5
'
donor
splice
site
,
results
in
subsequent
reading-through
into
intron
65
,
and
creates
a
stop
codon
immediately
following
the
amino
acids
encoded
by
exon
65
(
GTAA
→
TAA
)
.
This
is
predicted
to
produce
a
truncated
protein
lacking
of
1089
C-
terminal
amino
acids
downstream
.
The
latter
mutation
was
found
in
all
family
members
except
one
of
the
two
unaffected
sisters
.
Both
mutations
were
observed
concurrently
only
in
the
two
affected
brothers
.
Neither
mutation
was
discovered
in
136
unrelated
Chinese
control
individuals
.
This
study
reveals
novel
disease-causing
mutations
in
the
COL
7
A
1
gene
.