Download Hereditary Hyperferritinemia-Cataract Syndrome: Two Novel

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CORRESPONDENCE
367
10. Leinikki P, Granström M-L, Santavuori P, Pettay O: Epidemiology of cytomegalovirus infections during pregnancy and infancy. Scand
J Infect Dis 10:165, 1987
11. Ahlfors K, Ivarsson S-A, Johnsson T, Svensson I: Congenital and
acquired cytomegalovirus infections. Acta Paediatr Scand 67:321, 1978
12. Stuart-Harris C: The epidemiology and clinical presentation of
herpes virus infections. J Antimicrob Chemother 12:1, 1983
13. Lamy ME, Favart AM, Cornue C, Mendez M, Segas M,
Bortonboy G: Study of Epstein-Barr virus (EBV) antibodies. Acta Clin
Belg 37:281, 1982
14. Stollmann B, Fonatsch C, Havers W: Persistent Ebstein-Barr
virus infection associated with monosomy 7 or chromosome 3 abnormality in childhood myeloproliferative disorders. Br J Haematol 60:183,
1985
Hereditary Hyperferritinemia-Cataract Syndrome: Two Novel Mutations
in the L-Ferritin Iron-Responsive Element
To the Editor:
Cazzola et al1 recently reported two kindreds with hereditary
hyperferritinemia cataract syndrome (HHCS) associated with novel
point mutations within a regulatory stem-loop motif in the L-ferritin
mRNA termed the iron-responsive element (IRE). Affected individuals
showed a characteristic clinical phenotype of elevated serum ferritin
concentration and cataract developing early in life. The proposed
pathogenesis of this disorder is that nucleotide substitutions within the
IRE disrupt its specific interaction with the cytoplasmic iron regulatory
protein (IRP). Failure of optimal IRP-IRE binding in turn leads to
failure of suppression of L-ferritin translation.
There are now increasing numbers of reports that describe the
genotype-phenotype relationship in kindreds with naturally occurring IRE
mutations, and as Cazzola et al1 report, the phenotype varies with the position
of the mutation in the IRE. These descriptions now provide clinical data that
support the structural model of the IRE-IRP interaction deduced from in
vitro binding studies using artificially created IRE mutants.2-4
We have identified two further kindreds with HHCS and novel
mutations in the L-ferritin IRE that further support this model.
Kindred I. The 51-year-old male proband of English origin developed visual symptoms in his mid-thirties from cataracts, but was
otherwise asymptomatic. Investigations revealed a serum ferritin of
1,389 µg/L but normal transferrin saturation. Similar abnormalities were
noted in the proband’s sister, and liver biopsy specimens from both
these individuals showed no iron overload. Sequencing of genomic
DNA from the proband showed a heterozygous point mutation that
corresponded to a 139 C = U substitution in the L-ferritin mRNA.
Kindred 2. The 42-year-old female proband of English origin was
investigated for anemia detected at one of her regular blood transfusion
sessions. Although her red cell indices and transferrin saturation were
consistent with mild iron deficiency, her serum ferritin was elevated at 1,020
µg/L. The proband herself had had previous surgical extraction of cataracts,
and there were premature cataracts in 8 other family members. The son of the
proband required cataract extraction at 5 years old. Hyperferritinemia was
confirmed only in family members with cataract. Analysis of genomic DNA
also showed a heterozygous point mutation, this time corresponding to a 136
C = A substitution in the L-ferritin mRNA. This substitution created an Mse
I restriction site within the amplified sequence, and restriction digests from
additional family members confirmed that the substitution segregated with
the hyperferritinemia-cataract phenotype.
The nucleotide substitutions detected in kindreds 1 and 2 lie in the
apical loop and upper stem of the IRE, respectively (Fig 1). We note that
in both kindreds individuals display a severe phenotype, and this is
consistent with the observations of Cazzola et al that mutations near the
apex of the IRE result in higher serum ferritin concentrations and denser
cataracts. These results also comply with data from in vitro binding
studies; nucleotide substitutions in the apical loop of the IRE dramatically reduce IRP affinity, consistent with its putative role as the IRP
binding site.2,3 Individuals from kindred 1 with a naturally occurring
mutation at this site are therefore expected to have a severe defect in
L-ferritin regulation. In the case of kindred 2, artificially created
Fig 1. Schematic representation of the L-ferritin IRE adapted from
Cazzola et al showing the updated distribution of genotypic abnormalities in HHCS. Substitutions 139 C = U in kindred 1 and 136 C = A lie
within the apical loop and upper stem, respectively. (Adapted and
reprinted with permission.1)
nucleotide substitutions in the IRE upper stem exert a profound effect
on IRP binding in vitro, but only if complementary base pairing in the
stem is disrupted.4 Pairing of nucleotides may facilitate IRE-IRP
binding by maintaining an optimum secondary structure of the IRE. The
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368
CORRESPONDENCE
severe phenotype of kindred 2, who have a naturally occurring
noncomplementary nucleotide substitution close to the IRP binding site,
may therefore reflect a broader structural derangement of the IRE.
Our kindreds help clarify the relationship between genotype and
phenotype in HHCS, and the description of two novel mutations
illustrates the increasing genotypic diversity of this disorder. The
severity of the phenotype of our patients and the position of the
nucleotide substitution support the existing models of IRE-IRP interaction.
A.D. Mumford
T. Vulliamy
J. Lindsay
Imperial College School of Medicine
Hammersmith Hospital
London, UK
A. Watson
Stoke Mandeville Hospital NHS trust
Aylesbury, Bucks, UK
REFERENCES
1. Cazzola M, Bergamaschi G, Tonon L, Arbustini E, Grasso M,
Vercesi E, Baroi G, Bianchi PE, Cairo G, Arosio P: Hereditary
hyperferritinaemia-cataract syndrome: Relationship between phenotypes and specific mutations in the iron-responsive element of ferritin
light-chain mRNA. Blood 90:814, 1997
2. Bettany AJE, Eisenstein RS, Munro HN: Mutagenesis of the
iron-regulatory element further defines a role for RNA secondary
structure in the regulation of ferritin and transferrin receptor expression.
J Biol Chem 267:16531, 1992
3. Jaffrey SR, Haile DJ, Klausner RD, Harford JB: The interaction
between the iron-responsive element and its cognate RNA is highly
dependent upon both RNA sequence and structure. Nucleic Acids Res
21:4627, 1993
4. Leibold EA, Laudano A, Yu Y: Structural requirements of
iron-responsive element for binding of the protein involved in both
transferrin receptor and ferritin mRNA post-transcriptional regulation.
Nucleic Acids Res 18:1819, 1990
b-Spectrin Promissão: A Translation Initiation Codon Mutation of the b-Spectrin Gene (ATG = GTG)
Associated With Hereditary Spherocytosis and Spectrin Deficiency in a Brazilian Family
To the Editor:
Hereditary spherocytosis (HS) is a common inherited anemia characterized by the presence of spheroidal red cells and increased osmotic
fragility of erythrocytes.1 This disorder is heterogeneous in terms of its
clinical presentation, molecular basis, and inheritance.2 HS mutations
have been ascribed to several genes,1 including the b-spectrin gene. So
far 13 b-spectrin mutations have been described associated with HS.3-6
We have studied a Brazilian family with HS diagnosed in eight subjects
from two generations and inherited in an autosomal dominant fashion (Fig 1).
The propositus was a 28-year-old black man, who presented compensated
hemolytic disease with splenomegaly, hyperbilirubinemia, increased osmotic
fragility, and a regular number of spherocytes and acanthocytes in the blood
smear (Fig 1). His recent hematological profile was: hemoglobin (Hb) 15.0
g/dL, red blood cell 4.49 3 1012/L, mean corpuscular volume 88 fL, mean
corpuscular hemoglobin concentration 38.0 g/dL, reticulocyte count 530 3
109/L (11.8%). His mother, uncle, and two cousins were splenectomized.
Densitometric scans of Coomassie blue–stained sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) of the propositus membrane proteins showed an 18% reduction in spectrin content (Fig 1). This
pointed to the b-spectrin gene as the most likely candidate for bearing the
primary defect. Therefore, we started screening for mutations in the
b-spectrin gene. This was performed through the amplification of the
individual exons of the b-spectrin gene with intronic primers. The amplification products were submitted to nonradioactive single-strand conformation
polymorphism (SSCP) technique in a PhastSystem apparatus (Pharmacia,
Uppsalla, Sweden) to detect sequence abnormalities. The DNA amplification
products of exon 2 of the patient and his mother showed an identical band
shift in two independent experiments (Fig 2). No such band pattern was
observed in 2 independent controls, nor was it observed in 12 other HS
patients with spectrin deficiency and acanthocytes in the blood smear,
suggesting that this patient bore a unique or at least a rare sequence alteration
in this region of the gene. Sequencing revealed an heterozygous A = G
nucleotide substitution at the translation initiation codon of the b-spectrin
Fig 1. (Left) 3.5% to 17% exponential gradient SDS-polyacrylamide gel
of total membrane proteins stained
with Coomassie blue, showing a reduction of spectrin content in the
patient (lane 2) compared with the
control (lane 1). (Upper right) Blood
smear of the propositus showing
regular numbers of spherocytes and
acanthocytes. (Lower right) Family
pedigree showing all affected members from two generations. Splenectomized individuals are indicated by
asterix and the proband is indicated
by an arrow.
From www.bloodjournal.org by guest on June 18, 2017. For personal use only.
1998 91: 367-368
Hereditary Hyperferritinemia-Cataract Syndrome: Two Novel Mutations in
the L-Ferritin Iron-Responsive Element
A.D. Mumford, T. Vulliamy, J. Lindsay and A. Watson
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