Congenital polycythemia with homozygous and heterozygous mutations of von Hippel-Lindau gene: five new Caucasian patients.

Abstract

We report on five Caucasian patients with congenital polycythemia and mutations of the von Hipple-Lindau (VHL) gene: a compound heterozygote for the novel exon 1 (VHL 235C->T) and previously reported VHL 562C->G mutations; three homozygotes for Chuvash VHL 598C->T mutation; and a heterozygote for VHL 523->G mutation who also has ataxia-telangiectasia; a rare autosomal disease of childhood onset.

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Letters to the Editor
| 128 | haematologica/the hematology journal | 2005; 90(1)
Red Cell Disorders
Congenital polycythemia with homozygous and
heterozygous mutations of von Hippel-Lindau
gene: five new Caucasian patients
We report on five Caucasian patients with con-
genital polycythemia and mutations of the von
Hipple-Lindau (VHL) gene: a compound heterozy-
gote for the novel exon 1 (VHL 235C→
viously reported VHL 562C→
homozygotes for Chuvash VHL 598C→
tion; and a heterozygote for VHL 523A→
tion who also has ataxia-telangiectasia; a rare
autosomal disease of childhood onset.
©Ferrata Storti Foundation
→T) and pre-
→G mutations; three
→T muta-
→G muta-
haematologica 2005; 90:128-129
An essential function of red blood cells is to deliver oxy-
gen. Hypoxia sensing is crucial for energy metabolism,
angiogenesis, erythropoiesis and various other functions.
Hypoxia-inducible factor 1 (HIF1), a heterodimeric tran-
scription factor comprising a HIF-1α subunit and HIF-1β
(also known as the aryl hydrocarbon receptor nuclear
translocator (ARNT),1plays a central role in the response
to hypoxia. The HIF-1α subunit is regulated by oxygen. In
normoxia its proline is hydroxylated and binds to the von
Hippel-Lindau (VHL) protein and is rapidly degraded by
ubiquitinization.1In hypoxia, HIF-1α is stable and forms a
heterodimer with HIF-1β which results in the activation of
an array of genes expression of proteins such as those
involved in energy metabolism, vasculogenesis (e.g. vascu-
lar endothelial growth factor), iron metabolism (e.g. trans-
ferrin receptor) and erythropoiesis.1
Polycythemia is defined as an increased red cell mass.
Primary polycythemia is characterized by an augmented
response of erythroid progenitors to erythropoietin (Epo)
due to acquired somatic or inherited germline mutations
expressed within hematopoietic progenitors which cause
erythrocyte overproduction. In secondary polycythemias
the erythroid progenitors respond normally to Epo and
increased levels of circulating factors driving erythro-
poiesis, e.g. Epo, IGF1, cobalt. Both primary and second-
ary polycythemias can be congenital or acquired.2
Chuvash polycythemia (CP) is endemic in the Chuvash
region of Russia. It shares features of both primary and
secondary polycythemias, and is due to homozygosity for
the 598 C→T mutation in the VHL gene.3CP has also been
found in diverse ethnic and racial groups.4-6Rare poly-
cythemic subjects are heterozygous for a VHL mutation. In
this report we describe five additional polycythemic
patients with VHL mutations. The 5 new polycythemic
patients have 4 different VHL mutations. Four of the
patients have both VHL alleles mutated, one is a heterozy-
gote for a missense VHL mutation (Table 1).
Patient #1 is a compound heterozygote with a novel 235
C→T (R79C) VHL mutation in exon 1, and a 562C→G
(L188V) VHL mutation. The latter mutation has been pre-
viously described in a compound heterozygote of Anglo-
US American Indian background who also carried the
Chuvash 598 C→T VHL mutation. Patients #2-4 were
homozygous for the Chuvash 598 C→T (R200W) VHL
mutation. Patients #2 and #3 were US Caucasian brothers.
Patient #4, a 17-year old US Caucasian unrelated to the
http://www.haematologica.org/journal/2005/1/128
others, also had congenital polycythemia. All three were
polycythemic shortly after birth and were on a therapeu-
tic phlebotomy program to maintain their hematocrit
below 45%. They had the thrombotic complications
depicted in Table 1. Patient #2 died at the age of 41 years,
underscoring the thrombophilic nature of the Chuvash
598 C→T VHL mutation.7Patient #4 had recurrent deep
vein thrombosis with pulmonary embolism and mesen-
teric thrombosis at the age of 12 years and has been on
Table 1. Phenotypes of congenital polycythemia patients with VHL
gene mutations.
Patients
(Sex)
Age
(Years)
VHLSerum Epo Other clinical signs
Leveland symptomsMutations
1 (F) 33235 C→T (R79C)*
562 C→G (L188V)
Compound
heterozygote
highAsymptomatic
2 (M)38598 C→T (R200W)
Homozygote
highPortal and mesenteric
vein thrombosis
3 (M) 41598 C→T (R200W) high
Homozygote
Superficial venous
thrombosis
4 (F)17598 C→T (R200W) high
Homozygote
Deep vein thrombosis
pulmonary embolism
5 (F) 18523 A→G (Y175C)* normal
Heterozygote
Ataxia telangiectasia
*Mutations were not detected in 100 US Caucasian chromosomes by Mfe1
restriction enzyme digestion and not found in 100 Portuguese chromosomes.
Figure 1. Quantification of VHL mRNA expression in patient #5
and control. VHL mRNA expression of patient #6 was compared
to that of 4 normal controls, 3 patients with ataxia-telangiectasia
(AT), and the mother of patient #5. The mean values of cycle dif-
ferences from the h18S rRNA in real-time polymerase chain reac-
tions (PCR) are shown with their standard deviations calculated
from three independent experiments. Fewer cycles reflect a high-
er amount of mRNA. Each independent experiment contained
mRNA from the four controls and three AT patients. The real-time
PCR were run in duplicates. For each mRNA, the level is also
expressed as a percentage of the control values. No significant
difference was found between samples and controls (p> 0.05 cal-
culated by one-way ANOVA together with Tukey’s test).
Control
(100%)
AT pt#5
(123%)
pt#5 mother
(152%) (162%)
VHL
PCR cycle difference from h18s rRNA
0
1
2
3
4
5
6
7
8
9

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Letters to the Editor
haematologica/the hematology journal | 2005; 90(1) | 129 |
chronic warfarin therapy. All three patients were investi-
gated for thrombophilia and no underlying cause was
found. The VHL core haplotype that has been observed in
CP patients,8defined by six single nucleotide polymor-
phisms that span the 137.5 kb of the VHL gene, was found
in all these three patients.
Patient #5 is a Portuguese girl with a normal P50, normal
Epo level and no evidence of cardiac, renal, brain, or adre-
nal pathology who has polycythemia and ataxia-telangiec-
tasia (A-T). She is heterozygous for a novel 523 A→G
(Y175C) VHL mutation. This mutation is not in the
Universal VHL-mutation Database (www.umd.necker.fra);
however, a mutation in codon 175 was reported in a
Spanish patient with pheochromocytoma; no nucleotide
details were cited and no further details are available.9The
parents of our patient are hematologically normal and
there was no history of consanguinity. The VHL mutation
was inherited from her father. The VHL gene of her moth-
er was screened for aberrant mRNA transcripts by reverse
transcription polymerase chain reactions and the exons
and exon/intron boundaries were sequenced in both ori-
entations from genomic DNA, and no mutation was
found. A VHL null allele (or deletion) in the maternal gene
was ruled out since equal proportions of wild-type and
mutated nucleotides at 523 (A and G) were found in VHL
cDNA. We have also considered that the polycythemic
phenotype observed in A-T patient #5 may have been
caused by a decreased amount of VHL mRNA transcript,
perhaps caused by nonsense-mediated decay (NMD) sec-
ondary to the ATM defect, since the phosphorylation of
NMD protein Upf1, a smg2 homolog, is reported to be
ATM-dependent.10However, as we show in Figure 1, this
possibility was ruled out. In summary, we conclude that
defects in both alleles of the VHL gene may represent the
most frequent inherited genetic polycythemic defect; we
report two novel VHL mutations associated with poly-
cythemia. The molecular biology of the polycythemic
patients with a single mutated VHL allele remains obscure.
M. Celeste Bento,* Ko-Tung Chang,° Yongli Guan,° Enli Liu,°
Gabriela Caldas,* Richard A. Gatti,° Josef T. Prchal°
*Unidade de Hematologia Molecular, Centro Hospitalar
de Coimbra, Portugal; °Baylor College of Medicine and
Michael DeBakey VAH, Houston, Tx., USA;
#Pediatric Department, Hospital Garcia de Orta, Almada,
Portugal; @UCLA School of Medicine, Los Angeles,
Ca., USA
Funding: this work was supported by grants R01HL66333-04 and
R01HL5007-11 NHLBI from the National Institute of Health.
Acknowledgments: we are indebted to our clinical collaborators
who referred the patients, provided the clinical material,
and performed some of the studies: Drs. Stephen Moll,
Wes Lee, L. Brown, and Yves Pastore.
Key words: congenital polycythemia, VHL mutations,
ataxia-telangiectasia.
Correspondence: Josef T. Prchal, Baylor College of Medicine,
One Baylor Plaza, Suite 802E, Houston, TX 77030, USA.
Phone: international +1.713.7987210. Fax: international
+1.713.7986132. E-mail: jprchal@bcm.tmc.edu
References
1. Semenza GL. Hydroxylation of HIF-1: oxygen sensing at the
molecular level. Physiology (Bethesda) 2004;19:176-82.
2. Prchal JT. Classification and molecular biology of poly-
cythemias (erythrocytoses) and thrombocytosis. Hematol
Oncol Clin North Am 2003;17:1151-8.
3. Ang SO, Chen H, Hirota K, Gordeuk VR, Jelinek J, Guan Y, et
al. Disruption of oxygen homeostasis underlies congenital
Chuvash polycythemia. Nature Genet 2002;32:614-21.
4. Pastore YD, Jelinek J, Ang S, Guan Y, Liu E, Jedlickova K, et al.
Mutations in the VHL gene in sporadic apparently congenital
polycythemia. Blood 2003;101:1591-5.
5. Percy MJ, McMullin MF, Jowitt SN, Potter M, Treacy M,
Watson WH, et al. Chuvash-type congenital polycythemia in
4 families of Asian and Western European ancestry. Blood
2003;102:1097-9.
6. Pastore Y, Jedlickova K, Guan Y, Liu E, Fahner J, Hasle H, et al.
Mutations of von Hippel-Lindau tumor-suppressor gene and
congenital polycythemia. Am J Hum Genet 2003;73:412-9.
7. Gordeuk VR, Sergueeva AI, Miasnikova GY, Okhotin D,
Voloshin Y, Choyke PL, et al. Congenital disorder of oxygen-
sensing: association of the homozygous Chuvash poly-
cythemia VHL mutation with thrombosis and vascular abnor-
malities but not tumors. Blood 2004;103:3924-32.
8. Liu E, Percy MJ, Amos CI, Guan Y, Shete S, Stockton DW, et
al. The worldwide distribution of the VHL 598C→T mutation
indicates a single founding event. Blood 2004;103:1937-49.
9. Ruiz-Llorente S, Bravo J, Cebrian A, Cascon A, Pollan M,
Telleria D, et al. Genetic characterization and structural analy-
sis of VHL Spanish families to define genotype–phenotype
correlations Hum Mutat 2004;23:160-9.
10. Brumbaugh KM, Otterness DM, Geisen C, Oliveira V,
Brognard J, et al. The mRNA surveillance protein hSMG-1
functions in genotoxic stress response pathways in mam-
malian cells. Mol Cell 2004;14585-98.
Red Cell Disorders
Sustained response to interferon α-2a in
thalassemic patients with chronic hepatitis C.
A prospective 8-year follow-up study
Eighty-nine thalassemic patients with chronic hep-
atitis C were treated with interferon α-2a for 12
months and followed up for 8 years. Interferon
induced sustained virologic and biochemical response
in 45% of participants and histologic improvement in
50% of patients who had paired liver biopsies.
Splenectomy was the only independent predictor of
an unfavorable outcome.
haematologica 2005; 90:129-131
Several studies on chronic hepatitis C in thalassemic
patients have shown response rates to interferon higher
than those in non-thalassemics.1,2,3-7These somewhat sur-
prising findings are based on small number of patients with
no long-term follow up. Herein, we present the results of a
prospective 8-year follow-up study on the efficacy and
safety of interferon α-2a in the treatment of chronic hepa-
titis C in 89 patients with β-thalassemia major.
An open prospective study was conducted from
December 1994 through December 1995 to determine
the efficacy of interferon α-2a in the treatment of chronic
hepatitis C virus (HCV) infection in patients with β-tha-
lassemia major. The participants were recruited from a
cohort of 367 thalassemic patients who are followed up at
our institution. Eligible patients were those who had
detectable HCV RNA in serum, histologic findings consis-
tent with chronic hepatitis, and elevated values of serum
alanine aminotransferase. Patients with cardiovascular,
endocrine, renal and autoimmune diseases or cirrhosis
were excluded from the study as were those who had
received prior treatment against hepatitis C. All patients
were seronegative for human immunodeficiency virus
and immune against hepatitis B virus. The participants
were given 3MU of interferon α-2a (Roferon, Roche) sub-
cutaneously thrice weekly for 52 weeks.
At study entry, all participants underwent a physical
http://www.haematologica.org/journal/2005/1/129
©Ferrata Storti Foundation