Familial transient erythroblastopenia of childhood is associated with the chromosome19q13.2region but not caused by mutations in coding sequences of the ribosomal protein S19 (RPS19)gene
Peter Gustavsson,1Joakim Klar,1Hans Matsson,1Erik Forestier,2Jan-Inge Henter,3
Sreedhar Rao,4Martin Seip,5*Gunnar Skeppner6and Niklas Dahl11Section of Clinical Genetics, Department of Genetics and Pathology,Rudbeck Laboratory,Uppsala University Hospital,Uppsala,2Department of Clinical Sciences and Paediatrics,University of Umea?,Umea?,3Childhood Cancer Research Unit,Karolinska Institute, Paediatric Haematology and Oncology,Karolinska Hospital,Stockholm,Sweden,4Department of Pediatrics,
SUNY-Downstate Medical Center,Brooklyn,NY,USA,5Department of Paediatrics,National Hospital,Oslo,Norway, and6Department of Paediatrics,O¨rebro University Hospital,O¨rebro,Sweden
Received28December2001;accepted for publication28March2002
Summary.Transient erythroblastopenia of childhood(TEC) is a rare condition,which at onset may be dif?cult to dis-tinguish from Diamond–Blackfan anaemia(DBA).We have previously shown that mutations in the ribosomal protein S19gene(RPS19)cause DBA.In order to clarify whether TEC and DBA are allelic,we investigated the segregation of markers spanning the RPS19gene region on chromosome 19q13.2and performed sequence analysis of all exons in the RPS19gene in seven TEC sibling pairs.Linkage analysis supported allelism for TEC and DBA at the RPS19gene locus and implies molecular mechanisms other than struc-tural mutations in the RPS19gene.
Keywords:familial transient erythroblastopenia of child-hood(TEC),chromosome19q13.2,RPS19gene,mutation detection,linkage analysis.
Transient erythroblastopenia of childhood(TEC;MIM 227050)is a pure red cell aplasia that occurs in a previously healthy child,most commonly between 6months and4years of age(Wranne,1970;Glader, 1987).Laboratory investigations show a normocytic nor-mochromic anaemia with absence of reticulocytes in peripheral blood,sometimes associated with thrombocytosis and bone marrow erythroblastopenia(Glader,1987;Cher-rick et al,1994).The course is characterized by a complete recovery,usually within1–2months after diagnosis,and in most cases no therapy is necessary,although some children may need red cell transfusion(Glader,1987).
Laboratory?ndings in TEC may differ from Diamond–Blackfan anaemia(DBA).In TEC,red blood cells are of normal size and lack the fetal characteristics that are present in DBA(Glader,1987;Cherrick et al,1994).In addition,levels of red cell adenosine deaminase(ADA)are usually normal in TEC and elevated in DBA(Glader,1987). In contrast to DBA,no physical abnormalities have been reported in patients with TEC(Glader,1987;Cherrick et al, 1994).
It has been suggested that parvovirus B19infection may play an important role in the aetiology of TEC.However, this has not been supported by clinical or experimental data (Glader,1987).The majority of TEC cases are sporadic,but there are a few reports in the literature describing affected siblings(Labotka et al,1981;Seip,1982;Glader,1987;Rao et al,1990;Skeppner et al,1998).The gene,mutated in 25%of DBA cases,has been cloned(Draptchinskaia et al, 1999).The gene encodes the ribosomal protein S19that is part of the ribosomal subunit40S,but the role for RPS19in erythropoiesis is not yet known.
Correspondence:Dr Peter Gustavsson or Professor Niklas Dahl,
Section of Clinical Genetics,Department of Genetics and Pathology,
Rudbeck Laboratory,Uppsala University Hospital,S-75185
British Journal of Haematology,2002,119,261–264
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We hypothesized that a genetic factor is involved in familial cases of TEC,as has been shown for DBA.In this study,we collected blood samples from seven families in which siblings were diagnosed with TEC.Samples were analysed for the inheritance pattern of the DBA gene region on chromosome19q13.2and we performed a mutation screening of coding regions of the RPS19gene. PATIENTS AND METHODS
Patients.Peripheral blood samples were collected from family members(parents and children)in seven families with more than one affected sibling diagnosed with TEC (Table I).All affected individuals were ascertained by a haematologist in their country of origin according to the criteria for TEC(Glader,1987).Samples were obtained with local ethical board approval.Genomic DNA was extracted from peripheral blood lymphocytes according to standard procedures.Sib-pairs in families1–5were described previously(Seip,1982;Rao et al,1990;Skepp-ner et al,1998).In two families,one parent also had a history of a transient period of anaemia of childhood. Transient periods of anaemia in parents,age at diagnosis and time at diagnosis in affected individuals with TEC are shown in Table I.
Genotyping and linkage analysis.In order to study segre-gation of markers on chromosome19q13.2,four poly-morphic loci(D19S197,PG1,LIPE and D19S408)were analysed in seven families with TEC.The RPS19gene mutated in DBA is located between markers PG1and LIPE (Gustavsson et al,1998).Primer sequences and conditions for polymerase chain reaction(PCR)were used as previously described(Gustavsson et al,1998).32P-labelled PCR products were ampli?ed from genomic DNA,separ-ated on5%polyacrylamide gels and visualized by autoradiography.
Two-point LOD scores,assuming dominant inheritance, were calculated using the FASTLINK version3?0P from the LINKAGE package(Lathrop&Lalouel,1984).Different
penetrant models(range0?3–1?0)were used and the disease gene frequency was set to10)6with no sex difference.Allele frequencies were taken from the Genome Data Base(GDB) when possible.Parents with a history of anaemia were both regarded as affected and as phenotypically unknown. Apparently healthy parents were regarded as healthy or as individuals with an unknown phenotype.
Sequence analysis.All six exons of the RPS19gene, including the5￠UTR,were analysed for mutations in genomic DNA from one of each seven familial cases ascertained with TEC.The PCR and the sequence reac-tions,using forward and reverse intronic primers,were generated as previously described(Draptchinskaia et al, 1999).Fluorescent-labelled sequence reactions were separ-ated on an ABI377(Applied Biosystems,Foster City,CA, USA)and analysed by Sequencher(Gene Codes,Ann Arbor, MI,USA).
Following genotype analysis,chromosome19q13.2haplo-types were assigned in all available family members(Fig1). Segregation studies showed that all affected siblings shared at least one parental chromosome19q13.2haplotype. Healthy siblings,when available,did not share this chro-mosomal haplotype.In families1and3,where the parents had a history of transient anaemia of childhood,segregation of haplotypes suggested an autosomal dominant inheritance for the TEC phenotype.
Regarding two parents with a history of transient anaemia as affected,a two-point linkage analysis revealed a maximum pair-wise LOD score(Zmax)of1?76at D19S408,assuming a penetrance of0?95.The maximum LOD score was decreased to1?69or1?49by reducing the penetrance to0?7and0?3respectively.In a calculation model,where parents with a history of anaemia were treated as phenotypically unknown,a two-point LOD score of1?63was obtained at D19S408,assuming a penetrance of0?7.A recessive inheritance for a putative disease gene on chromosome19q13.2could be excluded in families2,3and 5as a result of the segregation pattern of the markers (Fig1).
Table I.Cases with familial TEC in seven families.
Family Siblings with TEC Parents with TEC
Age at diagnosis Age at diagnosis(months)Year and month of diagnosis(months)
Age(months)and time of diagnosis for affected siblings are shown.Transient periods of childhood
anaemia in parents were present in families1and3and are indicated.
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In order to identify sequence aberrations,we performed sequencing of all exons in the RPS19gene.The analysis of genomic DNA from individuals with a history of TEC revealed normal sequence chromatograms corresponding to the RPS19gene sequence.
The clinical overlap between TEC and DBA led us to investigate whether the two diseases are allelic and caused by mutations in the same gene.Previously,it has been shown that approximately25%of cases with DBA had alterations in the RPS19gene(Draptchinskaia et al,1999; Willig et al,1999).
The segregation of chromosome19q13haplotypes in familial TEC is compatible with a gene in the19q13region for TEC.A similar pattern is observed in familial DBA caused by mutations in the RPS19gene(Gustavsson et al,1997). No common haplotype was shared between any of the families,which excludes an apparent founder effect.The familial TEC patient material in this study was not suf?cient to establish a signi?cant LOD score for linkage to chromo-some19q13.2.
One explanation of our results from the TEC families is that the positive association was identi?ed by chance as a result of the small family material.However,our?ndings agree with the study where linkage analysis was per-formed in DBA and a signi?cant LOD score was obtained in the19q13.2region(Gustavsson et al,1997).In some of the families that segregated for the DBA gene on chromosome19q13.2,no mutation was identi?ed in the coding sequences of the RPS19gene(Draptchinskaia et al, 1999).
We suggest that mutations in regulatory or intronic sequences within the RPS19gene may be involved in the aetiology of familial TEC as well as familial DBA that are linked to the chromosome19q13.2region.In addition, complete deletions of the RPS19gene in TEC patients cannot be excluded.However,the polymorphic marker (PG1),located not more than10kb from the RPS19gene, was shown to be heterozygous in all affected TEC siblings which excludes large deletions in the gene region.A reduced RPS19level during erythropoiesis of childhood may mediate the disease phenotype.A compensatory mechanism by either an upregulation of RPS19levels or by other regulatory factors would result in a transient anaemic condition,whereas permanently low levels result in a chronic anaemia,i.e.DBA.
Our study implies that a genetic component is involved in the development of familial TEC.This is supported by the identi?cation of seven sibling pairs with TEC and that,in two families,the parents had a period of transient anaemia in childhood.In addition,time of development of the disease differed between affected siblings in each family,which contradicts a common environmental factor(Table I). Additional family material would be needed in order to identify a statistically signi?cant linkage.In
addition, Short Report263
analysis of RPS19levels from bone marrow in TEC patients with an ongoing anaemia may show reduced levels compared with healthy individuals. ACKNOWLEDGMENTS
We thank the families who took part in this study.This study was supported by the Beijer Foundation,Marcus Borgstro¨m’s Foundation,and Kristiane and O.F.Hedstro¨m’s Foundation.
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