- Email: [email protected]
Genetic origin and interaction of the Filipino β0-thalassemia with Hb E and α-thalassemia in a Thai family
Genetic origin and interaction of the Filipino b0-thalassemia with Hb E and a-thalassemia in a Thai family SUPAWADEE YAMSRI, KANOKWAN SANCHAISURIYA, GOONNAPA FUCHAROEN, and SUPAN FUCHAROEN KHON KAEN, THAILAND
We describe hematologic and molecular characteristics of a hitherto undescribed interaction between the Filipino deletional b0-thalassemia with Hb E and a-thalassemia in a Thai family. This study was conducted during the prenatal screening of a pregnant Thai woman and her family members. A prenatal diagnosis was performed at her second pregnancy by amniocentesis. Laboratory investigations identified that the pregnant woman was Hb E heterozygote with a1-thalassemia, whereas her husband was a double heterozygote for the Filipino deletional b0-thalassemia and a1-thalassemia. Their affected son was a patient with a previously undescribed condition of Hb E-b0-thalassemia with a1-thalassemia. Both a combined gap-polymerase chain reaction (PCR) and allele-specific PCR were used successfully in the prenatal diagnosis, which identified an affected fetus with Hb E-b0-thalassemia without a1-thalassemia. Beta globin gene haplotype analysis indicated the same origin of this Filipino b0-thalassemia in Asian populations. (Translational Research 2012;159:473–476) Abbreviations: Hb ¼ hemoglobin; PCR ¼ polymerase chain reaction
emoglobin (Hb) E-b-thalassemia is the most common form of b-thalassemia disease in northeast Thailand. The disease exhibits variable phenotypes ranging from severe transfusiondependent thalassemia major to a milder form of thalassemia intermedia, which affects the quality of life and cost of treatment in affected patients. A prenatal diagnosis is, therefore, offered to all couples at risk. Most of this prenatal diagnosis is preferably done by DNA analysis. b-Thalassemia is a heterogeneous disease caused by an absence (b0) or reduction (b1) of b-globin chain synthesis. Most cases are caused by
H
point mutations and more than 200 mutations have been documented in world populations. Deletions causing b-thalassemia are relatively rare.1 In northeast Thailand where the disease is common, 15 different mutations have been recognized and the 3.4 kb b-globin gene deletion is the only deletional mutant previously documented in the region.2 Now, we have reported a hitherto undescribed interaction of another b-thalassemia deletion with Hb E and a1-thalassemia found in a northeast Thai family during prenatal screening and examined its genetic origin by haplotype analysis.
From the Centre for Research and Development of Medical Diagnostic Laboratories, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand.
Reprint requests: Supan Fucharoen, PhD, Centre for Research and Development of Medical Diagnostic Laboratories, Khon Kaen University, 123 Mitaparb Road, Khon Kaen, Thailand 40002; e-mail: supan@ kku.ac.th.
Supported by Grant CHE-RES-RG-51 from the Office of the Higher Education Commission, a grant from the National Research University (NRU) Project, Khon Kaen University, and a grant from the Faculty of Associated Medical Sciences, Khon Kaen University, Thailand (to S.Y.)
1931-5244/$ - see front matter Ó 2012 Mosby, Inc. All rights reserved. doi:10.1016/j.trsl.2011.10.008
Submitted for publication September 4, 2011; revision submitted October 19, 2011; accepted for publication October 25, 2011.
473
474
Yamsri et al
Translational Research June 2012
AT A GLANCE COMMENTARY Yamsri S, et al. Background
Asian populations have high frequencies of thalassemias and other hemoglobinopathies. This study reported a genetic interaction of a deletional b0thalassemia with Hb E and a1-thalassemia found in a Thai family during prenatal screening and studied on the origin of this mutation in Asian populations. Translational Significance
Laboratory investigations identified an affected son as a patient with a previously undescribed condition of Hb E- Filipino deletional b0-thalassemia with a1-thalassemia and an affected fetus with Hb E-b0-thalassemia. The mutation should be included in the prenatal screening. Haplotype analysis indicated likely a single origin and spread of this mutation in Asian populations.
Fig 1. Pedigree of a Thai family at risk for b-thalassemia/Hb E disease. The arrow indicates the fetus whose sample was obtained by amniocentesis. The father was double heterozygote for b-thalassemia and a1-thalassemia, and the mother was a double Hb E/a1-thalassemia. The son had severe b-thalassemia/Hb E disease with a1-thalassemia. a- and b-globin genotypes as well as b-globin gene haplotypes associated with bA, bE, and bFIL of all family members are presented. ‘‘d’’ indicates the polymorphism within a deletion and hence could not be determined. (Color version of figure is available online.)
MATERIALS AND METHODS
Ethical approval of this study was obtained from the Institutional Review Board of Khon Kaen University, Thailand (HE522252). The study was performed on a pregnant Thai woman at her second pregnancy with a risk of having a baby with Hb E-b-thalassemia disease because she was a carrier of Hb E and her husband was a b-thalassemia carrier. Their affected son was a transfusion-dependent patient with Hb E-b-thalassemia disease (Fig 1). A prenatal diagnosis was taken at her 18th week of gestation by amniocentesis. Hematologic data were obtained using standard methods. DNA analysis. The identification of common thalassemia genes in Thailand including ao-thalassemia (SEA and THAI deletions), a1-thalassemia (3.7 and 4.2 kb deletions), Hb Constant Spring, Hb Pakse and b-thalassemia mutations are performed routinely in our laboratory using polymerase chain reaction (PCR)-based methods as described elsewhere.2-4 Identification of the Filipino b0-thalassemia deletion was performed as described by Waye et al.5 Beta-globin gene haplotype consisting of 7 polymorphic sites, including the 50 ε Hinc II site, Gg and Ag Hind III sites, jb and 30 jb Hinc II sites, b Ava II site, and 30 b Bam HI site, was determined by the PCR-restriction fragment length polymorphism method.6 Subjects.
RESULTS
The Hb profiles and globin genotypes of the family members are summarized in Fig 1. The pregnant woman
was the Hb E heterozygote with 27.7% Hb E, whereas her husband was a b-thalassemia carrier with an unusually high Hb A2 level (7.4%). Their affected son was suffering from a transfusion-dependent Hb E-b0-thalassemia disease. He had severe hypochromic microcytic anemia with Hb 6.9 g/dL, hematocrit 22.0%, mean corpuscular volume 51.9 fL, mean corpuscular hemoglobin 16.3 pg, and red blood cell distribution width 28.0%. After genetic counseling was given, prenatal diagnosis by amniocentesis was offered. Direct DNA sequencing of the amplified b-globin gene in the affected son revealed the homozygosity for Hb E mutation (GAG-AAG) at codon 26, which is inconsistent with the phenotype. This result pointed to the possibility of a DNA deletion in trans to the bE mutation. This deletion should remove the b-globin gene but leave the d-globin gene intact because of the high Hb A2 level of the patient (6.4%). We, therefore, looked for all deletions causing the high Hb A2 b-thalassemia trait in Asian populations.7 Among these, the 45 kb-Filipino b0-thalassemia deletion was also examined by PCR.5 With this analysis, we found that the father was a carrier of this Filipino b-thalassemia deletion. Direct DNA sequencing localized the similar 50 deletion breakpoint to the position -4279 relative to the messenger RNA cap site of the b-globin gene in the Thai patient, but the 30 breakpoint located in the L1 repetitive element could not be determined accurately (data not shown). A gapPCR method was used in combination with an allele-
Translational Research Volume 159, Number 6
Yamsri et al
475
Fig 2. Identifications of the Filipino b0-thalassemia deletion by gap-PCR and Hb E by allele specific PCR in prenatal diagnosis of a Thai family. (A) The locations and orientations of PCR primers used for detection of the Filipino b0-thalassemia deletion. The 482-bp fragment, generated from primers (P2 and P5) is a normal control fragment, whereas the 376-bp fragment with primer (P2 and P4) is the Filipino b0-thalassemia deletionspecific fragment. (B) Agarose gel electrophoresis. DNA analysis identified that the husband (F) carried the Filipino b0-thalassemia gene, whereas the pregnant woman (M) carried the Hb E gene. Their affected son (S) and the fetus (P) were diagnosed as having Hb E-b0-thalassemia disease.
specific PCR for the detection of a bE mutation3 in prenatal diagnosis. As shown in Fig 2, the father, the son, and the fetus were positive for this Filipino b0-thalassemia deletion, whereas the mother, the son, and the fetus, but not the father, carried the bE mutation. A routine aglobin gene analysis identified the 3.7 kb deletion a1thalassemia (-a3.7/aa) in the mother, the father, and the affected son but not the fetus. The fetus was, therefore, a compound heterozygote for the Filipino b0-thalassemia and Hb E. After these analyses, appropriate genetic counseling was provided. A subsequent haplotype analysis consisting of 7 polymorphic restriction sites in the b-globin gene cluster described in the Method section demonstrated that this Filipino b0-thalassemia in a Thai family was associated with the 50 haplotype; (1 2 2 2 2 d d). The last 2 polymorphic sites located within the deletion (b Ava II and 30 b Bam HI) could not be determined. DISCUSSION AND CONCLUSION
We have reported for the first time in the Thai population the interaction of a large deletional b0-thalassemia, namely the Filipino deletion, with Hb E and a1-thalassemia found during prenatal screening. This
Filipino b0-thalassemia deletion was reported first by Motum et al8 in 2 unrelated b-thalassemia carriers of Filipino descent and later in patients of Indonesian and Malaysian descent.9,10 Carriers of this b-thalassemia have an unusually high Hb A2 level. The findings of Hb A2 of 7.4% and 6.4% in the father and an affected son, respectively, confirm this although they both had a1thalassemia (-a3.7/aa) (Fig 1). This deletion removes the entire b-globin gene including the 50 promoter region, which might release the competition for upstream locus control region and leads to its increased interaction with the d-globin gene in cis, so enhancing its expression.11 A study in Indonesian patients demonstrated that a compound heterozygote for the Filipino b0-thalassemia/Hb E can express different clinical severity. Among the 3 Indonesian patients examined, 1 had mild disease whereas the other 2 were affected severely and transfusion dependent. No ameliorating genetic factors could explain this phenotypic variation.12 An affected patient in a Thai family with identical b-globin genotype but with coinheritance of a1-thalassemia had a severe phenotype and was transfusion dependent. Although it seems that the a1-thalassemia allele can not ameliorate the clinical severity of this patient, the coinherited a1-thalassemia in
476
Yamsri et al
an affected child likely made the phenotype milder, and the affected fetus may be expected to have a more severe thalassemia phenotype. The marked heterogeneity of the phenotype resulting from this Filipino b0-thalassemia/ HbE in the patients so far described could be related, in addition to coinherited a-thalassemia, to the presence or absence of other ameliorating determinants such as a-globin gene triplications or other rearrangements, BCL11A or HBS1L-MYB polymorphisms.13-16 Because the Filipino b0-thalassemia mutation has not been described in non-Asian individuals, the mutation might have its origin and spread within Asian populations. Although the b-globin gene haplotype linked to this mutation in the Filipino and Malaysian patients was not available, the identification of this mutation in a Thai patient on the same 50 b-globin haplotype with that reported for the Indonesian patients, (1 2 2 2 2)12 confirms this and likely indicates the same origin of this mutation in the region. It is conceivable, therefore, that the Filipino b0-thalassemia may not be uncommon and should be included in the prenatal screening of b-thalassemia in Asian populations. We thank the staff of the Anti-Natal Care Unit and the Department of Clinical Pathology of Sappasitthiprasong Hospital, Ubon Ratchathani province, Thailand for referring cases and allowing us to study them. We also thank Ian Thomas of the Faculty of Science, Khon Kaen University, for helpful comments on the manuscript. REFERENCES
1. Weatherall DJ, Clegg JB. Inherited hemoglobin disorders: an increasing global health problem. Bull World Health Organ 2001; 79:704–12. 2. Yamsri S, Sanchaisuriya K, Fucharoen G, et al. Prevention of severe thalassemia in northeast Thailand: 16 years of experience at a single university center. Prenat Diagn 2010;30:540–6. 3. Fucharoen S, Sanchaisuriya K, Fucharoen G, et al. Interaction of hemoglobin E and several forms of alpha-thalassemia in Cambodian families. Haematologica 2003;88:1092–8.
Translational Research June 2012
4. Siriratmanawong N, Fucharoen G, Sanchaisuriya K, Ratanasiri T, Fucharoen S. Rapid and simultaneous detection of b-thalassemia and a-thalassemia 1 (SEA type) in prenatal diagnosis of complex thalassemia syndrome. Clin Biochem 2001;34:377–80. 5. Waye JS, Eng B, Hunt JA, Chui DH. Filipino beta-thalassemia due to a large deletion: Identification of the deletion endpoints and polymerase chain reaction based diagnosis. Hum Genet 1994; 94:530–2. 6. Fucharoen G, Fucharoen S, Sanchaisuriya K, et al. Frequency distribution and haplotypic heterogeneity of bE-globin gene among eight minority groups of northeast Thailand. Hum Hered 2002;53: 18–22. 7. Weatherall DJ, Clegg JB. The thalassemia syndromes. Oxford, UK: Blackwell Science, 2001. 8. Motum PI, Kearney A, Hamilton TJ, Trent RJ. Filipino beta zero thalassaemia: a high Hb A2 beta zero thalassaemia resulting from a large deletion of the 50 beta globin gene region. J Med Genet 1993;30:240–4. 9. Eng B, Chui DH, Saunderson J, Olivieri NF, Waye JS. Identification of two novel beta zero-thalassemia mutations in a filipino family: frameshift codon 67 (-TG) and a beta-globin gene deletion. Hum Mutat 1993;2:375–9. 10. Thong MK, Rudzki Z, Hall J, et al. A single, large deletion accounts for all the beta-globin gene mutations in twenty families from Sabah (north Borneo). Malaysia. Hum Mutat 1999;13:413. 11. Thein SL. Genetic modifiers of b-thalassemia. Haematologica 2005;90:649–60. 12. Setianingsih I, Williumson R, Daud D, et al. Phenotypic variability of Filipino b0-thalassemia/Hb E patients in Indonesia. Am J Hematol 1999;62:7–12. 13. Giordano PC, Bakker-Verwij M, Harteveld CL. Frequency of aglobin gene triplications and their interaction with b-thalassemia mutations. Hemoglobin 2009;33:124–31. 14. Sedgewick AE, Timofeev N, Sebastiani P, et al. BCL11A is a major Hb F quantitative trait locus in three different populations with b-hemoglobinopathies. Blood Cells Mol Dis 2008;41:255–8. 15. Nguyen TK, Joly P, Bardel C, et al. The Xmn I (G) gamma polymorphism influences hemoglobin F synthesis contrary to BCL11A and HBS1L-MYB SNPs in a cohort of 57 b-thalassemia intermedia patients. Blood Cells Mol Dis 2010;45:124–7. 16. Galameau G, Palmev CD, Sankaran VG, et al. Fine-mapping at the three loci known to affect fetal hemoglobin levels explains additional genetic variation. Nat Genet 2010;42: 1049–51.
We describe hematologic and molecular characteristics of a hitherto undescribed interaction between the Filipino deletional b0-thalassemia with Hb E and a-thalassemia in a Thai family. This study was conducted during the prenatal screening of a pregnant Thai woman and her family members. A prenatal diagnosis was performed at her second pregnancy by amniocentesis. Laboratory investigations identified that the pregnant woman was Hb E heterozygote with a1-thalassemia, whereas her husband was a double heterozygote for the Filipino deletional b0-thalassemia and a1-thalassemia. Their affected son was a patient with a previously undescribed condition of Hb E-b0-thalassemia with a1-thalassemia. Both a combined gap-polymerase chain reaction (PCR) and allele-specific PCR were used successfully in the prenatal diagnosis, which identified an affected fetus with Hb E-b0-thalassemia without a1-thalassemia. Beta globin gene haplotype analysis indicated the same origin of this Filipino b0-thalassemia in Asian populations. (Translational Research 2012;159:473–476) Abbreviations: Hb ¼ hemoglobin; PCR ¼ polymerase chain reaction
emoglobin (Hb) E-b-thalassemia is the most common form of b-thalassemia disease in northeast Thailand. The disease exhibits variable phenotypes ranging from severe transfusiondependent thalassemia major to a milder form of thalassemia intermedia, which affects the quality of life and cost of treatment in affected patients. A prenatal diagnosis is, therefore, offered to all couples at risk. Most of this prenatal diagnosis is preferably done by DNA analysis. b-Thalassemia is a heterogeneous disease caused by an absence (b0) or reduction (b1) of b-globin chain synthesis. Most cases are caused by
H
point mutations and more than 200 mutations have been documented in world populations. Deletions causing b-thalassemia are relatively rare.1 In northeast Thailand where the disease is common, 15 different mutations have been recognized and the 3.4 kb b-globin gene deletion is the only deletional mutant previously documented in the region.2 Now, we have reported a hitherto undescribed interaction of another b-thalassemia deletion with Hb E and a1-thalassemia found in a northeast Thai family during prenatal screening and examined its genetic origin by haplotype analysis.
From the Centre for Research and Development of Medical Diagnostic Laboratories, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand.
Reprint requests: Supan Fucharoen, PhD, Centre for Research and Development of Medical Diagnostic Laboratories, Khon Kaen University, 123 Mitaparb Road, Khon Kaen, Thailand 40002; e-mail: supan@ kku.ac.th.
Supported by Grant CHE-RES-RG-51 from the Office of the Higher Education Commission, a grant from the National Research University (NRU) Project, Khon Kaen University, and a grant from the Faculty of Associated Medical Sciences, Khon Kaen University, Thailand (to S.Y.)
1931-5244/$ - see front matter Ó 2012 Mosby, Inc. All rights reserved. doi:10.1016/j.trsl.2011.10.008
Submitted for publication September 4, 2011; revision submitted October 19, 2011; accepted for publication October 25, 2011.
473
474
Yamsri et al
Translational Research June 2012
AT A GLANCE COMMENTARY Yamsri S, et al. Background
Asian populations have high frequencies of thalassemias and other hemoglobinopathies. This study reported a genetic interaction of a deletional b0thalassemia with Hb E and a1-thalassemia found in a Thai family during prenatal screening and studied on the origin of this mutation in Asian populations. Translational Significance
Laboratory investigations identified an affected son as a patient with a previously undescribed condition of Hb E- Filipino deletional b0-thalassemia with a1-thalassemia and an affected fetus with Hb E-b0-thalassemia. The mutation should be included in the prenatal screening. Haplotype analysis indicated likely a single origin and spread of this mutation in Asian populations.
Fig 1. Pedigree of a Thai family at risk for b-thalassemia/Hb E disease. The arrow indicates the fetus whose sample was obtained by amniocentesis. The father was double heterozygote for b-thalassemia and a1-thalassemia, and the mother was a double Hb E/a1-thalassemia. The son had severe b-thalassemia/Hb E disease with a1-thalassemia. a- and b-globin genotypes as well as b-globin gene haplotypes associated with bA, bE, and bFIL of all family members are presented. ‘‘d’’ indicates the polymorphism within a deletion and hence could not be determined. (Color version of figure is available online.)
MATERIALS AND METHODS
Ethical approval of this study was obtained from the Institutional Review Board of Khon Kaen University, Thailand (HE522252). The study was performed on a pregnant Thai woman at her second pregnancy with a risk of having a baby with Hb E-b-thalassemia disease because she was a carrier of Hb E and her husband was a b-thalassemia carrier. Their affected son was a transfusion-dependent patient with Hb E-b-thalassemia disease (Fig 1). A prenatal diagnosis was taken at her 18th week of gestation by amniocentesis. Hematologic data were obtained using standard methods. DNA analysis. The identification of common thalassemia genes in Thailand including ao-thalassemia (SEA and THAI deletions), a1-thalassemia (3.7 and 4.2 kb deletions), Hb Constant Spring, Hb Pakse and b-thalassemia mutations are performed routinely in our laboratory using polymerase chain reaction (PCR)-based methods as described elsewhere.2-4 Identification of the Filipino b0-thalassemia deletion was performed as described by Waye et al.5 Beta-globin gene haplotype consisting of 7 polymorphic sites, including the 50 ε Hinc II site, Gg and Ag Hind III sites, jb and 30 jb Hinc II sites, b Ava II site, and 30 b Bam HI site, was determined by the PCR-restriction fragment length polymorphism method.6 Subjects.
RESULTS
The Hb profiles and globin genotypes of the family members are summarized in Fig 1. The pregnant woman
was the Hb E heterozygote with 27.7% Hb E, whereas her husband was a b-thalassemia carrier with an unusually high Hb A2 level (7.4%). Their affected son was suffering from a transfusion-dependent Hb E-b0-thalassemia disease. He had severe hypochromic microcytic anemia with Hb 6.9 g/dL, hematocrit 22.0%, mean corpuscular volume 51.9 fL, mean corpuscular hemoglobin 16.3 pg, and red blood cell distribution width 28.0%. After genetic counseling was given, prenatal diagnosis by amniocentesis was offered. Direct DNA sequencing of the amplified b-globin gene in the affected son revealed the homozygosity for Hb E mutation (GAG-AAG) at codon 26, which is inconsistent with the phenotype. This result pointed to the possibility of a DNA deletion in trans to the bE mutation. This deletion should remove the b-globin gene but leave the d-globin gene intact because of the high Hb A2 level of the patient (6.4%). We, therefore, looked for all deletions causing the high Hb A2 b-thalassemia trait in Asian populations.7 Among these, the 45 kb-Filipino b0-thalassemia deletion was also examined by PCR.5 With this analysis, we found that the father was a carrier of this Filipino b-thalassemia deletion. Direct DNA sequencing localized the similar 50 deletion breakpoint to the position -4279 relative to the messenger RNA cap site of the b-globin gene in the Thai patient, but the 30 breakpoint located in the L1 repetitive element could not be determined accurately (data not shown). A gapPCR method was used in combination with an allele-
Translational Research Volume 159, Number 6
Yamsri et al
475
Fig 2. Identifications of the Filipino b0-thalassemia deletion by gap-PCR and Hb E by allele specific PCR in prenatal diagnosis of a Thai family. (A) The locations and orientations of PCR primers used for detection of the Filipino b0-thalassemia deletion. The 482-bp fragment, generated from primers (P2 and P5) is a normal control fragment, whereas the 376-bp fragment with primer (P2 and P4) is the Filipino b0-thalassemia deletionspecific fragment. (B) Agarose gel electrophoresis. DNA analysis identified that the husband (F) carried the Filipino b0-thalassemia gene, whereas the pregnant woman (M) carried the Hb E gene. Their affected son (S) and the fetus (P) were diagnosed as having Hb E-b0-thalassemia disease.
specific PCR for the detection of a bE mutation3 in prenatal diagnosis. As shown in Fig 2, the father, the son, and the fetus were positive for this Filipino b0-thalassemia deletion, whereas the mother, the son, and the fetus, but not the father, carried the bE mutation. A routine aglobin gene analysis identified the 3.7 kb deletion a1thalassemia (-a3.7/aa) in the mother, the father, and the affected son but not the fetus. The fetus was, therefore, a compound heterozygote for the Filipino b0-thalassemia and Hb E. After these analyses, appropriate genetic counseling was provided. A subsequent haplotype analysis consisting of 7 polymorphic restriction sites in the b-globin gene cluster described in the Method section demonstrated that this Filipino b0-thalassemia in a Thai family was associated with the 50 haplotype; (1 2 2 2 2 d d). The last 2 polymorphic sites located within the deletion (b Ava II and 30 b Bam HI) could not be determined. DISCUSSION AND CONCLUSION
We have reported for the first time in the Thai population the interaction of a large deletional b0-thalassemia, namely the Filipino deletion, with Hb E and a1-thalassemia found during prenatal screening. This
Filipino b0-thalassemia deletion was reported first by Motum et al8 in 2 unrelated b-thalassemia carriers of Filipino descent and later in patients of Indonesian and Malaysian descent.9,10 Carriers of this b-thalassemia have an unusually high Hb A2 level. The findings of Hb A2 of 7.4% and 6.4% in the father and an affected son, respectively, confirm this although they both had a1thalassemia (-a3.7/aa) (Fig 1). This deletion removes the entire b-globin gene including the 50 promoter region, which might release the competition for upstream locus control region and leads to its increased interaction with the d-globin gene in cis, so enhancing its expression.11 A study in Indonesian patients demonstrated that a compound heterozygote for the Filipino b0-thalassemia/Hb E can express different clinical severity. Among the 3 Indonesian patients examined, 1 had mild disease whereas the other 2 were affected severely and transfusion dependent. No ameliorating genetic factors could explain this phenotypic variation.12 An affected patient in a Thai family with identical b-globin genotype but with coinheritance of a1-thalassemia had a severe phenotype and was transfusion dependent. Although it seems that the a1-thalassemia allele can not ameliorate the clinical severity of this patient, the coinherited a1-thalassemia in
476
Yamsri et al
an affected child likely made the phenotype milder, and the affected fetus may be expected to have a more severe thalassemia phenotype. The marked heterogeneity of the phenotype resulting from this Filipino b0-thalassemia/ HbE in the patients so far described could be related, in addition to coinherited a-thalassemia, to the presence or absence of other ameliorating determinants such as a-globin gene triplications or other rearrangements, BCL11A or HBS1L-MYB polymorphisms.13-16 Because the Filipino b0-thalassemia mutation has not been described in non-Asian individuals, the mutation might have its origin and spread within Asian populations. Although the b-globin gene haplotype linked to this mutation in the Filipino and Malaysian patients was not available, the identification of this mutation in a Thai patient on the same 50 b-globin haplotype with that reported for the Indonesian patients, (1 2 2 2 2)12 confirms this and likely indicates the same origin of this mutation in the region. It is conceivable, therefore, that the Filipino b0-thalassemia may not be uncommon and should be included in the prenatal screening of b-thalassemia in Asian populations. We thank the staff of the Anti-Natal Care Unit and the Department of Clinical Pathology of Sappasitthiprasong Hospital, Ubon Ratchathani province, Thailand for referring cases and allowing us to study them. We also thank Ian Thomas of the Faculty of Science, Khon Kaen University, for helpful comments on the manuscript. REFERENCES
1. Weatherall DJ, Clegg JB. Inherited hemoglobin disorders: an increasing global health problem. Bull World Health Organ 2001; 79:704–12. 2. Yamsri S, Sanchaisuriya K, Fucharoen G, et al. Prevention of severe thalassemia in northeast Thailand: 16 years of experience at a single university center. Prenat Diagn 2010;30:540–6. 3. Fucharoen S, Sanchaisuriya K, Fucharoen G, et al. Interaction of hemoglobin E and several forms of alpha-thalassemia in Cambodian families. Haematologica 2003;88:1092–8.
Translational Research June 2012
4. Siriratmanawong N, Fucharoen G, Sanchaisuriya K, Ratanasiri T, Fucharoen S. Rapid and simultaneous detection of b-thalassemia and a-thalassemia 1 (SEA type) in prenatal diagnosis of complex thalassemia syndrome. Clin Biochem 2001;34:377–80. 5. Waye JS, Eng B, Hunt JA, Chui DH. Filipino beta-thalassemia due to a large deletion: Identification of the deletion endpoints and polymerase chain reaction based diagnosis. Hum Genet 1994; 94:530–2. 6. Fucharoen G, Fucharoen S, Sanchaisuriya K, et al. Frequency distribution and haplotypic heterogeneity of bE-globin gene among eight minority groups of northeast Thailand. Hum Hered 2002;53: 18–22. 7. Weatherall DJ, Clegg JB. The thalassemia syndromes. Oxford, UK: Blackwell Science, 2001. 8. Motum PI, Kearney A, Hamilton TJ, Trent RJ. Filipino beta zero thalassaemia: a high Hb A2 beta zero thalassaemia resulting from a large deletion of the 50 beta globin gene region. J Med Genet 1993;30:240–4. 9. Eng B, Chui DH, Saunderson J, Olivieri NF, Waye JS. Identification of two novel beta zero-thalassemia mutations in a filipino family: frameshift codon 67 (-TG) and a beta-globin gene deletion. Hum Mutat 1993;2:375–9. 10. Thong MK, Rudzki Z, Hall J, et al. A single, large deletion accounts for all the beta-globin gene mutations in twenty families from Sabah (north Borneo). Malaysia. Hum Mutat 1999;13:413. 11. Thein SL. Genetic modifiers of b-thalassemia. Haematologica 2005;90:649–60. 12. Setianingsih I, Williumson R, Daud D, et al. Phenotypic variability of Filipino b0-thalassemia/Hb E patients in Indonesia. Am J Hematol 1999;62:7–12. 13. Giordano PC, Bakker-Verwij M, Harteveld CL. Frequency of aglobin gene triplications and their interaction with b-thalassemia mutations. Hemoglobin 2009;33:124–31. 14. Sedgewick AE, Timofeev N, Sebastiani P, et al. BCL11A is a major Hb F quantitative trait locus in three different populations with b-hemoglobinopathies. Blood Cells Mol Dis 2008;41:255–8. 15. Nguyen TK, Joly P, Bardel C, et al. The Xmn I (G) gamma polymorphism influences hemoglobin F synthesis contrary to BCL11A and HBS1L-MYB SNPs in a cohort of 57 b-thalassemia intermedia patients. Blood Cells Mol Dis 2010;45:124–7. 16. Galameau G, Palmev CD, Sankaran VG, et al. Fine-mapping at the three loci known to affect fetal hemoglobin levels explains additional genetic variation. Nat Genet 2010;42: 1049–51.