Blood Cells, Molecules, and Diseases 36 (2006) 255 – 258
www.elsevier.com/locate/ybcmd
Prevalence of −α 3.7 and ααα anti3.7 alleles in sickle cell trait and
β-thalassemia patients in Mexico
María Paulina Nava a,b , Bertha Ibarra a,b , María Teresa Magaña
María de la Luz Chávez a , F. Javier Perea a,b,⁎
a
a,b
,
División de Genética, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Sierra Mojada No. 800,
Colonia Independencia, CP 44340, Guadalajara, Jalisco, México
b
Doctorado en Genética Humana, Universidad de Guadalajara, México
Submitted 25 November 2005; revised 7 December 2005
Available online 7 February 2006
(Communicated by E. Beutler, M.D., 7 December 2005)
Abstract
The aim of this study was to determine the frequency of α-globin gene mutations in three groups of Mexican unrelated individuals. The first
two groups were normal and sickle cell trait individuals from the Costa Chica region, a place with a 12.8% frequency of HbS carriers, and the third
group comprised of Mexican mestizo patients with β-thalassemia. We searched for −α3.7 and −α4.2 α+-thalassemia deletion alleles, as well as the
αααanti3.7 triplication through long-gap PCR. The alleles −α3.7 and αααanti3.7 were found in the heterozygote state only; 19% of the normal
subjects had the −α3.7 allele, and 2% showed the αααanti3.7 allele. In individuals with the sickle cell trait, 17% had the −α3.7 deletion, and the
αααanti3.7 triplication was observed in 3% of these individuals. We revealed that 16% of the subjects with β-thalassemia showed the −α3.7 deletion
and 28% the αααanti3.7 triplication. The −α4.2 deletion was not detected in any individual. The frequency of the −α3.7 allele was roughly the same
in the three groups studied; this can be explained by the fact that the three groups have common genes from Africa and the Mediterranean, where a
high prevalence of α+-thalassemia has been observed. To our knowledge, the frequency of αααanti3.7 triplication observed in the Mexican βthalassemia patients is the highest reported. As the −α3.7 and αααanti3.7 alleles are very common in our selected populations, we believe that there
is a need to investigate systematically the α-globin gene mutations in all hemoglobinopathies in the Mexican population.
© 2006 Elsevier Inc. All rights reserved.
Keywords: −α3.7 deletion; αααanti3.7 triplication; β-Thalassemia; Sickle cell trait; Mexico
Introduction
The most common α+-thalassemia deletional alleles are
−α3.7 and −α4.2. The allele −α3.7 has been observed all over the
world, with higher frequencies in some African populations,
India, Nepal, Sardinia and many other Mediterranean populations, China and other East Asian countries. The −α4.2 deletion
is present in Indian populations, Melanesia, Thailand and some
other Southeast Asian countries [1,2]. The αααanti3.7 allele
⁎ Corresponding author. División de Genética, Centro de Investigación
Biomédica de Occidente, Instituto Mexicano del Seguro Social, Sierra Mojada
No. 800, Colonia Independencia, CP 44340, Guadalajara, Jalisco, México. Fax:
+52 36 18 17 56.
E-mail address: [email protected] (F.J. Perea).
1079-9796/$ - see front matter © 2006 Elsevier Inc. All rights reserved.
doi:10.1016/j.bcmd.2005.12.003
triplication is present at low frequency in all the populations
investigated [3].
The coexistence of α+-thalassemia with other hemoglobinopathies such as β-thalassemia and sickle cell anemia has been
well documented [4–7]. The presence of β-thalassemia and
sickle cell trait in Mexico has been investigated, with the
frequency of β-thalassemia in hospital populations ranging
from 0.08% [8] to 0.15% [9], and, for HbS heterozygotes, the
range is 0.07% [9] to 0.35% [8]. In patients with suspected
hemoglobinopathy, the frequencies are 73% for β-thalassemia
and 22% for sickle cell trait [9]. A study in Mexican individuals
with African roots showed a frequency of 12.8% of HbS
heterozygotes, with a predominance of the Bantu haplotype
[10].
α+-Thalassemia has not been well investigated in individuals
with β-thalassemia and HbS. The frequency of −α3.7 type I
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M.P. Nava et al. / Blood Cells, Molecules, and Diseases 36 (2006) 255–258
allele carriers in the Mexican population selected by the
presence of microcytosis is 11% [11]. Here, we describe the
frequency of α + -thalassemia deletions in three Mexican
populations: afromestizo normal and sickle cell trait individuals
and mestizo β-thalassemic individuals.
Material and methods
α+-Thalassemia deletion alleles (−α3.7 and −α4.2) and the
αααanti3.7 triplication allele were investigated in DNA samples
from unrelated individuals distributed in three groups: M-AA,
which included 42 DNA samples of Mexican afromestizo
normal individuals from the Costa Chica region, a population
located in the west coast of Mexico at the Guerrero and Oaxaca
states; M-AS, comprising of 35 individuals with sickle cell trait
who had the same demographics as the first group; and MBThal, which included 32 DNA samples from Mexican mestizo
patients with β-thalassemia.
The alleles −α3.7, −α4.2 and αααanti3.7 were identified by
multiplex long polymerase chain reaction (PCR) amplification
with few modifications [12]. The primer sequences have been
previously described [13,14]. After 10 min at 95°C, the samples
were subjected to 30 cycles of amplification: the first 10 cycles
of 1.5 min denaturation at 96°C, 45 s annealing at 63°C and 5
min extension at 72°C; for the next 20 cycles, the extension time
was increased by 20 s after each cycle. Amplification was done
in a 25 μl reaction with 1× enhancer solution and 2.5 U/μl Taq
polymerase Platinium (Invitrogen).
Results
The allelic and carrier frequencies for the −α3.7 deletion
and αααanti3.7 triplication observed in the three studied groups
are shown in Table 1. The allelic frequency data for −α3.7,
ααα anti3.7 and −α 4.2 in normal individuals from other
populations are presented in Table 2. The allelic frequency
data from −α3.7, αααanti3.7 and −α4.2 in sickle cell trait and β-
Table 1
Allele and carrier frequency of deletional α+-thalassemia in the three Mexican
studied groups
M-AA (n = 42)
Allele
−α3.7
αααanti3.7
αα
Genotype
−α3.7/αα (%)
αααanti3.7/αα (%)
αα/αα (%)
0.09
0.01
0.90
19
2
79
M-AS (n = 35)
0.08
0.01
0.91
17
3
80
M-BThal (n = 32)
0.08
0.14
0.78
16
28
56
For the −α3.7 allele: there were differences not significant between the three
studied groups (P N 0.05). The allelic distributions were similar for all groups.
For the αααanti3.7 allele: a difference not significant between AA and AS
(P N 0.05) was observed, but a difference significant between β-thalassemia and
the other two groups was found (P b 0.05). The allelic distribution was similar
only for the AA and AS individuals, and it was different for the β-thalassemia
patients.
thalassemia trait subjects from other populations are shown in
Table 3.
The −α4.2 deletion was not detected in any individual. Both
the −α3.7 and αααanti3.7 alleles were found only in heterozygote
state. The −α3.7 allele frequency was similar in the three studied
groups; however, the αααanti3.7 allele frequency was similar
only between M-AA and M-AS subjects as there was a
statistically significant difference between both groups and the
M-BThal group (Table 1).
Discussion
−α3.7 allele
Normal individuals
The −α3.7 allele has been observed in almost every ethnic
group studied, although the allelic frequency in normal
individuals is variable, as high as 0.360 in Congo [15] and as
low as 0.006 in China [25] (Table 2). In African populations, the
distribution correlates with the pattern of malarial endemicity
[15]. In this study, we found that the allele frequency in M-AA
individuals is 0.090, a value not significantly different from the
Central African Republic, South African blacks, Namibian,
Algerian, Cypriote and Sri Lankan populations (Table 2). The
Mexican population studied is afromestizo which explains the
high frequency of α+-thalassemia [10].
Sickle cell trait
The frequencies of the −α3.7 allele in individuals with sickle
cell trait ranged from 0.44 in Congolese [15] to 0.080 in the
Mexican population, which showed a significant difference
from other studied populations (Table 3). The allele frequency
in Mexican AS individuals is not significantly different from the
Mexican normal ones (0.090), data similar to that observed in
individuals from other countries like Congo [15] and Nigeria
[18].
It is interesting to note that, in the studied populations, the
−α3.7 allele is more frequent than the βS one; for instance, in
Congo and Nigeria, the allelic frequency of βS ranges from 0.04
to 0.06, whereas the frequencies of the −α3.7 allele are 0.44 in
Congo [15] and 0.29 in Nigeria [18]. Similar results are
observed in Jamaica and Brasil [32–34]. In our study, the
afromestizo Mexican had an allelic frequency for βS gene of
0.06 [10], whereas the allelic frequencies of −α3.7 for the M-AA
and M-AS groups were 0.09 and 0.08 respectively (Table 1).
β-thalassemia
The distribution of −α3.7 allele frequencies in individuals
with β-thalassemia trait is variable; in our M-BThal group, it
was 0.080 and showed no significant difference from the Indian
population [4,23] (Table 3). These frequencies are significantly
different from the low levels observed in Chinese and
Argentinean populations [30,31].
It is noteworthy that the frequency of the −α3.7 allele was
similar in the three Mexican populations studied, even though
the β-thalassemia subjects were Mexican mestizos with a
Mediterranean component and the AA and AS were Mexican
M.P. Nava et al. / Blood Cells, Molecules, and Diseases 36 (2006) 255–258
257
Table 2
Allele frequency of −α3.7, αααanti3.7 and −α4.2 in normal subjects obtained in this work and other populations
Population
Number of chromosomes studied
−α3.7
αααanti3.7
−α4.2
Reference
Normal individuals
Congolese
United Arab Emirates
Togolese
Nigerian
Kenyan
Central African Republic
South African blacks
M-AA
Cypriote
Sri Lanka
Namibian
Algerian
Portuguese
Indian
Philippines
Chinese
Polynesian Samoans
124
836
342
154
114
14
306
84
990
1240
202
586
200
380
5908
500
120
0.360
0.284
0.266
0.240
0.220
0.140
0.110
0.090
0.076
0.065
0.060
0.050
0.035
0.021
0.008
0.006
0.000
*
*
0.011
*
0.008
*
0.01
0.01
0.01
*
0.01
*
0.020
0.000
*
0.008
0.058
*
0.0072
*
*
*
*
*
0.000
*
0.011
*
*
0.015
0.000
0.0001
*
0.000
[15]
[16]
[17]
[18]
[19]
[15]
[15]
This work
[20]
[21]
[15]
[15]
[22]
[23]
[24]
[25]
[26]
*Not studied.
with African ancestries. This can be explained because the three
groups have common genes from populations with a high
prevalence of α+-thalassemia.
αααanti3.7 allele
Normal individuals
The frequencies of αααanti3.7 allele range from 0.008 to
0.058 [15,17,19,20,25,26] (Table 2). M-AA individuals
showed an allelic frequency of 0.01. It is interesting to note
that in Native Americans the only α-globin gene alteration
reported to date is the αααanti3.7. For instance, in South
American Indians, the α-globin gene triplication was observed
Table 3
Allele frequency of −α3.7, αααanti3.7 and −α4.2 in Sickle cell trait and βthalassemia subjects obtained in this work and other populations
Number of
chromosomes
studied
−α3.7
208
60
48
126
0.440
0.350
0.290
0.277
*
0.000
*
0.015
*
0.150
*
0.007
[15]
[27]
[18]
[28]
70
0.080
0.010
0.00
This
work
β-thalassemia trait
Indian
M-Bthal
196
64
0.091
0.080
0.015
0.140
*
0.000
Indian
Chinese
Chinese
Argentinean
366
80
800
218
0.060
0.000
0.021
0.004
0.010
0.037
*
0.009
0.000
0.000
0.011
*
[4]
This
work
[23]
[29]
[30]
[31]
Population
Sickle cell trait
Congolese
Malaysian
Nigerian
Black sub-Saharan
or Caribbean
M-AS
*Not studied.
αααanti3.7
−α4.2
Reference
at frequencies of 0.022 and 0.047; and deletions were not
detected [35].
Sickle cell trait
To our knowledge, there is only one report about the allelic
frequency of the αααanti3.7 allele in individuals with sickle cell
trait. That study showed a frequency of 0.015 in black subSaharan or Caribbean populations living in Spain [28] (Table 3).
In our study, both M-AA and M-AS showed an allelic
frequency of 0.01. There are no reports about the allele
frequency in AS individuals in African populations, although in
SS patients frequencies of 0.010 in Senegalese and 0.005 in
Nigerian populations have been reported [15]. The low
frequencies of αααanti3.7 allele observed in both AS Mexican
and SS African individuals suggest that this allele has the same
origin and was introduced to our country during the slave trade.
The common origin can be supported with a further study of the
α-globin gene cluster haplotypes.
β-thalassemia
In the studied populations with β-thalassemia trait, the
frequency of the ααα anti3.7 allele has a heterogeneous
distribution with the highest frequency observed in our
population (0.140). This frequency is statistically significant
different with respect to the Indian, Chinese and Argentineans
[23,29,31] (Table 3). In the Spanish population, the αααanti3.7
allele was found with a 0.028 allele frequency [36]. The high
frequency of the triplication α-globin allele in our β-thalassemia
patients may be due to these patients being sent to our laboratory
because of their clinical severity, with severely affected subjects
more likely to have the triplicated α-gene allele.
This paper represent the first study of α+-thalassemia in
Mexican afromestizo and β-thalassemia patients, thus these
data demonstrate the need for systematic investigation of αglobin gene mutations in all cases of hemoglobinopathies in the
Mexican population.
258
M.P. Nava et al. / Blood Cells, Molecules, and Diseases 36 (2006) 255–258
Acknowledgments
This work was partially supported by a grant from Sistema
de Investigación José Ma. Morelos, Mexico; CONACYTREGIONAL No. 19990302015.
References
[1] T.H.J. Huisman, M.F.H. Carver, E. Baysal, A Syllabus of Thalassemia
Mutations, The Sickle Cell Anemia Foundation, G.A. Augusta, 1997.
[2] D.J. Weatherall, J.B. Clegg, D.R. Higgs, W.G. Wood, The hemoglobinopathies, in: C.R. Scriver, A.L. Beaudet, D. Valle, W.S. Sly (Eds.), Eighth
ed., The Metabolic and Molecular Basis of Inherited Disease, vol. III,
McGraw Hill, 2001, pp. 4571–4636.
[3] L.F. Bernini, C.L. Harteveld, Alpha-thalassaemia, in: G.P. Rodgers (Ed.),
Bailliere's Clinical Haematology International Practice and Research:
Sickle Cell Disease and Thalassaemia, vol. 11, no. 1, Bailliere Tindall,
London, 1998, pp. 53–90.
[4] I. Panigrahi, P.H. Rafeeq Ahmed, V.P. Choundhry, R. Saxena, High
frequency of deletional α-thalassemia in β-thalassemia trait: implications
for genetic counseling, Am. J. Hematol. 76 (2004) 297–299.
[5] E. Kanavakis, J. Traeger-Synodinos, S. Lafioniatis, C. Lazaporoulou, A
rare example that coinheritance of a severe form of beta-thalassemia and
alpha thalassemia interact in a “synergistic” manner to balance the
phenotype of classic thalassemic syndromes, Blood Cells Mol. Diseases 32
(2004) 319–324.
[6] W.S. Wong, A.Y. Chan, S.F. Yip, E.S. Ma, Thalassemia intermedia due to
co-inheritance of beta(0)/beta(+)-thalassemia and (- - SEA) alphathalassemia/Hb Westmead [alpha 122 (H 5) His N Gln (alpha2) in a
Chinese family, Hemoglobin 2 (2004) 151–156.
[7] Z. He, J.E. Russell, Antisickling effects of an endogenous human alphalike globin, Nat. Med. 4 (2004) 365–367.
[8] B. Ibarra, G. Vaca, E. Franco-Gamboa, D. García-Cruz, E. de la Mora, L.P.
Castro-Felix, L.C. Martínez-Orozco, J.M. Cantú, J.B. Wilson, H. Lam,
Abnormal hemoglobins in northwestern Mexico, Acta Anthropog. 6
(1982) 217–223.
[9] G. Ruiz-Reyes, Hemoglobinas anormales y talasemias en la República
Mexicana, Rev. Invest. Clin. 50 (1998) 163–170.
[10] M.T. Magaña, Z. Ongay, J. Tagle, G. Bentura, J.G. Cobian, F.J. Perea, M.
Casas-Castañeda, Y.J. Sánchez-López, B. Ibarra, Analysis of beta S and
beta A genes in a Mexican population with African roots, Blood Cell Mol.
Dis. 28 (2002) 121–126.
[11] M. Casas-Castañeda, I. Hernandez-Lugo, O. Torres, H. Barajas, S. Cibrian,
G. Zamudio, A.R. Villalobos-Arambula, R.M. Hermosillo-Bañuelos, F.J.
Perea, B. Ibarra, Alpha-thalassemia in a selected population of Mexico,
Rev. Invest. Clin. 50 (1998) 395–398.
[12] R.V. Shaji, A. Srivastava, M. Chandy, R. Krishnamoorthy, A single tube
multiplex PCR method to detect the common α+ thalassemia alleles, Blood
195 (2000) 1879–1880.
[13] N.S. Smetanina, T.H. Huisman, Detection of alpha-thalassaemia-2 (3.7
kb) anti corresponding triplication (alpha) (alpha) (alpha) (anti3.7 kb)
by PCR: an improved technical change, Am. J. Hematol. 53 (1996)
202–203.
[14] E. Baysal, T.H. Husiman, Detection of common deletional alphathalassaemia-2 determinants by PCR, Am. J. Hematol. 88 (1994)
300–306.
[15] R. Mouélé, O. Pambous, J. Feingold, F. Galactéros, α-Thalassemia in
Bantu Population from Congo-Brazzaville: its interaction with sickle cell
anemia, Hum. Hered. 50 (2000) 118–125.
[16] S. El-Kalla, E. Baysal, Alpha-thalassemia in the United Arab Emirates,
Acta Haematol. 100 (1998) 49–53.
[17] A.Y. Segbena, I. Kueviakoe, A.K. Messie, I.G. Napo-Koura, A. Vovor, M.
David, Hemoglobin anomalies at the university hospital center in Lome,
Togo. Hemoglobin 25 (2001) 273–283.
[18] A.G. Falusi, G.J. Esan, H. Ayyub, D.R. Higgs, Alpha-thalassaemia in
Nigeria: its interaction with sickle-cell disease, Eur. J. Haematol. 38 (1987)
370–375.
[19] P.J. Ojwang, T. Ogada, J.M. Gonzalez-Redondo, A. Kutlar, F. Kutlar, T.H.
Huisman, Beta S-haplotypes and alpha-thalassemia along the coast belt of
Kenya, East Afr. Med. J. 66 (1989) 377–380.
[20] K. Kyriacou, A. Kyrri, E. Kalogirou, P. Vasiliades, M. Angastiniotis, P.A.
Ioannou, M. Kleanthous, Hb Bart's levels in cord blood and alphathalassemia mutations in Cyprus, Hemoglobin 24 (2000) 171–180.
[21] C.A. Fisher, A. Premawardhena, S. de Silva, G. Perera, S. Rajapaksa, N.A.
Olivieri, J.M. Old, D.J. Weatherall, the Sri Lanka thalassemia group, The
molecular basis for the thalassemias in Sri Lanka, Br. J. Haematol. 121
(2003) 662–671.
[22] M.J. Peres, L. Romao, H. Carreiro, I. Picanco, L. Batalha, H.A. Magalhaes,
M.C. Martins, J. Lavinha, Molecular basis of alpha-thalassemia in
Portugal, Hemoglobin 19 (1995) 252–343.
[23] S. Agarwal, S. Sarwai, N. Nigam, P. Singhal, Rapid detection of alpha+
thalassaemia deletion and alpha-globin gene triplication by Gap-PCR in
Indian subjects, Med. Trop. 62 (2002) 51–54.
[24] T.M. Ko, H.L. Hwa, C.W. Liu, S.F. Li, J.Y. Chu, Y.P. Cheung, Prevalence
study and molecular characterization of alpha-thalassemia in Filipinos,
Ann. Hematol. 78 (1999) 355–357.
[25] J. Chen, W. Liu, M. Chen, Molecular diagnosis of beta-thalassemia
intermedia, Hum. Hered. 48 (1998) 121–125.
[26] L.E. Lie-Injo, I.G. Pawson, A. Solai, High frequency of triplicated αglobin loci and absence or low frequency of α thalassemia in Polynesian
Samoans, Hum. Genet. 70 (1985) 116–118.
[27] L.E. Lie-Injo, K. Hassan, K.S.K. Joishy, M.L. Lim, Sickle cell anemia
associated with α-thalassemia in Malaysian Indians, Am. J. Hematol. 22
(1986) 265–274.
[28] F.A. Gonzalez, C. Blázquez, P. Ropero, O. Briceño, C. Alaez, M. Polo, C.
Benavente, M. Mateo, A. Peña, A. Villegas, Association of hemoglobinopathies S and alpha thalassemia. Study of 45 patients, Med. Clin.
(Barcelona) 124 (2005) 726–729.
[29] S.K. Ma, W.Y. Au, A.Y. Chan, L.C. Chan, Clinical phenotype of triplicated
alpha-globin genes and heterozygosity for beta0-thalassemia in Chinese
subjects, Int. J. Mol. Med. 8 (2001) 171–175.
[30] J. Han, R. Zeng, B. Hu, The prevalence of beta-thalassemia heterozygotes
compound alpha-thalassemia in Guangdong district, Zhonghua Xueyexue
Zazhi 22 (2001) 514–516.
[31] I.M. Bragos, N.I. Noguera, M.P. Raviola, A.C. Milani, Triplication
(/αααanti3.7) or deletion (/−α3.7) association in Argentinean β-thalassemic
carriers, Ann. Hematol. 11 (2003) 696–698.
[32] I. Menezes Lyra, M. Souza Goncalves, J.A. Pellegrinei Braga, M. de
Fatima Gesteira, M. Helena Carvalho, S. Teresina Olalla Saad, M. Stella
Figueiredo, F. Ferreira Costa, Clinical, hematological, and molecular
characterization of sickle cell anemia pediatric patients from two different
cities in Brasil, Cad. Saude Publica 21 (2005) 1287–1290.
[33] N.A. Hanchard, I. Hambleton, R.M. Harding, C.A. McKenzie, The
frequency of the sickle allele in Jamaica has no declined over the last 22
years, Br. J. Haematol. 130 (2005) 939–942.
[34] G.R. Serjeant, B.E. Serjeant, M. Forbes, et al., Haemoglobin gene
frequencies in the Jamaican population: a study in 100,000 newborns, Br.
J. Haematol. 64 (1986) 253–262.
[35] M.A. Zago, E.J. Melo Santos, J.B. Clegg, J.F. Guerreiro, J.J. Martinson, J.
Norwich, M.S. Figueiredo, Alpha-globin gene haplotypes in South
American Indians, Hum. Biol. 67 (1995) 535–546.
[36] A. Villegas, P. Ropero, F.A. Gonzalez, E. Anguita, D. Espinós, The
thalassemia syndromes: molecular characterization in the Spanish
population, Hemoglobin 25 (2001) 273–283.