A Pilot Genome-Wide Association Study in Postmenopausal Mexican-Mestizo Women Implicates the RMND1/CCDC170 Locus Is Associated with Bone Mineral Density.

To identify genetic variants influencing bone mineral density (BMD) in the Mexican-Mestizo population, we performed a GWAS for femoral neck (FN) and lumbar spine (LS) in Mexican-Mestizo postmenopausal women. In the discovery sample, 300,000 SNPs were genotyped in a cohort of 411 postmenopausal women and seven SNPs were analyzed in the replication cohort (n = 420). The combined results of a meta-analysis from the discovery and replication samples identified two loci, RMND1 (rs6904364, P = 2.77 × 10-4) and CCDC170 (rs17081341, P = 1.62 × 10-5), associated with FN BMD. We also compared our results with those of the Genetic Factors for Osteoporosis (GEFOS) Consortium meta-analysis. The comparison revealed two loci previously reported in the GEFOS meta-analysis: SOX6 (rs7128738) and PKDCC (rs11887431) associated with FN and LS BMD, respectively, in our study population. Interestingly, rs17081341 rare in Caucasians (minor allele frequency < 0.03) was found in high frequency in our population, which suggests that this association could be specific to non-Caucasian populations. In conclusion, the first pilot Mexican GWA study of BMD confirmed previously identified loci and also demonstrated the importance of studying variability in diverse populations and/or specific populations.

Factores de riesgo para osteoporosis en mujeres posmenopáusicas de Guadalajara, Jalisco / Risk factors for osteoporosis in postmenopausal women from Guadalajara, Jalisco

Objetivo. Conocer los factores de riesgo y la frecuencia de osteoporosis (OP) en mujeres posmenopáusicas. Material y métodos. Se midió la densidad mineral ósea de columna en 513 mujeres posmenopáusicas de un hospital de Guadalajara, Jalisco durante 2007-2008. Los puntos de corte de las variables asociadas se obtuvieron por curvas ROC y la razón de momios (RM) mediante regresión logística. Resultados. El 25.2% (IC95% 21.44-28.96) de las mujeres mostró OP. Las variables asociadas a OP y sus puntos de corte fueron: edad >60 años, peso <71kg, talla <1.54m e IMC <29.2kg/m², con RM mayores a 3.19 (p<0.0001). Conclusiones. Se recomienda establecer puntos de corte para estimar factores de riesgo para OP con mayor precisión en cada población.

Objective. To know risk factors and the frequency of osteoporosis (OP) in postmenopausal women. Materials and methods. Bone mineral density was measured in lumbar spine of 513 postmenopausal women from a hospital of Guadalajara, Jalisco during 2007-2008. The cutoff points of the associated variables were obtained by ROC curves and odds ratio (OR) by logistic regression. Results. The 25.2% (95%CI 21.44-28.96) of the women was OP. The variables associated with OP and cutoff points were age >60 years, weight <71kg, height <1.54m and BMI <29.2kg/m², with OR greater than 3.19 (p<0.0001). Conclusions. It is recommended setting cutoff points to estimate risk factors for OP more accurately in each population.

[Risk factors for osteoporosis in postmenopausal women from Guadalajara, Jalisco]. / Factores de riesgo para osteoporosis en mujeres posmenopáusicas de Guadalajara, Jalisco.

OBJECTIVE: To know risk factors and the frequency of osteoporosis (OP) in postmenopausal women. MATERIALS AND METHODS: Bone mineral density was measured in lumbar spine of 513 postmenopausal women from a hospital of Guadalajara, Jalisco during 2007-2008. The cutoff points of the associated variables were obtained by ROC curves and odds ratio (OR) by logistic regression. RESULTS: The 25.2% (95%CI 21.44-28.96) of the women was OP. The variables associated with OP and cutoff points were age >60 years, weight <71 kg, height <1.54 m and BMI <29.2 kg/m(2), with OR greater than 3.19 (p<0.0001). CONCLUSIONS: It is recommended setting cutoff points to estimate risk factors for OP more accurately in each population.

Hb S [ß6(A3)Glu→Val, GAG>GTG] in Mexican Mestizos: frequency and analysis of the 5' ß-globin haplotype.

Between 1978 and 2009, we studied 1,863 Mexican Mestizo patients with clinical data compatible with a hemoglobinopathy. Of these patients, 382 had some hemoglobin (Hb) abnormality (20.5%), 128 had a sickle cell hemoglobinopathy, representing a general frequency of 6.9%, which is similar to the percentage observed in previous studies on Mexican Mestizos. We analyzed the 5' ß-globin haplotype (5'Hp) in 79 unrelated ß(S) chromosomes (26 ß(S)/ß(S), 14 ß(S)/ß(Thal), nine ß(S)/ß(A) and four ß(S)/ß(D)), and four haplotypes were observed: 72.2% CAR 24.1% Benin, 2.5% Senegal and 1.2% Cameroon; the last two are reported for first time in Mexico. In some Latin American populations such as Brazil, the Bantu haplotype predominates, while in others such as Jamaica, the Benin haplotype is the most frequent, showing heterogeneity of African genes as a consequence of different regions involved in the slave trade.

Analysis of linkage disequilibrium between the 5' and 3' haplotypes of the beta-globin gene cluster in Mexican afromestizos.

Analysis of the 5' and 3' haplotypes (Hps) of the beta-globin gene cluster was performed in 110 beta(A) chromosomes from unrelated Mexican afromestizo individuals in order to determine Hardy-Weinberg equilibrium, allelic frequencies, linkage disequilibrium (LD) and association between the 5' and 3' haplotypes. All sites were found to be in Hardy-Weinberg equilibrium (p>0.05). In the whole beta-cluster, only 12.87% of the pairs of loci exhibited significant LD (22/171) (r(2)>0.33). Within the 5'Hp, three pairs of loci were associated (epsilonHincII/(G)gammaHindIII, epsilonHincII/3'psibetaHincII and (G)gammaHindIII/3'psibetaHincII). In the 3'Hp, 19 pairs of loci showed significant LD and were distributed mostly among the -551, -340, Exon1nt6 and IVS2nt16 polymorphisms. The absence of pairs of loci significantly linked between both 5' and 3' Hps is noteworthy. The allelic combinations of the 40 studied polymorphisms (5 sites in the 5' Hp and 35 sites in the 3' Hp) displayed 69 distinct haplotypes, 22 of them belonging to group A, 27 to B, 18 to C and 2 to D, which denoted the great heterogeneity of our population. Further, 1a7A1, 1a7B1 and 1a1C1 were the most common sequences with 8, 9 and 9 chromosomes each. Association analysis between both 5' and 3' Hps revealed strong coherence with the proposed evolutionary histories for the beta-globin gene polymorphisms. 5'Hp1 (+----), which is considered to be an ancestral haplotype, was the most frequent haplotype found in our population and was linked to 24 different sequences in the 3'Hp, demonstrating great heterogeneity. A similar result was found in the 3' Hps, where older alleles (a17A1 and a7B1) were linked to a higher number of 5'Hps. This is the first time that an analysis of association among the 5' and 3' haplotypes and the LD has been performed with 40 polymorphisms distributed in the beta-globin gene cluster in the Mexican afromestizo population. The poor LD observed between and within the 5' and 3' Hps show that this region is very prone to recombination events.

Analysis of the SLC4A1 gene in three Mexican patients with hereditary spherocytosis: Report of a novel mutation.

We analyzed the SLC4A1 gene in three Mexican patients with Hereditary Spherocytosis (HS). The promoter and all 20 exons were investigated through heteroduplex analysis and DNA sequencing. No DNA changes were detected in one of the three patients. Two well-known polymorphisms, Memphis I and the Diego-a blood group, were detected in another one. In the third, the HS phenotype could be explained by the novel 1885_1888dupCCGG mutation found in heterozygosis. This frameshift mutation is predicted to result in a truncated and unstable protein lacking normal functions.

Analysis of the SLC4A1 gene in three Mexican patients with hereditary spherocytosis: report of a novel mutation

We analyzed the SLC4A1 gene in three Mexican patients with Hereditary Spherocytosis (HS). The promoter and all 20 exons were investigated through heteroduplex analysis and DNA sequencing. No DNA changes were detected in one of the three patients. Two well-known polymorphisms, Memphis I and the Diego-a blood group, were detected in another one. In the third, the HS phenotype could be explained by the novel 1885_1888dupCCGG mutation found in heterozygosis. This frameshift mutation is predicted to result in a truncated and unstable protein lacking normal functions.

HB Fannin-Lubbock-I with a single GGC>GAC mutation at beta119(GH2)Gly-->Asp in a homozygous Mexican patient.

We studied a fast-moving, abnormal hemoglobin (Hb) identified as Fannin-Lubbock-I [beta119(GH2)Gly-->Asp] in a homozygous Mexican girl. To date, homozygosity for the Hb Fannin-Lubbock-I variant has not been reported. Her parents and five other relatives were heterozygotes. The 5' beta-globin haplotype analysis showed that the mutation was associated with haplotype 2 [- + + - +]for the epsilon, (G)gamma, (A)gamma, 5' and 3 'psibeta-globin sites, and also segregated with the TGTTC haplotype, which was constructed with five polymorphic sites of the beta-globin gene [exon 1-nucleotide (nt) 6 (C>T) and IVS-II-16 (C>G), IVS-II-46 (T>C), IVS-II-74 (G>T), and IVS-II-81 (C>T). In 1994, a variant with an additional mutation at codon 111 [beta111(G13)Val-->Leu] was described in five Spanish families. This variant was termed Hb Fannin-Lubbock-II, and the question of the existence of Hb Fannin-Lubbock-I arose. However, based on our findings, we were able to confirm the existence of Hb Fannin-Lubbock-I and propose that this mutation has a different origin from the one identified in Spanish families.

Diversity of the 5' beta-globin haplotype of four beta-thalassemia mutations in the Mexican population.

beta-Globin haplotypes have been used to investigate the origin and spread of beta-globin mutations such as Hb S [beta 6(A3)Glu-->Val, GAG>GTG], Hb E [beta 26(B8)Glu-->Lys, GAG>AAG], and beta-thalassemia (beta-thal). Molecular analyses revealed the presence of 17 beta-thal mutations in the Mexican population; the most frequent of these are the nonsense codon 39 (C>T), IVS-I-1 (G>A), IVS-I-110 (G>A), and -28 (A>C). To improve our knowledge about their origin, we analyzed the 5' haplotypes by restriction fragment length polymorphism. The codon 39 mutation (n = 17) was observed with five 5' haplotypes: 1 (59%), 2 (23%), and 4, 6, and 9 (6% each). The IVS-I-1 mutation (n = 15) was found with five 5' haplotypes: 1 (73.6%), 2, 3, 5, and 11 (6.6% each), whereas the IVS-I-110 (n = 9) and -28 mutations (n = 1) were only associated with haplotype 1. In the population studied, the codon 39 and IVS-I-1 mutations show a multicentric origin, whereas the IVS-I-110 and -28 mutations have an apparent single origin. Further investigation is required for the analysis of the polymorphisms surrounding the beta-globin gene.

Types and frequencies of hemoglobin disorders in the pacific coast of four states of Mexico.

INTRODUCTION: Hemoglobin disorders are classified into three main groups: structural variants, thalassemias (thal) and hereditary persistence of fetal hemoglobin (HPFH). OBJECTIVE. This study describes the types and frequencies of hemoglobinopathies from four states of the Pacific coast of Mexico (Jalisco, Colima, Nayarit and Michoacan). MATERIAL AND METHODS. We studied 1513 Mexican individuals by hematological and biochemical analysis following the conventional methods, DNA analysis was carried out in abnormal samples. RESULTS. The frequency of hemoglobinopathies was 1.258%. Structural variants were the most common type (0.726%), with seven carriers (0.462%) and one homozygote (0.066%) for Hb S, and three heterozygotes of the following hemoglobins: C (beta6 Glu-->Lys), Fannin-Lubbock I (beta119 Gly-->Asp) and Colima (beta49 Ser-->Cys), with a frequency of 0.066% each. We observed a frequency of 0.466% for the thalassemia group, with one homozygote for the alpha3.7 (-thal) allele (0.066%), and 6 heterozygotes for beta-thal (0.40%), with the allele IVS1:110 G-->A in three subjects, and the alleles Cd 39, IVS1:5 G-->A and -28 A-->C in the three other. HPFH was detected in one subject (0.066%). Jalisco and Colima had the highest frequencies of hemoglobinopathies, 3.015% and 1.331% respectively, and the latter showed the most diversity of hemoglobin disorders. CONCLUSIONS: The observed heterogeneity of types and frequencies of hemoglobinopathies in the regions studied illustrate the importance of further investigation of these abnormalities in Mexico.

Genetic variation of the FMR1 gene among four Mexican populations: Mestizo, Huichol, Purepecha, and Tarahumara.

Fragile X syndrome is the most common cause of inherited mental retardation; it is caused by expansion of CGG repeats in the first exon of the FMR1 gene. The number of CGG repeats varies between 6 and 50 triplets in normal individuals; the most common alleles have 29 or 30 repeats. Allelic patterns in the global populations are similar; however; some reports show statistical differences among several populations. In Mexico, except by a single report on a western Mestizo population, the allelic frequencies of the FMR1 gene are unknown. In this study, we analyze 207, 140, 138, and 40 chromosomes from Mestizos, Tarahumaras, Huichols, and Purepechas respectively. After PCR amplification on DNA modified by sodium bisulfite treatment, molecular analysis of the FMR1 gene showed 30 different alleles among the 525 chromosomes evaluated. Trinucleotide repeat number in the different Mexican populations varied from 15 to 87, with modal numbers of 32 and 30 in Mestizos and Tarahumaras, 29 and 32 in Purepechas and 30 among Huichols. Together, these allelic patterns differ significantly from those reported for Caucasian, Chinese, African, Indonesian, Brazilian, and Chilean populations. The increased number of the unusual allele of 32 repeats observed in the Mexican mestizo population can be explained from its frequency in at least two Mexican native populations.

Genetic relationship of a Mexican Afromestizo population through the analysis of the 3' haplotype of the beta globin gene in betaA chromosomes.

We analyzed 112 beta(A) chromosomes from the Costa Chica region, with the aim of determining the 3' haplotype (3'Hp) in Afromestizo individuals and its relationship with the reported populations. Thirty polymorphic sites were identified by sequencing and two by restriction fragment length polymorphisms. Genetic variability, genetic distances and neutrality tests were performed with the computer program Arlequin 3.0. Three groups were constructed, which we named 3 kb-Hp, 330 bp-Hp and 2.67 kb-Hp with 32, 15 and 17 polymorphic sites respectively. In 3 kb-Hp, 34 different 3' haplotypes (14 of them new) were found; the three most common were 7B1 (17.8%), 7A1 (17.0%) and 1C1 (14.3%). 330 bp-Hp revealed 18 different allelic sequences; the most frequent were the 1 (AT(9)T(5), 22.3%), 2 (AT(8)T(5), 20.5%) and 3 (AT(7)T(7), 20.5%). 2.67 kb-Hp displayed 14 distinct haplotypes, with B1 (30.3%), A1 (28.6%) and C1 (21.4%) having the highest frequencies. The gene diversity of the Costa Chica population was only significantly different to Gambia. In the genetic distances, the p values were not significant for Vanuatu, Sumatra and Central African Republic. The neutrality tests showed that the patterns of diversity in the Costa Chica population deviate significantly from the expectations of the standard neutral model. This is the first work performed in Mexico in which the extended 3'Hp was analyzed in beta(A) chromosomes. The study showed clearly the presence of African and Asian genes in the Costa Chica population.

Molecular characterization of the--SEA alpha thalassemia allele in Mexican patients with HbH disease.

Alpha-Thalassemia is one of the most prevalent hemoglobin disorders in the world, in South-East Asians, the --SEA allele is widely found in the HbH disease patients. The purpose of this work is to describe the molecular characteristics of Hemoglobin H disease in three patients from two Mexican families, as well to analyze the DNA sequence of the --SEA allele to determine the precise site of the crossover. The -alpha 3.7 and --SEA alleles were identified using an established long-PCR method modified in our laboratory. The crossover site of --SEA mutation was analyzed by DNA sequencing. The three HbH subjects showed the same genotype -alpha3.7/--SEA. The -alpha3.7 allele has been observed in almost every racial studied group, whereas the --SEA allele is predominant in South-East Asian countries. DNA analysis through the breakpoint sites of the SEA allele in both families showed the 5' breakpoint at the third base of codon 28 in the psi alpha 2 gene and the 3' breakpoint within an Alu-Jo sequence, 1,328 nucleotides upstream of the 3'HVR. Therefore the size of the deletion is 19,303 nucleotides. This is the first report in which the flanking deletion sites of the --SEA mutation have been analyzed in Mexican patients, the 5' and 3' ends of the deletion is well determined.

[Polymorphism analysis of G199A, Ncol in ANK1 and Memphis I in SLC4A1 genes in Mexican healthy individuals and subjects affected with hereditary spherocytosis]. / Andálisis de los polimorfismos G199A, NcoI del gen ANK1 y Memphis I del gen SLC4A1 en individuos sanos y pacientes mexicanos con esferocitosis hereditaria.

BACKGROUND: In Mexico, Hereditary Spherocytosis (HS) is the main cause of hereditary hemolytic anemia, due to mutations of one or more genes involved in the erythrocyte membrane, making it difficult to identify the primary gene. OBJECTIVE: With the purpose of estimating the use of the polymorphisms G199A and NcoI of ANK1 gene, and Memphis I of SLC4A1 gene, as genetic markers to screen this disease, we searched the allelic and genotypic frequencies in 45 DNA samples of HS patients and 28 from healthy individuals. RESULTS: Allelic and genotypic frequencies were similar in both studied groups for the G199A and Memphis I polymorphisms, with low frequency of heterozygosis showing its limited use as a genetic marker. The allelic and genotypic frequencies of the NcoI polymorphism were also similar in both groups, however a higher heterozygote frequency was observed (0.49 and 0.43 in patients and healthy individuals), a feature that may turn it into a useful genetic marker. CONCLUSIONS: Since there are other genes implicated in the molecular pathology of the HS, we consider it necessary to continue analyzing other polymorphisms of the genes involved in Hereditary Spherocytosis among the Mexican population.

Andálisis de los polimorfismos G199A, NcoI del gen ANK1 y Memphis I del gen SLC4A1 en individuos sanos y pacientes mexicanos con esferocitosis hereditaria / Polymorphism analysis of G199A, Ncol in ANK1 and Memphis I in SLC4A1 genes in Mexican healthy individuals and subjects affected with hereditary spherocytosis

Antecedentes. En México la esferocitosis hereditaria (EH) es la causa principal de anemia hemolítica hereditaria y se debe a mutaciones en uno o más genes implicados en la membrana eritrocitaria, lo que dificulta la identificación del gen primario. Objetivo. Con el fin de valorar la utilización de los polimorfismos G199A y NcoI del gen ANK1, y Memphis I del gen SLC4A1 como marcadores genéticos para identificar esta enfermedad, estimamos sus frecuencias alélicas y genotípicas en 45 muestras de ADN de pacientes con EH y 28 de individuos sanos, las cuales fueron similares en uno y otro grupos para los polimorfismos G199A y Memphis I, con baja frecuencia de heterocigotos, lo que limita su utilidad como marcador genético. Resultados. El polimorfismo NcoI no mostró diferencias alélicas y genotípicas en los grupos de estudio, pero sí mayor frecuencia de heterocigotos (0.49 y 0.43 en enfermos y sanos respectivamente), característica que le confiere ventajas para ser utilizado como marcador genético en familias con EH. Conclusiones. Finalmente, debido a que existen otros genes implicados en la patología molecular de la EH, consideramos que es necesario analizar otros polimorfismos de genes que codifican para las proteínas involucradas en las deficiencias que conducen a esferocitosis hereditaria en la población mexicana.

BACKGROUND: In Mexico, Hereditary Spherocytosis (HS) is the main cause of hereditary hemolytic anemia, due to mutations of one or more genes involved in the erythrocyte membrane, making it difficult to identify the primary gene. OBJECTIVE: With the purpose of estimating the use of the polymorphisms G199A and NcoI of ANK1 gene, and Memphis I of SLC4A1 gene, as genetic markers to screen this disease, we searched the allelic and genotypic frequencies in 45 DNA samples of HS patients and 28 from healthy individuals. RESULTS: Allelic and genotypic frequencies were similar in both studied groups for the G199A and Memphis I polymorphisms, with low frequency of heterozygosis showing its limited use as a genetic marker. The allelic and genotypic frequencies of the NcoI polymorphism were also similar in both groups, however a higher heterozygote frequency was observed (0.49 and 0.43 in patients and healthy individuals), a feature that may turn it into a useful genetic marker. CONCLUSIONS: Since there are other genes implicated in the molecular pathology of the HS, we consider it necessary to continue analyzing other polymorphisms of the genes involved in Hereditary Spherocytosis among the Mexican population.

Molecular characterization of the - -SEA alpha thalassemia allele in Mexican patients with HbH disease / Caracterización molecular del alelo - -SEA de talasemia alfa en pacientes mexicanos con enfermedad por HbH

α-Thalassemia is one of the most prevalent hemoglobin disorders in the world, in South-East Asians, the--SEA allele is widely found in the HbH disease patients. The purpose of this work is to describe the molecular characteristics of Hemoglobin H disease in three patients from two Mexican families, as well to analyze the DNA sequence of the --SEA allele to determine the precise site of the crossover. The -α3.7 and --SEA alleles were identified using an established long-PCR method modified in our laboratory. The crossover site of --SEA mutation was analyzed by DNA sequencing. The three HbH subjects showed the same genotype -α3.7/--SEA. The -α3.7 allele has been observed in almost every racial studied group, whereas the --SEA allele is predominant in South-East Asian countries. DNA analysis through the breakpoint sites of the --SEA allele in both families showed the 5' breakpoint at the third base of codon 28 in the ψα2 gene and the 3' breakpoint within an Alu-Jo sequence, 1,328 nucleotides upstream of the 3'HVR. Therefore the size of the deletion is 19,303 nucleotides. This is the first report in which the flanking deletion sites of the--SEA mutation have been analyzed in Mexican patients, the 5' and 3' ends of the deletion is well determined.

La Talasemia-α es uno de los desórdenes de la hemoglobina más prevalences en el mundo. En el sureste de Asia, --SEA es el alelo más frecuente en pacientes con enfermedad por HbH (EHbH). En el presente trabajo se describen las características moleculares de tres pacientes con EHbH de dos familias mexicanas, y se analiza la secuencia de DNA del alelo --SEA, para determinar los sitios de ruptura. Los alelos -α3.7y --SEA se identificaron por un método de PCR modificado en nuestro laboratorio y los sitios de ruptura por secuenciación de DNA. Los tres pacientes con EHbH mostraron el genotipo -a3.7/--SEA. El alelo -α3.7 está ampliamente distribuido en el mundo, mientras que el alelo--SEA predomina en los países del sureste de Asia. El análisis de DNA del alelo--SEA mostró en 5' el sitio de ruptura en el codón 28 del pseudogén ψα2 y en 3', dentro de la secuencia Alu-Jo, localizada a 1,328 nucleótidos de la región HVR3', lo que da un segmento delecionado de 19,303 nucleótidos. Éste es el primer reporte en el que se analizan los sitios que flanquean la deleción del alelo --SEA en pacientes mexicanos y se definen con precisión los extremos 5' y 3' de la deleción.

Prevalence of -alpha(3.7) and alpha alpha alpha(anti3.7) alleles in sickle cell trait and beta-thalassemia patients in Mexico.

The aim of this study was to determine the frequency of alpha-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 beta-thalassemia. We searched for -alpha(3.7) and -alpha(4.2) alpha(+)-thalassemia deletion alleles, as well as the alpha alpha alpha(anti3.7) triplication through long-gap PCR. The alleles -alpha(3.7) and alpha alpha alpha(anti3.7) were found in the heterozygote state only; 19% of the normal subjects had the -alpha(3.7) allele, and 2% showed the alpha alpha alpha(anti3.7) allele. In individuals with the sickle cell trait, 17% had the -alpha(3.7) deletion, and the alpha alpha alpha(anti3.7) triplication was observed in 3% of these individuals. We revealed that 16% of the subjects with beta-thalassemia showed the -alpha(3.7) deletion and 28% the alpha alpha alpha(anti3.7) triplication. The -alpha(4.2) deletion was not detected in any individual. The frequency of the -alpha(3.7) 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 alpha(+)-thalassemia has been observed. To our knowledge, the frequency of alpha alpha alpha(anti3.7) triplication observed in the Mexican beta-thalassemia patients is the highest reported. As the -alpha(3.7) and alpha alpha alpha(anti3.7) alleles are very common in our selected populations, we believe that there is a need to investigate systematically the alpha-globin gene mutations in all hemoglobinopathies in the Mexican population.

3' haplotypes of the beta-globin gene in beta(S)-chromosomes of Mexican individuals.

The beta-globin gene cluster has shown high polymorphic diversity organized in 5' and 3' haplotypes (Hps). beta(S)-Chromosomes are in linkage disequilibrium with the 5' Hps Bantu, Benin, Senegal, Cameroon, and Arab-Indian. In Mexican mestizos with African west coast origins, we observed the following 5' Hps in beta(S)-chromosomes: Bantu, 78.8%; Benin, 18.2%; and atypical Hp 9, 3.0%. With the purpose of establishing the 3' Hps, we analyzed 35 polymorphic sites--6 by RFLP analysis and 29 by DNA sequencing--in 33 unrelated beta(S)-chromosomes. The polymorphic sites were structured according to Harding et al. [R.M. Harding, S.M. Fullerton, R.C. Griffiths, J.B. Clegg, Archaic African and Asian lineages in the genetic ancestry of modern humans, Am. J. Hum. Genet. 60 (1997) 772-789] and Lapoumeroulie et al. [C. Lapoumeroulie, O. Dunda, R. Ducrocq, G. Trabuchet, M. Mony-Lobe, J.M. Bodo, P. Carnevale, D. Labie, J. Elion, R. Krishnamoorthy, A novel sickle cell mutation of yet another origin in Africa: the Cameroon type, Hum. Genet. 89 (1992) 333-337]. All Bantu beta(S)-chromosomes showed the 12A1 3' Hp with (AT)6T9 repeats (84.9%), a novel 3' Hp. The Benin Hp was 2B2, with (AT)8T4 (12.1%), and the atypical Hp 9 4B1, (AT)8T5 (3.0%). Because of the high linkage disequilibrium observed for the Bantu and 12A1 Hps, we expect that, if there is a single origin of the Bantu beta(S) mutation, all must show the 12A1 polymorphic DNA sequence in the 3' Hp. A correlation between the 5' and 3' Hps could be observed with the other beta(S) mutations. The atypical Hp 9 was also atypical at the 3' Hp, with the same repeats as observed with the Cameroon beta(S) mutation; however, it differed in one position from the typical Lapoumeroulie Cameroon Hp, indicating that these beta(S)-chromosomes arose by different genetic mechanisms or by a novel beta(S) mutation. We stress the importance of the study of DNA polymorphisms at 3' Hp to allow understanding of the genetic diversity of beta(S)-chromosomes, as well as their implications in beta(S) gene expression and the possible effects on the clinical phenotype.

A frameshift at codons 77/78 (-C): a novel beta-thalassemia mutation.

We identified and characterized a novel beta-thalassemia (beta-thal) mutation due to a deletion of cytosine at codons 77/78 (-C) [CAC(His) CA- or CTG(Leu)--> -TG] found in a heterozygous state in four members of a Mexican family. The beta haplotype analysis performed on the family revealed that the frameshift at codons 77/78 (-C) mutation in this family is associated with haplotype V [- + - - - + ] and framework 2. Ten beta-thal alleles with a cytosine deletion are described at the Globin Gene Server, two of which are very near codon 77. The molecular pathology of beta-thal in the Mexican population has been shown to be heterogeneous, because some Mediterranean, Asian, private and rare alleles have been observed, a similar fact as has been observed in populations with a low frequency of beta-thal.