Percorrer por autor "Pena, Rita"
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- Ancestry of the major long-range regulatory site of the α-globin genes in the Portuguese population with the common 3.7 kb α-thalassemia deletionPublication . Pena, Rita; Lopes, Pedro; Gaspar, Gisela; Miranda, Armandina; Faustino, PaulaBackground: The α-Major Regulatory Element (α-MRE), also known as HS-40, is located upstream of the α-globin gene cluster and has a crucial role in the long-range regulation of the α-globin gene expression. This enhancer is polymorphic and several haplotypes were identified in different populations, with haplotype D almost exclusively found in African populations. The purpose of this research was to identify the HS-40 haplotype associated with the 3.7 kb α-thalassemia deletion (-α3.7del) in the Portuguese population, and determine its ancestry and influence on patients' hematological phenotype. Methods and results: We selected 111 Portuguese individuals previously analyzed by Gap-PCR to detect the presence of the -α3.7del: 50 without the -α3.7del, 34 heterozygous and 27 homozygous for the -α3.7del. The HS-40 region was amplified by PCR followed by Sanger sequencing. Four HS-40 haplotypes were found (A to D). The distribution of HS-40 haplotypes and genotypes are significantly different between individuals with and without the -α3.7del, being haplotype D and genotype AD the most prevalent in patients with this deletion in homozygosity. Furthermore, multiple correspondence analysis revealed that individuals without the -α3.7del are grouped with other European populations, while samples with the -α3.7del are separated from these and found more closely related to the African population. Conclusion: This study revealed for the first time an association of the HS-40 haplotype D with the -α3.7del in the Portuguese population, and its likely African ancestry. These results may have clinical importance as in vitro analysis of haplotype D showed a decrease in its enhancer activity on α-globin gene.
- Ancestry of the major long-range regulatory site of the α-globin genes in the Portuguese population with the common 3.7kb α-thalassemia deletionPublication . Pena, Rita; Lopes, Pedro; Gaspar, Gisela; Miranda, Armandina; Faustino, PaulaThe α-major regulatory element (known as HS-40) has a crucial role in the long-range regulation of the α-globin gene expression. This element is genetically polymorphic and six haplotypes (A to F) have been identified in different populations, with haplotype D almost exclusively found in African populations. This study aimed to identify the HS-40 haplotype associated with the common 3.7kb α-thalassemia deletion (-α3.7del) in the Portuguese population, and investigate its ancestry. We searched for the -α3.7del in 111 selected Portuguese individuals by Gap-PCR. In addition, a DNA fragment containing the HS-40 was amplified by PCR and Sanger sequenced. Statistical analysis was performed using R software. Fifty individuals have the wild-type α-globin genotype (group I), 34 are heterozygous for the -α3.7del (group II) and 27 are homozygous (group III). Regarding the HS-40, four haplotypes were found (A to D). The distribution of HS-40 haplotypes and genotypes are significantly different between groups with and without the -α3.7del (p<0.001), being haplotype D and genotype AD the most prevalent in group III. Furthermore, multiple correspondence analysis revealed that individuals without the -α3.7del are grouped with other European populations, while samples with the -α3.7del are split from these and found more related to the African population. This study revealed for the first time an association of a specific HS-40 haplotype with the -α3.7del in the Portuguese population, and its likely African ancestry. These results may have a clinical importance as in vitro analysis of haplotype D showed a descrease in its enhancer activity on α-globin genes.
- Ancestry of the α-MRE Associated with the 3.7kb α-Thalassemia Deletion in the Portuguese PopulationPublication . Pena, Rita; Lopes, Pedro; Gaspar, Gisela; Miranda, Armandina; Faustino, PaulaThe α-major regulatory element (α-MRE), also known as HS-40, is located upstream of the α-globin gene cluster and has a crucial role in the long-range regulation of the α-globin gene expression. It is genetically polymorphic and six haplotypes (A to F) have been identified in different populations. The D haplotype was primary described in African populations and is nearly absent in other populations. The aims of this study were to identify the α-MRE haplotype associated with the common 3.7kb α-thalassemia deletion (-α3.7del) in the Portuguese population, and to investigate its ancestry. We searched for the -α3.7del in 111 selected Portuguese individuals by Gap-PCR. In addition, a DNA fragment containing the α-MRE was amplified by PCR and Sanger sequenced. Statistical analysis was performed using R software. Fifty individuals have the wild-type α-globin genotype (group I), 34 are heterozygous for the -α3.7del (group II) and 27 are homozygous (group III). Regarding the α-MRE, four haplotypes were found (A to D). The ancestral A haplotype is predominant in all groups. The B haplotype is the second most frequent in groups I and II, whereas in group III haplotype D is the second most prevalent. Concerning genotypes, the α-MRE AA and AB are the most common in group I, while genotype AD is more prevalent in group III. In fact, 71.4% of AD individuals are homozygous for the -α3.7del. Moreover, the distribution of α-MRE haplotypes and genotypes are significantly different between groups with and without the -α3.7del (p<0.001). Furthermore, multiple correspondence analysis revealed that individuals without the -α3.7del are grouped with other European populations, while samples with the -α3.7del are split from these and found to be more closely related to the African population. This study revealed for the first time an association of a specific α-MRE haplotype with the common -α3.7del in the Portuguese population, and its likely African ancestry. These results may have clinical importance as the D haplotype has an alteration in the consensus sequence for the AP-1/NF-E2 binding site and in vitro experiments showed a decrease in its enhancer activity on α-globin genes.
- Unravelling the genetic basis of complex clinical cases of hemoglobinopathiesPublication . Silva, Eduarda; Pena, Rita; Miranda, Armandina; Costa, Alcina; Gaspar, Gisela; Lopes, Pedro; Faustino, PaulaHemoglobinopathies encompass all genetic diseases of hemoglobin (Hb), the iron-containing oxygen-transport protein present in red blood cells. They occur due to mutations in globin genes or in their regulatory regions, and are classified as Hb variants and thalassemias. The aim of this work was to identify the molecular lesions in the origin of complex cases of hemoglobinopathies and understand the underlying pathophysiological mechanisms. We investigated 15 clinical cases suspected of having one or more hemoglobinopathy, presenting with atypical hematological phenotypes. The study included the search for alterations in beta- and alpha-globin gene clusters by PCR, Gap-PCR, Sanger sequencing, and Multiplex Ligation-dependent Probe Amplification. In silico analyses were performed using Polyphen-2, SIFT, and varSeak. Two beta-thalassemia carriers with abnormally low HbA2 level were found to have double heterozygosity for a mutation in HBB gene (c.92+1G>A, c.92+6T>C) and a delta-chain Hb variant (Hb A2-Yialousa). Another case was justified by a novel large deletion, which removes the entire beta-globin gene cluster as well as the olfactory receptor genes, OR52A1 and OR51V1. Changes in HbA2 values were also justified by a deletion that eliminates the HBD (Corfu deletion) or by the presence of the HbA2´variant. Atypically high levels of fetal Hb were explained by alterations in promoters of HBG genes (HBG1:c.-248C>G, HBG1:c.-228T>C, HBG2:c.-211C>T) or by deletions that remove both HBD and HBB (HPFH-1, HPFH-2). An even more complex case was originated by triple heterozygosity involving the Southeast Asian alpha-thalassemia deletion, the alpha-chain variant Hb Westmead, and the beta-chain variant HbE. As far as we know, this is the first case in which the three alterations were found in the same individual. Individuals presenting abnormal phenotypes due to more than one hemoglobinopathy may be misdiagnosed if not correctly studied. Unravelling the genetic basis of complex clinical cases allows a better referral to genetic counselling, improves the understanding of the pathophysiology of the disease and its modifying factors, and may reveal new therapeutic targets.