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George Patrinos and colleagues report the first implementation of the microattribution approach to systematically document genetic variation associated with a disease, applied here to hemoglobinopathies and thalassemias. They developed a series of connected locus-specific databases that document genotype and phenotype information for genetic variation in 37 globin and erythroid protein genes in individuals with globin disorders, with reciprocal attribution to data contributors. We developed a series of interrelated locus-specific databases to store all published and unpublished genetic variation related to hemoglobinopathies and thalassemia and implemented microattribution to encourage submission of unpublished observations of genetic variation to these public repositories. A total of 1,941 unique genetic variants in 37 genes, encoding globins and other erythroid proteins, are currently documented in these databases, with reciprocal attribution of microcitations to data contributors. Our project provides the first example of implementing microattribution to incentivise submission of all known genetic variation in a defined system. It has demonstrably increased the reporting of human variants, leading to a comprehensive online resource for systematically describing human genetic variation in the globin genes and other genes contributing to hemoglobinopathies and thalassemias. The principles established here will serve as a model for other systems and for the analysis of other common and/or complex human genetic diseases.

β-Type hemoglobinopathies are characterized by vast phenotypic diversity as far as disease severity is concerned, while differences have also been observed in hydroxyurea (HU) treatment efficacy. These differences are partly attributed to the residual expression of fetal hemoglobin (HbF) in adulthood. The Krüppel-like family of transcription factors (KLFs) are a set of zinc finger DNA-binding proteins which play a major role in HbF regulation. Here, we explored the possible association of variants in gene family members with response to HU treatment efficacy and disease severity in β-hemoglobinopathies patients. Six tag single nucleotide polymorphisms, located in four  genes, namely and , were analyzed in 110 β-thalassemia major patients (TDT), 18 nontransfusion dependent β-thalassemia patients (NTDT), 82 sickle cell disease/β-thalassemia compound heterozygous patients and 85 healthy individuals as controls. Our findings show that a genomic variant (rs2236599) is associated with HU treatment efficacy in sickle cell disease/β-thalassemia compound heterozygous patients and two genomic variants (rs980112, rs3191333) are associated with persistent HbF levels in NTDT patients. Our findings provide evidence that genomic variants located in gene may be considered as potential prognostic biomarkers of β-thalassemia clinical severity and an additional variant in gene as a pharmacogenomic biomarker, predicting response to HU treatment.

Hemoglobinopathies constitute a major health problem worldwide, with a high carrier frequency, particularly in certain regions where malaria has been endemic. These disorders are characterized by a vast clinical and hematological phenotypic heterogeneity. Over 1,200 different genetic alterations that affect the DNA sequence of the human α‐like (HBZ, HBA2, HBA1, and HBQ1) and β‐like (HBE1, HBG2, HBG1, HBD, and HBB) globin genes are mainly responsible for the observed clinical heterogeneity. These mutations, together with detailed information about the resulting phenotype, are documented in the globin locus‐specific HbVar database. Family studies and comprehensive hematological analyses provide useful insights for accurately diagnosing thalassemia at the DNA level. For this purpose, numerous techniques can provide accurate, rapid, and cost‐effective identification of the underlying genetic defect in affected individuals. The aim of this article is to review the diverse methodological and technical platforms available for the molecular diagnosis of inherited disorders, using thalassemia and hemoglobinopathies as a model. This article also attempts to shed light on issues closely related to thalassemia diagnostics, such as prenatal and preimplantation genetic diagnoses and genetic counseling, for better‐quality disease management. Hum Mutat 26(5), 399–412, 2005. © 2005 Wiley‐Liss, Inc.

The exponential discovery rate of new genomic alterations, leading to inherited disorders, as well as the need for comparative studies of different population's mutation frequencies necessitates recording their population‐wide spectrum in online mutation databases. We report the construction of the Hellenic National Mutation database (http://www.goldenhelix.org/hellenic), a prototype database derived from a multicenter academic initiative, aiming to provide high quality and up‐to‐date information on the underlying genetic heterogeneity of inherited disorders found in the Hellenic population. Database records include informative summaries of the various genetic disorders studied in the Hellenic population, focused in particular on their incidence in Greece, a comprehensive reference list, and a well‐structured query interface, which provides easy access to the list of the different mutations responsible for the inherited disorders in the Hellenic population. Also, extensive links to the respective Online Mendelian Inheritance in Man (OMIM) entries and, when available, to the locus‐specific databases are provided, so that the user can retrieve the maximum amount of information from a single website. Furthermore, the Hellenic National Mutation database design allows easy data entry and curation. Creation of the Hellenic National Mutation database will significantly facilitate molecular diagnosis of inherited disorders in Greece and will motivate further investigation of yet unknown genetic diseases in the Hellenic population. Hum Mutat 25:327–333, 2005. © 2005 Wiley‐Liss, Inc.

Nondeletional hereditary persistence of fetal hemoglobin (nd-HPFH), a rare hereditary condition resulting in elevated levels of fetal hemoglobin (Hb F) in adults, is associated with promoter mutations in the human fetal globin (HBG1 and HBG2) genes. In this paper, we report a novel type of nd-HPFH due to a HBG2 gene promoter mutation (HBG2:g.-109G>T). This mutation, located at the 3' end of the HBG2 distal CCAAT box, was initially identified in an adult female subject of Central Greek origin and results in elevated Hb F levels (4.1%) and significantly increased Gγ-globin chain production (79.2%). Family studies and DNA analysis revealed that the HBG2:g.-109G>T mutation is also found in the family members in compound heterozygosity with the HBG2:g.-158C>T single nucleotide polymorphism or the silent HBB:g.-101C>T β-thalassemia mutation, resulting in the latter case in significantly elevated Hb F levels (14.3%). Electrophoretic mobility shift analysis revealed that the HBG2:g.-109G>T mutation abolishes a transcription factor binding site, consistent with previous observations using DNA footprinting analysis, suggesting that guanine at position HBG2/1:g.-109 is critical for NF-E3 binding. These data suggest that the HBG2:g-109G>T mutation has a functional role in increasing HBG2 transcription and is responsible for the HPFH phenotype observed in our index cases.

The coexistence of beta- and gamma-globin gene mutations in the compound heterozygous state presents a rare in vivo model that provides important data on gene regulation of clinical interest. In this unique comparative study we present the hematological, biosynthetic, and molecular data from six adult compound heterozygotes for the Greek nondeletional hereditary persistence of fetal hemoglobin (nd-HPFH, Agamma-117 G-->A) and four frequent beta-thalassemia mutations (IVS I-110 G-->A, Cd 39 C-->T, IVS I-1 G-->A, and IVS I-6 T-->C) found in the Hellenic population. Fetal hemoglobin (HbF) levels were found to be considerably higher (25-50%) than in 19 Greek nd-HPFH heterozygotes (HbF=9.7+/-1.7%) and, interestingly, to depend on the type of the respective beta-thalassemia mutation, in trans to the nd-HPFH allele. All cases presented a typical beta-thalassemia heterozygote's phenotype despite the increased HbF and the normal HbA2 levels, as indicated by both the hematological indices and the biosynthetic ratios. These data were compared with those from two unique cases of Greek origin: a homozygous case of the Greek nd-HPFH and a compound heterozygote with HbS. Our data suggest that in these compound heterozygous cases the beta-thalassemic chromosome indirectly determines the final outcome of the gamma- and of the in cis beta-globin gene expression, most likely at the post-transcriptional level.

We developed a series of interrelated locus-specific databases to store all published and unpublished genetic variation related to these disorders, and then implemented microattribution to encourage submission of unpublished observations of genetic variation to these public repositories 1. A total of 1,941 unique genetic variants in 37 genes, encoding globins (HBA2, HBA1, HBG2, HBG1, HBD, HBB) and other erythroid proteins (ALOX5AP, AQP9, ARG2, ASS1, ATRX, BCL11A, CNTNAP2, CSNK2A1, EPAS1, ERCC2, FLT1, GATA1, GPM6B, HAO2, HBS1L, KDR, KL, KLF1, MAP2K1, MAP3K5, MAP3K7, MYB, NOS1, NOS2, NOS3, NOX3, NUP133, PDE7B, SMAD3, SMAD6, and TOX) are currently documented in these databases with reciprocal attribution of microcitations to data contributors. Our project provides the first example of implementing microattribution to incentivise submission of all known genetic variation in a defined system. It has demonstrably increased the reporting of human variants and now provides a comprehensive online resource for systematically describing human genetic variation in the globin genes and other genes contributing to hemoglobinopathies and thalassemias. The large repository of previously reported data, together with more recent data, acquired by microattribution, demonstrates how the comprehensive documentation of human variation will provide key insights into normal biological processes and how these are perturbed in human genetic disease. Using the microattribution process set out here, datasets which took decades to accumulate for the globin genes could be assembled rapidly for other genes and disease systems. The principles established here for the globin gene system will serve as a model for other systems and the analysis of other common and/or complex human genetic diseases.

Nondeletional hereditary persistence of fetal hemoglobin (nd-HPFH), a rare hereditary condition resulting in elevated levels of fetal hemoglobin (Hb F) in adults, is associated with promoter mutations in the human fetal globin ( and ) genes. In this paper, we report a novel type of nd-HPFH due to a gene promoter mutation (:g.-109G>T). This mutation, located at the 3′ end of the distal CCAAT box, was initially identified in an adult female subject of Central Greek origin and results in elevated Hb F levels (4.1%) and significantly increased Gγ-globin chain production (79.2%). Family studies and DNA analysis revealed that the :g.-109G>T mutation is also found in the family members in compound heterozygosity with the :g.-158C>T single nucleotide polymorphism or the silent :g.-101C>T β-thalassemia mutation, resulting in the latter case in significantly elevated Hb F levels (14.3%). Electrophoretic mobility shift analysis revealed that the :g.-109G>T mutation abolishes a transcription factor binding site, consistent with previous observations using DNA footprinting analysis, suggesting that guanine at position :g.-109 is critical for NF-E3 binding. These data suggest that the :g-109G>T mutation has a functional role in increasing transcription and is responsible for the HPFH phenotype observed in our index cases.

The coexistence of [beta]- and [gamma]-globin gene mutations in the compound heterozygous state presents a rare in vivo model that provides important data on gene regulation of clinical interest. In this unique comparative study we present the hematological, biosynthetic, and molecular data from six adult compound heterozygotes for the Greek nondeletional hereditary persistence of fetal hemoglobin (nd-HPFH, A[gamma]-117 G[arrow right]A) and four frequent [beta]-thalassemia mutations (IVS I-110 G[arrow right]A, Cd 39 C[arrow right]T, IVS I-1 G[arrow right]A, and IVS I-6 T[arrow right]C) found in the Hellenic population. Fetal hemoglobin (HbF) levels were found to be considerably higher (25-50%) than in 19 Greek nd-HPFH heterozygotes (HbF=9.7±1.7%) and, interestingly, to depend on the type of the respective [beta]-thalassemia mutation, in trans to the nd-HPFH allele. All cases presented a typical [beta]-thalassemia heterozygote's phenotype despite the increased HbF and the normal HbA2 levels, as indicated by both the hematological indices and the biosynthetic ratios. These data were compared with those from two unique cases of Greek origin: a homozygous case of the Greek nd-HPFH and a compound heterozygote with HbS. Our data suggest that in these compound heterozygous cases the [beta]-thalassemic chromosome indirectly determines the final outcome of the [gamma]- and of the in cis [beta]-globin gene expression, most likely at the post-transcriptional level.

A scanning strategy for the detection of ´-globin gene mutations and polymorphisms is presented. This procedure is based on the denaturing gradient gel electrophoresis (DGGE) of four different artificially amplified DNA fragments which cover the promoter, the exons, as well as IVS I of the reported gene. To estimate the efficiency and sensitivity of the proposed procedure, we analysed the appropriate controls of ´-thalassemic carriers, uncharacterised ´-thalassemias and cases with normal hematological phenotype, but slightly increased (up to 3.5%) HbA2. DGGE results permitted the identification of ´-globin gene mutations and the polymorphism - 199 (T[arrow right]C). Three novel base substitutions inside the promoter region of the gene [-65(A[arrow right]G), -55(T[arrow right]C), -36(C[arrow right]A)], were also revealed. These changes are either linked in cis with other mutations or are responsible for thalassemias or for positive regulatory effect in ´-globin gene expression. The proposed experimental strategy consists of an accurate, rapid, safe and inexpensive screening procedure for establishing the molecular basis of ´-globin gene defects, suitable for the application for both research and diagnostics. Hum Mutat 9:465-472, 1997 © 1997 Wiley-Liss, Inc.