Assuntos
Estudos de Associação Genética , Predisposição Genética para Doença , Variação Genética , Proteínas Nucleares/genética , Fatores de Elongação da Transcrição/genética , Talassemia beta/diagnóstico , Talassemia beta/genética , Biomarcadores , Feminino , Estudos de Associação Genética/métodos , Humanos , MasculinoRESUMO
Implementation of multiplex ligation-dependent probe amplification (MLPA) for thalassemia causing deletions has lead to the detection of new rearrangements. Knowledge of the exact breakpoint sequences should give more insight into the molecular mechanisms underlying these rearrangements, and would facilitate the design of gap-PCRs. We have designed a custom fine-tiling array with oligonucleotides covering the complete globin gene clusters. We hybridized 27 DNA samples containing newly identified deletions and nine positive controls. We designed specific primers to amplify relatively short fragments containing the breakpoint sequence and analyzed these by direct sequencing. Results from nine positive controls showed that array comparative genomic hybridization (aCGH) is suitable to detect small and large rearrangements. We were able to locate all breakpoints to a region of approximately 2 kb. We designed breakpoint primers for 22 cases and amplification was successful in 19 cases. For 12 of these, the exact locations of the breakpoints were determined. Seven of these deletions have not been reported before. aCGH is a valuable tool for high-resolution breakpoint characterization. The combination of MLPA and aCGH has lead to relatively cheap and easy to perform PCR assays, which might be of use for laboratories as an alternative for MLPA in populations where only a limited number of specific deletions occur with high frequency.
Assuntos
Hibridização Genômica Comparativa/métodos , Análise Mutacional de DNA/métodos , Análise de Sequência com Séries de Oligonucleotídeos/métodos , alfa-Globinas/genética , Talassemia alfa , Globinas beta/genética , Talassemia beta , Pontos de Quebra do Cromossomo , Primers do DNA , Éxons , Rearranjo Gênico , Humanos , Reação em Cadeia da Polimerase , Deleção de Sequência , Talassemia alfa/diagnóstico , Talassemia alfa/genética , Talassemia beta/diagnóstico , Talassemia beta/genéticaAssuntos
Deleção Cromossômica , Cromossomos Humanos Par 19/genética , Craniossinostoses , Hemoglobina Fetal/metabolismo , Fatores de Transcrição Kruppel-Like/genética , Transtornos do Desenvolvimento da Linguagem , Transtornos Psicomotores , Craniossinostoses/sangue , Craniossinostoses/genética , Feminino , Hemoglobina Fetal/genética , Humanos , Transtornos do Desenvolvimento da Linguagem/sangue , Transtornos do Desenvolvimento da Linguagem/genética , Masculino , Transtornos Psicomotores/sangue , Transtornos Psicomotores/genéticaRESUMO
Hemoglobinopathies are the most common monogenic disorders in the world with an ever increasing global disease burden each year. As most hemoglobinopathies show recessive inheritance carriers are usually clinically silent. Programmes for preconception and antenatal carrier screening, with the option of prenatal diagnosis are considered beneficial in many endemic countries. With the development of genetic tools such as Array analysis and Next Generation Sequencing in addition to state of the art screening at the hematologic, biochemic and genetic level, have contributed to the discovery of an increasing number of rare rearrangements and novel factors influencing the disease severity over the recent years. This review summarizes the basic requirements for adequate carrier screening analysis, the importance of genotype-phenotype correlation and how this may lead to the unrevealing exceptional interactions causing a clinically more severe phenotype in otherwise asymptomatic carriers. A special group of patients are ß-thalassemia carriers presenting with features of ß-thalassemia intermedia of various clinical severity. The disease mechanisms may involve duplicated α-globin genes, mosaic partial Uniparental Isodisomy of chromosome 11p15.4 where the HBB gene is located or haplo-insufficiency of a non-linked gene SUPT5H on chromosome 19q, first described in two Dutch families with ß-thalassemia trait without variants in the HBB gene.
Assuntos
Hemoglobinopatias , Talassemia beta , Feminino , Genótipo , Hemoglobinopatias/diagnóstico , Hemoglobinopatias/genética , Humanos , Proteínas Nucleares/genética , Fenótipo , Gravidez , Diagnóstico Pré-Natal , Fatores de Elongação da Transcrição/genética , alfa-Globinas/genética , Talassemia beta/genéticaRESUMO
Alpha-thalassemia is an inherited hemoglobin disorder characterized by a microcytic hypochromic anemia caused by a quantitative reduction of the alpha-globin chain. The majority of the alpha-thalassemias is caused by deletions in the alpha-globin gene cluster. A deletion in the alpha-globin gene cluster, which was found in a Dutch family, was characterized by MLPA, long-range PCR and direct sequencing. We describe the molecular characterization of a novel 8.2kb deletion (--(AW)), involving both alpha-globin genes in cis. The deletion is caused by a non-homologous recombination event between an Alu and an L1-repeat sequence. This deletion is the third example of a non-homologous recombination event involving an Alu and an L1 repeat, and the first described in the human alpha-globin gene cluster. Because of a 25% risk of Hb Bart's with hydrops foetalis in the offspring when in combination with another alpha(0)-thalassemia allele, it is important to diagnose this deletion.