Severe beta(0) thalassemia/hemoglobin E disease caused by de novo 22-base pair duplication in the paternal allele of beta globin gene

A Novel Pathogenic β-Thalassemia Mutation Identified at Codon 8 (HBB: c.27delG) in a Bangladeshi Family Acquired De Novo

In Bangladesh, the practice of β-thalassemia (β-thal) carrier screening and prenatal diagnosis (PND) by β-globin gene sequencing has been initiated to prevent the birth of affected children. The study aimed to describe a novel de novo mutation of the β-globin gene and its clinical implication. Out of 100 Bangladeshi β-thal carrier families, one patient with hematological and clinical features associated with β-thal and her parents were included. Molecular characterizations of β-globin gene mutations were performed by direct sequencing. A novel nucleotide deletion mutation at codon 8 in the first exon of the β-globin gene (HBB: c.27delG) was found in a 1-year-old child of the studied family in a heterozygous state along with common Hb E (HBB: c.79G>A). The mutation caused a frameshift to a new stop codon at codon 18 resulting in a β⁰-thal phenotype. The proband exhibited a β-thal intermedia (β-TI)-like genotype, however, showed β-thal major (β-TM)-like complications and was transfusion-dependent. Her mother had a profile consistent with the Hb E trait, while the father had normal hematological indices. Mutation analyses revealed the mother to be heterozygous for Hb E, while the father had a normal genotype. The novel mutation was assumed to be inherited de novo by the paternity test. The study documented a novel pathogenic mutation in the β-globin gene in a Bangladeshi family by β-globin gene sequencing.

Molecular mechanisms of a novel β-thalassaemia mutation due to the duplication of tetranucleotide 'AGCT' at the junction IVS-II/exon 3

We report a new β-thalassaemia allele detected in a young Italian woman, suffering with mild non-haemolytic anaemia (Hb < 10 g/dL) and not showing Hb variant or Heinz bodies. The allele is characterised by duplication of tetranucleotide 'AG/CT' (+1344/+1347) including the invariant dinucleotide 'AG' of IVS-II acceptor splicing site and the first two nucleotides of codon 105. β-Globin complementary DNA (cDNA) sequencing did not reveal any mutation and qualitative analysis of the reverse transcription PCR reaction showed that only the proximal 3' splice site present in the duplicated gene is used giving race to an anomalous messenger RNA (mRNA) present in trace (1.5 %) because, most probably, rapidly degraded. In the anomalous mRNA, the insertion causes a frameshift and synthesis of an abnormal truncated β-chain (139 residues), unable to form Hb variant because of the severe conformational changes. The duplication might have arisen from secondary structures generated by quasi-palindromic sequence 5'-CCCA(C)AG/CT(CC)TGGG-3'. Restriction fragment length polymorphism analysis for the β-globin haplotype and familiar segregation analysis indicated that the mutant β-globin gene was associated with the haplotype V.

A novel de novo BRCA1 mutation in a Chinese woman with early onset breast cancer

Germline mutations in the two breast cancer susceptibility genes, BRCA1 and BRCA2 account for a significant portion of hereditary breast/ovarian cancer. De novo mutations such as multiple exon deletion are rarely occurred in BRCA1 and BRCA2. During our mutation screening for BRCA1/2 genes to Chinese women with risk factors for hereditary breast/ovarian cancer, we identified a novel germline mutation, consisting of a deletion from exons 1 to 12 in BRCA1 gene, in a patient diagnosed with early onset triple negative breast cancer with no family history of cancer. None of her parents carried the mutation and molecular analysis showed that this novel de novo germline mutation resulted in down-regulation of BRCA1 gene expression.

Hemoglobin H disease due to a de novo mutation at the α2-globin gene and an inherited common α-thalassemia deletion found in a Chinese boy

Hemoglobin (Hb) H disease is a moderate form of α-thalassemia resulting from various genetic defects. A novel frameshift mutation cd 43/44(-C) at the α2-globin gene was identified in a Chinese boy with hemoglobin H disease by sequencing. The proband's mother carries a common α-thalassemia deletion while his father was normal both in the hematological phenotype and α-globin genotype, which suggested that it occurred as a de novo mutation. Molecular studies revealed a compound heterozygote for the Southeast Asian α-thalassemia deletion and this novel spontaneous mutation (-/α(T)α) and the patient exhibited the clinical manifestation of classic hemoglobin H disease. Based on the results of excluding the possibility of a somatic mosaicism of a point mutation in the α2-globin gene, we progress that this de novo single-base deletion should have arisen during the spermatogenic process or earlier embryonic stage. The present study provides information in determining a supplementary model of inheritance for α-thalassemia, which should be useful in genetic counseling.