A mass spectrometry assay for detection of endogenous and lentiviral engineered hemoglobin in cultured cells and sickle cell disease mice.

Sickle cell disease (SCD) results from a sequence defect in the ß-globin chain of adult hemoglobin (HbA) leading to expression of sickle hemoglobin (HbS). It is traditionally diagnosed by cellulose-acetate hemoglobin electrophoresis or high-performance liquid chromatography. While clinically useful, these methods have both sensitivity and specificity limitations. We developed a novel mass spectrometry (MS) method for the rapid, sensitive and highly quantitative detection of endogenous human ß-globin and sickle hß-globin, as well as lentiviral-encoded therapeutic hßAS3-globin in cultured cells and small quantities of mouse peripheral blood. The MS methods were used to phenotype homozygous HbA (AA), heterozygous HbA-HbS (AS) and homozygous HbS (SS) Townes SCD mice and detect lentiviral vector-encoded hßAS3-globin in transduced mouse erythroid cell cultures and transduced human CD34+ cells after erythroid differentiation. hßAS3-globin was also detected in peripheral blood 6 weeks post-transplant of transduced Townes SS bone marrow cells into syngeneic Townes SS mice and persisted for over 20 weeks post-transplant. As several genome-editing and gene therapy approaches for severe hemoglobin disorders are currently in clinical trials, this MS method will be useful for patient assessment before treatment and during follow-up.

Clinical characteristics, laboratory features and genetic profile of hemoglobin E (HBB:c.79 G > A)/ß (nucleotide -28 A > G) (HBB:c.-78 A > G) -thalassemia subjects identified from community- and hospital-recruited cohorts.

Despite several existing laboratory-based studies of hemoglobin (Hb) E (HBB:c.79 G > A)/ ß (nucleotide (NT) -28 A > G) (HBB:c.-78 A > G) -thalassemia, no reports have ever provided clinical severity information as well as dependency of blood transfusion. Previously, a comparative study of community- and hospital-recruited Hb E/ß-thalassemia subjects was conducted in the lower northern Thailand between June 2020 and December 2021. A mobile medical team visited each community hospital on-site, collecting clinical severity parameters, and conducting Hb and DNA analyses. The control included Hb E/ß-thalassemia patients undergoing transfusions. Subgroup study of adult Hb E/ß (NT -28 A > G) -thalassemia subjects was subsequently conducted. Additional pediatric individuals were recruited from prenatal diagnosis databases. Twenty adult and nine pediatric subjects were enrolled; all were classified as having mild disease severity. Twenty-two individuals (75.9 %) were asymptomatic. Six adults (20.7 %) required blood transfusion. The mean Hb level of subjects without transfusion (23 [79.3 %]) was 10.77 ± 1.10 g/dL. Hb analysis revealed a distinct EFA pattern with low Hb F fraction. The positive impact of genetic modifiers could not be statistically demonstrated except rs7482144-XmnI. These findings could provide essential information for parents carrying fetuses with Hb E/ß (NT -28 A > G) -thalassemia.

ß0-Thalassemia Caused by a Novel Nonsense Mutation [HBB:c.199A > T].

We report two hemoglobinopathy cases involving a novel ß-thalassemia (ß-thal) nonsense mutation, HBB:c.199A > T. One patient had Hb S/ß-thal, and a second unrelated patient had Hb D-Punjab/ß-thal. The HBB:c.199A > T mutation introduces a premature termination codon at amino acid codon 66 (AAA→TAA) in exon 2, resulting in typical high Hb A2 ß0-thal.

Newborn Screening for ß-Thalassemia Identifies a Complex Genotype Involving a Novel ß-Globin Gene Mutation (HBB:c.336dup).

Newborn screening identified a Chinese-Canadian infant who was positive for possible ß-thalassemia (ß-thal). Detailed family studies demonstrated that the proband was a compound heterozygote for the Chinese Gγ(Aγδß)0-thal deletion and a novel frameshift mutation within exon 3 (HBB:c.336dup), and heterozygous for the Southeast Asian α-thal deletion (--SEA/αα). This case illustrates the importance of follow-up molecular testing of positive newborn screening results to confirm the diagnosis and define risks for future pregnancies.

Splice Acceptor Mutation [HBB:c.93-2A > T] in a Patient with Hb S/ß0-Thalassemia.

We report a case of Hb S/ß0-thalassemia (Hb S/ß0-thal) in a patient who is a compound heterozygote for the Hb Sickle mutation (HBB:c.20A > T) and a mutation of the canonical splice acceptor sequence of IVS1 (AG > TG, HBB:c.93-2A > T). This is the fifth mutation involving the AG splice acceptor site of IVS1, all of which prevent normal splicing and cause ß0-thal.

A Novel Frameshift Mutation of HBB Causing Dominant ß-Thalassemia in a Chinese Individual.

We reported a rare ß-thalassemia patient, a 41-year-old Chinese male with small cell hypopigmentation anemia, jaundice and splenomegaly as the main clinical symptoms. By using Next-Generation Sequencing (NGS), we identified a novel de novo HBB mutation(c.358_365dup, p.Phe123Alafs*39) which resulted in an abnormally prolonged ß-globin chain comprising 159 amino acid residues. The secondary and three-dimensional structures of the ß-globin predicted that the novel prolonged ß-globin chain has a considerable risk of instability in the hemoglobin, and leads to clinical phenotype. This study contributes to the enrichment of the genetic pathogenic mutation database for thalassemia and underscores the significance of NGS in the screening of mutations for thalassemia families.

A novel gain-of-function PIP4K2A mutation elevates the expression of ß-globin and aggravates the severity of α-thalassemia.

Haemoglobin H (Hb H) disease (intermediate status of α-thalassemia) shows marked phenotypic variability from asymptomatic to severe anaemia. Apart from the combined ß-thalassemia allele ameliorating clinical severity, reports of genetic modifier genes affecting the phenotype of Hb H disease are scarce which bring inconvenience to precise diagnosis and genetic counselling of the patients. Here, we present a novel mutation (c.948C>A, p.S316R) in the PIP4K2A gene in a female Hb H disease patient who displayed moderate anaemia and a relatively high Hb H level. Haematological analysis in her family members revealed that individuals carrying this mutation have upregulated ß-globin expression, leading to a more imbalanced ß/α-globin ratio and more Hb H inclusion bodies in peripheral red blood cells. According to functional experiments, the mutant PIP4K2A protein exhibits enhanced protein stability, increased kinase activity and a stronger regulatory effect on downstream proteins, suggesting a gain-of-function mutation. Moreover, introduction of the S316R mutation into HUDEP-2 cells increased expression of ß-globin, further inhibiting erythroid differentiation and terminal enucleation. Thus, the S316R mutation is a novel genetic factor associated with ß-globin expression, and the PIP4K2A gene is a new potential modifier gene affecting the α-thalassemia phenotype.

Hemoglobin ß-Globin Variants In Hispanic Patients: An Institutional Experience From Dallas, Texas.

Hemoglobinopathies are the most common single-gene disorders in humans. There are 1,424 variants of human hemoglobin described with 951 involving the ß-globin gene. Ancestry and geography play a significant role in the incidence and nature of hemoglobinopathies, with African, Asian, and Mediterranean populations and their descendants being amongst the most affected. Investigation of variants in individuals of Hispanic descent is needed to reflect the changing demographics of the United States. Hemoglobin ß-globin evaluation through gel electrophoresis, high-performance liquid chromatography, and HBB gene sequencing was performed on patients from Texas hospitals between 2010 and 2015 and demographic parameters (age, sex, ethnicity) was subsequently analyzed. A total of 846 patients underwent hemoglobinopathy evaluation. A ß chain variant was detected in 628 of the 846 total patients. Hispanic patients represented 37% (314/846 patients), which were equally distributed between females (50%; 156/314) and males (50%; 156/314). A ß-globin chain variant was found in 67% of Hispanic patients with a distribution across 10 variants seen in greater than 1% of patients. For hemoglobin variants, an understanding of the regional and ethnic prevalence will improve patient care through more effective screening and identification of the variant, early diagnosis, and appropriate treatment if necessary, and better genetic counseling.

Novel Promoter Mutation (HBB:C.-139_-138del) Associated with ß-Thalassemia Trait Detected by Next-Generation Sequencing in Southern China.

Here we report a novel ß-globin gene mutation in the promoter (HBB:c.-139_-138delAC) detected by next-generation sequencing (NGS). The proband was a 28-year-old Chinese male, living in Shenzhen City, Guangdong Province, who originates from Hunan Province. The red cell indices were almost normal, with a slightly decreased Red Cell volume Distribution Width(RDW). Capillary electrophoresis (CE) showed the Hb A (93.1%) value was below normal, while the Hb A2 (4.2%) and Hb F (2.7%) values were both beyond normal. A set of genetic tests of the α and ß-globin genes were then performed to determine whether the subject carried any causative mutations. The results of NGS revealed a two-base pair deletion at position -89 to -88(HBB:c.-139_-138delAC）in the heterozygous state, which was subsequently confirmed by Sanger sequencing.

Hb Ryazan: An Elongated C-Terminal ß-Chain Due to a New Frameshift Mutation, HBB: c.396delG p.Val133Trpfs*25.

We identified a novel abnormal hemoglobin variant caused by a frameshift mutation at nucleotide position 396 in exon 3 of the ß-globin gene (HBB): NM_000518:c.396delG. This variant causes an emergence of alternative amino acid sequence starting at codon 133 and a new stop codon formed in the 3' untranslated region (3'UTR) of the HBB gene at amino acid position 158. This ß-globin gene variant was identified in a woman with a long history of hemolytic anemia. We named this variant Hb Ryazan after the proband's city of origin.