bims-conane 2024-12-01 papers

Front Genet. 2024 ;15 1460974

Genetic screening of α-thalassemia fusion gene using routine flow-through hybridization.

Yingbei Huang, Aiping Ju, Lihong Zheng, Biqiu Xu, Liang Liang, Youqiong Li.

Objective: The fusion gene is a rare form of α-thalassemia. Patients carrying the fusion gene could be misdiagnosed as normal or -α4.2deletion by the conventional thalassemia detection methods. The aim of this study was to present the detection of fusion genes using routine flow-through hybridization, as well as to analyze hematological and molecular characteristics.
Methods: Samples were collected at our hospital from January 2019 to January 2024. Common thalassemia mutations in the Chinese population were conducted by flow-through hybridization. Samples showing faint coloration at the -α4.2 mutation site on hybridization membrane were considered suspicious. Samples detected as suspicious for -α4.2deletion were rechecked by conventional Gap-PCR. Those samples suspected of having -α4.2deletions were finally confirmed with specific primers for Gap-PCR and Sanger sequencing.
Results: Of the 32,083 samples, 25 samples (0.08%) were detected as suspected of having -α4.2 deletion by flow-through hybridization. However, upon reevaluation wtih conventional Gap-PCR reagents capable of detecting -α4.2 deletion, all were found to be negative for the deletion. Specific primers for Gap-PCR were designed, and fusion gene fragments were amplified. DNA sequencing of the HBA gene showed a 7-base mutation corresponding to the α-thalassemia fusion gene. Among the 25 samples, 22 were heterozygous carriers. Three samples were combined: one with Hb QS, one with β-thalassemia, and one with Hb G-Honolulu.Most hematological indices and capillary electrophoresis results were in the normal reference range.
Conclusion: The fusion gene was present in 0.08% of the population in the Guangzhou region of Guangdong province, southern China. Conventional genetic methods tend to misdiagnose the fusion gene but can be effectively screened with flow-through hybridization.

Keywords: -α 4.2; Gap-PCR; flow-through hybridization; fusion gene; thalassemia

DOI: https://doi.org/10.3389/fgene.2024.1460974

Genetics. 2024 Nov 28. pii: iyae170. [Epub ahead of print]

Functional analysis of G6PD variants associated with low G6PD activity in the All of Us Research Program.

Nicholas R Powell, Renee C Geck, Dongbing Lai, Tyler Shugg, Todd C Skaar, Maitreya J Dunham.

The glucose-6-phosphate dehydrogenase (G6PD) enzyme protects red blood cells against oxidative damage. Individuals with G6PD-impairing polymorphisms are at risk of hemolytic anemia from oxidative stressors. Prevention of G6PD deficiency-related hemolytic anemia is achievable by identifying affected individuals through G6PD genetic testing. However, accurately predicting the clinical consequence of G6PD variants is limited by over 800 G6PD variants which remain of uncertain significance (VUS). There also remains inconsistency in which deficiency-causing variants are included in genetic testing arrays: many institutions only test c.202G > A, though dozens of other variants can cause G6PD deficiency. Here, we improve G6PD genotype interpretations using the All of Us Research Program data and a yeast functional assay. We confirm that G6PD coding variants are the main contributor to decreased G6PD activity and that 13% of individuals in the All of Us data with deficiency-causing variants would be missed by only genotyping for c.202G > A. We expand clinical interpretation for G6PD VUS, reporting that c.595A > G ("Dagua" or "Açores") and the novel variant c.430C > G reduce activity sufficiently to lead to G6PD deficiency. We also provide evidence that 5 missense VUS are unlikely to lead to G6PD deficiency, and we applied the new World Health Organization (WHO) guidelines to recommend classifying 2 synonymous variants as WHO Class C. In total, we provide new or updated clinical interpretations for 9 G6PD variants. We anticipate these results will improve the accuracy, and prompt increased use, of G6PD genetic tests through a more complete clinical interpretation of G6PD variants.

Keywords: Saccharomyces cerevisiae ; ACMG; All of Us; ClinGen; ClinVar; G6PD; G6PD deficiency; GWAS; LOINC; WHO; functional assay; glucose-6-phosphate dehydrogenase; hemolytic anemia; permutation testing; pharmacogenetics; phenotype curation; power simulation; variant interpretation

DOI: https://doi.org/10.1093/genetics/iyae170

J Clin Med. 2024 Nov 19. pii: 6966. [Epub ahead of print]13(22):

Beta Thalassemia in Children: Established Approaches, Old Issues, New Non-Curative Therapies, and Perspectives on Healing.

Raffaella Origa, Layal Issa.

Despite a decrease in prevalence and incidence rates, beta thalassemia continues to represent a significant public health challenge worldwide. In high-resource settings, children with thalassemia have an open prognosis, with a high chance of reaching adulthood and old age with a good quality of life. This is achievable if transfusion therapy is properly managed, effectively mitigating ineffective erythropoiesis and its associated complications while also minimizing excessive iron accumulation. Adequate iron chelation is essential to maintain reactive forms of iron within the normal range throughout life, thus preventing organ damage caused by hemosiderosis, which inevitably results from a regular transfusion regimen. New therapies, both curative, such as gene therapy, and non-curative, such as modulators of erythropoiesis, are becoming available for patients with transfusion-dependent beta thalassemia. Two curative approaches based on gene therapy have been investigated in both adults and children with thalassemia. The first approach uses a lentivirus to correct the genetic defect, delivering a functional gene copy to the patient's cells. The second approach employs CRISPR/Cas9 gene editing to directly modify the defective gene at the molecular level. No non-curative therapies have received approval for pediatric use. Among adults, the only available drug is luspatercept, which is currently undergoing clinical trials in pediatric populations. However, in many countries around the world, the new therapeutic options remain a mirage, and even transfusion therapy itself is not guaranteed for most patients, while the choice of iron chelation therapy depends on drug availability and affordability.

Keywords: anemia; beta thalassemia; chelation; gene editing; gene therapy; iron overload; monogenic disorder; serum ferritin; transfusion therapy

DOI: https://doi.org/10.3390/jcm13226966

Br J Haematol. 2024 Nov 29.

Elucidating loss-of-function mechanisms of monoallelic EPAS1 mutations underlying congenital hypoplastic anaemia in a paediatric anaemia cohort.

Jiasheng Zhang, Jin Sun, Wan Huai, Jie Tang, Jing Chen, Ruen Yao, Tingting Yu.

HIF-2α, encoded by EPAS1, plays a dominant role in regulating erythropoietin (EPO) production, maintaining the dynamic balance of erythropoiesis. Gain-of-function mutations in EPAS1 cause erythrocytosis. However, anaemia caused by EPAS1 loss-of-function mutations has been confined to only one case report, and the underlying mechanism remains unclear. Herein, the reanalysis of high-throughput sequencing data from 311 patients with anaemia identified three monoallelic EPAS1 variants from three unrelated families in a paediatric anaemia cohort. The probands showed highly consistent clinical phenotypes with normocytic and normochromic anaemia, reticulocytopenia and relative deficiency of serum EPO, characterised as congenital hypoplastic anaemia. In vitro studies suggested that defects in steady-state protein abundance, nuclear localisation and binding with co-activator in EPAS1 variants lead to impaired EPO transcriptional activation. Therefore, loss-of-function mutations in EPAS1 can cause erythroid hypoplasia in an EPO-dependent manner. This study identified a new causative gene for congenital hypoplastic anaemia and clarified the molecular aetiology of loss-of-function EPAS1 mutations.

Keywords: EPAS1 mutation; HIF‐2α; congenital hypoplastic anaemia; erythropoietin; loss‐of‐function mechanism

DOI: https://doi.org/10.1111/bjh.19930

Hemoglobin. 2024 Nov 26. 1-3

Hereditary Hemolytic Anemia Due to PIEZO1 Red Blood Cell Membrane Defect.

Georgios Dryllis, Roberta Russo, Immacolata Andolfo, Achille Iolascon, Barbara Eleni Rosato, Kostas Konstantopoulos.

PIEZO1 (piezo-type mechanosensitive ion channel component 1) is a mechanosensitive ion channel protein. Gain-of-function variants in the PIEZO1 gene are known to cause dehydrated hereditary stomatocytosis (DHS) also termed hereditary xerocytosis. This is a rare autosomal dominant condition characterized by variable-degree anemia with a tendency toward hemolysis, erythrocyte dehydration and iron overload. While the diagnostic workflow for DHS is well-established, diagnosis is often delayed due to overlapping clinical features with other hemolytic anemias and the pleiotropic effects of PIEZO1 variants. We describe the case of a Greek patient with a compensating hemolysis since birth. DHS diagnosis was established only after a prolonged history of repeated investigations spanning from his early life to 70 years of age, when a conclusive testing was achieved.

Keywords: Dehydrated hereditary stomatocytosis (DHS); PIEZO1; hemolysis; hereditary xerocytosis; macrocytosis

DOI: https://doi.org/10.1080/03630269.2024.2427187