Ankyrin-linked hereditary spherocytosis in an African-American kindred

Forward Genetics in Apicomplexa Biology: The Host Side of the Story

Forward genetic approaches have been widely used in parasitology and have proven their power to reveal the complexities of host-parasite interactions in an unbiased fashion. Many aspects of the parasite’s biology, including the identification of virulence factors, replication determinants, antibiotic resistance genes, and other factors required for parasitic life, have been discovered using such strategies. Forward genetic approaches have also been employed to understand host resistance mechanisms to parasitic infection. Here, we will introduce and review all forward genetic approaches that have been used to identify host factors involved with Apicomplexa infections, which include classical genetic screens and QTL mapping, GWAS, ENU mutagenesis, overexpression, RNAi and CRISPR-Cas9 library screens. Collectively, these screens have improved our understanding of host resistance mechanisms, immune regulation, vaccine and drug designs for Apicomplexa parasites. We will also discuss how recent advances in molecular genetics give present opportunities to further explore host-parasite relationships.

A previously unrecognized Ankyrin-1 mutation associated with Hereditary Spherocytosis in an Italian family

Hereditary spherocytosis is the most common inherited hemolytic anemia characterized by the presence of spherical-shaped erythrocytes on peripheral blood smear. The clinical manifestations of HS are highly variable, from severe forms to asymptomatic forms. HS is caused by defects in red blood cell membrane proteins, encoded by the ANK1, EPB42, SLC4A1, SPTA1 and SPTB genes. Mutation of the ANK 1 gene is the most common and inheritance is autosomal dominant in 75% of cases. In our case, heterozygous an ANK1 c.4123C > T mutation was identified in a 4-year-old girl, using targeted next-generation sequencing and Sanger sequencing.

Spectrum of Ankyrin Mutations in Hereditary Spherocytosis: A Case Report and Review of the Literature

BACKGROUND/AIMS

Hereditary spherocytosis (HS) is a common pediatric hemolytic anemia caused by congenital red blood cell defects. HS due to ankyrin 1 (ANK1) mutations is the most common type. We explored an ANK1 mutation from an HS patient and reviewed the literature.

METHODS

We detected the mutation in a Chinese family in which 2 members were diagnosed with HS by next-generation sequencing. The proband was diagnosed with HS in the newborn period, based on clinical manifestations, laboratory data, and family history. The mutation spectrum of the ANK1 gene was summarized based on 85 patients diagnosed with HS carrying ANK1 mutations, and the ANK1 mutation spectrum was summarized and analyzed.

RESULTS

We identified a novel mutation affecting ANK1 gene splicing (a splicing mutation) in both the patient and her mother, which is a substitution of T>G 2 nt after exon 25 in intron 26. The study expands our knowledge of the ANK1 gene mutation spectrum, providing a molecular basis for HS.

CONCLUSION

A novel ANK1 mutation (NM_000037.3, c.2960+2T>G, intron 26) that is potentially associated with HS was identified. To date, 80 ANK1 mutations have been reported to be associated with HS in humans.

Exome sequencing confirms molecular diagnoses in 38 Chinese families with hereditary spherocytosis

Hereditary spherocytosis (HS), the most common cause of congenital hemolytic anemia, is caused by deficiency of the erythrocyte membrane proteins. Five causative genes (ANK1, SPTB, SPTA1, SLC4A1, and EPB42) have been identified. To date, molecular genetic studies have been performed in different populations, including the American, European, Brazilian, Japanese and Korean populations, whereas only a few studies have been described in the Chinese population. Here, by reanalysis of the exome data, we revealed causative mutations and established a definitive diagnosis of HS in all 38 Chinese families. We found 34 novel mutations and four reported mutations in three known HS-causing genes-17 in ANK1, 17 in SPTB and four in SLC4A1, suggesting that ANK1 and SPTB are the major genes in Chinese patients with HS. All of the ANK1 or SPTB mutations, scattered throughout the entire genes, are non-recurrent; and most of them are null mutations, which might cause HS via a haploinsufficiency mechanism. De novo mutations in ANK1 or SPTB often occur with an unexpected high frequency (87.5% and 64.2%, respectively). Our study updates our knowledge about the genetic profile of HS in Chinese and shows that family-based, especially parent-offspring trio, sequencing analysis can help to increase the diagnostic power and improve diagnostic efficiency.

Ankyrin-1 Gene Exhibits Allelic Heterogeneity in Conferring Protection Against Malaria

Allelic heterogeneity is a common phenomenon where a gene exhibits a different phenotype depending on the nature of its genetic mutations. In the context of genes affecting malaria susceptibility, it allowed us to explore and understand the intricate host–parasite interactions during malaria infections. In this study, we described a gene encoding erythrocytic ankyrin-1 (Ank-1) which exhibits allelic-dependent heterogeneous phenotypes during malaria infections. We conducted an ENU mutagenesis screen on mice and identified two Ank-1 mutations, one resulting in an amino acid substitution (MRI95845), and the other a truncated Ank-1 protein (MRI96570). Both mutations caused hereditary spherocytosis-like phenotypes and confer differing protection against Plasmodium chabaudi infections. Upon further examination, the Ank-1^(MRI96570) mutation was found to inhibit intraerythrocytic parasite maturation, whereas Ank-1^(MRI95845) caused increased bystander erythrocyte clearance during infection. This is the first description of allelic heterogeneity in ankyrin-1 from the direct comparison between two Ank-1 mutations. Despite the lack of direct evidence from population studies, this data further supported the protective roles of ankyrin-1 mutations in conferring malaria protection. This study also emphasized the importance of such phenomena in achieving a better understanding of host–parasite interactions, which could be the basis of future studies.

Mutational characteristics of ANK1 and SPTB genes in hereditary spherocytosis

The aim of this study was to describe the mutational characteristics in Korean hereditary spherocytosis (HS) patients. Relevant literatures including genetically confirmed cases with well-documented clinical summaries and relevant information were also reviewed to investigate the mutational gene- or domain-specific laboratory and clinical association. Twenty-five HS patients carried one heterozygous mutation of ANK1 (n = 13) or SPTB (n = 12) but not in SPTA1, SLC4A1, or EPB42. Deleterious mutations including frameshift, nonsense, and splice site mutations were identified in 91% (21/23), and non-hotspot mutations were dispersed across multiple exons. Genotype-phenotype correlation was clarified after combined analysis of the cases and the literature review; anemia was most severe in HS patients with mutations on the ANK1 spectrin-binding domain (p < 0.05), and SPTB mutations in HS patients spared the tetramerization domain in which mutations of hereditary elliptocytosis and pyropoikilocytosis are located. Splenectomy (17/75) was more frequent in ANK1 mutant HS (32%) than in HS with SPTB mutation (10%) (p = 0.028). Aplastic crisis occurred in 32.0% of the patients (8/25; 3 ANK1 and 5 SPTB), and parvovirus B19 was detected in 88%. The study clarifies ANK1 or SPTB mutational characteristics in HS Korean patients. The genetic association of laboratory and clinical aspects suggests comprehensive considerations for genetic-based management of HS.

A pediatrician's practical guide to diagnosing and treating hereditary spherocytosis in neonates

Newborn infants who have hereditary spherocytosis (HS) can develop anemia and hyperbilirubinemia. Bilirubin-induced neurologic dysfunction is less likely in these neonates if the diagnosis of HS is recognized and appropriate treatment provided. Among neonates listed in the USA Kernicterus Registry, HS was the third most common underlying hemolytic condition after glucose-6-phosphate dehydrogenase deficiency and ABO hemolytic disease. HS is the leading cause of direct antiglobulin test (direct Coombs) negative hemolytic anemia requiring erythrocyte transfusion in the first months of life. We anticipate that as physicians become more familiar with diagnosing HS in the newborn period, fewer neonates with HS will develop hazardous hyperbilirubinemia or present to emergency departments with unanticipated symptomatic anemia. We predict that early suspicion, prompt diagnosis and treatment, and anticipatory guidance will prevent adverse outcomes in neonates with HS. The purpose of this article was to review the neonatal presentation of HS and to provide practical and up-to-date means of diagnosing and treating HS in neonates.

Evaluating eosin-5-maleimide binding as a diagnostic test for hereditary spherocytosis in newborn infants

OBJECTIVE

Neonates with undiagnosed hereditary spherocytosis (HS) are at risk for developing hazardous hyperbilirubinemia and anemia. Making an early diagnosis of HS in a neonate can prompt anticipatory guidance to prevent these adverse outcomes. A recent comparison study showed that a relatively new diagnostic test for HS, eosin-5-maleimide (EMA)-flow cytometry, performs better than other available tests in confirming HS. However, reports have not specifically examined the performance of this test among neonates.

STUDY DESIGN

We compared EMA-flow cytometry from blood samples of healthy control neonates vs samples from neonates suspected of having HS on the basis of severe Coombs-negative jaundice and spherocytes on blood film. The diagnosis of HS was later either confirmed or excluded based on clinical findings and next generation sequencing (NGS) after which we correlated the EMA-flow results with the diagnosis.

RESULT

EMA-flow was performed on the blood of 31 neonates; 20 healthy term newborns and 11 who were suspected of having HS. Eight of the 11 were later confirmed positive for HS and one was confirmed positive for hereditary elliptocytosis (HE). All nine had persistently abnormal erythroid morphology, reticulocytosis and anemia, and eight of the nine had relevant mutations discovered using NGS. The other was confirmed positive for HS on the basis that a parent had HS, and the neonate's spherocytosis, reticulocytosis and anemia persisted. The 20 healthy controls and the 2 in whom HS was initially suspected but later excluded all had EMA-flow results in the range reported in healthy children and adults. In contrast, all nine in whom HS or HE was confirmed had abnormal EMA-flow results consistent with previous reports in older children and adults with HS.

CONCLUSION

Although our sample size is small, our findings are consistent with the literature in older children and adults suggesting that EMA-flow cytometric testing performs well in supporting the diagnosis of HS/HE during the early neonatal period.