Prenatal diagnosis of inherited hemoglobinopathies

In this paper we reviewed the different methods presently available for prenatal diagnosis of hemoglobin disorders and the impact of this technology in the control of beta-thalassemia in several Mediterranean populations. The vast majority of the inherited hemoglobinopathies can now be detected in the fetus by amniocyte or trophoblast DNA analysis. alpha-thalassemias, delta beta-thalassemias and gamma delta beta-thalassemias, which are usually caused by a gross structural rearrangement of the DNA, may be directly detected by Southern blot analysis. Only a few beta-thalassemia lesions are caused by gene deletion or affect a restriction recognition site and thus may be directly identified by this method. The major part of beta-thalassemia are due to single nucleotide substitution, small deletion or addition which do not alter a restriction recognition site. These mutations may be directly detected by complementary oligonucleotide probes. Alternatively, when normal or affected children are available, fetal diagnosis may be accomplished by linkage analysis with polymorphic restriction sites. Fetal blood analysis is used at present time for those cases presenting too late in the pregnancy for characterization of the molecular defect and in prospective parents in whom the defect is not known. Introduction of prenatal diagnosis in combination with carrier screening in several mediterranean populations led to a consistent reduction in the incidence of homozygous beta-thalassemia.     

Haptoglobin for the treatment of sickle cell disease

There are three haptoglobin phenotypes in humans designated: Hp1–1, Hp2–1, and Hp2–2. The Hp1–1 phenotype has been shown to be protective against certain diseases, and this has been suggested to be the result of better anti-inflammatory and antioxidative properties compared to haptoglobin polymers of the other phenotypes when clearing cell-free haemoglobin. We propose the use of haptoglobin for the treatment of sickle cell disease, where an oxidative state exists caused by a high level of cell-free haemoglobin. A significant number of sickle cell disease patients are severely affected and experience regular acute painful episodes resulting in hospitalisation.Therapeutic treatments for sickle cell disease are limited and therefore haptoglobin could represent a vital alternative therapy. A method has been developed as part of the commercial fractionation of plasma for preparing haptoglobin enriched for dimers. This is significant as it uses a mixture of plasma of all haptoglobin phenotypes, and allows annual production of hundreds of kilograms quantities of haptoglobin that may be required to allow treatment of thousands of sickle cell disease patients worldwide.     

Prenatal diagnosis of globoid cell leukodystrophy (Krabbe's disease)

Summary A case of globoid cell leukodystrophy (Krabbe's disease) was diagnosed prenatally by demonstrating a profound deficiency of cerebroside -galactosidase in cultured amniotic cells. The diagnosis was confirmed in the fetus aborted in the 19th week. In the cell-free amniotic fluid, normal enzyme activity was found. This finding, which had been demonstrated in a previous case, is discussed.     

Gene therapy for sickle cell disease: An update

Sickle cell disease (SCD) is one of the most common life-threatening monogenic diseases affecting millions of people worldwide. Allogenic hematopietic stem cell transplantation is the only known cure for the disease with high success rates, but the limited availability of matched sibling donors and the high risk of transplantation-related side effects force the scientific community to envision additional therapies. Ex vivo gene therapy through globin gene addition has been investigated extensively and is currently being tested in clinical trials that have begun reporting encouraging data. Recent improvements in our understanding of the molecular pathways controlling mammalian erythropoiesis and globin switching offer new and exciting therapeutic options. Rapid and substantial advances in genome engineering tools, particularly CRISPR/Cas9, have raised the possibility of genetic correction in induced pluripotent stem cells as well as patient-derived hematopoietic stem and progenitor cells. However, these techniques are still in their infancy, and safety/efficacy issues remain that must be addressed before translating these promising techniques into clinical practice.     

Prenatal diagnosis of hemoglobinopathies: evaluation of techniques for analysing globin-chain synthesis in blood samples obtained by fetoscopy.

Three techniques for analysing hemoglobin synthesis in blood samples obtained by fetoscopy were evaluated. Of the fetuses studied, 12 were not at risk of genetic disorders, 10 were at risk of beta-thalassemia, 2 were at risk of sickle cell anemia and 1 was at risk of both diseases. The conventional method of prenatal diagnosis of hemoglobinopathies, involving the separation of globin chains labelled with a radioactive isotope on carboxymethyl cellulose (CMC) columns, was compared with a method involving globin-chain separation by high-pressure liquid chromatography (HPLC) and with direct analysis of labelled hemoglobin tetramers obtained from cell lysates by chromatography on ion-exchange columns. The last method is technically the simplest and can be used for diagnosing beta-thalassemia and sickle cell anemia. However, it gives spuriously high levels of adult hemoglobin in samples containing nonlabelled adult hemoglobin. HPLC is the fastest method for prenatal diagnosis of beta-thalassemia and may prove as reliable as the CMC method. Of the 13 fetuses at risk for hemoglobinopathies, 1 was predicted to be affected, and the diagnosis was confirmed in the abortus. Of 12 predicted to be unaffected, 1 was aborted spontaneously and was unavailable for confirmatory studies, as were 3 of the infants; however, the diagnosis was confirmed in seven cases and is awaiting confirmation when the infant in 6 months old in one case. Couples at risk of bearing a child with a hemoglobinopathy should be referred for genetic counselling before pregnancy or, at the latest, by the 12th week of gestation so that prenatal diagnosis can be attempted by amniocentesis, safer procedure, with restriction endonuclease analysis of the amniotic fluid cells.     

Prenatal diagnosis of I-cell disease.

A pregnancy from a family in risk of I-cell disease was monitored. The fetus was diagnosed as having I-cell disease based on the findings that (1) lysosomal enzyme activities except for acid phosphatase and alpha glucosidase were clearly elevated in amniotic fluid and were reduced in cultivated amniotic fluid cells, and (2) cytoplasmic inclusions were seen in cultivated amniotic cells by phase contrast microscopy. The accuracy of prediction was confirmed by cultured skin fibroblast of the aborted fetus.     

Prenatal screening for hemoglobinopathies. II. Evaluation of counseling.

Learning during genetic counseling is often below expectations, especially in the context of genetic screening. In this report we describe learning as a result of genetic counseling of 298 pregnant women identified as hemoglobinopathy carriers, 234 with sickle cell trait and 64 with beta-thalassemia trait. Counseling was designed to provide the information needed in a simple, clear, and nondirective manner. A special videotape produced for this purpose provided dramatization and a role model illustrating an appropriate response. After viewing the videotape the counselee had an opportunity to question the counselor and to have any misconceptions corrected. Questionnaires revealed significantly increased knowledge as a result of counseling in each of the three hemoglobinopathy subject areas tested-namely, clinical manifestations, genetics, and prenatal diagnosis. Five factors correlated with higher knowledge scores after counseling-namely, a younger patient age, more years of education, knowledge of having trait before this identification, knowledge of the baby's father having trait before counseling, and having no prior children.     

The association of Hp 1 and sickle cell disease

The distribution of gene frequencies and types for haptoglobin (Hp) were studied in a normal black population and one with sickle cell disease. The statistical analysis of our findings indicated a significant association between sickle cell disease and the Hp 1 type.     

The role of fibrocytes in sickle cell lung disease

Background

Interstitial lung disease is a frequent complication in sickle cell disease and is characterized by vascular remodeling and interstitial fibrosis. Bone marrow-derived fibrocytes have been shown to contribute to the pathogenesis of other interstitial lung diseases. The goal of this study was to define the contribution of fibrocytes to the pathogenesis of sickle cell lung disease.

Methodology/Principal Findings

Fibrocytes were quantified and characterized in subjects with sickle cell disease or healthy controls, and in a model of sickle cell disease, the NY1DD mouse. The role of the chemokine ligand CXCL12 in trafficking of fibrocytes and phenotype of lung disease was examined in the animal model. We found elevated concentration of activated fibrocytes in the peripheral blood of subjects with sickle cell disease, which increased further during vaso-occlusive crises. There was a similar elevations in the numbers and activation phenotype of fibrocytes in the bone marrow, blood, and lungs of the NY1DD mouse, both at baseline and under conditions of hypoxia/re-oxygenation. In both subjects with sickle cell disease and the mouse model, fibrocytes expressed a hierarchy of chemokine receptors, with CXCR4 expressed on most fibrocytes, and CCR2 and CCR7 expressed on a smaller subset of cells. Depletion of the CXCR4 ligand, CXCL12, in the mouse model resulted in a marked reduction of fibrocyte trafficking into the lungs, reduced lung collagen content and improved lung compliance and histology.

Conclusions

These data support the notion that activated fibrocytes play a significant role in the pathogenesis of sickle cell lung disease.     

The proteome of sickle cell disease: insights from exploratory proteomic profiling

The expanding realm of exploratory proteomics has added a unique dimension to the study of the complex pathophysiology involved in sickle cell disease. A review of proteomic studies published on sickle cell erythrocytes and plasma shows trends of upregulation of antioxidant proteins, an increase in cytoskeletal defects, an increase in protein repair and turnover components, a decrease in lipid raft proteins and apolipoprotein dysregulation. Many of these findings are consistent with the pathophysiology of sickle cell disease, including high oxidant burden, resulting in damage to cytoskeletal and other proteins, and erythrocyte rigidity. More unexpected findings, such as a decrease in lipid raft components and apolipoprotein dysregulation, offer previously unexplored targets for future investigation and potential therapeutic intervention. Exploratory proteomic profiling is a valuable source of hypothesis generation for the cellular and molecular pathophysiology of sickle cell disease.     

Prenatal diagnosis of trisomy 21: registration results from a single genetic center

This is a retrospective review of all collected amniotic fluid samples, chorionic villus samples and other fluid-aspirations (hygroma colli fluid/urine from megacystis) over an 11-year period (1996-2006) in a single Genetic Center (University Hospital Gasthuisberg, Leuven), looking at the prenatal diagnosis of trisomy 21. In this study a total of 404 diagnoses of trisomy 21 were made on 29696 samples (1.4%). The prenatal diagnosis of trisomy 21 increased over the years with 0.88% (21/2363) in 1996 and 1.99% (50/2512)in 2006. Also the type of invasive testing changed over the years with an increase of the proportion of trisomy 21- diagnoses by chorionic villussampling from 2001. Looking at the registry for perinatal activities in Flanders for the year 2006 the live birth incidence for trisomy 21 was 1/1782 and this is lower than the often reported incidence oftrisomy 21 at birth of 1/800: it is likely that the use of more sensitive screening methods for the prenatal detection of trisomy 21 and the election of termination for most affected pregnancies affects the birth incidence oftrisomy 21.