Diverse genetic mechanisms operate to generate atypical betaS haplotypes in the population of Guadeloupe.

In a survey of the chromosomal background associated with the sickle cell gene in Guadeloupe, a French Caribbean island, we identified 37 unrelated patients with sickle cell disease (27 SS, nine SC, and one S-beta-thalassemia) of 477 unrelated sickle cell patients where the beta3 gene was linked to 20 different atypical haplotypes. These atypical chromosomes account for about 5% of the overall betaS chromosomes in this population. To investigate the origin of these atypical betaS haplotypes, we performed extensive typing of betaS and betaA chromosomes. Twenty-two different 5' subhaplotypes were identified among the betaS chromosomes. Fifteen of 20 different atypical haplotypes are likely to be the product of recombination by a single crossover around the <> 5' to the beta-globin gene, or between a major betaS haplotype and one of the betaS haplotypes present in the population. The remaining cases require genetic mechanisms (gene conversions, additional substitutions in a given haplotype) other than crossovers to generate these atypical haplotypes.

Prevalence, clinical features, and risk factors of osteonecrosis of the femoral head among adults with sickle cell disease.

This prospective study examined the prevalence, clinical features, and risk factors of osteonecrosis of the femoral head among adult sickle cell disease patients in Guadeloupe. Screening of osteonecrosis of the femoral head was performed using radiography, bone scintigraphy, and tomodensitometry. One hundred thirteen adults with sickle cell disease (67 SS and 46 SC patients) comprised the study population. Forty-two (37.2%) patients had osteonecrosis of one or both hips (67 [29.6%] hips) without association to a particular genotype, although bilateral involvement was more frequent among SS patients. While the prevalence of femoral head osteonecrosis increased with age, patients of all ages were affected, particularly young SC adults. Osteonecrosis of the femoral head was diagnosed at preradiographic stages (stage I) in 30% of hips and was frequently asymptomatic (60% of all cases; 95% and 90% of stages I and II, respectively). Osteonecrosis of the femoral head was significantly associated with a history of leg ulcer and osteonecrosis of the humeral head. SS patients with higher hemoglobin levels had an increased risk of osteonecrosis of the femoral head.

Morphological features of the human umbilical vein in normal, sickle cell trait, and sickle cell disease pregnancies.

Pathological changes often occur in the placenta of women with sickle cell disease (SCD). These alterations are caused by sickling of erythrocytes and vasoocclusion in the placental circulation, leading to regional hypoxia. However, the morphological status of the umbilical cord, which is in close physical association with the placenta, is not documented under such conditions. To explore this, the umbilical vein structure in healthy, sickle cell trait (the heterozygous state), and SCD pregnancies was studied using scanning (SEM) and transmission electron microscopy (TEM). Interestingly, the sickle cell trait umbilical vein architecture was morphologically similar to that in control veins, whereas numerous alterations were seen in the SCD umbilical vein wall. In SEM, the SCD umbilical vein endothelial cells showed atypical morphologies. TEM analysis of the tunica media showed (1) smooth muscle cell proliferation and increase in the thickness of the basement membrane underlying the cells; (2) areas of necrosis; (3) reduplication of the inner elastic lamina. Such features were often seen in sickle patients vasculature at autopsy. Our findings could have importance because tissue hypoxemia is an integral part of vasoocclusion. We conclude that the SCD umbilical vein may be an additional tool for studying vasoocclusion in sickle cell disease.

Genetic and hematological studies in a group of 114 adult patients with SC sickle cell disease.

The clinical and biological heterogeneity of sickle cell hemoglobin (Hb) C disease (SC disease) is similar to sickle cell anemia, but has a much milder course. The effect of genetic factors such as alpha thalassemia or beta-globin gene haplotype has been analyzed in a limited number of cases. In this work, we report about 114 adult SC patients, aged 15 to 65 years (M/F = 0.93). The frequency of deletional alpha thalassemia (alpha(-3.7)) was found to be about 35%. The coinheritance of an alpha-thalassemia trait with SC disease had no effect on the hemoglobin level but hemolysis was significantly reduced. In these patients, as described for homozygous Hb S individuals, the Hb F level was higher in females than in males and in individuals carrying the beta(s)-Senegal haplotype. This haplotype involves the presence of an Xmnl site 5' to Ggamma, which is considered responsible for an increased Ggamma/Agamma ratio. Our survey showed that some genetic factors may modulate hematological parameters in SC disease.

Prevalence of fragile-X syndrome and FRAXE among children with intellectual disability in a Caribbean island, Guadeloupe, French West Indies.

Fragile-X syndrome (FXS) is the most common cause of inherited intellectual disability. Although FXS has been identified in all the main ethnic groups, little is known about its prevalence with respect to ethnicity. Since the identification of the FXS primary defect, diagnosis involving DNA analysis has been made possible, allowing efficient screening strategies to be considered. The present authors have carried out FXS screening among children belonging mainly to the Afro-Caribbean ethnic group (163 boys and 85 girls) affected with moderate to severe intellectual disability of previously unknown origin. We have found a 6.7% and 0% prevalence among boys and girls, respectively, yielding a minimum FXS incidence of 0.42 per 1000 male births per year. Family studies have resulted in genetic counselling for several individuals. FRAXE screening was also achieved and no FRAXE case was detected in this study.

Sickle cell disorder, beta-globin gene cluster haplotypes and alpha-thalassemia in neonates and adults from Guadeloupe.

We have studied haplotype of beta(S) chromosome and alpha-globin gene status in 534 patients (255 adults and 279 children of whom 159 neonates) from Guadeloupe with various sickle cell-related conditions, namely SS (n = 298), SC (n = 170), S-beta-thal (n = 56), and other rare forms (n = 10). Haplotype data on beta(S) chromosomes confirm our previous observation that Benin type is the most prevalent (75%) beta(S) chromosome in Guadeloupe, in disagreement with the historical records. Comparison of the frequency of distribution of various beta(S) haplotypes between neonates and adults on the one hand and between SS and SC cases on the other shows that the current beta(S) haplotype distribution in this island is not distorted by haplotype-related differential survival. We also show that the frequency of alpha-thalassemia (-3.7 kb) in Guadeloupe is one of the highest recorded in this region involved in Atlantic slave trade and also failed to reveal any age-dependent increase in frequency. We conclude that the African component of Guadeloupe is distinct from that of Brazil and Cuba but is close to that of Jamaica.

[Conditions of use and access to care of sickle cell anemia patients. Analysis of the literature]. / Conditions d'usage et d'accès aux soins des drépanocytaires. Analyse de la littérature.

In order to identify the care access and life conditions and non-compliance risk factors of sickle-cell patients, we performed a literature survey on these subjects, and on other chronic pathologies and care systems used as references. The data showed a positive influence of good quality of life, social support and family environment on diabetes mellitus patients compliance, and the negative effect of poor socioeconomic status on adequate prenatal care. Concerning sickle-cell disease, there were few data on the non-compliance risk factors. However, the authors identified factors which influence the patient health status and showed the negative result of the disease on the quality of life of the patient and his family. A new study has been induced by these conclusions on the sickle-cell disease cohort of Guadeloupe reference center.

Efficiency of prenatal counselling for sickle cell disease in Guadeloupe.

As in most caribbean countries, Sickle Cell Disease (SCD) is a major public health problem in Guadeloupe. A prenatal counselling program was developed, at an early stage of pregnancy, for at-risk couples. Over a 6 year period, 144 couples at-risk of having a child with homozygous sickle cell (SS: n = 103) or sickle cell C disease (SC: n = 41) were seen for prenatal counselling. Among those belonging to the SS risk group, 64 (62%) underwent prenatal diagnosis (PND), which allowed identification of 27 SS fetuses, with an induced abortion rate of 70%. Among those of the SC risk group, 14 (34%) accepted PND and the diagnosis of SC was made in 5 cases with an induced abortion rate of 60%. Factors, appeared to play a role in seeking PND and induced abortion, were the type of risk (SS or SC), multiparity, existence of affected child in the family and gestational age at the time of counselling. Our experience reveals that, an early prospective identification of at-risk couples combined with education to increase the awareness of the problem at the individual and population level need to be achieved to further improve the efficiency of our prevention program.

Molecular characterization of beta-thalassemia mutations in Guadeloupe.

In order to perform genetic counselling and prenatal diagnosis of Hb-S-beta-thalassemia disease and beta-thalassemia, we have delineated the spectrum of beta-thalassemia alleles in the Guadeloupean population. A sample of 63 unrelated families was analyzed including 70 beta-thalassemia carriers, 52 Hb-S-beta-thalassemia, and 8 patients with different beta-thalassemic hemoglobinopathies. Among the eleven mutations identified, four of them [-29 (A --> G), IVS-I-5 (G --> A), IVS-II-1 (G --> A), and IVS-I-5 (G --> C)] account for 77.6% of the beta-thalassemia chromosomes present in the studied families. The seven other variants, CD 24 (T --> A), IVS-I-2 (T --> C), Poly A (T --> C), -88 (C --> T), IVS- 11-849 (A --> G), Hb E, and Hb Lepore are less frequent. As a result, Hb S-beta+-thalassemia type 1 (low Hb A values: 5-15%) together with Hb S-beta(omicron)-thalassemia phenotypes are as frequent as Hb S-beta+-thalassemia type 2 (high Hb A values: 20-30%) in the Guadeloupean population. Patients with Hb S-beta+-thalassemia type 2 have milder hematological manifestations of the disease compared to patients with Hb S-beta(omicron)-thalassemia and Hb S-beta+-thalassemia type 1. This first report on the type and nature of beta-thalassemia mutations in Guadeloupe shows that prenatal diagnosis of Hb S-beta-thalassemia and beta-thalassemia should be feasible by direct detection of point mutation in most cases.

beta S haplotypes, alpha-globin gene status, and hematological data of sickle cell disease patients in Guadeloupe (F.W.I.).

The beta gene cluster haplotypes, alpha gene status, Hb F level and hematological parameters have been characterized in 154 unrelated Guadeloupe patients with sickle cell disease: 112 with sickle cell anemia, 26 with SC disease, 15 with Hb S-beta-thalassemia, and one patient with Hb S in association with the hereditary persistence of fetal hemoglobin. Fourteen haplotypes in 16 combinations were found, the three major African haplotypes were present on 92% of all chromosomes: 73% Benin, 11% Bantu, 8% Senegal. Among SS patients, 57% were Benin homozygotes, one patient was a Senegal homozygote, one patient was a Bantu homozygote, and all the others were heterozygous. The A gamma T chain was observed on seven chromosomes and about 5% of the analyzed beta S chromosomes exhibited atypical haplotypes. The common haplotype beta C was found in all patients with SC disease. An interesting feature was the high frequency (44%) of deletional alpha-thalassemia among SS patients. Two patients have an alpha-gene globin triplication. The DNA haplotypes and alpha-gene status have been correlated with hematological parameters in these patients. The anthropological aspect of these data is interesting as the haplotypes of the beta-globin gene throw light on the slave trade from the various parts of Africa to the Caribbean Islands in particular, and North America in general.

Characterization of phosphoinositide kinases in normal and sickle anaemia red cells.

PtdIns and PtdInsP kinases from normal erythrocyte (AA) membranes and sickle cell anaemia erythrocyte (SS) membranes have been characterized. PtdIns kinase was studied in native membranes under conditions in which PtdInsP kinase and PtdInsP phosphatase do not express any activity. Kinetic analysis of the AA and SS PtdIns kinases indicate similar Km values for PtdIns and ATP but higher Vmax values for SS PtdIns kinase. PtdInsP kinase was partially purified from erythrocyte ghosts by NaCl extraction. The kinetic parameters of PtdInsP kinase determined under these conditions were similar in AA and SS NaCl extracts. These data suggest the presence of some effector of PtdIns kinase in SS cell membranes, resulting in a greater activity of the enzyme. This leads consequently, to increase the PtdIns4P pool and to activate PtdInsP kinase, in agreement with our previous observations of a greater [32P]Pi incorporation in both polyphosphoinositides in SS cells relatively to AA cells.

[Health policies and sickle cell disease]. / Politiques de santé et drépanocytose.

Issues of public health raised by sickle cell disease and available solutions vary greatly between countries. Two main variables lead the choices: the affordable health resources, and the distribution of the abnormal genes in the population. Three examples have been chosen to illustrate these challenges. 1. In continental France, the level of health resources is good but the distribution of sickle traits is very heterogeneous among the population. Health policies against sickle cell disease aim at organizing screening and care to reach populations at risk, and concentrate the efforts upon them. This task is made difficult by two usual characteristics of these minorities: their rather poor social condition, and their cultural isolation. 2. In Guadeloupe (French West Indies) available health resources are similar to those of France but the sickle trait is common and has a homogeneous distribution in the population (14% carriers). Sickle cell disease is a health priority. Such conditions have recently favoured the organization of an efficient program for prevention and care of the disease. 3. In Benin (West Africa) a very high prevalence of sickle trait (more than 30% individuals are carriers, and about 4% have the disease) comes along with quite precarious resources that have to be shared with several other health priorities. An efficient and sustained policy against sickle cell disease has not yet been developed, which impedes a rational use of the few available resources, and creates much distress for diseased individuals.

Hemoglobin S Antilles: a variant with lower solubility than hemoglobin S and producing sickle cell disease in heterozygotes.

We have found a sickling variant, Hb S Antilles, alpha 2 beta 2(6 Glu----Val, 23 Val----Ile), that has the same electrophoretic mobility as Hb S but a distinct isoelectric focus and produces sickling in the carriers of the Hb A/S Antilles trait. The carriers' erythrocytes tend to sickle at O2 partial pressures similar to those that induce sickling in Hb S/C disease. Pure deoxy-Hb S Antilles is 50% as soluble as deoxy-Hb S (saturating concentration = 11 g X dl-1 compared to 18.4 for Hb S). Dilute solutions of pure Hb S Antilles have a lower oxygen affinity than those of Hb A or Hb S (partial pressure for 50% binding is 9 mm Hg compared to 5.5 mm Hg for Hb A or S at pH 7.00). A/S Antilles erythrocytes have a much lower oxygen affinity than A/S cells; this is further decreased in dense cells fractionated on a Percoll density gradient. Their oxygen equilibrium curves had anomalous shapes like those of S/S cells. Fiber formation in the erythrocytes of Hb S Antilles carriers is clearly due to its low solubility and oxygen affinity, showing that heterozygosity for this hemoglobin presents another sickle cell syndrome and suggesting that Hb S heterozygotes who exhibit symptoms of sickle cell disease should be carefully screened for double mutations.

Hemoglobin La Desirade alpha A2 beta 2 129 (H7) Ala----Val: a new unstable hemoglobin.

Hemoglobin La Desirade is a new unstable hemoglobin variant arising from the substitution of beta 129 (H7) Ala for Val. Hb La Desirade exhibits a low oxygen affinity and normal heme-heme interaction. The variant was found in two unrelated black families in association with Hb S, Hb C or beta o thalassemia.

Hemoglobin Roseau-Pointe a Pitre alpha 2 beta 2(90) (F6) Glu----Gly: a new hemoglobin variant with slight instability and low oxygen affinity.

A Dominican neonate carrying a new abnormal hemoglobin, hemoglobin Roseau Pointe-à-Pitre alpha 2 beta 2(90)(F6) Glu----Gly, was detected in Guadeloupe during application of a cord blood screening program. This variant behaved in isoelectrofocusing as an Hb D, and displayed instability and low whole blood oxygen affinity. In the affected family it was present, either isolated, or in association with a beta+ thalassemia trait.

Kinetic anticooperativity in pre-steady-state formation of tryptophanyl adenylate by tryptophanyl-tRNA synthetase from beef pancreas. A consequence of the tryptophan anticooperative binding.

The kinetics of formation of tryptophanyl adenylate by tryptophanyl-tRNA synthetase from beef pancreas has been followed by stopped-flow, using the quenching of fluorescence of the enzyme linked to the amino acid activation reaction. Both subunits of this alpha 2 enzyme catalyze the adenylate formation. At saturation with substrates the rate constant of the activation reaction is the same for both subunits. The same behaviour is observed for the pyrophosphorolysis reaction. Both subunits exhibit the same affinity for ATP-Mg in the forward reaction and the same affinity for magnesium pyrophosphate in the backward reaction. On the contrary the formation of tryptophanyl adenylate follows biphasic kinetics when tryptophan concentration is much below saturation. This is independent of ATP-Mg concentration and is the consequence of different affinities of the two subunits for tryptophan as already observed by Graves et al. (1979, Eur. J. Biochem. 96, 509-518) in equilibrium dialysis experiments. A monoadenylate-enzyme complex on one subunit has been prepared. This complex made possible the study of the formation of the second adenylate on the other subunit. The formation of this second adenylate followed first-order kinetics at all ATP-Mg and tryptophan concentrations. The tryptophan concentration dependence of the rate of formation of this second adenylate leads to a Michaelis constant close to the dissociation constant of the low affinity tryptophan site of the enzyme. No isomerization step could be evidenced. The experiments were carried out under two conditions corresponding to those used by Merault et al. (1978. Eur. J. Biochem. 87, 541-550) in the steady state of the tRNATrp aminoacylation reaction (10 mM total magnesium in 100 mM KCl and 1 mM free magnesium ions, both at pH 8.0.25 C). No great difference either in the mechanism or in the dissociation and rate constants was observed but an inhibitory effect of KCl. It is concluded that the enzyme is symmetrical as far as the ATP-Mg and the magnesium pyrophosphate sites are concerned and that the rate of the activation reaction reflects the anticooperative occupancy of the tryptophan sites carried by the two subunits.