OCEANOGRAPHY. Contrasting futures for ocean and society from different anthropogenic CO₂ emissions scenarios

The ocean moderates anthropogenic climate change at the cost of profound alterations of its physics, chemistry, ecology, and services. Here, we evaluate and compare the risks of impacts on marine and coastal ecosystems—and the goods and services they provide—for growing cumulative carbon emissions under two contrasting emissions scenarios. The current emissions trajectory would rapidly and significantly alter many ecosystems and the associated services on which humans heavily depend. A reduced emissions scenario—consistent with the Copenhagen Accord's goal of a global temperature increase of less than 2°C—is much more favorable to the ocean but still substantially alters important marine ecosystems and associated goods and services. The management options to address ocean impacts narrow as the ocean warms and acidifies. Consequently, any new climate regime that fails to minimize ocean impacts would be incomplete and inadequate.

OCEANOGRAPHY. Contrasting futures for ocean and society from different anthropogenic CO₂ emissions scenarios

The ocean moderates anthropogenic climate change at the cost of profound alterations of its physics, chemistry, ecology, and services. Here, we evaluate and compare the risks of impacts on marine and coastal ecosystems—and the goods and services they provide—for growing cumulative carbon emissions under two contrasting emissions scenarios. The current emissions trajectory would rapidly and significantly alter many ecosystems and the associated services on which humans heavily depend. A reduced emissions scenario—consistent with the Copenhagen Accord's goal of a global temperature increase of less than 2°C—is much more favorable to the ocean but still substantially alters important marine ecosystems and associated goods and services. The management options to address ocean impacts narrow as the ocean warms and acidifies. Consequently, any new climate regime that fails to minimize ocean impacts would be incomplete and inadequate.

Profile of attachment and suicidal ideation during a major depressive episode

During a major depressive episode, suicidal risks are increased and the possibility of request of help and treatment is conditionedby the way the subject structured its attachment in the childhood. We present a study which concerns the detailed examination, during 6 months, mental states of 40 patients presenting a major depressive episode and frequenting a Medical psychological Center connected with a Psychiatric hospital. The collection of the data is made with tools stemming from various fields (DSM4, theory of the attachment, the psychoanalytical psychology)“.The population is divided to three Camire profiles (Pierre Humbert et al, 1996) (Secure, Preoccupied, Avoidant). We chose 3 markers which can inform us about the evolution of the crisis according to the profile of attachment :

1-Intensity of the suicidal idéation « SSI » (Beck et all.1979)

2-therapeutic Alliance “WAI” Horvath et Greenberg, 1989)

3-Intensité of the depression. (Hamilton HAMD-21)

Hypothesis

The attachment says “sécure” facilitate better scores in these 3 markers.

Results

1)

Genetics of infantile seizures with paroxysmal dyskinesia: the infantile convulsions and choreoathetosis (ICCA) and ICCA-related syndromes

The relationship between paroxysmal movement disorders (PD: paroxysmal dyskinesia) and epilepsy continues to present a challenging problem. Attacks of PD and epileptic seizures have several characteristics in common: both are paroxysmal in nature with a tendency to spontaneous remission, and a subset of PD responds well to anticonvulsants. In 1997, description of the ICCA (infantile convulsions and choreoathetosis) syndrome and linkage to chromosome 16p12-q12 provided the first genetic evidence for common mechanisms shared by benign infantile seizures and PD. The chromosome 16 ICCA locus is by far the most frequently involved in such associations as well as in pure forms of benign infantile seizures. The ICCA region at the pericentromeric area of chromosome 16 shows complicated genomic architecture and the ICCA gene still remains unknown. Genetic studies focusing on PD with or without epilepsy have led to the identification of other genes linked to chromosomes 2q35 and 10q22. Alterations of ion channel and ion pump subunits could provide a simple, albeit probably non-unique, explanation for the pathophysiology of the link between epilepsy and PD. The aim of this review is to update genetic aspects of infantile epileptic seizures and PD and their association in the context of ICCA and ICCA related syndromes.

Development of H1e histone linker-specific antibodies by means of synthetic peptides

A large body of data suggests that the linker histones family (H1) affects gene expression. Investigation of the linker histones role is then of a major interest in cell cycle studies with implications in gene therapy. Indeed, it has been shown that in most tissues a switch of histone subtypes occurs when the cells cease to divide. To investigate linker histone role in gene or transgene expression, an antibody against subtypes of H1 would be useful for immunoprecipitation experiments and further assays measuring H1subtypes-DNA interactions in living cells. In order to produce an antibody against the H1e subtype of linker histones, two synthetic peptides derived from two regions of the H1e mouse histone protein were examined for their potential, [as keyhole limpet hemocyanin (KLH) conjugates] to elicit polyclonal anti-H1e antibodies in New Zealand white rabbits. Selection of the peptide sequences was based on amino acid differences within the different classes of histones and between mice and rabbit histones as well. The evaluation of their potential immunogenic properties was based on examination of peptide hydropathy using predicting algorithms. Immunoglobulins (IgG) obtained from immunized and nonimmunized rabbits were tested using enzyme-linked immunosorbent assay (ELISA) procedures, Western immunoblot, and immunofluorescence experiments. Results showed that the selected synthetic peptides gave rise to a high-titer polyclonal antibody able to recognize the H1e histone under various conditions. This polyclonal antibody did not cross-react with other histones. To our knowledge, this is the first antibody produced against the mouse H1e linker histone.

Reverse cascade screening of newborns for hereditary haemochromatosis: a model for other late onset diseases?

BACKGROUND

Genetic testing can determine those at risk for hereditary haemochromatosis (HH) caused by HFE mutations before the onset of symptoms. However, there is no optimum screening strategy, mainly owing to the variable penetrance in those who are homozygous for the HFE Cys282Tyr (C282Y) mutation. The objective of this study was to identify the majority of individuals at serious risk of developing HFE haemochromatosis before they developed life threatening complications.

METHODS

We first estimated the therapeutic penetrance of the C282Y mutation in people living in la Somme, France, using genetic, demographic, biochemical, and follow up data. We examined the benefits of neonatal screening on the basis of increased risk to relatives of newborns carrying one or two copies of the C282Y mutation. Between 1999 and 2002, we screened 7038 newborns from two maternity hospitals in the north of France for the C282Y and His63Asp (H63D) mutations in the HFE gene, using bloodspots collected on Guthrie cards. Family studies and genetic counselling were undertaken, based on the results of the baby's genotype.

FINDINGS

In la Somme, we found that 24% of the adults homozygous for the C282Y mutation required at least 5 g iron to be removed to restore normal iron parameters (that is, the therapeutic penetrance). In the reverse cascade screening study, we identified 19 C282Y homozygotes (1/370), 491 heterozygotes (1/14) and 166 compound heterozygotes (1/42) in 7038 newborns tested. The reverse cascade screening strategy resulted in 80 adults being screened for both mutations. We identified 10 previously unknown C282Y homozygotes of whom six (four men and two women) required venesection. Acceptance of neonatal screening was high; parents understood the risks of having HH and the benefits of early detection, but a number of parents were reluctant to take the test themselves. Neonatal screening for HH is straightforward. Reverse cascade screening increased the efficiency of detecting affected adults with undiagnosed haemochromatosis. This strategy allows almost complete coverage for HH and could be a model for efficient screening for other late onset genetic diseases.

Bases moléculaires des hémochromatoses génétiques

PURPOSE

Recent discoveries in molecular mechanisms of iron metabolism have changed the classical view of hereditary iron overload conditions. We present natural mutations in newly discovered genes and related phenotypes observed in patients with different form of haemochromatosis.

CURRENT KNOWLEDGE AND KEY POINTS

Most haemochromatosis patients are homozygous for the C282Y mutation in the HFE gene. Ferroportin, TFR2, hemojuvelin and hepcidin mutations also cause iron overload. Recent data support the hypothesis that haemochromatosis should no longer be considered a monogenic disease but rather an oligogenic disorder. Several results suggest that haemochromatosis could result from digenic inheritance of mutations in HFE and HAMP.

FUTURE PROSPECTS AND PROJECTS

Other modifier genes probably influence penetrance in C282Y homozygous patients. Such genes could enhance or reduce the phenotypic expression in various iron overload conditions.

[Advances in iron metabolism: a transition state]

PURPOSE

Advances towards the understanding of gene regulation and protein function recently discovered through iron metabolism disorders are the subject of this review.

CURRENT KNOWLEDGE AND KEY POINTS

Within a few years the discovery of genes that determine heritable defects of cellular iron uptake or regulation in mice as in humans have provided new insights for investigation into iron metabolism pathways.

FUTURE PROSPECTS AND PROJECTS

It is still unclear how connections are made between new proteins in iron uptake, trafficking and regulation of iron homeostasis. Gene expression studies using microarrays technology in different iron conditions should help to explore iron homeostasis further.

The 16189 variant of mitochondrial DNA occurs more frequently in C282Y homozygotes with haemochromatosis than those without iron loading

BACKGROUND

Patients with hereditary haemochromatosis (HH) are usually homozygous for the C282Y mutation in the HFE gene. They have variable expression of iron overload and present with a variety of complications, including liver disease, diabetes, arthropathy, fatigue, and cardiomyopathy. The mitochondrial 16189 variant is associated with diabetes, dilated cardiomyopathy, and low body fat at birth, and might contribute to genetic predisposition in further multifactorial disorders. The objective of this study was to determine the frequency of the 16189 variant in a range of patients with haemochromatosis, who had mutations in the HFE gene.

METHODS

Blood DNA was analysed for the presence of the 16189 variant in British, French, and Australian C282Y homozygotes and controls, with known iron status, and in birth cohorts.

RESULTS

The frequency of the mitochondrial 16189 variant was found to be elevated in individuals with haemochromatosis who were homozygous for the C282Y allele, compared with population controls and with C282Y homozygotes who were asymptomatic (42/292 (14.4%); 102/1186 (8.6%) (p = 0.003); and 2/64 (3.1%) (p = 0.023), respectively).

CONCLUSIONS

Iron loading in C282Y homozygotes with HH was exacerbated by the presence of the mitochondrial 16189 variant.

A targeted approach significantly increases the identification rate of patients with undiagnosed haemochromatosis

OBJECTIVE

To determine the optimal means of identifying patients with undiagnosed haemochromatosis.

DESIGN

Case-control study where cases are defined by the presence of specific clinical diagnoses or symptoms.

SETTING

Primary care patients were recruited from three Oxfordshire practices and secondary care patients were recruited from those patients attending specialist clinics in Amiens University Hospital.

SUBJECTS

A total of 569 patients recruited via hospital clinics and 60 primary care patients (recruited from 4022 consultations) presenting with the following haemochromatosis associated conditions, diabetes, arthralgia/chronic fatigue, osteoporosis or arthropathy were studied. The control group, a total of 991 healthy volunteers, were recruited through a Health Appraisal Centre. Patients and controls were included in the study if they or their family members had not previously been diagnosed with hereditary haemochromatosis.

MAIN OUTCOME MEASURES

Serum ferritin concentration, transferrin saturation (Tsat) and presence of HFE mutations, C282Y and H63D. The check-up in controls consisted of a questionnaire, clinical examination, biochemical tests and screening for the presence of the C282Y and H63D mutations.

RESULTS

Patient groups presenting with unstable diabetes or chronic fatigue and arthralgia together with a raised serum ferritin concentration showed an enrichment in the haemochromatosis-associated genotype HH/YY, odds ratio (OR) = 40.1, confidence interval (CI) = 8.0-202.1 and OR = 103, CI = 22.9-469.7, respectively.

CONCLUSION

Patients presenting to hospital clinics with haemochromatosis associated conditions should be screened biochemically for iron overload. Only those with a serum ferritin >300 microg L-1 or Tsat >40% should subsequently go on to be genotyped for HFE mutations. The patients at greatest risk of having undiagnosed haemochromatosis are those presenting with unstable diabetes, or fatigue and/or arthralgia in the absence of any other explanation.

Geography of HFE C282Y and H63D mutations

Hereditary hemochromatosis (HH) is a common autosomal recessive disorder causing inappropriate dietary iron absorption that affects North Europeans. HH is associated with the C282Y mutation of the HFE gene, and the H63D mutation to a lesser degree. Both mutations are abundant in Europe, with H63D also appearing in North Africa, the Middle East, and Asia. Emigration from Europe over the past 500 years has introduced C282Y and H63D to America, Australia, New Zealand, and South Africa in an essentially predictable fashion. The distinctive characteristics of the population genetics of HH are the confined racial distribution and high frequency in North European peoples. C282Y frequencies in North Europeans are typically between 5% and 10%, with homozygotes accounting for between 1/100 and 1/400 of these populations. The scarcity of the C282Y mutation in other populations accounts for the lack of HH in non-Europeans.

A 3-dimensional model building by homology of the HFE protein: molecular consequences and application to antibody development

Genetic hemochromatosis (GH) is a common inherited disease of iron metabolism affecting 2-5 in 1000 individuals of European origin. A candidate gene for GH, namely HFE has been recently characterized. Structural studies of the protein product of the HFE gene are of major interest for a better understanding of the molecular physiopathology in iron overload. We have built a 3-dimensional model of the HFE protein based on congruent with40% homology of sequence identity with HLA-Aw68, another MHC class I molecule. This work presents the first 3-dimensional structure of HFE available in the public domain (http://swift.embl-heidelberg.de/service/francois). The 3-dimensional characteristics of the protein complexed with the beta2-microglobulin are presented. The model has been used to predict immunogenic loops and to develop an antibody able to recognize a protein exhibiting the same molecular weight as HFE. Structural consequences of two common mutations are debated and evolutionary hypotheses are considered in the discussion of the particular biological activity of HFE. This study shows that a strategy based on homology modeling is sufficient to undertake biological investigations.

An integrated map of human 6q22.3-q24 including a 3-Mb high-resolution BAC/PAC contig encompassing a QTL for fetal hemoglobin

Genetic studies have previously assigned a quantitative trait locus (QTL) for hemoglobin F and F cells to a region of approximately 4 Mb between the markers D6S408 and D6S292 on chromosome 6q23. An initial yeast artificial chromosome contig of 13 clones spanning this region was generated. Further linkage analysis of an extended kindred refined the candidate interval to 1-2 cM, and key recombination events now place the QTL within a region of <800 kb. We describe a high-resolution bacterial clone contig spanning 3 Mb covering this critical region. The map consists of 223 bacterial artificial chromosome (BAC) and 100 P1 artificial chromosome (PAC) clones ordered by sequence-tagged site (STS) content and restriction fragment fingerprinting with a minimum tiling path of 22 BACs and 1 PAC. A total of 194 STSs map to this interval of 3 Mb, giving an average marker resolution of approximately one per 15 kb. About half of the markers were novel and were isolated in the present study, including three CA repeats and 13 single nucleotide polymorphisms. Altogether 24 expressed sequence tags, 6 of which are unique genes, have been mapped to the contig.

Born to clot: the European burden

Venous thrombosis is a common problem, predominantly afflicting people of European origin. This European predisposition has been explained to some extent by the recent characterization of factor V Leiden, and the G20210A prothrombin variant. Although it is clear that factor V Leiden is largely confined to Europeans, the world distribution of the prothrombin variant is not known. We have analysed samples from 22 different non-European countries and shown that this prothrombin variant is very rare outside Europe: one case occurring in India. The reason for the confined distribution of these two mutations is unclear.

Multicentric origin of hemochromatosis gene (HFE) mutations

Genetic hemochromatosis (GH) is believed to be a disease restricted to those of European ancestry. In northwestern Europe, >80% of GH patients are homozygous for one mutation, the substitution of tyrosine for cysteine at position 282 (C282Y) in the unprocessed protein. In a proportion of GH patients, two mutations are present, C282Y and H63D. The clinical significance of this second mutation is such that it appears to predispose 1%-2% of compound heterozygotes to expression of the disease. The distribution of the two mutations differ, C282Y being limited to those of northwestern European ancestry and H63D being found at allele frequencies>5%, in Europe, in countries bordering the Mediterranean, in the Middle East, and in the Indian subcontinent. The C282Y mutation occurs on a haplotype that extends </=6 Mb, suggesting that this mutation has arisen during the past 2,000 years. The H63D mutation is older and does not occur on such a large extended haplotype, the haplotype in this case extending </=700 kb. Here we report the finding of the H63D and C282Y mutations on new haplotypes. In Sri Lanka we have found H63D on three new haplotypes and have found C282Y on one new haplotype, demonstrating that these mutations have arisen independently on this island. These results suggest that the HFE gene has been the subject of selection pressure. These selection pressures could be due to infectious diseases, environmental conditions, or other genetic disorders such as anemia.

Familial infantile convulsions and paroxysmal choreoathetosis: a new neurological syndrome linked to the pericentromeric region of human chromosome 16

Benign infantile familial convulsions is an autosomal dominant disorder characterized by nonfebrile seizures, with the first attack occurring at age 3-12 mo. It is one of the rare forms of epilepsy that are inherited as monogenic Mendelian traits, thus providing a powerful tool for mapping genes involved in epileptic syndromes. Paroxysmal choreoathetosis is an involuntary-movement disorder characterized by attacks that occur spontaneously or are induced by a variety of stimuli. Classification is still elusive, and the epileptic nature of this movement disorder has long been discussed and remains controversial. We have studied four families from northwestern France in which benign infantile convulsions was inherited as an autosomal dominant trait together with variably expressed paroxysmal choreoathetosis. The human genome was screened with microsatellite markers regularly spaced, and strong evidence of linkage for the disease gene was obtained in the pericentromeric region of chromosome 16, with a maximum two-point LOD score, for D16S3133, of 6.76 at a recombination fraction of 0. Critical recombinants narrowed the region of interest to a 10-cM interval around the centromere. Our study provides the first genetic evidence for a common basis of convulsive and choreoathetotic disorders and will help in the understanding and classification of paroxysmal neurological syndromes.

Genetic heterogeneity in heterocellular hereditary persistence of fetal hemoglobin

A large English pedigree in which heterocellular hereditary persistence of fetal hemoglobin (HPFH) segregates is described. beta-globin cluster deletions and gamma gene promoter mutations associated with HPFH have been excluded. Of particular importance in this pedigree is the absence of any cosegregating hemoglobinopathy, thus allowing observation of the segregation pattern of this form of HPFH without the complicating effect of a beta-globin gene mutation. Information gained in this study confirms that the extent of elevation of hemoglobin (Hb) F and F cells varies between affected individuals. There are one example of incomplete penetrance and three examples of father-to-son transmission, thus excluding X-linked inheritance. Consistent with previous reports, the most likely mode of inheritance is autosomal codominant. Linkage studies using a beta-globin cluster microsatellite show no evidence of linkage to this chromosomal region implicating the presence of trans-acting regulatory factor(s). We have recently mapped one such locus to the chromosome 6q region in a very large Asian-Indian pedigree. Linkage to chromosome 6q in the English pedigree was excluded, thus indicating the presence of genetic heterogeneity in heterocellular HPFH.

Chromosomal stabilisation by a subtelomeric rearrangement involving two closely related Alu elements

We have characterised a subtelomeric rearrangement involving the short arm of chromosome 16 that gives rise to alpha-thalassaemia by deleting the major, remote regulatory element controlling alpha-globin expression. The chromosomal breakpoint lies in an Alu family repeat located only approximately 105 kb from the 16p subtelomeric region. The broken chromosome has been stabilised with a newly positioned telomere acquired by recombination between this 16p Alu element and a closely related subtelomeric Alu element of the Sx subfamily. It seems most likely that this abnormal chromosome has been rescued by the mechanism of telomere capture which may reflect a more general process by which subtelomeric sequences are normally dispersed between chromosomal ends.

A novel silent posttranslational mechanism converts methionine to aspartate in hemoglobin Bristol (beta 67[E11] Val-Met->Asp)

The first reported case of congenital Heinz body hemolytic anemia was subsequently shown to be caused by an unstable hemoglobin, Hb Bristol [beta 67(E11) Val-Asp]. This has become one of the classic models of an unstable hemoglobin, the hydrophilic aspartate disrupting the hydrophobic heme pocket. We have restudied this original case, who remains clinically well after nearly 50 years of severe hemolysis with a hemoglobin level of about 7 g/dL and two unrelated Japanese cases. Surprisingly, all three cases show the same DNA changes, predicting a valine to methionine change at beta 67, rather than the expected aspartate. Further analysis with electrospray ionization mass spectrometry and globin chain biosynthesis strongly suggests that this anomaly is because of a novel posttranslational mechanism, with slow conversion of the translated methionine into an aspartate residue. The proximity of the heme and oxygen may be important in facilitating the reaction. These findings show the importance of complete characterization of variant hemoglobins using protein, DNA, and biosynthetic analyses.

Hb Sun Prairie: diagnostic pitfalls in thalassemic hemoglobinopathies

We report an Asian Indian family in which two daughters have Hb Sun Prairie, a known unstable alpha 2-globin variant [codon 130, GCT-->CCT; alpha 2 130(H13)Ala-->Pro beta 2]. While the homozygous probands have chronic hemolysis-the same phenotype as previously reported, the heterozygous parents are asymptomatic with a thalassemia carrier phenotype, distinct from the chronic hemolytic state previously described in a heterozygote. Unlike the earlier cases in which family studies were not available, this family clearly exhibits autosomal recessive inheritance, unusual amongst variants within the same region of helix H. Globin chain biosynthesis ratios initially suggested a beta-thalassemic hemoglobinopathy-this was excluded by normal sequence analysis of both beta-globin genes. This case report further illustrates the complexity of phenotypes in the thalassemic hemoglobinopathies. It also demonstrates inversion of the alpha/beta-globin chain biosynthesis ratio, a phenomenon which had been noted in other alpha-globin variants and can be a confounding factor in the investigation of thalassemic hemoglobinopathies.

Moderate reduction of beta-globin gene transcript by a novel mutation in the 5' untranslated region: a study of its interaction with other genotypes in two families

We have identified two individuals of Greek Cypriot origin with thalassemia intermedia. Molecular analysis has shown that each individual is a compound heterozygote for a previously described beta zero thalassemia allele and a novel mutation, C-->G in position +33, in the 5' untranslated region of the beta globin gene. In both families the beta +33 allele is associated with the same beta haplotype (-++- ) suggesting that it is likely to be of a single origin, beta-cDNAs from normal and mutant beta alleles were isolated from peripheral blood reticulocytes using the technique of reverse transcription-polymerase chain reaction. Because the beta +33 (C-->G) mutation creates a cutting site for the restriction enzyme NlalV, we could demonstrate by differential restriction analysis that the beta gene with +33 mutation showed 25% to 35% residual activity compared with normal. The additive effect of this moderate deficit in beta globin production with the beta zero thalassemia mutation would explain the clinical phenotypes observed in the two probands. In contrast, two siblings of one proband who were also compound heterozygotes for the same beta thalassemia mutations, as well as heterozygotes for a nondeletional alpha thalassemia variant, and two other compound heterozygotes for the beta +33 and a beta+ thalassemia allele were completely asymptomatic. Individuals heterozygous for the beta +33 C-G mutation alone are clinically and hematologically silent, with normal red blood cell indices and normal levels of hemoglobin (Hb) A2. A direct relationship between genotypic and phenotypic severity is clearly demonstrated in these cases with obvious implications for prenatal diagnosis.

Dissecting the loci controlling fetal haemoglobin production on chromosomes 11p and 6q by the regressive approach

The changes in the type of haemoglobin (Hb) produced during embryonic, fetal and adult life, have served as a paradigm for understanding the developmental regulation of human genes. A genetically determined persistence of fetal Hb synthesis has an ameliorating effect on beta thalassaemia and sickle cell anaemia, globally the commonest single gene disorders. The search for the putative gene(s) controlling the level of fetal Hb production has been extremely difficult because this trait may be influenced by several factors. We have studied a large kindred with hereditary persistence of fetal haemoglobin (HPFH). Using a genetic mapping strategy and statistical methods that account simultaneously for the effects of several genetic factors, we have demonstrated that in addition to the two factors (beta thalassaemia and Xmn I-G gamma site) on chromosome 11p, there is a third major genetic determinant for fetal Hb production localized on chromosome 6q.

Fetal hemoglobin levels in adults

The synthesis of fetal hemoglobin (HbF) is normally reduced to very low levels of less than 0.6% of the total hemoglobin in adults. The HbF is restricted to a sub-population of erythrocytes termed 'F-cells'; 85% of the normal adult population have 0.3% to 4.4% F-cells. The levels of HbF and F-cells vary by more than 10-fold in normal adults; family studies show that these levels are genetically controlled but the number and nature of these genetic factors are still poorly understood. HbF levels may be increased in adults in a number of inherited and acquired disorders, accompanied by an increase in both the number of F-cells and the amount of HbF per F-cell. The clinical significance of these conditions with raised HbF relates to their interaction in disorders such as sickle cell disease and beta thalassaemia in which raised levels of HbF can lead to considerable amelioration of disease severity. Study of the 'natural' mutants primarily associated with increased HbF has provided considerable insight into the understanding of the control of globin gene regulation and hemoglobin switching. Currently considerable effort is being channelled into clinical trials and the search for the 'ideal' therapeutic agents which could increase HbF in adult life with minimal drug toxicity.

Detection of a major gene for heterocellular hereditary persistence of fetal hemoglobin after accounting for genetic modifiers

"Heterocellular hereditary persistence of fetal hemoglobin" (HPFH) is the term used to describe the genetically determined persistence of fetal hemoglobin (Hb F) production into adult life, in the absence of any related hematological disorder. Whereas some forms are caused by mutations in the beta-globin gene cluster on chromosome 11, others segregate independently. While the latter are of particular interest with respect to the regulation of globin gene switching, it has not been possible to determine their chromosomal location, mainly because their mode of inheritance is not clear, but also because several other factors are known to modify Hb F production. We have examined a large Asian Indian pedigree which includes individuals with heterocellular HPFH associated with beta-thalassemia and/or alpha-thalassemia. Segregation analysis was conducted on the HPFH trait FC, defined to be the percentage of Hb F-containing cells (F-cells), using the class D regressive model. Our results provide evidence for the presence of a major gene, dominant or codominant, which controls the FC values with residual familial correlations. The major gene was detected when the effects of genetic modifiers, notably beta-thalassemia and the XmnI-G gamma polymorphism, are accounted for in the analysis. Linkage with the beta-globin gene cluster is excluded. The transmission of the FC values in this pedigree is informative enough to allow detection of linkage with an appropriate marker(s). The analytical approach outlined in this study, using simple regression to allow for genetic modifiers and thus allowing the mode of inheritance of a trait to be dissected out, may be useful as a model for segregation and linkage analyses of other complex phenotypes.

Association of a novel high oxygen affinity haemoglobin variant with delta beta thalassaemia

We report an uncommon association of delta beta thalassaemia and a haemoglobin (Hb) variant with high oxygen affinity in an Asian Indian family. Minimal polycythaemia was seen in a heterozygote for this novel Hb variant, Hb Headington (beta 72 (E16) Ser-->Arg), while compound heterozygosity for Hb Headington and the Indian G gamma (A gamma delta beta)(0) thalassaemia produces a marked increase in erythrocytosis with a concomitant increase in the level of the variant Hb. The HbF in such compound heterozygotes remains at a level consistent with that usually observed in individuals heterozygous for the G gamma (A gamma delta beta)(0) thalassaemia alone. The purified Hb variant showed an increased oxygen affinity, moderately decreased co-operativity and a normal Bohr effect. Results of functional studies suggest that the high oxygen affinity of Hb Headington is due to the Ser-->Arg substitution which disrupts the normal and tight interaction between A, B and E helices leading to a destabilization of the T deoxy-structure of the abnormal haemoglobin.

Rapid analysis of -alpha 3.7 thalassaemia and alpha alpha alpha anti 3.7 triplication by enzymatic amplification analysis

In this report we describe a PCR-based method for the diagnosis of the most common form of alpha thalassaemia, the -alpha 3.7 deletion which occurs throughout all tropical and subtropical regions of the world. The same procedure also identifies the reciprocal recombinant chromosome (alpha alpha alpha anti 3.7). Restriction mapping of the PCR products has enabled us to distinguish between the type I (-alpha 3.7 I), type II (-alpha 3.7 II) and type III (-alpha 3.7 III) deletions. This strategy will be very useful in screening programmes of alpha thalassaemia occurring on its own or in association with beta thalassaemia and sickle cell disease.

Locus assignment of human alpha globin mutations by selective amplification and direct sequencing

We describe a simple approach for molecular characterization and locus assignment of structural mutants by direct sequencing of enzymatically amplified DNA selective to alpha 1 and alpha 2 globin gene regions. Nucleotide substitution of two structural variants (Stanleyville II alpha 2(78Lys) and J Mexico alpha 2(54Glu) were determined and their encoding loci were specified. The amplified segment encompasses sequences upstream of the CAAT box to downstream of the Poly(A) addition signal. Hence all of the alpha globin structural variants and most of the nondeletion alpha thalassaemic mutants should be characterizable by this approach.

Level and composition of fetal hemoglobin expression in normal newborn babies are not dependent on beta cluster DNA haplotype

Interindividual variations in the level and composition of fetal hemoglobin observed in 604 cord blood samples from normal white and nonwhite newborns, unlike those in adults, are not dependent on beta gene cluster DNA haplotype. The data suggest that the mechanism(s) involved in the neonatal expression of Hb F is distinct from that at the adult stage.

Effect of ligand-affinity differences of human hemoglobin variants on electrophoretic behavior and their isolation and functional characterization

A natural sulfated polysaccharide (agaropectin), contained in crude agar, can be used as a medium for electrophoretic separation of hemoglobin mutants, constituting a particular class of protein-ligand interactions. Mutations which either modify the electrostatic charge at the surface of the hemoglobin molecule or not, have been studied according to their putative interaction with the medium. Using conformational specificities of the hemoglobin molecule, we have also demonstrated that isoelectric focusing on a polyacrylamide gel in the absence of heme ligands represents a useful, convenient and rapid procedure for isolating silent Hb variants in their native form, provided that they exhibit an abnormal Bohr effect.

Autosomal dominant polycystic kidney disease and alpha -4.2 thalassemia in a Caucasian family

We describe the first known association between autosomal dominant polycystic kidney disease (ADPKD) and alpha-4.2 thalassemia in a Caucasian family. Linkage studies have been carried out using two probes (3'HVR and 24-1) linked to ADPKD on locus PKD1 and two probes (alpha 1-PstI and BamH-I/EcoRI-zeta 2 fragment) allowing detection of alpha-thalassemia with either a 3.7-kb deletion or a 4.2-kb deletion. Our results show that to avoid misinterpretation it is important to investigate the occurrence of an alpha-gene deletion when polymorphisms situated in the alpha-globin locus are used for linkage studies on ADPKD. The studied family is one of the rare cases of leftward deletional thalassemia described in a non-Asian population.

Analysis of crossover type in the alpha -3.7 haplotype among sickle cell anemia patients from various parts of Africa

The frequency of alpha+-thalassemia has been determined in African populations carrying beta S-chromosomes of different origins. All these alpha+ thalassemias result from a right-ward deletion. Restriction mapping of the alpha -3.7/haplotype with the enzyme ApaI only showed the presence of a type I crossover. RsaI polymorphism at the 5' end of Z alpha 2 is largely represented in the normal population (gene frequency 23%) but, in our series, never associated with the alpha -3.7/haplotype.

Detection of Duchenne muscular dystrophy carriers: quantitative echography and creatine kinasemia

Data obtained from simultaneous determinations of serum creatine-kinase levels and estimation of ultrasound attenuation values in muscles greatly improved the detection of obligate carriers of Duchenne muscular dystrophy than when only one of these methods was employed alone. Eleven carriers out of 19 had a high creatine-kinasemia level and nine carriers out of 19 had a high (abnormal) attenuation value. Because of the limited overlapping between the two parameters studied, we were able to recognize 17 obligate carriers out of the 19. This indicates that the parameters studied concern different features of the disease, and the practical and theoretical considerations are discussed. The techniques are discussed together with molecular genetic investigations.

Strategy for structural characterization of haemoglobin variants

High-performance liquid chromatography allows one to perform effective and rapid separations on microquantities of material. The miniaturization of the techniques led to new approaches involving isoelectric focusing (IEF) of immobilized pH gradient IEF for haemoglobin preparation, successive enzymic hydrolyses for isolating abnormal peptides and amino acid composition determination after precolumn derivatization.

Haemoglobin disorders among Southeast-Asian refugees in France

Haemoglobin disorders were studied among Southeast-Asian refugees (Vietnamese, Cambodians and Laotians). Phenotypic haemoglobin investigations and genotypical studies concerning the alpha loci were carried out. Most of the observed cases of microcytosis were related to a thalassaemic defect. High prevalence of Hb E and alpha-thalassaemia were found.

Isolation of human haemoglobin variants with altered Bohr effect. Application to haemoglobin Rainier

Isoelectric focusing on polyacrylamide gel in the absence of haem ligands represents a useful, convenient and rapid procedure to isolate silent Hb variants in their native forms, provided that they exhibit an abnormal Bohr effect. The amount of material which is eluted is sufficient for both a limited functional study and a structural determination using microscale high-performance liquid chromatography. This is exemplified by the isolation and the study of Hb Rainier.

Electrophoretic and chromatographic techniques for the differential diagnosis of a haemoglobin abnormality: Hb E heterozygosity

A method is described for separating haemoglobin (Hb) E (beta 26 Gly----Lys) from Hb A2 (a normal minor Hb component in adult blood). The technique allows the distinction between subjects carrying beta-thalassaemia trait and patients who are simultaneously alpha-thalassaemic and heterozygous for Hb E, the standard electrophoretic pattern often being similar in these two circumstances. Complete separation between Hb E and Hb A2 (2 mm empty space in between) is obtained by isoelectric focusing in immobilized pH gradients in an ultra-narrow pH 7.55-7.65 gradient. The apparent pI values of the two species (at 10 degrees C and at an average ionic strength of 5.6 mequiv. l-1) have been calculated to be 7.603 for Hb E and 7.607 for Hb A2. Thus, the system reported here affords a resolution of at least 0.004 pH unit.