Isolation of NF-E2-related factor 2 (Nrf2), a NF-E2-like basic leucine zipper transcriptional activator that binds to the tandem NF-E2/AP1 repeat of the beta-globin locus control region

Hypersensitive site 2 located in the beta-globin locus control region confers high levels of expression to the genes of the beta-globin cluster. A tandem repeat of the consensus sequence for the transcription factors AP1 and NF-E2 (activating protein 1 and nuclear factor erythroid 2, respectively) is present within hypersensitive site 2 and is absolutely required for strong enhancer activity. This sequence binds, in vitro and in vivo, to ubiquitous proteins of the AP1 family and to the recently cloned erythroid-specific transcription factor NF-E2. Using the tandem repeat as a recognition site probe to screen a lambda gt11 cDNA expression library from K562 cells, we isolated several DNA binding proteins. Here, we report the characterization of one of the clones isolated. The gene, which we named Nrf2 (NF-E2-related factor 2), is encoded within a 2.2-kb transcript and predicts a 66-kDa protein with a basic leucine zipper DNA binding domain highly homologous to that of NF-E2. Although Nrf2 is expressed ubiquitously, a role of this protein in mediating enhancer activity of hypersensitive site 2 in erythroid cells cannot be excluded. In this respect, Nrf2 contains a powerful acidic activation domain that may participate in the transcriptional stimulation of beta-globin genes.

Improvement of prenatal diagnosis of Wilson disease using microsatellite markers

This paper describes a case of prenatal diagnosis for Wilson disease (WD) carried out in an at-risk couple of Sardinian descent, following non-directive genetic counselling. Diagnosis was obtained by using eight microsatellites located within or flanking the WD locus, six of which were 100 per cent and two 50 per cent informative. The use of several markers may limit the occurrence of misdiagnosis resulting from recombination or instability of repeats.

Umbilical artery velocity waveforms before and after chorionic villus sampling

Because a vascular aetiology has been suggested for the limb and oromandibular defects described after chorionic villus sampling (CVS), to determine whether transabdominal (TA) CVS causes noticeable changes in umbilical artery velocity waveforms in first-trimester pregnancies, the pulsatility index (PI) of the umbilical artery was evaluated before and after TA-CVS in 175 pregnancies sampled between 10.0 and 13.0 weeks' gestation. In 139 uncomplicated pregnancies, the mean PI values (with 95 per cent confidence interval) were before TA-CVS 2.751 (2.692-2.809), after 10 min 2.723 (2.697-2.809), and after 1 h 2.781 (2.722-2.840). There were no significant changes in PI relative to the CVS procedure either in pregnancies with an abnormal result or in those ending in spontaneous abortion. Our data do not support any statistically significant change in umbilical artery PI relative to TA-CVS in first-trimester pregnancies. This procedure, despite its invasive character, does not appear to affect the feto-placental circulation.

Healing of broken human chromosomes by the addition of telomeric repeats

We have characterized and compared a series of naturally occurring chromosomal truncations involving the terminal region of the short arm of human chromosome 16 (16p13.3). All six broken chromosomes appear to have been stabilized by the direct addition of telomeric repeats (TTAGGG)n to nontelomeric DNA. In five of the six chromosomes, sequence analysis shows that the three of four nucleotides preceding the point of telomere addition are complementary to and in phase with the putative RNA template of human telomerase. Otherwise we have found no common structural features around the breakpoint regions. These findings, together with previously reported in vitro data, suggest that chromosome-healing events in man can be mediated by telomerase and that a small region of complementarity to the RNA template of telomerase at the end of a broken chromosome may be sufficient to prime healing in vivo.

Thermal behavior and elastic properties of dimyristoyl phosphatidylcholine bilayers under the effect of pentoxifylline

We have investigated the effect on dimyristoyl phosphatidylcholine bilayers of pentoxifylline, a derivative of xanthine by using two optical techniques, quasi-elastic light scattering (QLS) and Fourier transform infrared spectroscopy (FT-IR). The results show that in the presence of pentoxifylline, the bilayer phase transition point is lowered and that the elastic modulus is decreased. The FT-IR results indicate strong interactions in the aqueous interface regions of the bilayers. We discussed these results comparatively with those obtained from flavonoid derivatives whose effect was analogous and previously studied.

Blepharophimosis, ptosis, epicanthus inversus syndrome, a new case associated with de novo balanced autosomal translocation [46,XY,t(3;7)(q23;q32)]

This paper reports a further case of blepharophimosis, ptosis, epicanthus inversus (BPES) syndrome associated with a reciprocal translocation [46,XY,t(3;7)(q23;q32)], involving band 3q23. This case supports the assignment of a BPES gene(s) to the 3q23 region.

A gene dosage effect of the DQA1*0501/DQB1*0201 allelic combination influences the clinical heterogeneity of celiac disease

This study reports the HLA-DR and DQ molecular characterization of 62 CD patients of Sardinian descent. Patients were divided in two groups (36 in group I and 26 in group II) according to the clinical features at the disease onset. Among the patients of group I, having the fully expressed form of CD and a mean age of 3 years at disease onset, a significant increase of DRB1*0301, DQA1*0501, DQB1*0201 homozygotes, encoding in cis two DQ (alpha 1*0501, beta 1*0201) susceptibility heterodimers, was observed when compared either with the patients of group II (pIII < 0.012) or with healthy individuals (pI < 10(-6)). On the other hand, in the patients of group II, presenting oligosymptomatic forms and a mean age of 5.7 years at the disease onset, the haplotype combinations encoding in cis or in trans only one DQ (alpha 1*0501, beta 1*0201) heterodimer were significantly increased in comparison either with the patients of group I (pIII < 0.026) or with controls (pII < 10(-6)). These findings suggest that a double dose of DQA1*0501, DQB1*0201 genes may predispose a person to an earlier onset and to more severe disease manifestations. Genotype analysis showed that only three patients (all in group I) failed to form in trans or in cis the DQ (alpha 1*0501, beta 1*0201) heterodimer and carried the DQA1*0101,DQB1*0501 haplotype, suggesting its possible role in CD susceptibility. In addition, a significant increment of DQB1*0501 gene (pc < 0.0065) was found comparing the frequency of DQB1 alleles in CD patients and healthy controls, after exclusion of DQB1*0201 chromosomes.(ABSTRACT TRUNCATED AT 250 WORDS)

HLA-DQB1*0305 and -DQB1*0304 alleles among Sardinians. Evolutionary and practical implications for oligotyping

This study, performed in individuals of Sardinian descent, reports an epidemiologic and molecular analysis of the recently identified DQB1*0304 and DQB1*0305 alleles. These two alleles having a gene frequency of 0.017 and 0.005, respectively, are not uncommon in Sardinia and are distributed fairly uniformly on the island. The analysis of DQB1 second and third exons of the two alleles revealed that although they have always been found included within the same DRB1*0403-DQA1*03 haplotype, they had a different origin. The sequence pattern of DQB1*0305 confirmed that it originated from the DQB1*0302 "recipient" gene by the insertion of a DQB1*0402 nucleotide stretch, within its beta-sheet region, while that of DQB1*0304 suggested that it originated from the DQB1*0301 gene, either by a single point mutation at codon 57 (GCC instead of GAC) or, alternatively, by a segmental transfer of a DQB1*0302 motif, including codon 57, within its alpha-helic region. Independently from the mechanism of generation, the fact that DQB1*0304 originated from DQB1*0301 allele was intriguing considering that, in over 1500 HLA class II Sardinian haplotypes examined, neither the putative parental DRB1*0403-DQA1*03-DQB1*0301 haplotypes were found. Finally, since the assignment of DQB1*0305 may be inaccurate with the traditional panel of probes commonly used for DQB1 oligotyping, the use of an additional oligonucleotide probe is recommended.

A report on 528 intragenic deletions detected in DMD and BMD patients by an Italian collaborative study

The results of a collaborative study involving about one third of the total DMD and BMD cases living in the Italian territory are reported. The analysis of the breakpoint frequency by intron revealed significant differences among regional groups of DMD patients (for introns 2, 11 and 50 in Sardinia and for introns 9 and 45 in northeastern Italy), whereas no regional differences were observed among regional groups of BMD patients. These differences involve the same Italian regions which previous studies, performed by different markers, identified as "genetically differentiated". The data support the possibility of a differential distribution among populations of some intronic sequences, facilitating the origin of deletion breakpoints within the dystrophin gene.

Genotype-phenotype correlations in beta-thalassemias

In this paper we review the molecular basis of the marked heterogeneity of the thalassemia syndromes as well as the relative implications for carrier screening and prenatal diagnosis. The classical phenotype of heterozygous beta-thalassemia may be modified by a number of environmental and genetic interacting factors--among which the most relevant are: (1) coinheritance of alpha-thalassemia, which may normalize the red blood cell indices; (2) the presence of a mild beta-thalassemia mutation; (3) cotransmission of delta-thalassemia which may reduce the increase of HbA2 typical of heterozygous beta-thalassemia to normal values and (4) the presence of a silent mutation which can be defined only by imbalanced beta-globin chain synthesis. A number of molecular mechanisms are able to produce the non transfusion dependent attenuated forms of thalassemia syndromes referred to as thalassemia intermedia. The most common are homozygosity for mild beta-thalassemia mutations, coinheritance with homozygous beta-thalassemia of alpha-thalassemia or genetic determinants able to sustain a continuous production of HbF in adult life or the presence of heterozygosity for hyperunstable globin variants.

Hepatitis C virus in multiple episodes of acute hepatitis in polytransfused thalassaemic children

We investigated the course of distinct episodes of acute non-A, non-B (NANB) hepatitis in three polytransfused thalassaemic children. In each case, the first episode was associated with the appearance of serum hepatitis C virus (HCV) RNA and anti-HCV seroconversion. The second episode was accompanied by the reappearance of HCV viraemia, which in two patients was due to reinfection with a different HCV strain and in the third could be the result of either reactivation of primary infection or reinfection with a new but closely related strain. Thus HCV infection may not induce protective immunity, which has implications for vaccine development.

Psychological implications and acceptability of preimplantation diagnosis

The aim of this study was to ascertain the degree of acceptability of preimplantation diagnosis with blastocentesis in 180 women at risk for beta-thalassaemia awaiting chorionic villus sampling (CVS). The women were asked to fill in a questionnaire some days before sampling. All women who had had previous therapeutic abortion found blastocentesis acceptable. Only 30% of women who had not had previous therapeutic abortion chose blastocentesis, whilst 25% of primigravid women opted for blastocentesis. From these preliminary data it seems that obstetric experience is an important factor in the reproductive choice of women at high genetic risk.

Hypothalamic growth hormone deficiency in a patient with ring chromosome 18

We report on a boy with a ring 18 chromosome associated with hypothalamic growth hormone (GH) deficiency. A 12-month trial of GH replacement therapy (0.5 U/kg/week) resulted in a marked growth acceleration. Our findings emphasise the need of evaluating GH secretion in patients with abnormalities of the 18 chromosome.

Serum erythropoietin and erythropoiesis in high- and low-fetal hemoglobin beta-thalassemia intermedia patients

Clinical data suggest that in beta-thalassemia-intermedia patients, higher levels of circulating fetal hemoglobin (HbF) are associated with greater disease severity at comparable degrees of anemia. We assessed the influence of the amount of circulating HbF on serum erythropoietin (s-Epo) levels and on serum transferrin receptor, a measure of erythropoiesis, in 30 beta-thalassemia-intermedia patients. Twenty-four showed more than 40% HbF (21 of whom with beta (0)-thalassemia) and 6 presented lower HbF levels (beta(+)-thalassemia). The two groups of patients did not differ in age (15.3 v 19 years, respectively) or degree of anemia (Hb = 8.8 g/dL in both groups). Log (s-Epo) was correlated inversely with Hb (r = -0.47; P < .01), and directly with HbF (r = .55; P < .001). Multivariate regression analysis showed that Hb and HbF were independently correlated with s-Epo levels. High-HbF patients had greater s-Epo values at the same Hb level than low-HbF patients. Considering that iron-deficiency anemia control patients represented the predicted physiologic response of s-Epo to anemia, the observed/predicted s-Epo ratio in low-HbF thalassemic patients was no different from controls, but was increased in the high-HbF group. High-HbF patients also showed an expansion of erythropoiesis as much as four to nine times the normal value at the same Hb level as low-HbF patients. We conclude that HbF exerts an independent regulatory effect on erythropoietin production and erythropoiesis that is detectable only when HbF levels exceed 40%.

A novel Mediterranean "delta beta-thalassemia" determinant containing the delta (+) 27 and beta (0) 39 point mutations in cis

The term delta beta-thalassemia with normal HbF has been recently proposed to define heterogenous delta and beta globin gene molecular defects involving the same chromosome in cis. Here, we describe a Sardinian family in which three members showing microcytosis, border-line HbA2 levels and normal HbF proved to be heterozygotes for delta(+) 27 and beta(0) 39 point mutations in cis by allele specific oligonucleotide hybridization as well as by ECO 0 109 I endonuclease digestion and electrophoresis. As some of these beta-thalassemia carriers shows normal HbA2 levels, knowledge of the molecular basis of this novel delta beta-thalassemia silent phenotype would be useful in thalassemia screening and genetic counselling.

Identification of a novel T-insertion polymorphism at the DMD locus

We have identified a novel T-insertion polymorphism located in the second intron of the dystrophin gene. This polymorphism should prove useful in linkage studies in Duchenne and Becker muscular dystrophy families in addition to the previously described markers.

Combinations of specific DRB1, DQA1, DQB1 haplotypes are associated with insulin-dependent diabetes mellitus in Sardinia

The Sardinian population has an extremely high incidence of IDDM (30.2 of 100.000 in the age group of 0-14 years). This study reports the molecular characterization of HLA class II genes in 120 IDDM sporadic patients and 89 healthy subjects of Sardinian origin. Compared with other Caucasians, both Sardinian patients and controls had an unusual distribution of haplotypes and genotypes. In particular, there was a high gene frequency of the DRB1*0301, DQA1*0501, DQB1*0201 susceptibility haplotype both in patients (0.58) and controls (0.23) while a reduction of the DRB1*1501, DQA1*0102, DQB1*0602 protective haplotype (0.03) was observed in the healthy population. This distribution may partially explain the high incidence of IDDM reported in Sardinia. The analysis of the DQ beta 57 and DQ alpha 52 residues showed that the absence of Asp 57 and the presence of Arg 52 were associated with IDDM in a dose-response manner. On the other hand, we found that (a) a very similar distribution of these residues was found when comparing Sardinians with another healthy Caucasian population from the same latitude but with a lower rate of IDDM incidence; (b) several genotypes encoding the identical DQ alpha 52/DQ beta 57 phenotype carried very different relative risks; and (c) the DRB1*0403, DQA1*0301, DQB1*0304 haplotype (DQ beta 57 Asp-neg and DQ alpha 52 Arg-pos) was found in 40% of the DR4-positive controls but not in patients (p = 0.00034), while the DRB1*0405, DQA1*0301, and DQB1*0302 haplotype carrying the same residues at the same positions was found in 70% of the DR4-positive patients and in only one control (p = 0.00003). These findings suggest that IDDM susceptibility cannot be completely explained by the model in which only DQ alpha 52 and DQ beta 57 residues are taken into account.

Normal individuals with high Hb A2 levels

Increased haemoglobin (Hb) A2 levels associated with reduced mean corpuscular volume (MCV) and Hb content per cell (MCH) are the most typical features of heterozygous beta thalassaemia. However, double heterozygotes for alpha and beta thalassaemia may have normal MCV and MCH but Hb A2 always in the carrier range. In this report we describe two Sardinian families who have increased Hb A2 levels, normal red blood cell indices and normal globin chain synthesis and in whom DNA sequence analysis of beta and delta globin genes did not reveal any abnormality. Our findings demonstrate the existence of a genetic trait not resulting from a defect of the beta globin gene cluster, transmitted in a dominant manner and manifested as isolated increase of Hb A2.

Germinal mosaicism in a Duchenne muscular dystrophy family: implications for genetic counselling

In this study we describe a three-generation family in which two siblings were affected by Duchenne muscular dystrophy (DMD). Immunohistochemical analysis of muscle dystrophin and haplotype analysis of the DMD locus revealed that the X chromosome carrying the DMD gene was transmitted from the healthy maternal grandfather to his three daughters, including the proband's mother. These findings indicate that the grandfather was a germinal mosaic for the DMD gene. The definition of the carrier status in two possible carriers led us to give accurate genetic counselling and to prevent the birth of an affected boy. The results of this study demonstrate the usefulness of haplotype analysis and immunohistochemical muscle dystrophin studies to detect hidden germinal mosaicism and to improve genetic counselling.

Screening and prenatal diagnosis of the haemoglobinopathies

In this paper we have reviewed the social and technical aspects of carrier screening and prenatal diagnosis of the inherited haemoglobinopathies. The characteristics of programmes based on carrier screening and prenatal diagnosis ongoing in a number of at-risk Mediterranean populations have been described. The most relevant and common aspects of these programmes are the continuous educational campaign directed to the population at large, the voluntary basis and non-directive counselling. The target population has been most commonly couples before or after marriage. The vast majority of couples counselled accepted prenatal diagnosis. All programmes have encountered a high degree of success as indicated by the marked reduction in the birth rate of infants with thalassaemia major. No significant adverse effects have been reported. A programme with similar characteristics and for which the preliminary results are encouraging, is operating for sickle cell anaemia in the Cuban population. In a population with high frequency of hydrops fetalis, screening for deletion alpha-thalassaemia is recommended to prevent the negative effects on a pregnant woman of the presence of an hydropic fetus. Thalassaemia carrier screening is now carried out by automatic red cell indices and HbA2 determination. Definition of atypical cases may require iron studies, globin chain synthesis determination and/or alpha, beta- and delta-globin gene analysis. Identification of the carrier state is followed by definition of the mutation on enzymatically amplified DNA. Known mutations may be detected by restriction endonuclease analysis, non-denaturing polyacrylamide gel electrophoresis, allele-specific primers or allele-specific probes. The most promising procedures, which are also amenable to complete automation are reverse oligonucleotide hybridization and primer-specific amplification. Unknown mutations are defined by denaturing gradient gel electrophoresis, single-strand conformation polymorphism analysis, and chemical mismatch cleavage analysis followed by direct sequencing. The same methods on enzymatically amplified chorionic villus DNA are used for prenatal diagnosis. The potential pitfall resulting from maternal contamination can be avoided by careful dissection of the maternal decidua from the chorion and by the simultaneous amplification of a suitable polymorphism.

Dystrophin analysis using a panel of anti-dystrophin antibodies in Duchenne and Becker muscular dystrophy

Dystrophin, the protein product of the Duchenne muscular dystrophy (DMD) gene, was studied in 19 patients with Xp21 disorders and in 25 individuals with non-Xp21 muscular dystrophy. Antibodies raised to seven different regions spanning most of the protein were used for immunocytochemistry. In all patients specific dystrophin staining anomalies were detected and correlated with clinical severity and also gene deletion. In patients with Becker muscular dystrophy (BMD) the anomalies detected ranged from inter- and intra-fibre variation in labelling intensity with the same antibody or several antibodies to general reduction in staining and discontinuous staining. In vitro evidence of abnormal dystrophin breakdown was observed reanalysing the muscle of patients, with BMD and not that of non-Xp21 dystrophies, after it has been stored for several months. A number of patients with DMD showed some staining but this did not represent a diagnostic problem. Based on the data presented, it was concluded that immunocytochemistry is a powerful technique in the prognostic diagnosis of Xp21 muscular dystrophies.

Early transabdominal chorionic villus sampling in couples at high genetic risk

OBJECTIVE

The purpose of the study was to evaluate the feasibility and safety of transabdominal chorionic villus sampling before 9 weeks' gestation.

STUDY DESIGN

Two hundred pregnancies at risk for beta-thalassemia (n = 198) or Duchenne muscular dystrophy (n = 2) underwent transabdominal CVS at 6 through 8 weeks. Sampling success and fetal loss are expressed in percentages.

RESULTS

Sampling was successful in all cases (100%). Forty-eight fetuses were affected by beta-thalassemia and one by Duchenne muscular dystrophy. The percentage of fetal loss, expressed as a proportion of continuing pregnancies, was 4.0%. All women (n = 144) have been delivered, and no misdiagnoses have occurred. We observed one anencephalus and one mild limb defect consisting of absence of distal phalanges of index and little fingers of both hands and distal phalanges of both little toes.

CONCLUSION

Transabdominal CVS before 9 weeks is a reliable and relatively safe method for prenatal diagnosis in patients at high risk for genetic diseases. However, further studies are necessary to assess the risk to the fetus.

Diagnosis of DMD carrier status in a family with no known affected males

A 30-year-old woman and her two-year-old daughter were found by chance to have moderately raised serum creatine kinase (CK) levels. Since the mother was pregnant, the authors investigated the possibility that the two females were carriers of the common Duchenne muscular dystrophy (DMD) gene. No immunohistochemical abnormality was detected in the mother, but in the daughter a clear mosaic pattern of dystrophin positive and negative fibres was found, indicating carrier status for DMD. These data indicate that a diagnosis of DMD carrier status can be made even in families without a positive history for this disorder; therefore, immunocytochemical studies, using antidystrophin antibodies, should be performed on all females with raised CK levels, including the youngest.

Thermal behavior and elastic properties of phospholipid bilayers under the effect of a synthetic flavonoid derivative, LEW-10

We have investigated the effect on phospholipidic bilayers of LEW-10, a synthetic flavonoid, derivative of diosmin. Two optical techniques, Quasi-elastic Light Scattering (QLS) and Fourier Transform Infrared Spectroscopy (FT-IR) were used. The results show that in the presence of LEW-10, the phase transition of the bilayers is lowered and that the elastic modulus is decreased. The FT-IR results indicate interactions in the aqueous interface regions of the bilayers. We also discuss LEW-10 comparatively with another derivative, LEW-7/S1, whose effect has been previously studied.

A simple electrophoretic procedure for fetal diagnosis of beta-thalassaemia due to short deletions

This study describes three couples at risk for homozygous beta-thalassaemia in which one of the partners carried a short deletion beta-thalassaemia defect. Detection of short deletions in trophoblast DNA was accomplished by the very simple procedure of non-denaturing polyacrylamide gel electrophoresis. This method may be applied to detect beta-thalassaemia mutations due to deletion or addition of more than two nucleotides.

Transabdominal chorionic villus sampling: fetal loss rate in relation to maternal and gestational age

In this paper we report the fetal loss rate in relation to both maternal and gestational age in 1764 pregnant women who underwent transabdominal chorionic villus sampling (TA-CVS) between January 1986 and August 1990. The fetal loss rate, considered as a proportion of continuing pregnancies, decreased with advancing gestational age at sampling from 4.3 per cent before 9 weeks to 0.4 per cent at or after 13 weeks, the difference being statistically significant (p < 0.025). The fetal loss rate increased from 1.6 per cent in women under 30 to 2.4 per cent in women of 40 years or over, but the difference was not statistically significant. Considering that the total fetal loss rate before 28 weeks' gestation was on average 1.91 per cent (1.3 per cent under 35 years and 2.8 per cent in women of 35 or over), we believe that TA-CVS is a safe and effective technique for prenatal diagnosis of genetic diseases.

Hemoglobin Sabine [beta 91 (F7) Leu-->Pro]: occurrence in a Sardinian individual with hemolytic anemia and inclusion bodies

BACKGROUND

Hemoglobin (Hb) Sabine (beta 91 Leu-->Pro) is an unstable variant detected for the first time in a 16-year-old Scottish-English-German girl affected by moderately severe hemolytic anemia. A second case was described in a patient of Yugoslavian descent. We report another case of this Hb variant arising as a de novo mutation in a Sardinian patient.

METHODS

Definition of the mutation was obtained by DNA direct sequencing on amplified beta-globin gene, as well as by structural analysis of the hemoglobin variant.

RESULTS AND CONCLUSION

The patient presented a moderately severe hemolytic anemia with red blood cell inclusion bodies. Hemoglobin electrophoresis showed that quantitatively the abnormal fraction represented 9% of the total Hb amount. beta globin gene analysis revealed a single nucleotide substitution, T-->C, at codon 91, which gives rise to a leucine-->proline substitution. Structural analysis of the variant confirmed the amino acid substitution (Leu-->Pro) predicted by DNA sequencing.

Human alpha-globin gene expression is silenced by terminal truncation of chromosome 16p beginning immediately 3' of the zeta-globin gene

The high level expression of the human alpha-globin genes in erythroid tissue appears to require a set of DNaseI hypersensitive sites located upstream of the human alpha-globin gene cluster. These sequences, termed the locus control region (LCR), include two erythroid specific and a number of less restricted DNaseI hypersensitive sites. In this report we describe an individual with alpha-thalassemia associated with a truncation of the short arm of chromosome 16 that removes the LCR region and inactivates the adjacent intact alpha-globin genes. This genetic study supports the critical role of the LCR in the transcriptional activation of the human alpha-globin gene cluster and substantiates the importance of LCR deletions in the etiology of alpha-thalassemia.

Feasibility of prenatal diagnosis of beta-thalassemia using two highly polymorphic microsatellites 5' to the beta-globin gene

Short tandem repeats (STRs) are highly informative loci within the human genome, consisting of short nucleotide sequences tandemly repeated in variable numbers. This results in different alleles of variable length. Herein we describe two STRS located 5' to the beta-globin gene. They can be detected by non radioactive methods and may be used to make prenatal diagnosis of beta-thalassemia.

A beta-thalassaemia phenotype not linked to the beta-globin cluster in an Italian family

This paper describes a family of Central Italian origin in which three patients in two generations had either thalassaemia intermedia or a late presenting form of thalassaemia major. Sequence analysis of the patients' DNA revealed that only one of the beta-globin genes was affected by a beta-thalassaemia mutation (the codon 39 nonsense mutation), the other being completely normal, apart from the complex rearrangement (-T +ATA) at position -530 5' to the CAP site of the beta-globin gene, which has uncertain clinical significance. Haematologically, all these patients were characterized by unusually low HbF levels (1.8-7.3%) for a beta-thalassaemia major or intermedia phenotype. The mother of the two patients with thalassaemia intermedia was heterozygous for beta-thalassaemia (codon 39 nonsense mutation), while the father had thalassaemia-like red cell indices, an increased alpha/non alpha chain synthesis ratio, a slight increase of HbF and a low HbA2 level, but showed entirely normal beta-globin gene sequences, apart from the complex rearrangement (-T +ATA) at position -530 5' to the CAP site. One of the thalassaemia intermedia patients married a normal woman and they had a child with thalassaemia major who inherited only the codon 39 nonsense mutation but not the complex rearrangement at position -530. The clinical phenotype of thalassaemia-intermedia or major in the patients from this family may be explained by postulating the inheritance of the double heterozygous state for beta-thalassaemia and for a mutation in a gene coding for an erythroid-specific DNA binding protein which may impair the function of the normal beta-globin gene. Heterozygosity for this postulated mutation (father of the patients with thalassaemia intermedia) may result in the production of a beta-thalassaemia carrier state with normal HbA2 level.

The HLA DQB1*0502 allele is neutrally associated with insulin-dependent diabetes mellitus in the Sardinian population

In the Sardinian population a very high incidence of insulin-dependent diabetes mellitus (IDDM) and the lack of HLA-DR2 protective effect due to the high frequency of the A2, Cw7, B17, 3F31, DR2, DQw1 extended haplotype has been reported. This haplotype, carrying a Serine at position 57 of the DQB1*0502 allele, has been previously reported to be underrepresented in patients when compared to controls. In order to provide an explanation for this finding, we defined by RFLP analysis the HLA haplotype of 45 Sardinian IDDM patients and 49 controls. All DR-2DQw1 subjects were molecularly characterized at the HLA DQA and DQB loci. All DR2-positive patients and the vast majority of the DR2-positive controls had the DQB1*0502 allele at the DR2-linked DQB1 locus, with no statistically significant difference between the two groups. All DQA1 genes were the ones expected, with only two exceptions. Nine out of 10 of the DR2-positive patients were compound heterozygotes for DQB1*0201/DQB1*0502 alleles; only this allele combination was significantly increased (p less than 0.0003). Our data suggests that a) the DQB1*0502 allele is neutral for IDDM development and b) the susceptibility to IDDM in our DR2-positive patients is related to the compound heterozygous state between the neutral DQA1*0102/DQB1*0502 and the susceptibility DQA1*0501/DQB1*0201 alleles.

X-linked mental retardation and characteristic physical features in two brothers with duplication Xp22-Xpter

Two brothers are reported who share mental retardation, conjunctival teleangectasias (mainly equatorial) and characteristic flat face with small mouth and thin prolabia. At the neuropsychological examination, the older brother at 14 years showed a full scale IQ of 40 (WISC), with verbal IQ 45 and performance IQ 44. The younger brother at 7 years showed a full scale IQ of 58 (WPPSI), with verbal IQ 67 and performance IQ 55. Chromosome studies showed a duplication Xp22-Xpter in both brothers and in the inactivated X of their mother. The anomaly was not present in a 3rd healthy brother and in other healthy relatives. The mother has normal intelligence and did not present any of the physical features of her affected sons.

Prenatal diagnosis of inherited hemoglobinopathies

This paper reviews the techniques presently available for the prenatal diagnosis of inherited hemoglobinopathies. At the present time, mutations of the globin genes are detected directly in trophoblast DNA, enzymatically amplified by polymerase chain reaction. Known mutations may be defined by restriction endonuclease digestion, non denaturing gradient gel electrophoresis, allele specific oligonucleotide probes or allele specific oligonucleotide primers. Unknown mutations are detected by denaturing gradient gel electrophoresis followed by direct sequencing. Other potentially useful methods for unknown mutations are single strand conformation polymorphism analysis and chemical mismatch cleavage analysis. A potential pitfall for all procedures based on analysis of amplified DNA is the coamplification of maternal sequences. This may be avoided by a careful dissection of maternal decidua from fetal trophoblast, by using an amount of chorionic villi not inferior to 5-10 mg and by reducing the number of amplifying cycles to approximately 20. Monitoring the presence of co-amplified maternal sequences by the analysis of polymorphic sequences is strongly recommended. Future perspectives consist of preimplantation diagnosis by biopsy of the morula or blastula or ova genotyping by analysis of the second polar body.