Maria Cristina Rosatelli

A common mutation in Sardinian autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy patients

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED; also called APS-1,) is a rare autosomal recessive disorder that is more frequent in certain isolated populations. It is characterized by two of the three major clinical symptoms that may be present: Addison’s disease, and/or hypoparathyroidism and/or chronic mucocutaneous candidiasis. We have recently identified the gene for APECED, which we termed AIRE (for autoimmune regulator). AIRE is expressed in thymus, lymph nodes and fetal liver, and encodes a protein with two putative zinc fingers and other motifs suggestive of a transcriptional regulator. Seven mutations have been described to date, including R257X, the predominant Finnish and northern Italian APECED allele, which has also been observed in other patients of diverse origin on different haplotypes. A 13-bp deletion (1094–1106del) has also been observed in several patients of different geo-ethnic origin. The other described mutations appear to be rare. We present mutational analyses of the AIRE gene in ten Sardinian APECED families and show that there is a mutation, R139X, associated with one predominant haplotype unique to the Sardinian patients (18/20 independent alleles). The carrier frequency of R139X in Sardinia is 1.7%, giving an estimated population frequency of APECED of 1/14,400. Using linkage disequilibrium data, the estimated age of the R139X mutation is between 20 and 25 generations. A previously described 13-bp deletion was also observed on an allele of one patient. The identification of a single common Sardinian APECED mutation will facilitate its genetic diagnosis. Given the carrier frequency of R139X in the Sardinian population, AIRE may be implicated in the pathogenesis of other autoimmune diseases in the Sardinian population, particularly those affecting the endocrine system.

Screening for thalassemia: a model of success.

Programs of prospective carrier screening and genetic counseling for beta-thalassemia among couples planning marriage, preconception, or during early pregnancy are ongoing in several at-risk populations in the Mediterranean area, including Greeks, Greek Cypriots and Continental Italians. Carrier detection is carried out by haematological analysis followed by mutation detection by DNA analysis. Once carrier couples are identified, prenatal diagnosis is accomplished by mutation analysis on PCR amplified DNA from chorionic villi. These programs have been very effective, due to education programs and subsequent acceptance of screening. Future prospects include automation of the process of mutation detection by microchips analysis, introduction of preconception and preimplantation diagnosis and hopefully fetal diagnosis by analysis of fetal cells in maternal circulation.

Autoimmune polyendocrine syndrome type 1: an extensive longitudinal study in Sardinian patients.

CONTEXT Autoimmune polyendocrine syndrome type 1 (APS1) is a childhood-onset monogenic disorder caused by mutations in the autoimmune regulator (AIRE) gene, including the distinctive R139X in Sardinia. Its rarity and great variability in manifestations/onset ages make early diagnosis difficult. To date, very few longitudinal studies of APS1 patients have been reported. OBJECTIVE The aim of this study was to describe the features and clinical course of APS1 and correlate them with AIRE and HLA class II genotypes in a large homogeneous cohort of Sardinian patients followed for up to 25 yr. PATIENTS Twenty-two pediatric APS1 patients were studied prospectively. RESULTS This Sardinian series (female/male ratio, 1.44; median current age, 30.7 yr; range, 1.8-46 yr) showed early disease onset (age range, 0.3-10 yr; median, 3.5 yr) and severe phenotype (on average, seven manifestations per patient). Besides the classic triad of chronic mucocutaneous candidiasis, hypoparathyroidism, and Addisons disease, autoimmune hepatitis was a serious and surprisingly common/early/presenting feature (27%; two deaths), with a 5:1 female bias (median age, 6 yr; range, 2.5-11 yr). By contrast, type 1 diabetes was rare (one patient), and hypothyroidism was not seen. Additional disease components (several of them potentially life-threatening) appeared in adulthood. The major nonsense mutation, R139X, was found in 93% of the mutant AIRE alleles. High-titer interferon (IFN)-ω and IFN-α autoantibodies were detected in all patients tested, even preclinically at 4 months of age in one sibling. HLA alleles appear to influence the exact phenotype-the most interesting apparent association being between HLA-DRB1*0301-DQB1*0201, liver-kidney microsome autoantibodies (anti-CYP1A2), and autoimmune hepatitis. CONCLUSION APS1 in Sardinia is characterized by severe phenotype, marked clinical heterogeneity, and relative genetic homogeneity. The single AIRE mutation, R139X, and the anti-IFN-ω and IFN-α autoantibodies are helpful for earlier diagnosis, especially when APS1 presents unusually. HLA genotypes can modify the phenotype.

Molecular screening and fetal diagnosis of β-thalassemia in the Italian population

SummaryThis paper reports our experience of molecular screening and fetal diagnosis of β-thalassemia in 457 at risk couples of Italian descent. Molecular screening was carried out by dot blot analysis on amplified DNA with oligonucleotide probes complementary to the eight most common mutations in Italians [β∘39 (C→T); ∘6 (-A); β+-87 (C→G); β+ IVSI nt 110 (G→A); β∘IVSI nt 1 (G→A); β+ IVSI nt 6 (T→C); β∘ IVSII nt 1 (G→A); β+ IVSII nt 745 (C→G)]. By using this approach, we have been able to define the mutation in 92.8% of cases. The rest (all but four) were defined by direct sequencing and this led to the detection of nine rare mutations [β∘76 (-C); β+ IVSI nt 5 (G→A); β+ IVSI nt 5 (G→C); β+ IVSI -1 (cod 30) (G→C); β+-87 (C→T), β∘-290 bp del.; β+-101 (C→T)], and to the characterization of a novel mutation consisting of the deletion of the G at the invariant AG of the IVSII splice acceptor site of the β-globin gene (β IVSII nt 850-1 bp). In the remaining four cases, the β-globin gene showed entirely normal sequences and the β-globin gene cluster was intact, as indicated by Southern blot analysis. Fetal diagnosis was carried out by dot blot analysis with the oligonucleotide probes defined in the parents. The procedure is simple and reliable, and the results can be obtained within 1 week of sampling. No misdiagnosis has so far occurred. The results indicate that fetal diagnosis of β-thalassemia by DNA analysis may be obtained in practically all cases (even in a population showing marked heterogeneity of β-thalassemia) by the combination of dot blot analysis for detecting common mutations, and direct sequencing for defining those that are uncommon.

Genotype-phenotype correlations in β-thalassemias

Abstract 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 β-thalassemia may be modified by a number of evironmental and genetic interacting factors—among which the most relevant are: (1) coinheritance of α-thalassemia, which may normalize the red blood cell indices; (2) the presence of a mild β-thalassemia mutation; (3) cotrasmission of δ-thalassemia which may reduce the increase of HbA2 typical of heterozygous β-thalassemia to normal values and (4) the presence of a silent mutation which can be defined only by imbalanced β-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 β-thalassemia mutations, coinheritance with homozygous β-thalassemia of α-thalassemia or genetic determinants able to substain a continuous production of HbF in adult life or the presence of heterozygosity for hyperunstable globin variants.

9 Screening and prenatal diagnosis of the haemoglobinopathies

Summary 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 α-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 HbA 2 determination. Definition of atypical cases may require iron studies, globin chain synthesis determination and/or α, β- and δ-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.

Population-based genetic screening

A preventive genetic programme aimed to control beta-thalassemia in the Sardinian population is based on a combination of increased awareness of the population, carrier screening, genetic counselling and prenatal diagnosis. As a result, the registry of thalassemia major demonstrated a profound decline in the incidence of this disease from 1 per 250 to 1 per 1200 live births, with 90% of cases effectively prevented.

A novel silent beta-thalassemia mutation in the distal CACCC box affects the binding and responsiveness to EKLF

The silent β‐thalassemia mutation, β+‐101C→T, is the only mutation currently described in the distal β‐globin CACCC box. We present a novel mutation, a C→G transversion, in the same position. Expression analysis in heterozygous subjects demonstrated that the mutation determines a 20% reduction in the output of the β‐globin gene. DNA–protein interaction and transactivation analysis correlated the decrease in the β‐globin synthesis with the reduced binding and transactivation of EKLF to the mutant promoter. These data predict that the β‐101C→G mutation will display a silent thalassemia phenotype similar to that of the β‐101C→T mutation.

Antenatal Diagnosis of β-Thalassemia in Sardiniaa

: This paper reviews the characteristics and the results of 15 years of experience with a preventive program, based on carrier screening and prenatal diagnosis, designed to control thalassemia major in the Sardinian population. The education of the population about thalassemia and the modalities for its prevention was accomplished via the mass media. Carrier screening was carried out voluntarily on couples of child-bearing age. Prenatal diagnosis was initially carried out by fetal blood analysis; since 1983, it has been done by DNA analysis on non-amplified or amplified DNA. Different chorionic villous sampling procedures have been used. Nowadays, we have adopted the transabdominal approach because, in our experience, it seems to be associated with a low risk (2%) of fetal mortality. At the present time, the beta-thalassemia mutations are detected directly by dot-blot analysis of amplified DNA with 32P- or horseradish peroxidase-labeled allele-specific oligonucleotide probes. Two oligonucleotide probes, one complementary to the codon-39 nonsense mutation, which accounts for 95.7% of the beta-thalassemia chromosomes in the Sardinian population, and the other complementary to the frameshift at codon 6, which is the second most common mutation in our population (2.1%), allow us to make prenatal diagnosis in the large majority of cases. Notwithstanding a careful dissection of maternal decidua from chorionic villi, co-amplification of maternal sequence was detected in 4 out of 425 cases tested by this procedure. In order to avoid this pitfall, the simultaneous amplification of highly polymorphic VNTR (variable number of tandem repeats) segments could be used. On the whole we have so far carried out 2711 prenatal tests: 1130 by fetal blood analysis, 1156 by oligonucleotide hybridization on electrophoretically separated DNA fragments, and 425 by dot-blot analysis on amplified DNA with allele-specific oligonucleotide probes. Two errors occurred by fetal blood analysis and none by DNA analysis. The incidence of thalassemia major declined from 1:250 live births in the absence of prevention to 1:1000 after the establishment of this program, indicating that carrier screening and prenatal diagnosis are effective means for preventing thalassemia major at the population level.

Neonatal onset of nephrogenic syndrome of inappropriate antidiuresis

This paper describes the manifestaton in a child of a new syndrome characterized by unusual, severe, persistent hyponatremia associated with hyposmolarity, euvolemia, inappropriately concentrated urine and elevated natriuresis. This is the fourth case of this syndrome reported to date, and the first to be reported in a neonate. The clinical features resemble those typically observed in patients with inappropriate antidiuretic hormone secretion, although high arginine vasopressin (AVP) levels are lacking. The findings led the authors to hypothesise a nephrogenic syndrome of inappropriate antidiuresis (NSIAD). The previously described R137C gain-of-function mutation was detected by means of mutation analysis of the V2R gene. Our results indicate that NSIAD is already present during the neonatal period and that molecular analysis of the V2R receptor should therefore be carried out, in all newborns with prolonged euvolemic hyponatremia with hypo-osmolarity, high urinary sodium and normal/low or undetectable AVP levels.