Microcytic Anaemia as Susceptibility Factors in Bipolar Spectrum Disorders: Review of the Literature, Replication Survey, and Co-Segregation within Families.

BACKGROUND: Potential interactions between mood disorders and microcytic anaemias have been suggested by case reports, surveys of haematological parameters in psychiatric populations, and surveys of psychiatric morbidity in thalassaemic carriers. OBJECTIVES: a) To review published studies.b) To study the prevalence of microcytic anaemia in a sample of Sardinian outpatients with recurrent mood disorders.c) To check whether mood disorders and microcytic anaemia co-segregate within families. METHODS: We extracted data on blood count and serum iron concentrations from the records of patients admitted between January 1st, 2001 and December 31st, 2016, to our clinic for mood disorders. Moreover, we studied siblings of subjects with both major mood disorders (according to Research Diagnostic Criteria) and heterozygous thalassaemia (according to Mean Corpuscular Volume, serum iron, and haemoglobin A2 concentrations). Siblings affected with a major mood disorder were examined for haematological concordance with the proband (reduced MCV and/or increased HbA2 in case of heterozygous ß-thalassaemia, or presence of gene deletions in case of α-thalassaemia). RESULTS: Microcytic anaemia was highly prevalent (81/337 = 24.0%) among outpatients with mood disorders. Starting from 30 probands with heterozygous ß-thalassaemia, concordance for reduced MCV and/or increased HbA2 was found in 78% (35/45) of affected siblings. Starting from 3 probands with heterozygous α-thalassaemia, only one of the 5 affected siblings carried four α-globin functional genes. CONCLUSION: Based on the review of the literature, the high prevalence of microcytic anaemia in outpatients, and the concordance between affected siblings, we can conclude that a role of heterozygous thalassaemias is highly probable. Future studies are required to establish the relevance of heterozygous thalassaemias and evaluate the magnitude of the effect, possibly using a molecular diagnosis also in the case of heterozygous ß-thalassaemia.

Hematological phenotypes in children according to the α-globin genotypes.

Limited information is available on the hematological characterization of the α-thalassemia carrier in pediatric age. The objective of this report was to evaluate the red cell indices according to the α-globin genotype in a cohort of children evaluated in Sardinia. Moreover, we verified the frequency of different α-globin genotypes in this cohort. A total of 453 subjects were investigated for hematological indices and for the most common α-globin defects present in Sardinia. Of them, 352 with HbA2≤3.2%, and no iron deficiency anemia were taken into consideration to evaluate the red cell indices according to the α-globin genotype in pediatric age. A total of 11 different α-genotypes were detected, confirming the wide heterogeneity of α-thalassemia in Sardinia. Moreover, our results showed that the hematological parameters in normal children may be conditioned by the clinically occult coinheritance of mild α-thalassemia alleles as already described in the adult population while microcytosis and hypocromia in children without iron deficiency should suggest the coexistence of two α-globin defects. We concluded that recognizing the α-globin gene mutations for a particular population with their particular red cell indices may help pediatricians to perform a correct diagnosis distinguishing among physiological and pathological types of microcytosis and hypocromia.

Changes in HbA2 and HbF in alpha thalassemia carriers with KLF1 mutation.

α-thalassemia carriers are common in Mediterranean regions, particularly in the Sardinian population. Their haematological phenotype is characterized by reduced MCV and/or MCH with normal or slightly reduced HbA2 levels and normal HbF. Krüppel-like factor 1 (KLF1) is a pleiotropic erythroid transcription factor that is essential for haematopoiesis. Mutations in the KLF1 gene trigger a series of benign human red blood phenotypes, such as an increase in HbA2 and HBF. Recently, it has been found that KLF1 mutations were a frequent cause of borderline HbA2 levels in a group of Sardinian subjects. Here, we found that KLF1 mutations modulate the phenotype in a cohort of α-thalassemia carriers.

The Problem of Borderline Hemoglobin A2 Levels in the Screening for ß-Thalassemia Carriers in Sardinia.

BACKGROUND: The increase in HbA2 is the most important parameter for the identification of thalassemia carriers. However, in routine screening for hemoglobinopathies, some cases are difficult to classify because the level of HbA2 is not typically elevated. In this work, we report the results of a molecular investigation on a cohort of subjects with borderline HbA2. METHODS: All subjects with a ß-thalassemia carrier partner and a borderline percentage level of HbA2 were investigated for the presence of a pathological mutation in the ß-globin gene. All negative subjects were screened for both the KLF1 mutation and the presence of ααα/ or αααα/ alleles. The subjects with reduced MCV and/or MCH were also screened for deletional and nondeletional α-globin gene defects. RESULTS: Various ß-globin mutations and KLF1 gene defects are the most common genetic determinants responsible for this phenotype in our population. CONCLUSION: KLF1 mutations are important in a screening program for hemoglobinopathies. An increase in HbF in association with borderline HbA2 levels is a useful but not exclusive marker that suggests the investigation of this gene. On the basis of our findings, we are able to suggest the molecular procedure to use in a population characterized by a high prevalence of thalassemia carriers.

A genetic score for the prediction of beta-thalassemia severity.

Clinical and hematologic characteristics of beta(ß)-thalassemia are determined by several factors resulting in a wide spectrum of severity. Phenotype modulators are: HBB mutations, HBA defects and fetal hemoglobin production modulators (HBG2:g.-158C>T polymorphism, HBS1L-MYB intergenic region and the BCL11A). We characterized 54 genetic variants at these five loci robustly associated with the amelioration of beta-thalassemia phenotype, to build a predictive score of severity using a representative cohort of 890 ß-thalassemic patients. Using Cox proportional hazard analysis on a training set, we assessed the effect of these loci on the age at which patient started regular transfusions, built a Thalassemia Severity Score, and validated it on a testing set. Discriminatory power of the model was high (C-index=0.705; R(2)=0.343) and the validation conducted on the testing set confirmed its predictive accuracy with transfusion-free survival probability (P<0.001) and with transfusion dependency status (Area Under the Receiver Operating Characteristic Curve=0.774; P<0.001). Finally, an automatized on-line calculation of the score was made available at http://tss.unica.it. Besides the accurate assessment of genetic predictors effect, the present results could be helpful in the management of patients, both as a predictive score for screening and a standardized scale of severity to overcome the major-intermedia dichotomy and support clinical decisions.

First detection of Hb Taybe [α38(C3) or α39(C4) Thr→0 (α1)] in an Italian child.

Hb Taybe [α38(C3) or α39(C4) Thr→0 (α1)] is an unstable hemoglobin (Hb) variant caused by a deletion of a threonine residue at codon 39 of the α1-globin chain. Usually asymptomatic or with minimal hematological abnormalities in the heterozygous state, Hb Taybe becomes clinically evident in compound heterozygosity with α-thalassemia (α-thal) or in homozygous patients. To date, Hb Taybe has been described in Israeli-Arab and Greek individuals. We report, for the first time, a patient with chronic hemolytic anemia due to the presence of Hb Taybe in trans to the α2 initiation codon mutation ATG>ACG in an Italian child. Hb Taybe was not evident at Hb analysis with cellulose acetate electrophoresis and high performance liquid chromatography (HPLC). Globin biosynthetic studies revealed an α/ß-globin ratio in the range of ß-thal trait. Consequently, an investigation of the α- and ß-globin genes was requested in order to avoid missing any rare globin chain variant and to offer accurate genetic counseling.

A new ß chain hemoglobin variant with increased oxygen affinity: Hb Santa Giusta Sardegna [ß93(F9)Cys→Trp; HBB c.282T>G].

During a screening program for the identification of ß-thalassemia (ß-thal) carriers in Sardinia, Italy, we identified two subjects with increased hemoglobin (Hb) levels and an abnormal Hb variant. The same variant was detected in a family member. DNA sequencing revealed a TGT > TGG mutation at codon 93 of the ß-globin gene. Structural analysis demonstrated that the cystine residue at position 93 of the ß chain was substituted by tryptophan. Since this amino acid substitution had not yet been reported, we designated this variant Hb Santa Giusta Sardegna for the place of birth of the subjects. This amino acid substitution occurs at the tyrosine pocket of the ß chain as well as at the α1ß2/α2ß1 contact of the quaternary structure of the molecule. The presence of this Hb in the hemolysate causes an increased oxygen affinity, a slightly reduced Bohr effect and a reduced heme-heme interaction (n(50), Hill's constant) in comparison with those of Hb A.

Structural and Functional Characterization of a New Double Variant Haemoglobin (HbG-Philadelphia/Duarte α(2)ß(2)).

WE REPORT THE FIRST CASE OF COSEGREGATION OF TWO HAEMOGLOBINS (HBS): HbG-Philadelphia [α68(E17)Asn → Lys] and HbDuarte [ß62(E6)Ala → Pro]. The proband is a young patient heterozygous also for ß°-thalassaemia. We detected exclusively two haemoglobin variants: HbDuarte and HbG-Philadelphia/Duarte. Functional study of the new double variant HbG-Philadelphia/Duarte exhibited an increase in oxygen affinity, with a slight decrease of cooperativity and Bohr effect. This functional behaviour is attributed to ß62Ala → Pro instead of α68Asn → Lys substitution. Indeed, HbG-Philadelphia isolated in our laboratory from blood cells donor carrier for this variant is not affected by any functional modification, whereas purified Hb Duarte showed functional properties very similar to the double variant. NMR and MD simulation studies confirmed that the presence of Pro instead of Ala at the ß62 position produces displacement of the E helix and modifications of the tertiary structure. The substitution α68(E17)Asn → Lys does not cause significant structural and dynamical modifications of the protein. A possible structure-based rational of substitution effects is suggested.

KLF1 gene mutations cause borderline HbA(2).

Increased hemoglobin A(2) (HbA(2); ie, levels > 3.9%) is the most important feature of ß-thalassemia carriers. However, it is not uncommon to find persons with borderline HbA(2) (levels, 3.3%-3.8%), who pose a relevant screening problem. Several genotypes have been associated with borderline HbA(2), but sometimes the reasons for this unusual phenotype are unknown. In this paper, we report, for the first time, that mutations of KLF1 result in HbA(2) levels in the borderline range. Six different KLF1 mutations were identified in 52 of 145 subjects with borderline HbA(2) and normal mean corpuscular volume and mean corpuscular hemoglobin. Two mutations (T327S and T280_H283del) are here reported for the first time. The prevalent mutation in Sardinians is S270X, which accounts for 80.8% of the total. The frequent discovery of KLF1 mutations in these atypical carriers may contribute significantly to the thalassemia screening programs aimed at identification of at risk couples.

Association of α globin gene quadruplication and heterozygous ß thalassemia in patients with thalassemia intermedia.

Ten patients with thalassemia intermedia with variable severity and apparent simple heterozygosis for beta0 39 C>T nonsense mutation were submitted to clinical, hematologic and molecular studies. The presence of an unknown molecular defect (silent beta-thalassemia) unlinked to the beta cluster interacting with the heterozygous beta thalassemia, was previously postulated in these families. Analysis of the alpha globin gene cluster with PCR-based methods (MLPA, GAP-PCR, digestion with restriction enzymes) detected complex rearrangements in the alpha cluster. A duplication of the alpha globin gene locus, including the upstream regulatory region, was present in all the patients, associated in some of them with deletion or non-deletion alpha thalassemia. The variability of the clinical phenotype correlates with the degree of the globin chain imbalance. The presence of alpha globin cluster duplication should be considered in patients heterozygote for beta-thalassemia with thalassemia intermedia phenotype and in the carriers of suspected silent beta thalassemia.

Amelioration of Sardinian beta0 thalassemia by genetic modifiers.

Sardinian beta-thalassemia patients all are homozygotes for the same null allele in the beta-globin gene, but the clinical manifestations are extremely variable in severity. Previous studies have shown that the coinheritance of alpha-thalassemia or the presence of genetic variants that sustain fetal hemoglobin production has a strong impact on ameliorating the clinical phenotype. Here we evaluate the contribution of variants in the BCL11A, and HBS1L-MYB genes, implicated in the regulation of fetal hemoglobin, and of alpha-thalassemia coinheritance in 50 thalassemia intermedia and 75 thalassemia major patients. We confirm that alpha-thalassemia and allele C of single nucleotide polymorphism rs-11886868 in BCL11A were selectively represented in thalassemia intermedia patients. Moreover, allele G at single nucleotide polymorphism rs9389268 in the HBS1L-MYB locus was significantly more frequent in the thalassemia intermedia patients. This trio of genetic factors can account for 75% of the variation differences in phenotype severity.

Structure-function relationship in a variant hemoglobin: a combined computational-experimental approach.

Our study examines the functional and structural effects of amino acid substitution in the distal side of beta-chains of human Hb Duarte (alpha(2)beta(2)(62Ala-->Pro)). We have compared the functional properties of the purified Hb Duarte with those of HbA, and through proton NMR and molecular dynamics simulations we have investigated their tertiary and quaternary structures. The variant exhibits an increased oxygen affinity with a normal Hill coefficient and Bohr effect. The abnormal function of Hb Duarte is attributed to the presence of a proline residue at the beta62 position, since the functional properties of another Hb variant in the same position, Hb J-Europa (beta(62Ala-->Asp)), have been described as normal. Thereafter (1)H-NMR studies have shown that the beta62 Ala-->Pro substitution causes structural modifications of the tertiary structure of the beta globins, leaving the quaternary structure unaltered. These results have been confirmed by extensive all-atom molecular dynamics simulations. All these findings lead to the conclusion that the beta62 Ala-->Pro substitution produces a destabilization of the E-helix extending downward to the CD corner. Particularly, a cavity near the distal histidine of the beta-chains, connecting the heme pocket to the solvent, is affected, altering the functional properties of the protein molecule.