Hannah Tamary

Elevated growth differentiation factor 15 expression in patients with congenital dyserythropoietic anemia type I

Congenital dyserythropoietic anemia (CDA) is a rare group of red blood cell disorders characterized by ineffective erythropoiesis and increased iron absorption. To determine whether growth differentation factor 15 (GDF15) hyper-expression is associated with the ineffective erythropoiesis and iron-loading complications of CDA type I (CDA I), GDF15 levels and other markers of erythropoiesis and iron overload were studied in blood from 17 CDA I patients. Significantly higher levels of GDF15 were detected among the CDA I patients (10 239 +/- 3049 pg/mL) compared with healthy volunteers (269 +/- 238 pg/mL). In addition, GDF15 correlated significantly with several erythropoietic and iron parameters including Hepcidin-25, Ferritin, and Hepcidin-25/Ferritin ratios. These novel results suggest that CDA I patients express very high levels of serum GDF15, and that GDF15 contributes to the inappropriate suppression of hepcidin with subsequent secondary hemochromatosis.

CATSPER2, a human autosomal nonsyndromic male infertility gene.

In the course of positional cloning of the Congenital Dyserythropoietic Anemia type I (CDAI) [MIM 224120] gene on 15q15.1–15.3, we examined a family of French origin, in which the propositus suffered from asthenoteratozoospermia and nonsyndromic deafness in addition to CDAI. Two of his brothers had a similar phenotype. All three siblings were homozygous carriers of the CDA1 mutation as well as of a distally located ∼70 kb deletion of the proximal copy of a 106 kb tandem repeat on chromosome 15q15. These repeats encode four genes whose distal copies may be considered pseudogenes. Lack of functional stereocilin and CATSPER2 (a voltage-gate cation channel expressed specifically in spermatozoa) may explain the observed deafness and male infertility phenotypes. To the best of our knowledge, the involvement of CATSPER2 in asthenoteratozoospermia is the first description of a human autosomal gene defect associated with nonsyndromic male infertility.

A Dominant Mutation in the Gene Encoding the Erythroid Transcription Factor KLF1 Causes a Congenital Dyserythropoietic Anemia

The congenital dyserythropoietic anemias (CDAs) are inherited red blood cell disorders whose hallmarks are ineffective erythropoiesis, hemolysis, and morphological abnormalities of erythroblasts in bone marrow. We have identified a missense mutation in KLF1 of patients with a hitherto unclassified CDA. KLF1 is an erythroid transcription factor, and extensive studies in mouse models have shown that it plays a critical role in the expression of globin genes, but also in the expression of a wide spectrum of genes potentially essential for erythropoiesis. The unique features of this CDA confirm the key role of KLF1 during human erythroid differentiation. Furthermore, we show that the mutation has a dominant-negative effect on KLF1 transcriptional activity and unexpectedly abolishes the expression of the water channel AQP1 and the adhesion molecule CD44. Thus, the study of this disease-causing mutation in KLF1 provides further insights into the roles of this transcription factor during erythropoiesis in humans.

Congenital dyserythropoietic anemia type I is caused by mutations in codanin-1.

Congenital dyserythropoietic anemias (CDAs) constitute a rare group of inherited red-blood-cell disorders associated with dysplastic changes in late erythroid precursors. CDA type I (CDAI [MIM 224120], gene symbol CDAN1) is characterized by erythroid pathological features such as internuclear chromatin bridges, spongy heterochromatin, and invagination of the nuclear membrane, carrying cytoplasmic organelles into the nucleus. A cluster of 45 highly inbred Israeli Bedouin with CDAI enabled the mapping of the CDAN1 disease gene to a 2-Mb interval, now refined to 1.2 Mb, containing 15 candidate genes on human chromosome 15q15 (Tamary et al. 1998). After the characterization and exclusion of 13 of these genes, we identified the CDAN1 gene through 12 different mutations in 9 families with CDAI. This 28-exon gene, which is transcribed ubiquitously into 4738 nt mRNA, was reconstructed on the basis of gene prediction and homology searches. It encodes codanin-1, a putative o-glycosylated protein of 1,226 amino acids, with no obvious transmembrane domains. Codanin-1 has a 150-residue amino-terminal domain with sequence similarity to collagens and two shorter segments that show weak similarities to the microtubule-associated proteins, MAP1B (neuraxin) and synapsin. These findings, and the cellular phenotype, suggest that codanin-1 may be involved in nuclear envelope integrity, conceivably related to microtubule attachments. The specific mechanisms by which codanin-1 underlies normal erythropoiesis remain to be elucidated.

Serum ferritin level as a predictor of impaired growth and puberty in thalassemia major patients.

Abstract:  Objective: Previous studies suggested that in patients with thalassemia major, initiating deferoxamine (DFO) therapy before puberty can prevent iron‐induced failure of growth and puberty. However, early initiation of chelation has also been associated with DFO toxicity. The aim of this retrospective study was to determine the prevalence rates of endocrine complications and DFO bone toxicity in our thalassemia major patients and to correlate them with the degree of iron chelation. Methods: Thirty‐nine patients with thalassemia major were followed for a median of 16.3 yr (range 2–28). Individual mean serum ferritin level during the study period was calculated using repeated annual measurements. Bone DFO toxicity was assessed by wrist and spine radiographs; endocrine dysfunction by anthropometric measurements and pubertal stage; and hypogonadotropic hypogonadism by lack of luteinizing hormone response to gonadotropin‐releasing hormone. Results: Chelation therapy was initiated at median age 4.9 yr. Mean serum ferritin level during the study period was 2698 ± 1444 ng/mL. Hypogonadism was noted in 59% of the patients who reached pubertal age, and short stature was found in 36% of patients who reached final height. Mean ferritin level of 2500 ng/mL during puberty was the cut‐off for hypogonadism, and ferritin level of 3000 ng/mL during prepuberty was the cut‐off for final short stature. None of the patients who attained final height had signs of DFO bone toxicity. Conclusions: High serum ferritin levels during puberty are a risk factor for hypogonadism, and high serum ferritin levels during the first decade of life predict final short stature. It remains to be determined whether improving chelation by earlier initiation of DFO or by the combined use of DFO and deferiprone will lead to better growth and sexual development without DFO toxicity.

Newly diagnosed immune thrombocytopenia in children and adults: A comparative prospective observational registry of the intercontinental cooperative immune thrombocytopenia study group

Background Primary immune thrombocytopenia is a bleeding diathesis with an unknown etiology in predisposed individuals with immune disturbances. Although it is claimed that children and adults differ in clinical and laboratory aspects, few data exist to corroborate this observation. Our objective was to assess comparative data from children and adults with newly diagnosed immune thrombocytopenia. Design and Methods Clinical and laboratory data of 1,784 children and 340 adults were extracted from the Pediatric and Adult Registry on Chronic Immune Thrombocytopenia. The registry represents a prospective cohort of children and adults with newly diagnosed immune thrombocytopenia. Participating investigators registered their patients immediately after the diagnosis using a web based data transfer. Children aged under 16 years were compared with adults aged 16 years and over with descriptive statistical analyses. Results The presenting mean platelet count of children and adults was 18.1 and 25.4×109/L. Signs of bleeding were reported in 24% of children and in 23% of adults, and intracranial hemorrhage in 10 of 1,784 children and in 6 of 340 adults. Co-morbidity was observed in 3.9% of children and in 30% of adults. Bone marrow aspiration and laboratory tests (antinuclear antibodies, human immunodeficiency and hepatitis C virus) were performed more frequently in adults. Children and adults were followed with a ‘watch and wait’ strategy in 20% and in 29%, respectively. Immunoglobulins were used more frequently in children and corticosteroids in adults. Conclusions Comparative data of children and adults with newly diagnosed immune thrombocytopenia revealed similarities in presenting platelet counts and in bleeding, whereas differences occurred in co-morbidity, diagnostic procedures and therapy.

Risk Factors for Central Venous Catheter Thrombotic Complications in Children and Adolescents With Cancer

The use of central venous catheters (CVCs) has greatly improved the quality of care in children with cancer, yet these catheters may cause serious infectious and thrombotic complications. The aim of this prospective registry study was to assess the host and CVC‐related risk factors for CVC‐created thrombotic complications.

Congenital dyserythropoietic anemias: molecular insights and diagnostic approach.

The congenital dyserythropoietic anemias (CDAs) are hereditary disorders characterized by distinct morphologic abnormalities of marrow erythroblasts. The unveiling of the genes mutated in the major CDA subgroups (I-CDAN1 and II-SEC23B) has now been completed with the recent identification of the CDA III gene (KIF23). KIF23 encodes mitotic kinesin-like protein 1, which plays a critical role in cytokinesis, whereas the cellular role of the proteins encoded by CDAN1 and SEC23B is still unknown. CDA variants with mutations in erythroid transcription factor genes (KLF1 and GATA-1) have been recently identified. Molecular diagnosis of CDA is now possible in most patients.

Reversal of cardiac complications in thalassemia major by long‐term intermittent daily intensive iron chelation

Objectives: In patients with thalassemia major (TM) who are non‐compliant with long‐term deferoxamine (DFO) chelation, survival is limited mainly because of cardiac complications of transfusional siderosis. It was recently shown in a small group of TM patients with established cardiac damage that continuous 24‐h DFO infusion via an indwelling intravenous (i.v.) catheter is effective in reversing cardiac toxicity. The aim of the present study was to evaluate the results with intermittent daily (8–10 h) i.v. DFO.

How high are carrier frequencies of rare recessive syndromes? Contemporary estimates for Fanconi Anemia in the United States and Israel

For many recessive genetic syndromes, carrier frequencies have been assessed through screening studies in founder populations but remain unclear in heterogeneous populations. One such syndrome is Fanconi Anemia (FA). FA is a model disease in cancer research, yet there are no contemporary data on carrier frequency or prevalence in the general United States (US) population or elsewhere. We inferred carrier frequency from birth incidence using the Hardy–Weinberg law. We estimated prevalence using birth incidence and survival data. We defined “plausible ranges” to incorporate uncertainty about completeness of case ascertainment. We made estimates for the US and Israel using demographic data from the Fanconi Anemia Research Fund and Israeli Fanconi Anemia Registry. In the US, a plausible range for the carrier frequency is 1:156–1:209 [midpoint 1:181]; we estimate that 550–975 persons were living with FA in 2010. For Israel, a plausible range for the carrier frequency is 1:66–1:128 [midpoint 1:93] in line with founder screening studies; we estimate that 40–135 Israelis were living with FA in 2008. The estimated US FA carrier frequency of 1:181 is significantly higher than the historical estimate of 1:300; hence, the gap may be narrower than previously recognized between the US carrier frequency and higher carrier frequencies of around 1:100 in several founder groups including Ashkenazi Jews. Assessment of cancer risks in heterozygous carriers merits further study. Clinical trials in FA will require co‐ordination and innovative design because the number of living US patients is probably less than 1,000. Published 2011 Wiley‐Liss, Inc.