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Mutational spectrum in congenital dyserythropoietic anemia type II: identification of 19 novel variants in SEC23B gene.

ABSTRACT: SEC23B gene encodes an essential component of the coat protein complex II (COPII)-coated vesicles. Mutations in this gene cause the vast majority the congenital dyserythropoietic anemia Type II (CDA II), a rare disorder resulting from impaired erythropoiesis. Here, we investigated 28 CDA II patients from 21 unrelated families enrolled in the CDA II International Registry. Overall, we found 19 novel variants [c.2270 A>C p.H757P; c.2149-2 A>G; c.1109+1 G>A; c.387(delG) p.L129LfsX26; c.1858 A>G p.M620V; c.1832 G>C p.R611P; c.1735 T>A p.Y579N; c.1254 T>G p.I418M; c.1015 C>T p.R339X; c.1603 C>T p.R535X; c.1654 C>T p.L552F; c.1307 C>T p.S436L; c.279+3 A>G; c. 2150(delC) p.A717VfsX7; c.1733 T>C p.L578P; c.1109+5 G>A; c.221+31 A>G; c.367 C>T p.R123X; c.1857_1859delCAT; p.I619del] in the homozygous or the compound heterozygous state. Homozygosity or compound heterozygosity for two nonsense mutations was never found. In four cases the sequencing analysis has failed to find two mutations. To discuss the putative functional consequences of missense mutations, computational analysis and sequence alignment were performed. Our data underscore the high allelic heterogeneity of CDA II, as the most of SEC23B variations are inherited as private mutations. In this mutation update, we also provided a tool to improve and facilitate the molecular diagnosis of CDA II by defining the frequency of mutations in each exon.

SUBMITTER: Russo R

PROVIDER: S-EPMC3015065 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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Mutational spectrum in congenital dyserythropoietic anemia type II: identification of 19 novel variants in SEC23B gene.

Russo Roberta R Esposito Maria Rosaria MR Asci Roberta R Gambale Antonella A Perrotta Silverio S Ramenghi Ugo U Forni Gian Luca GL Uygun Vedat V Delaunay Jean J Iolascon Achille A

American journal of hematology 20101201 12

SEC23B gene encodes an essential component of the coat protein complex II (COPII)-coated vesicles. Mutations in this gene cause the vast majority the congenital dyserythropoietic anemia Type II (CDA II), a rare disorder resulting from impaired erythropoiesis. Here, we investigated 28 CDA II patients from 21 unrelated families enrolled in the CDA II International Registry. Overall, we found 19 novel variants [c.2270 A>C p.H757P; c.2149-2 A>G; c.1109+1 G>A; c.387(delG) p.L129LfsX26; c.1858 A>G p.M ...[more]

PMID: 20941788

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Project description:BackgroundCongenital dyserythropoietic anemia type II (CDAII), the most common form of CDA, is an autosomal recessive condition. CDAII diagnosis is based on invasive, expensive, and time consuming tests that are available only in specialized laboratories. The recent identification of SEC23B mutations as the cause of CDAII opens new possibilities for the molecular diagnosis of the disease. The aim of this study was to characterize molecular genomic SEC23B defects in 16 unrelated patients affected by CDAII and correlate the identified genetic alterations with SEC23B transcript and protein levels in erythroid precursors.MethodsSEC23B was sequenced in 16 patients, their relatives and 100 control participants. SEC23B transcript level were studied by quantitative PCR (qPCR) in peripheral erythroid precursors and lymphocytes from the patients and healthy control participants. Sec23B protein content was analyzed by immunoblotting in samples of erythroblast cells from CDAII patients and healthy controls.ResultsAll of the investigated cases carried SEC23B mutations on both alleles, with the exception of two patients in which a single heterozygous mutation was found. We identified 15 different SEC23B mutations, of which four represent novel mutations: p.Gln214Stop, p.Thr485Ala, p.Val637Gly, and p.Ser727Phe. The CDAII patients exhibited a 40-60% decrease of SEC23B mRNA levels in erythroid precursors when compared with the corresponding cell type from healthy participants. The largest decrease was observed in compound heterozygote patients with missense/nonsense mutations. In three patients, Sec23B protein levels were evaluated in erythroid precursors and found to be strictly correlated with the reduction observed at the transcript level. We also demonstrate that Sec23B mRNA expression levels in lymphocytes and erythroblasts are similar.ConclusionsIn this study, we identified four novel SEC23B mutations associated with CDAII disease. We also demonstrate that the genetic alteration results in a significant decrease of SEC23B transcript in erythroid precursors. Similar down-regulation was observed in peripheral lymphocytes, suggesting that the use of these cells might be sufficient in the identification of Sec23B gene alterations. Finally, we demonstrate that decreased Sec23B protein levels in erythroid precursors correlate with down-regulation of the SEC23B mRNA transcript.

Project description:Congenital dyserythropoietic anemia type II (CDAII) is an autosomal recessive disease resulting from loss-of-function mutations in SEC23B, which encodes a component of coat complex protein II (COPII) vesicles. We have previously shown that the expression of SEC23A, a paralogous protein for SEC23B, is significantly lower than that of SEC23B in human erythroid cells and that increased SEC23A expression rescues CDAII. In this study, we generated a human erythroid cell line that expresses eGFP from the endogenous genomic locus of SEC23A and performed a small molecule screen to identify compounds that increase the SEC23A-eGFP level. The top compound passing all filters was an LSD1 inhibitor. We validated that LSD1 inhibition with RN1 i) results in increased SEC23A mRNA and protein levels in primary erythroid cells derived from CD34+ human hematopoietic stem and progenitor cells (HSPCs), at doses that do not impair erythroid cell growth or differentiation and ii) rescues the defect resulting from SEC23B deletion in primary human erythroid cells. We validated LSD1 as the target of RN1 by showing that genetic downregulation of LSD1 also led to a profound induction of SEC23A mRNA levels in HPSC-derived erythroid cells. Subsequently, we validated our findings in vivo, demonstrating that deletion of Lsd1 in mouse erythroid cells results in increased Sec23a expression and that RN1 treatment rescues the erythroid defect observed in CDAII mice. Finally, using CUT&RUN, we found that LSD1 occupies a sequence in the SEC23A promoter, which when deleted, results in increased SEC23A expression and rescue of CDAII. These finding suggest that LSD1 occupies the SEC23A promoter, repressing SEC23A transcription and that in the setting of LSD1 inhibition, SEC23A expression is de-repressed, resulting in CDAII rescue. Therefore, using an unbiased screen, we have identified and validated a novel promising therapeutic strategy for CDAII, using a compound that inhibit LSD1 or a genetic approach based on deleting the SEC23A promoter sequence that is occupied by LSD1.

Dataset Information

Mutational spectrum in congenital dyserythropoietic anemia type II: identification of 19 novel variants in SEC23B gene.

Publications

Mutational spectrum in congenital dyserythropoietic anemia type II: identification of 19 novel variants in SEC23B gene.

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