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2.
Hum Mutat ; 2021 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-33410562

RESUMO

ABCC8 encodes the SUR1 subunit of the ß-cell ATP-sensitive potassium channel whose loss of function causes congenital hyperinsulinism (CHI). Molecular diagnosis is critical for optimal management of CHI patients. Unfortunately, assessing the impact of ABCC8 variants on RNA splicing remains very challenging as this gene is poorly expressed in leukocytes. Here, we performed bioinformatics analysis and cell-based minigene assays to assess the impact on splicing of 13 ABCC8 variants identified in 20 CHI patients. Next, channel properties of SUR1 proteins expected to originate from minigene-detected in-frame splicing defects were analyzed after ectopic expression in COSm6 cells. Out of the analyzed variants, seven induced out-of-frame splicing defects and were therefore classified as recessive pathogenic, whereas two led to skipping of in-frame exons. Channel functional analysis of the latter demonstrated their pathogenicity. Interestingly, the common rs757110 SNP increased exon skipping in our system suggesting that it may act as a disease modifier factor. Our strategy allowed determining the pathogenicity of all selected ABCC8 variants, and CHI-inheritance pattern for 16 out of the 20 patients. This study highlights the value of combining RNA and protein functional approaches in variant interpretation and reveals the minigene splicing assay as a new tool for CHI molecular diagnostics.

3.
J Clin Immunol ; 41(3): 639-657, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33417088

RESUMO

PURPOSE: Germline heterozygous mutations of GATA2 underlie a variety of hematological and clinical phenotypes. The genetic, immunological, and clinical features of GATA2-deficient patients with mycobacterial diseases in the familial context remain largely unknown. METHODS: We enrolled 15 GATA2 index cases referred for mycobacterial disease. We describe their genetic and clinical features including their relatives. RESULTS: We identified 12 heterozygous GATA2 mutations, two of which had not been reported. Eight of these mutations were loss-of-function, and four were hypomorphic. None was dominant-negative in vitro, and the GATA2 locus was found to be subject to purifying selection, strongly suggesting a mechanism of haploinsufficiency. Three relatives of index cases had mycobacterial disease and were also heterozygous, resulting in 18 patients in total. Mycobacterial infection was the first clinical manifestation in 11 patients, at a mean age of 22.5 years (range: 12 to 42 years). Most patients also suffered from other infections, monocytopenia, or myelodysplasia. Strikingly, the clinical penetrance was incomplete (32.9% by age 40 years), as 16 heterozygous relatives aged between 6 and 78 years, including 4 older than 60 years, were completely asymptomatic. CONCLUSION: Clinical penetrance for mycobacterial disease was found to be similar to other GATA2 deficiency-related manifestations. These observations suggest that other mechanisms contribute to the phenotypic expression of GATA2 deficiency. A diagnosis of autosomal dominant GATA2 deficiency should be considered in patients with mycobacterial infections and/or other GATA2 deficiency-related phenotypes at any age in life. Moreover, all direct relatives should be genotyped at the GATA2 locus.

5.
Mol Cell Endocrinol ; 518: 111025, 2020 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-32916194

RESUMO

Insulin gene mutation is the second most common cause of neonatal diabetes (NDM). It is also one of the genes involved in maturity-onset diabetes of the young (MODY). We aim to investigate molecular behaviors of different INS gene variants that may correlate with the clinical spectrum of diabetes phenotypes. In this study, we concentrated on two previously uncharacterized MODY-causing mutants, proinsulin-p.Gly44Arg [G(B20)R] and p.Pro52Leu [P(B28)L] (a novel mutant identified in one French family), and an NDM causing proinsulin-p.(Cys96Tyr) [C(A7)Y]. We find that these proinsulin mutants exhibit impaired oxidative folding in the endoplasmic reticulum (ER) with blocked ER export, ER stress, and apoptosis. Importantly, the proinsulin mutants formed abnormal intermolecular disulfide bonds that not only involved the mutant proinsulin, but also the co-expressed WT-proinsulin, forming misfolded disulfide-linked proinsulin complexes. This impaired the intracellular trafficking of WT-proinsulin and limited the production of bioactive mature insulin. Notably, although all three mutants presented with similar defects in folding, trafficking, and dominant negative behavior, the degrees of these defects appeared to be different. Specifically, compared to MODY mutants G(B20)R and P(B28)L that partially affected folding and trafficking of co-expressed WT-proinsulin, the NDM mutant C(A7)Y resulted in an almost complete blockade of the ER export of WT-proinsulin, decreasing insulin production, inducing more severe ER stress and apoptosis. We thus demonstrate that differences in cell biological behaviors among different proinsulin mutants correlate with the spectrum of diabetes phenotypes caused by the different INS gene mutations.

6.
Blood Rev ; 42: 100710, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32532454

RESUMO

Myeloproliferative neoplasms (MPN) are clonal hematological malignancies that lead to overproduction of mature myeloid cells. They are due to acquired mutations in genes encoding for AK2, MPL and CALR that result in the activation of the cytokine receptor/JAK2 signaling pathway. In addition, it exists germline variants that can favor the initiation of the disease or may affect its phenotype. First, they can be common risk alleles, which correspond to frequent single nucleotide variants present in control population and that contribute to the development of either sporadic or familial MPN. Second, some variants predispose to the onset of MPN with a higher penetrance and lead to familial clustering of MPN. Finally, some extremely rare genetic variants can induce MPN-like hereditary disease. We will review these different subtypes of germline genetic variants and discuss how they impact the initiation and/or development of the MPN disease.

8.
Hum Mutat ; 41(5): 884-905, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32027066

RESUMO

The most common genetic cause of neonatal diabetes and hyperinsulinism is pathogenic variants in ABCC8 and KCNJ11. These genes encode the subunits of the ß-cell ATP-sensitive potassium channel, a key component of the glucose-stimulated insulin secretion pathway. Mutations in the two genes cause dysregulated insulin secretion; inactivating mutations cause an oversecretion of insulin, leading to congenital hyperinsulinism, whereas activating mutations cause the opposing phenotype, diabetes. This review focuses on variants identified in ABCC8 and KCNJ11, the phenotypic spectrum and the treatment implications for individuals with pathogenic variants.

9.
Bone Marrow Transplant ; 55(8): 1614-1622, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31992846

RESUMO

ELANE neutropenia is associated with myelodysplasia and acute leukemia (MDS-AL), and severe infections. Because the MDS-AL risk has also been shown to be associated with exposure to GCSF, since 2005, in France, patients receiving high daily GCSF doses (>15 µg/kg/day) are eligible for HSCT, in addition to classic indications (MDS-AL or GCSF refractoriness). We analyzed the effect of this policy. Among 144 prospectively followed ELANE-neutropenia patients enrolled in the French Severe Congenital Neutropenia Registry, we defined two groups according to period: "before 2005" for those born before 2005 and followed until 31/12/2004 (1588 person-years); and "after 2005" comprised of those born after 2005 or born before 2005 but followed after 2005 until 31/03/2019 (1327 person-years). Sixteen of our cohort patients underwent HSCT (14 long-term survivors) and six developed MDS-ALs. Six leukemic transformations occurred in the before-2005 group and none after 2005 (respective frequencies 3.8 × 10-3 vs. 0; P < 0.01), while four HSCTs were done before 2005 and 12 since 2005 (respective HSCT rates increased 2.5 × 10-3 vs. 9 × 10-3; P < 0.01). Our results support early HSCT for patients with ELANE mutations who received high GCSF doses, as it might lower the risk of leukemic transformation.

10.
Eur J Hum Genet ; 28(1): 56-63, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31481685

RESUMO

The prevalence of neurological involvement in patients with a deletion of or a variant in the HNF1B gene remains discussed. The aim of this study was to investigate the neuropsychological outcomes in a large cohort of children carrying either a HNF1B whole-gene deletion or a disease-associated variant, revealed by the presence of kidney anomalies. The neuropsychological development-based on school level-of 223 children included in this prospective cohort was studied. Data from 180 children were available for analysis. Patients mean age was 9.6 years, with 39.9% of girls. Among these patients, 119 carried a HNF1B deletion and 61 a disease-associated variant. In the school-aged population, 12.7 and 3.6% of patients carrying a HNF1B deletion and a disease-associated variant had special educational needs, respectively. Therefore, the presence of a HNF1B deletion increases the risk to present with a neuropsychiatric involvement when compared with the general population. On the other hand, almost 90% of patients carrying a HNF1B disease-associated variant or deletion have a normal schooling in a general educational environment. Even if these findings do not predict the risk of neuropsychiatric disease at adulthood, most patients diagnosed secondary to kidney anomalies do not show a neurological outcome severe enough to impede standard schooling at elementary school. These results should be taken into account in prenatal counseling.

11.
J Diabetes ; 12(1): 48-57, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31166087

RESUMO

BACKGROUND: Liver adenomatosis (LA) is a rare disease resulting from biallelic inactivation of the hepatocyte nuclear factor-1 alpha (HNF1A) gene, which induces the proliferation of adenoma cells in liver parenchyma. Liver adenomatosis has only been documented in case reports from patients carrying a HNF1A germline mutation. We have evaluated the frequency of LA among a large cohort of patients with HNF1A-maturity onset diabetes of the young (MODY), previously termed "MODY3," and herein describe its clinical, radiological, and pathological characteristics. METHODS: In all, 137 HNF1A-MODY subjects from 74 families were screened by liver ultrasonography in 13 centers, and 15 additional cases of LA were later included in the series. Liver adenomatosis was confirmed by liver computed tomography, magnetic resonance imaging (MRI), and/or histopathology. RESULTS: Among 137 carriers of an HNF1A mutation, 9 patients (6.5%) from seven families were diagnosed with LA. Diabetes mellitus was present in 87.5% of patients with LA. In 25% of patients, LA was diagnosed due to intra-abdominal or intratumoral bleeding. Liver biochemistry was near normal in all patients. Liver imaging showed adenomas of various sizes and numbers. On MRI, most nodules had the radiological characteristics of steatotic adenomas. Histopathological confirmation of LA was available in 13 cases, and these adenomas were mostly steatotic. Surgery was initially performed in 37.5% of patients, and liver disease progression was observed in 30%. No disease progression was observed in 14 pregnancies. CONCLUSIONS: The frequency of LA in a cohort of screened HNF1A-MODY patients and the high incidence of LA progression and/or hemorrhage warrants systematic screening for liver adenomatosis in HNF1A-MODY families.


Assuntos
Adenoma/genética , Diabetes Mellitus Tipo 2/genética , Fator 1-alfa Nuclear de Hepatócito/genética , Neoplasias Hepáticas/genética , Mutação , Adenoma/diagnóstico por imagem , Adenoma/patologia , Adolescente , Adulto , Criança , Estudos de Coortes , Diabetes Mellitus Tipo 2/diagnóstico por imagem , Diabetes Mellitus Tipo 2/patologia , Diagnóstico por Imagem/métodos , Saúde da Família , Feminino , França , Fator 1-alfa Nuclear de Hepatócito/metabolismo , Humanos , Neoplasias Hepáticas/diagnóstico por imagem , Neoplasias Hepáticas/patologia , Masculino , Pessoa de Meia-Idade , Adulto Jovem
12.
BMC Med ; 17(1): 132, 2019 07 11.
Artigo em Inglês | MEDLINE | ID: mdl-31291970

RESUMO

BACKGROUND: Monogenic diabetes (MgD) accounts for 1-2% of all diabetes cases. In adults, MgD is difficult to distinguish from common diabetes causes. We assessed the diagnosis rate and genetic spectrum of MgD using next-generation sequencing in patients with late adolescence/adult-onset diabetes referred for a clinical suspicion of MgD. METHODS: This cross-sectional study was performed in 1564 probands recruited in 116 Endocrinology departments. Inclusion criteria were the absence of diabetes autoantibodies, and at least two of the three following criteria: an age ≤ 40 years and a body mass index (BMI) < 30 kg/m2 at diagnosis in the proband or in at least two relatives with diabetes, and a family history of diabetes in ≥ 2 generations. Seven genes (GCK, HNF1A, HNF4A, HNF1B, ABCC8, KCNJ11, and INS) were analyzed. Variant pathogenicity was assessed using current guidelines. RESULTS: Pathogenic variants were identified in 254 patients (16.2%) and in 23.2% of EuroCaucasian patients. Using more stringent selection criteria (family history of diabetes in ≥ 3 generations, age at diabetes ≤ 40 years and BMI < 30 kg/m2 in the proband, EuroCaucasian origin) increased the diagnosis rate to 43%, but with 70% of the identified cases being missed. GCK (44%), HNF1A (33%), and HNF4A (10%) accounted for the majority of the cases. HNF1B (6%), ABCC8/KCNJ11 (4.4%), and INS (2.8%) variants accounted for 13% of the cases. As compared to non-monogenic cases, a younger age, a lower BMI and the absence of diabetes symptoms at diagnosis, a EuroCaucasian origin, and a family history of diabetes in ≥ 3 generations were associated with MgD, but with wide phenotype overlaps between the two groups. In the total population, two clusters were identified, that mainly differed by the severity of diabetes at onset. MgDs were more prevalent in the milder phenotypic cluster. The phenotypes of the 59 patients (3.8%) with variants of uncertain significance were different from that of patients with pathogenic variants, but not from that of non-monogenic patients. CONCLUSION: Variants of HNF1B and the K-ATP channel genes were more frequently involved in MgD than previously reported. Phenotype overlapping makes the diagnosis of MgD difficult in adolescents/adults and underlies the benefit of NGS in clinically selected patients.


Assuntos
Diabetes Mellitus Tipo 2/diagnóstico , Testes Genéticos/métodos , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Adolescente , Adulto , Estudos Transversais , Feminino , Humanos , Masculino , Adulto Jovem
13.
Blood ; 134(3): 277-290, 2019 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-31151987

RESUMO

Shwachman-Diamond syndrome (SDS) is a recessive disorder typified by bone marrow failure and predisposition to hematological malignancies. SDS is predominantly caused by deficiency of the allosteric regulator Shwachman-Bodian-Diamond syndrome that cooperates with elongation factor-like GTPase 1 (EFL1) to catalyze release of the ribosome antiassociation factor eIF6 and activate translation. Here, we report biallelic mutations in EFL1 in 3 unrelated individuals with clinical features of SDS. Cellular defects in these individuals include impaired ribosomal subunit joining and attenuated global protein translation as a consequence of defective eIF6 eviction. In mice, Efl1 deficiency recapitulates key aspects of the SDS phenotype. By identifying biallelic EFL1 mutations in SDS, we define this leukemia predisposition disorder as a ribosomopathy that is caused by corruption of a fundamental, conserved mechanism, which licenses entry of the large ribosomal subunit into translation.


Assuntos
Mutação , Fatores de Alongamento de Peptídeos/genética , Fatores de Iniciação de Peptídeos/biossíntese , Ribonucleoproteína Nuclear Pequena U5/genética , Síndrome de Shwachman-Diamond/genética , Síndrome de Shwachman-Diamond/metabolismo , Adolescente , Animais , Células Cultivadas , Análise Mutacional de DNA , Modelos Animais de Doenças , Suscetibilidade a Doenças , Feminino , Estudo de Associação Genômica Ampla , Humanos , Lactente , Masculino , Camundongos , Camundongos Transgênicos , Modelos Moleculares , Linhagem , Fatores de Alongamento de Peptídeos/química , Fatores de Alongamento de Peptídeos/metabolismo , Fenótipo , Conformação Proteica , Ribonucleoproteína Nuclear Pequena U5/química , Ribonucleoproteína Nuclear Pequena U5/metabolismo , Síndrome de Shwachman-Diamond/diagnóstico , Relação Estrutura-Atividade , Sequenciamento Completo do Genoma
14.
J Endocr Soc ; 2(9): 997-1000, 2018 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-30140784

RESUMO

Classic forms of 21-hydroxylase deficiency (21OHD) are usually diagnosed at birth by salt wasting or precocious puberty in male patients. Here we report the case of a 32-year-old male patient who presented with azoospermia and bilateral testicular tumors. He was referred to our endocrine unit after testicular surgery. His gonadotropins were undetectable. Liquid chromatography-tandem mass spectrometry revealed a high serum progesterone level, high 17-hydroxyprogesterone (17OHP) (255 ng/mL), and high levels of 17OHP metabolites, suggesting a classic form of 21OHD. His blood pressure was normal. Molecular analysis showed a homozygous large 21-hydroxylase gene (CYP21A2) conversion. Furthermore, an adrenal CT scan revealed voluminous, heterogeneous bilateral and asymmetric adrenal masses containing calcifications. Our case report illustrates the fact that a classic form of 21OHD can be diagnosed in late adulthood, manifested by azoospermia and large adrenal tumors, associated with elevated 17OHP.

15.
Blood ; 132(12): 1318-1331, 2018 09 20.
Artigo em Inglês | MEDLINE | ID: mdl-29914977

RESUMO

Congenital neutropenias (CNs) are rare heterogeneous genetic disorders, with about 25% of patients without known genetic defects. Using whole-exome sequencing, we identified a heterozygous mutation in the SRP54 gene, encoding the signal recognition particle (SRP) 54 GTPase protein, in 3 sporadic cases and 1 autosomal dominant family. We subsequently sequenced the SRP54 gene in 66 probands from the French CN registry. In total, we identified 23 mutated cases (16 sporadic, 7 familial) with 7 distinct germ line SRP54 mutations including a recurrent in-frame deletion (Thr117del) in 14 cases. In nearly all patients, neutropenia was chronic and profound with promyelocytic maturation arrest, occurring within the first months of life, and required long-term granulocyte colony-stimulating factor therapy with a poor response. Neutropenia was sometimes associated with a severe neurodevelopmental delay (n = 5) and/or an exocrine pancreatic insufficiency requiring enzyme supplementation (n = 3). The SRP54 protein is a key component of the ribonucleoprotein complex that mediates the co-translational targeting of secretory and membrane proteins to the endoplasmic reticulum (ER). We showed that SRP54 was specifically upregulated during the in vitro granulocytic differentiation, and that SRP54 mutations or knockdown led to a drastically reduced proliferation of granulocytic cells associated with an enhanced P53-dependent apoptosis. Bone marrow examination of SRP54-mutated patients revealed a major dysgranulopoiesis and features of cellular ER stress and autophagy that were confirmed using SRP54-mutated primary cells and SRP54 knockdown cells. In conclusion, we characterized a pathological pathway, which represents the second most common cause of CN with maturation arrest in the French CN registry.


Assuntos
Doenças da Medula Óssea/genética , Estresse do Retículo Endoplasmático , Insuficiência Pancreática Exócrina/genética , Lipomatose/genética , Mutação , Neutropenia/congênito , Partícula de Reconhecimento de Sinal/genética , Adolescente , Adulto , Apoptose , Autofagia , Doenças da Medula Óssea/metabolismo , Doenças da Medula Óssea/patologia , Criança , Pré-Escolar , Síndrome Congênita de Insuficiência da Medula Óssea , Insuficiência Pancreática Exócrina/metabolismo , Insuficiência Pancreática Exócrina/patologia , Feminino , Humanos , Lactente , Recém-Nascido , Lipomatose/metabolismo , Lipomatose/patologia , Masculino , Pessoa de Meia-Idade , Neutropenia/genética , Neutropenia/metabolismo , Neutropenia/patologia , Síndrome de Shwachman-Diamond , Regulação para Cima , Adulto Jovem
16.
Diabetes ; 67(9): 1903-1907, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29895593

RESUMO

There is wide variation in the age at diagnosis of diabetes in individuals with maturity-onset diabetes of the young (MODY) due to a mutation in the HNF1A gene. We hypothesized that common variants at the HNF1A locus (rs1169288 [I27L], rs1800574 [A98V]), which are associated with type 2 diabetes susceptibility, may modify age at diabetes diagnosis in individuals with HNF1A-MODY. Meta-analysis of two independent cohorts, comprising 781 individuals with HNF1A-MODY, found no significant associations between genotype and age at diagnosis. However after stratifying according to type of mutation (protein-truncating variant [PTV] or missense), we found each 27L allele to be associated with a 1.6-year decrease (95% CI -2.6, -0.7) in age at diagnosis, specifically in the subset (n = 444) of individuals with a PTV. The effect size was similar and significant across the two independent cohorts of individuals with HNF1A-MODY. We report a robust genetic modifier of HNF1A-MODY age at diagnosis that further illustrates the strong effect of genetic variation within HNF1A upon diabetes phenotype.


Assuntos
Diabetes Mellitus Tipo 2/genética , Predisposição Genética para Doença , Fator 1-alfa Nuclear de Hepatócito/genética , Mutação de Sentido Incorreto , Polimorfismo de Nucleotídeo Único , Idade de Início , Alelos , Substituição de Aminoácidos , Estudos de Coortes , Análise Mutacional de DNA , Bases de Dados Genéticas , Diabetes Mellitus Tipo 2/metabolismo , Inglaterra , Feminino , Frequência do Gene , Estudos de Associação Genética , Estudo de Associação Genômica Ampla , Fator 1-alfa Nuclear de Hepatócito/química , Fator 1-alfa Nuclear de Hepatócito/metabolismo , Humanos , Masculino , Paris , Reprodutibilidade dos Testes
17.
Haematologica ; 103(8): 1278-1287, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29724903

RESUMO

Heterozygous germline GATA2 mutations strongly predispose to leukemia, immunodeficiency, and/or lymphoedema. We describe a series of 79 patients (53 families) diagnosed since 2011, made up of all patients in France and Belgium, with a follow up of 2249 patients/years. Median age at first clinical symptoms was 18.6 years (range, 0-61 years). Severe infectious diseases (mycobacteria, fungus, and human papilloma virus) and hematologic malignancies were the most common first manifestations. The probability of remaining symptom-free was 8% at 40 years old. Among the 53 probands, 24 had missense mutations including 4 recurrent alleles, 21 had nonsense or frameshift mutations, 4 had a whole-gene deletion, 2 had splice defects, and 2 patients had complex mutations. There were significantly more cases of leukemia in patients with missense mutations (n=14 of 34) than in patients with nonsense or frameshift mutations (n=2 of 28). We also identify new features of the disease: acute lymphoblastic leukemia, juvenile myelomonocytic leukemia, fatal progressive multifocal leukoencephalopathy related to the JC virus, and immune/inflammatory diseases. A revised International Prognostic Scoring System (IPSS) score allowed a distinction to be made between a stable disease and hematologic transformation. Chemotherapy is of limited efficacy, and has a high toxicity with severe infectious complications. As the mortality rate is high in our cohort (up to 35% at the age of 40), hematopoietic stem cell transplantation (HSCT) remains the best choice of treatment to avoid severe infectious and/or hematologic complications. The timing of HSCT remains difficult to determine, but the earlier it is performed, the better the outcome.


Assuntos
Deficiência de GATA2/epidemiologia , Mutação em Linhagem Germinativa , Adulto Jovem , Adolescente , Adulto , Bélgica , Criança , Pré-Escolar , França , Deficiência de GATA2/complicações , Deficiência de GATA2/genética , Deficiência de GATA2/terapia , Neoplasias Hematológicas/etiologia , Transplante de Células-Tronco Hematopoéticas/métodos , Humanos , Lactente , Recém-Nascido , Infecções/etiologia , Pessoa de Meia-Idade , Mortalidade , Prognóstico , Inquéritos e Questionários
19.
Haematologica ; 103(4): 575-586, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29269524

RESUMO

Primary familial and congenital polycythemia is characterized by erythropoietin hypersensitivity of erythroid progenitors due to germline nonsense or frameshift mutations in the erythropoietin receptor gene. All mutations so far described lead to the truncation of the C-terminal receptor sequence that contains negative regulatory domains. Their removal is presented as sufficient to cause the erythropoietin hypersensitivity phenotype. Here we provide evidence for a new mechanism whereby the presence of novel sequences generated by frameshift mutations is required for the phenotype rather than just extensive truncation resulting from nonsense mutations. We show that the erythropoietin hypersensitivity induced by a new erythropoietin receptor mutant, p.Gln434Profs*11, could not be explained by the loss of negative signaling and of the internalization domains, but rather by the appearance of a new C-terminal tail. The latter, by increasing erythropoietin receptor dimerization, stability and cell-surface localization, causes pre-activation of erythropoietin receptor and JAK2, constitutive signaling and hypersensitivity to erythropoietin. Similar results were obtained with another mutant, p.Pro438Metfs*6, which shares the same last five amino acid residues (MDTVP) with erythropoietin receptor p.Gln434Profs*11, confirming the involvement of the new peptide sequence in the erythropoietin hypersensitivity phenotype. These results suggest a new mechanism that might be common to erythropoietin receptor frameshift mutations. In summary, we show that primary familial and congenital polycythemia is more complex than expected since distinct mechanisms are involved in the erythropoietin hypersensitivity phenotype, according to the type of erythropoietin receptor mutation.


Assuntos
Mutação em Linhagem Germinativa , Policitemia/etiologia , Receptores da Eritropoetina/genética , Sequência de Aminoácidos , Animais , Linhagem Celular , Eritropoetina/farmacologia , Humanos , Camundongos , Proteínas Mutantes , Policitemia/genética , Multimerização Proteica/genética , Estabilidade Proteica , Receptores da Eritropoetina/metabolismo
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