nibrin Dotaz Zobrazit nápovědu
Nijmegen breakage syndrom (NBS) patří do skupiny primárních imunodeficiencí asociovaných se zvýšenou lomivostí chromozomů. Jeho příčinou je mutace genu NBN1 (dříve NBS1 ), nejčastěji se jedná o tzv. slovanskou mutaci c.657del5. Klinicky se toto onemocnění projevuje vrozenou mikrocefalií, růstovou retardací, sklonem k lymfoidním malignitám, radiosenzitivitou, různým stupně m postižení imunitního systému a hypergonadotropním hypogonadismem. Prezentujeme 4 kazuistiky nemocných s NBS, z nichž 2 pacienti byli diagnostikováni již v kojeneckém věku při alergologicko-imunologickém vyšetření, naproti tomu další 2 až ve věku pubertálním při výskytu maligního onemocnění. Naše pozorování ukazuje na význam včasného zachycení této diagnózy, kdy alergologicko-imunologické vyšetření může sehrát velmi významnou roli.
Nijmegen Breakage Syndrome (NBS) belongs to the group of primary immunodeficiency diseases associated with increased chromosoma l instability. NBS is caused by mutation in NBN1 (formely NBS1 ) gene, the most frequent is so-called „Slavic“ mutation c.657del5. The disease manifests by congenital microcephaly, growth retardation, tendency to malignancies, radiosensitivity, variable defects of the i mmune system and hypergonadotropic hypogonadism. Here we present 4 case-reports of patients with NBS, 2 of them were diagnosed in infancy during the allergo-immunologic investi gation, while the remaining 2 in the pubertal age after the development of malignant lymfoproliferative diseases. Our observation shows the importance of early recognition of NBS, where the allergo-immunologic examination may play a crucial role.
- Klíčová slova
- hypogamaglobulinémie, T-buněčný imunodefict, nibrin,
- MeSH
- dítě MeSH
- dysgamaglobulinemie diagnóza MeSH
- faciální stigmatizace MeSH
- genetická predispozice k nemoci MeSH
- lidé MeSH
- mladiství MeSH
- mutace genetika MeSH
- nádory genetika MeSH
- syndrom Nijmegen breakage diagnóza genetika komplikace MeSH
- syndromy imunologické nedostatečnosti diagnóza komplikace MeSH
- tolerance záření genetika MeSH
- vrozené vady genetika MeSH
- Check Tag
- dítě MeSH
- lidé MeSH
- mladiství MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- kazuistiky MeSH
BACKGROUND: Nijmegen breakage syndrome (NBS) is an autosomal recessive chromosomal instability disorder with hypersensitivity to ionising radiation. The clinical phenotype is characterised by congenital microcephaly, mild dysmorphic facial appearance, growth retardation, immunodeficiency, and greatly increased risk for lymphoreticular malignancy. Most NBS patients are of Slavic origin and homozygous for the founder mutation 657del5. The frequency of 657del5 heterozygotes in the Czech population is 1:150. Recently, another NBS1 mutation, 643C>T(R215W), with uncertain pathogenicity was found to have higher frequency among tumour patients of Slavic origin than in controls. This alteration results in the substitution of the basic amino acid arginine with the non-polar tryptophan and thus could potentially interfere with the function of the NBS1 protein, nibrin. METHODS AND RESULTS: Children with congenital microcephaly are routinely tested for the 657del5 mutation in the Czech and Slovak Republics. Here, we describe for the first time a severe form of NBS without chromosomal instability in monozygotic twin brothers with profound congenital microcephaly and developmental delay who are compound heterozygotes for the 657del5 and 643C>T(R215W) NBS1 mutations. Both children showed reduced expression of full length nibrin when compared with a control and a heterozygote for the 657del5 mutation. Radiation response processes such as phosphorylation of ATM and phosphorylation/stabilisation of p53, which are promoted by NBS1, are strongly reduced in cells from these patients. CONCLUSIONS: Interestingly, the patients are more severely affected than classical NBS patients. Consequently, we postulate that homozygosity for the 643C>T(R215W) mutation will also lead to a, possibly very, severe disease phenotype.
- MeSH
- chromozomální nestabilita MeSH
- financování organizované MeSH
- fosforylace MeSH
- geny recesivní MeSH
- jaderné proteiny genetika metabolismus MeSH
- lidé MeSH
- mapování chromozomů MeSH
- mikrocefalie genetika MeSH
- mutace MeSH
- nemoci u dvojčat MeSH
- polymerázová řetězová reakce MeSH
- proteiny buněčného cyklu genetika metabolismus MeSH
- substituce aminokyselin MeSH
- syndrom Nijmegen breakage genetika MeSH
- Check Tag
- lidé MeSH
- Geografické názvy
- Česká republika MeSH
The most frequent Nijmegen breakage syndrome (NBS)-causing mutation is a 5-base pair deletion in gene coding for nibrin (NBN 657del5), which results in a non-fully functional protein product and is particularly frequent in Central and Eastern Europe. Recent studies have investigated whether NBN 657del5 carriage may predispose to an increased risk of different types of cancer. The Czech Republic has one of the highest incidences of colorectal cancer in the world as well as high incidence of NBS. To assess whether NBN 657del5 associates with an increased risk of sporadic colorectal cancer, we have screened 771 colorectal cancer patients, 614 controls with negative colonoscopy and 818 healthy blood donors from the Czech Republic. There were no significant differences between the frequencies of heterozygous carriers among the three groups. The present results do not provide any evidence that the exceeding risk of CRC in this population is attributable to the high frequency of heterozygous carriage of the NBN 657del5.
- MeSH
- dospělí MeSH
- genetická predispozice k nemoci MeSH
- genotyp MeSH
- heterozygot MeSH
- jaderné proteiny MeSH
- kolorektální nádory genetika MeSH
- lidé středního věku MeSH
- lidé MeSH
- mutace MeSH
- proteiny buněčného cyklu MeSH
- sekvenční delece MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
BACKGROUND: Nibrin, as part of the NBN/MRE11/RAD50 complex, is mutated in Nijmegen breakage syndrome (NBS), which leads to impaired DNA damage response and lymphoid malignancy. RESULTS: Telomere length (TL) was markedly reduced in homozygous patients (and comparably so in all chromosomes) by ~40% (qPCR) and was slightly reduced in NBS heterozygotes older than 30 years (~25% in qPCR), in accordance with the respective cancer rates. Humanized cancer-free NBS mice had normal TL. Telomere elongation was inducible by telomerase and/or alternative telomere lengthening but was associated with abnormal expression of telomeric genes involved in aging and/or cell growth. Lymphoblastoid cells from NBS patients with long survival times (>12 years) displayed the shortest telomeres and low caspase 7 activity. CONCLUSIONS: NBS is a secondary telomeropathy. The two-edged sword of telomere attrition enhances the cancer-prone situation in NBS but can also lead to a relatively stable cellular phenotype in tumor survivors. Results suggest a modular model for progeroid syndromes with abnormal expression of telomeric genes as a molecular basis. METHODS: We studied TL and function in 38 homozygous individuals, 27 heterozygotes, one homozygous fetus, six NBS lymphoblastoid cell lines, and humanized NBS mice, all with the same founder NBN mutation: c.657_661del5.
- MeSH
- dítě MeSH
- heterozygot MeSH
- homeostáza telomer genetika MeSH
- homozygot MeSH
- jaderné proteiny genetika MeSH
- karyotypizace MeSH
- kojenec MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- modely nemocí na zvířatech MeSH
- myši transgenní MeSH
- myši MeSH
- nádorové buněčné linie MeSH
- předškolní dítě MeSH
- progerie genetika patologie MeSH
- proteiny buněčného cyklu genetika MeSH
- syndrom Nijmegen breakage komplikace genetika patologie MeSH
- telomerasa metabolismus MeSH
- telomery patologie MeSH
- zvířata MeSH
- Check Tag
- dítě MeSH
- kojenec MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- myši MeSH
- předškolní dítě MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The vast majority of patients with Nijmegen Breakage Syndrome (NBS) are of Slavic origin and carry a deleterious deletion (c.657del5; rs587776650) in the NBN gene on chromosome 8q21. This mutation is essentially confined to Slavic populations and may thus be considered a Slavic founder mutation. Notably, not a single parenthood of a homozygous c.657del5 carrier has been reported to date, while heterozygous carriers do reproduce but have an increased cancer risk. These observations seem to conflict with the considerable carrier frequency of c.657del5 of 0.5% to 1% as observed in different Slavic populations because deleterious mutations would be eliminated quite rapidly by purifying selection. Therefore, we propose that heterozygous c.657del5 carriers have increased reproductive success, i.e., that the mutation confers heterozygote advantage. In fact, in our cohort study of the reproductive history of 24 NBS pedigrees from the Czech Republic, we observed that female carriers gave birth to more children on average than female non-carriers, while no such reproductive differences were observed for males. We also estimate that c.657del5 likely occurred less than 300 generations ago, thus supporting the view that the original mutation predated the historic split and subsequent spread of the 'Slavic people'. We surmise that the higher fertility of female c.657del5 carriers reflects a lower miscarriage rate in these women, thereby reflecting the role of the NBN gene product, nibrin, in the repair of DNA double strand breaks and their processing in immune gene rearrangements, telomere maintenance, and meiotic recombination, akin to the previously described role of the DNA repair genes BRCA1 and BRCA2.
- MeSH
- detekce genetických nosičů MeSH
- dospělí MeSH
- efekt zakladatele * MeSH
- haplotypy MeSH
- jaderné proteiny genetika MeSH
- kohortové studie MeSH
- lidé středního věku MeSH
- lidé MeSH
- mutace * MeSH
- oprava DNA MeSH
- poškození DNA MeSH
- proteiny buněčného cyklu genetika MeSH
- rozmnožování genetika MeSH
- syndrom Nijmegen breakage etnologie genetika MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Česká republika MeSH
- Slovenská republika MeSH
