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Nijmegen breakage syndrome (NBS), also known as Berlin breakage syndrome, ataxia telangiectasia variant 1 (AT-V1) and Seemanova syndrome,〔Seemanova, E., Passarge, E., Beneskova, D., Houstek, J., Kasal, P., Sevcikova, M. Familial microcephaly with normal intelligence, immunodeficiency, and risk of lymphoreticular malignancies: a new autosomal recessive disorder. Am. J. Med. Genet. 20: 639-648, 1985. PMID 3857858〕 is a rare autosomal recessive congenital disorder causing chromosomal instability, probably as a result of a defect in the Double Holliday junction DNA repair mechanism and/or the Synthesis Dependent Strand Annealing mechanism for repairing double strand breaks in DNA (see Homologous recombination).〔http://omim.org/entry/251260〕 NBS1 codes for a protein that has two major functions: (1) to stop the cell cycle in the S phase, when there are errors in the cell DNA (2) to interact with FANCD2 that can activate the BRCA1/BRCA2 pathway of DNA repair. This explains why mutations in the NBS1 gene lead to higher levels of cancer (see Fanconi anemia, Cockayne syndrome.) The name derives from the Dutch city Nijmegen where the condition was first described. Most people with NBS have West Slavic origins. The largest number of them live in Poland. ==Characteristics== It is characterized by microcephaly, a distinct facial appearance, short stature, immunodeficiency, radiation sensitivity and a strong predisposition to lymphoid malignancy.〔 ''(Full text )''〕 NBS is caused by a mutation in the ''NBS1'' gene. It is thus not surprising that many of the features are similar to ataxia telangiectasia (AT), and this syndrome is sometimes termed AT-variant 1; in AT, an abnormal ATM protein, the normal correlate of which interacts with the MRE11/RAD50/NBS1 (MRN) complex.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Nijmegen breakage syndrome」の詳細全文を読む スポンサード リンク
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