Identification of the gene defect underlying ICF2 syndrome

鉴定 ICF2 综合征背后的基因缺陷

• 批准号: 7953512
• 负责人: SILVERE M VAN DER MAAREL
• 金额: $ 13.1万
• 依托单位: LEIDEN UNIVERSITY MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-06-03 至 2012-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7953512
• 关键词: 20q; Agammaglobulinemia; B-Lymphocytes; Birth; Bone Marrow; Bone Marrow Transplantation; Candidate Disease Gene; Cell Culture Techniques; Cells; Chromosomes; Codon Nucleotides; Computer software; Congenital Abnormality; DNA; DNA Methylation; DNA Methyltransferase; DNA Methyltransferase 3B; DNA Modification Methylases; DNA Sequence; DNMT3B gene; Data; Databases; Defect; Diagnosis; Disease; Exons; Genes; Genetic; Genetic Counseling; Genome; Genotype; Human; Human Genome; Immune; Intervention; Introns; Life Expectancy; Long-Term Effects; Maps; Methods; Molecular; Mutation; Online Mendelian Inheritance In Man; Patients; Phytohemagglutinins; Play; Recurrence; Reporting; Role; Sequence Determination; Single Nucleotide Polymorphism; Syndrome; Testing; Variant; base; clinical phenotype; disease diagnosis; exome; gastrointestinal infection; gene function; genetic linkage; genetic linkage analysis; genome-wide; immunodeficiency-centromeric instability-facial anomalies syndrome; improved; postnatal; prenatal; public health relevance; respiratory

DESCRIPTION (provided by applicant): Patients with ICF (Immunodeficiency, Centromeric instability, and Facial anomalies) syndrome suffer from recurrent and often fatal respiratory and gastrointestinal infections due to agammaglobulinemia with B cells as well as a variety of congenital malformations. In approximately half of the patients mutations in the DNA methyltransferase 3B (DNMT3B) gene have been identified as the underlying cause of ICF syndrome (ICF1), while in the remainder of patients the gene defect is unknown. These ICF2 patients without DNMT3B defect show a clinical phenotype identical to ICF1 patients. All patients with ICF, both ICF1 and ICF2, suffer from agammaglobulinemia with B cells. Upon phytohaemagglutinin stimulation, multiradiate chromosomes can be identified in all ICF patients. In addition, specific DNA repeats show pronounced hypomethylation. Both observations are considered molecular hallmarks for ICF syndrome. Since all ICF2 patients show alpha-satellite repeat hypomethylation, which distinguishes them from ICF1 patients, the involvement of a second disease locus (gene defect) in ICF2 syndrome is expected. This is further substantiated by the identification of three ICF2 cases in which the DNMT3B gene is excluded by genetic studies. The central premise of this application is to identify the gene defect and primary pathogenic mechanism underlying ICF2 syndrome. First, using the method of homozygosity mapping, candidate loci that show homozygosity by descent in five consanguineous ICF2 patients will be identified. Additional ICF2 cases are available to aid the mapping study. Second, by sequence determination of the whole human exome in two consanguineous ICF2 patients using the Illumina/Solexa Genome Analyzer, all homozygous DNA variants in these patients in all regions of homozygosity will be identified. Candidate genes carrying homozygous DNA variants will be prioritized for their causal involvement in ICF2 based on the absence of the identified sequence variants in SNP databases, gene function and codon change. Finally, by direct sequencing of all exons and exon-intron boundaries of the prioritized candidate genes in the remaining patients in combination with expression studies of the candidate genes in cell cultures of ICF2 patients, the gene defect underlying ICF2 syndrome will be identified. PUBLIC HEALTH RELEVANCE: The central premise of this application is to identify the gene defect in ICF2 syndrome, a primary immune deficiency. This will increase our understanding of the molecular mechanism underlying ICF2 syndrome, and may provide new clues for therapy. Additionally, it will improve prenatal and postnatal diagnosis of the disease and facilitate genetic counseling.

描述（由申请方提供）：ICF（免疫缺陷、着丝粒不稳定和面部异常）综合征患者因无丙种球蛋白血症伴B细胞以及各种先天性畸形而发生复发性且通常致命的呼吸道和胃肠道感染。在大约一半的患者中，DNA甲基转移酶3B（DNMT 3B）基因突变已被确定为ICF综合征（ICF 1）的潜在原因，而在其余患者中，基因缺陷尚不清楚。这些没有DNMT 3B缺陷的ICF 2患者显示出与ICF 1患者相同的临床表型。所有ICF患者（包括ICF 1和ICF 2）均患有无丙种球蛋白血症伴B细胞。在植物血凝素刺激，多辐射染色体可以确定在所有ICF患者。此外，特定的DNA重复序列显示出明显的低甲基化。这两个观察结果被认为是ICF综合征的分子标志。由于所有ICF 2患者均显示α-卫星重复低甲基化，这将其与ICF 1患者区分开来，因此预期ICF 2综合征中涉及第二个疾病位点（基因缺陷）。这进一步证实了三个ICF 2的情况下，其中DNMT 3B基因被排除在遗传研究的鉴定。本申请的中心前提是确定ICF 2综合征的基因缺陷和主要致病机制。首先，使用纯合性作图方法，将识别出五名血缘ICF 2患者中通过血统表现出纯合性的候选基因座。其他ICF 2病例可用于辅助标测研究。第二，通过使用Illumina/Solexa基因组分析仪对两名近亲ICF 2患者中的整个人外显子组进行序列测定，将鉴定这些患者中所有纯合性区域中的所有纯合DNA变体。携带纯合DNA变体的候选基因将根据SNP数据库中不存在鉴定的序列变体、基因功能和密码子变化，优先考虑其与ICF 2的因果关系。最后，通过对剩余患者中优先候选基因的所有外显子和外显子-内含子边界进行直接测序，并结合对ICF 2患者细胞培养物中候选基因的表达研究，将鉴定ICF 2综合征潜在的基因缺陷。 公共卫生相关性：本申请的中心前提是确定ICF 2综合征（一种原发性免疫缺陷）中的基因缺陷。这将增加我们对ICF 2综合征的分子机制的理解，并可能为治疗提供新的线索。此外，它将改善产前和产后诊断的疾病，并促进遗传咨询。