Genetic Heterogeneity and Protein Function in DBA

Diamond Blackfan贫血（DBA）是一种先天性贫血，在出生时或出生后不久发生，并且是由于红细胞及其前体的生产失败，具有正常或接近正常的骨髓和血小板谱系。 患者可以完全释放皮质类固醇或可能对治疗产生抗药性，然后需要定期输血，或骨髓移植，如果有组织相容性的同胞供体。 DBA患者患白血病和其他恶性肿瘤的风险增加。 DBA在大约10- 15%的病例中是遗传的，大多数是常染色体显性遗传。 最近的遗传学研究已经导致了染色体19q13.2上核糖体蛋白基因RPS 19突变的惊人鉴定，约25%的家族性和散发性病例（DBA 1）。 多重DBA家族中的连锁分析显示，在约40%的家族中存在染色体8 p上另一个基因（DBA 2）的强有力证据，而其他家系没有显示与染色体8 p或19 q连锁的证据，表明进一步的遗传异质性。 本提案的长期目标是鉴定和分离DBA 2基因。 因此，本研究的具体目标是：（1）进一步确定染色体8 p的遗传图谱，通过连锁分析和单倍型分析寻找侧翼区的重组，并通过细胞遗传学技术筛选缺失和易位;（2）利用基因的cDNA阵列和表达序列标签（EST）在关键区域中，通过检查候选基因在红系细胞中表达的RNA的模式，并通过比较正常和患者基因组DNA与这些阵列的杂交以寻找杂合性缺失来确定候选基因;和（3）通过SSCP、PCR杂合性筛选和序列分析，检测作为目标1和/或目标2进展的结果而鉴定的候选基因在8号染色体连锁家族中的突变。引起DBA的其他基因的知识可能会提供新的见解红细胞生成的分子调控和干细胞向红系谱系的承诺的过程中，它是可能的，由染色体8 p上的基因编码的蛋白质与RPS 19在一个新的途径相互作用。 此外，这些患者中恶性肿瘤的风险增加表明该蛋白可能作为肿瘤抑制因子。 因此，分离导致DBA的基因可能不仅对于为这些患者设计新的治疗方法很重要，而且对于更好地理解红细胞生成的调节和恶性肿瘤的发展也很重要。

Diamond Blackfan anemia (DBA) is a congenital anemia that develops at birth or soon after, and is due to failure of production of erythrocytes and their precursors, with normal or near normal myeloid and platelet lineages. Patients can emit completely on corticosteroids or may become resistant to treatment, and then require regular blood transfusions, or bone marrow transplant if a histocompatible sibling donor is available. DBA patients are at increased risk of developing leukemia and other malignancies. DBA is inherited in about 10-15 percent of cases, mostly as an autosomal dominant. Recent genetic studies have led to the the surprising identification of mutations in a ribosomal protein gene, RPS19, on chromosome 19q13.2, in about 25 percent of both familial and sporadic cases (DBA1). Linkage analysis in multiplex DBA families shows strong evidence for another gene on chromosome 8p (DBA2) in about 40 percent of families, and other pedigrees do not show evidence for linkage to either chromosome 8p or 19q, indicating further genetic heterogeneity. The long term objective of this proposal is to identify and isolate the DBA2 gene. Therefore the specific aims are to (1), further define the chromosome 8p genetic map by ascertaining more families to search by linkage and haplotype analysis for recombinations in the flanking regions, and screen by cytogenetic techniques for deletions and translocations; (2) use cDNA arrays of the genes and expressed sequence tags (ESTs) in the critical region to define candidate genes by examining their pattern of expressed RNAs in erythroid cells, and by comparing the hybridization of normal and patient genomic DNA to these arrays to look for loss of heterozygosity; and (3), test candidate genes identified either as a result of progress in aim 1 and/or aim 2 for mutations in chromosome 8 linked families by SSCP, PCR heterozygosity screening and sequence analysis. Knowledge of additional genes that cause DBA may offer new insights into the molecular regulation of erythropoiesis and the process of stem cell commitment to the erythroid lineage, and it is possible that the protein encoded by the gene on chromosome 8p interacts with RPS19 in a novel pathway. Furthermore, the increased risk of malignancy in these patients suggests that the protein may act as a tumor suppressor. Thus isolating the genes that cause DBA may be important not only for devising new treatment for these patients but also for a better understanding of the regulation of erythropoiesis and the development of malignancy.