GENETIC CONTROL OF FETAL Y-GLOBIN IN ADULT RED CELLS

胎儿血红蛋白(HbF)存在于胎儿和新生儿中，并有少量的 在正常成人中发现的量(不到1%)。伽玛的两种类型 在大多数情况下，Hb F链(伽马和伽马)以70：30的比例存在 新生儿和大多数成年人为40：60。然而，大约20%的黑人SS患者 具有高比例(60：40)的G-伽马链和A-伽马链。一种特定的 β-珠蛋白限制性内切酶多态位点的单倍型 基因簇仅在G-Gamma大于或的SS个体中发现 相当于总伽马链的50%；这表明高 贝塔-珠蛋白基因簇的G-伽马遗传决定因素。三 观察表明，这个行列式接近(可能是5‘to)， G-伽马和/或A-伽马基因：1)亚单倍型，+-++，用于 Gamma基因及其附近的PSBeta基因与高G-Gamma相关 在黑色SS中，在沙特阿拉伯形式的SS中，在低HBF中 G-Gamma-B+-HPFH，尽管完整的单倍型(7个位点)不同。2)在 新生儿，混合基因--伽马--产生伽马 G-伽马基因预期水平的多肽。3)5‘端突变为 GGamma基因被认为是导致高GGamma水平的原因 Hb F GGamma-B+-HPFH。 这一建议提出了一种假设，即DNA序列变异接近 GGamma和/或AGamma基因改变它们的相对转录速率， 作为特定DNA序列与成体相互作用改变的结果 红系细胞因子。为了测试这一点，我们将对 具有低G-γ单倍型的黑色SS的G-γ单倍型，以及两种类型的 高伽马HPFH(高和低Hb F GGamma-Beta+-HPFH)和低GGamma HPFH(AGamma-B+-HPFH)，用于以下内容：1)GGamma和 AGamma基因，包括侧翼区域；这也将对三个 其他高伽马单倍型-两种见于黑贝塔地中海贫血，以及 沙特党卫军的。2)成熟和前体伽马和伽马水平 在网织红细胞和骨髓细胞中的mRNA，以及甲基化的程度 后者的DNA对DNase I超敏。3)基因表达 稳定转染非红系细胞中γ-γ和γ-γ基因的克隆(L) 细胞和红系(小鼠红白血病)细胞。4)In的影响 体外DNA序列改变对克隆DNA中γ基因表达的影响， 以确认在AIM#1中发现的突变对表达的影响。 在检验这一假说时获得的数据将提供重要信息 关于控制成人G-伽马：A-伽马遗传决定因素的性质 比率和Hb-F水平。

Fetal hemoglobin (Hb F) is present in fetuses and newborn, and a small amount (less than 1%) is found in normal adults. The two types of Gamma chains of Hb F (Ggamma and Agamma) are found in a 70:30 ratio in most newborn and 40:60 in most adults. However, about 20% of Black SS patients have a high (60:40) ratio of G-gamma to A-gamma chains. A specific haplotype for polymorphic restriction endonuclease sites in the Beta-globin gene cluster is found only in SS individuals with G-gamma greater than or equal 50% of total Gamma chain; this suggests close linkage of a high G-gamma genetic determinant to the Beta-globin gene cluster. Three observations suggest that this determinant is near (and possibly 5' to), the G-gamma and/or A-gamma genes: 1) A subhaplotype, + - + +, for sites in the Gamma genes and near the PSBeta gene, is associated with high G-gamma in Black SS, in the Saudi Arabian form of SS, and in low HbF G-gamma-B+-HPFH, although the full haplotypes (for 7 sites) differ. 2) In the newborn baby, the hybrid gene -Ggamma Agamma-produces Agamma polypeptide at levels expected for the G-gamma gene. 3) A mutation 5' to the Ggamma gene is hypothesized as the cause of high Ggamma levels in high Hb F Ggamma-B+-HPFH. This proposal presents the hypothesis that DNA sequence variation near Ggamma and/or Agamma genes changes their relative rates of transcription, as the result of altered interactions of specific DNA sequences with adult erythroid cell factors. To test this, comparisons will be made of the high G-gamma haplotype of Black SS with a low G-gamma haplotye, and two types of high Ggamma HPFH (high and low HB F Ggamma-Beta+-HPFH) with a low Ggamma HPFH (Agamma-B+-HPFH), for the following: 1) DNA sequence of Ggamma and Agamma genes, including flanking regions; this will also be done for three other high Ggamma haplotypes - two seen in Black Beta-thalassemia, and that of Saudi SS. 2) Levels of mature and precursor Ggamma and Agamma mRNA, in reticulocytes and bone marrow cells, and the extent of methylation and DNase I hypersensitivity of DNA of the latter. 3) mRNA expression of cloned Ggamma and Agamma genes in stably-transfected non-erythroid (L) cells and erythroid (mouse erythroleukemia) cells. 4) The effect of in vitro alterations of DNA sequence on gamma-gene expression of cloned DNA, to confirm the effects on expression of mutations found in aim #1. Data obtained in testing this hypothesis will provide important information on the nature of genetic determinants controlling adult G-gamma:A-gamma ratios and HB F levels.