Identifying the molecular basis for hormonal influence on hematopoiesis

描述（由申请人提供）：长期以来，人们都知道一个人的荷尔蒙环境会影响骨髓功能。然而，发生这种情况的精确分子机制尚不清楚。表观遗传变化，如甲基与DNA的连接和组蛋白的改变，可以调节干细胞分化所必需的基因的表达。该建议利用表达DNMT3B7的动物模型来探究DNA甲基化变化是否会影响血细胞的发育。DNMT3B7是一种截断的DNA甲基化酶3B亚型，通常在人类癌症中表达。为了检测DNMT3B7表达对血细胞发育的影响，我们将表达DNMT3B7的胎肝细胞或野生型E14.5胎肝细胞移植到受体动物体内。有趣的是，在接受表达dnmt3b7的细胞移植后的头两个月，女性受体的外周血计数未能达到正常水平，而男性受体的外周血计数正常。将其移植到缺乏雌性激素的雌性中，结果表明所观察到的效果消失，这表明雌性激素环境抑制了表达dnmt3b7的干细胞功能。因此，我们发现DNMT3B7的表达揭示了性别，即激素环境对干细胞功能的显著影响。我假设DNMT3B7的表达通过改变DNA甲基化模式，从而使雌性小鼠的HSC对激素环境更加敏感，从而改变与HSC自我更新和分化相关的基因的表达。我将使用三个特定的目标来验证我的假设：(1)测试DNMT3B7表达对造血干细胞和祖细胞的影响，包括(a)诱导的表观遗传变化和(b)在存在和不存在性别特异性激素的情况下它们的体外集落形成潜力；(2)测定性激素对造血干细胞骨髓归巢的影响；(3)探讨DNMT3B7表达使造血干细胞对雌性激素产生反应的机制。这项工作将使我们更深入地了解在性别特异性激素存在下促进HSC植入和重建的机制，因此可能对临床干细胞移植产生重大影响。

DESCRIPTION (provided by applicant): It has been known for a long time that the hormonal environment of a person influences bone marrow function. However, the precise molecular mechanism by which this occurs is not known. Epigenetic changes, such as the attachment of a methyl group to DNA and the alteration of histone proteins can regulate the expression of genes that are necessary for stem cell differentiation. This proposal utilizes an animal model that expresses DNMT3B7, a truncated DNA methyltransferase 3B isoform that is commonly expressed in human cancers, to interrogate whether DNA methylation changes can influence the development of blood cells. To test the influence of DNMT3B7 expression on blood cell development, DNMT3B7-expressing fetal liver cells or wild-type E14.5 fetal liver cells were transplanted into recipient animals. Interestingly, female recipients failed to achieve normal peripheral blood counts in the first two months after undergoing transplantation with DNMT3B7-expressing cells, but male recipients had normal blood counts. Transplantation into females that lacked female hormones demonstrated loss of the observed effect, suggesting that the female hormonal milieu is suppressive to DNMT3B7-expressing stem cell function. Thus, we have found that DNMT3B7 expression uncovers a striking influence of gender i.e., hormonal milieu, on stem cell function. I hypothesize that the expression of DNMT3B7 renders HSCs more sensitive to the hormonal milieu in female mice by altering DNA methylation patterns, and thus the expression of genes associated with HSC self- renewal and differentiation. I will use three specific aims to test my hypothesis: (1) Test the impact of DNMT3B7 expression on hematopoietic stem and progenitor cells regarding (a) induced epigenetic changes and (b) their in vitro colony forming potential in the presence and absence of sex-specific hormones; (2) Measure the influence of sex hormones on the homing of HSCs to the bone marrow; (3) Examine the mechanism by which DNMT3B7 expression renders HSCs responsive to female hormones. The proposed work will give us more insight into the mechanisms that promote HSC engraftment and reconstitution in the presence of sex-specific hormones and therefore could have a significant impact on clinical stem cell transplantation.