Regulation of E2A in Normal and Aged B Lymphopoiesis

描述(申请人提供)：E2a基因编码基本螺旋-环-螺旋蛋白(E47和EL2)，它们对调节骨髓内B系细胞的发育至关重要。E2a影响B淋巴细胞前体细胞的Ig基因重排、增殖、存活和分化。在小鼠的衰老过程中，B淋巴细胞的发育减弱，尤其是前B细胞的数量普遍减少。鉴于E2a的重要性，我们假设，在老年，E2a的表达在B淋巴细胞生成过程中受到失调。这可能是衰老过程中B淋巴细胞生成减少的原因之一。为了检验这一假设，我们提出了三个相互关联的具体目标。在特定的目标1中，我们将评估在衰老的B细胞分化的不同阶段，E2A作为mRNA和蛋白质的相对表达水平，以确定E2A的表达和/或功能可能在哪里发生下降。特定目的2询问转录或转录后机制是否导致衰老B细胞前体细胞E2A表达减少。这一特定的目的将建立导致B细胞前体细胞内E2A失调的分子机制，尤其是泛素-蛋白酶体途径。具体目标3将确定骨髓内外源性(微环境)信号的变化以及内在信号，特别是通过前B细胞受体的变化是否有助于衰老B细胞前体中E2A表达的失调。将评估特定的骨髓辅助细胞群体(例如，基质)在支持B细胞前体细胞在衰老中的生长和发育方面的功能。这些研究将促进对E2A在B淋巴细胞生成中的正常作用以及E2A在衰老过程中对B淋巴细胞生成的影响的理解。更广泛地说，这些研究将进一步加深我们对老年伴随的免疫缺陷及其细胞和分子机制的理解。

DESCRIPTION (provided by applicant): The E2A gene encodes basis helix-loop-helix proteins (E47 and El2) which are crucial to the regulation of B lineage cell development within the bone marrow. E2A affects Ig gene rearrangement, proliferation, survival, and differentiation among B lymphocyte precursors. In murine senescence, B lymphocyte development is diminished and, in particular, pre-B cell numbers are generally decreased. Given the importance of E2A, we hypothesize that, in old age, expression of E2A is dysregulated during B lymphopoiesis. This may contribute to reduced B lymphopoiesis in senescence. In order to test this hypothesis, we propose three interrelated Specific Aims. In Specific Aim 1, we will assess the relative levels of expression of E2A, as both mRNA and protein, at distinct stages of B cell differentiation hi senescence in order to determine where decline hi E2A expression and/or function may occur. Specific Aim 2 asks whether transcriptional or post-transcriptional mechanisms result in reduced E2A expression in senescent B cell precursors. This Specific Aim will establish the molecular mechanisms responsible for E2A dysregulation within B cell precursors with particular emphasis on the ubiquitin-proteasome pathway. Specific Aim 3 will establish whether alterations in extrinsic (microenvironmental) signaling within the bone marrow as well as intrinsic signaling, particularly via the pre-B cell receptor, contribute to dysregulation of E2A expression hi senescent B cell precursors. The function of particular bone marrow accessory cell populations (e.g., stroma) in supporting B cell precursor growth and development in senescence will be assessed. These studies will promote understanding of the normal role of E2A hi B lymphopoiesis and the affects of E2A dysregulation on B lymphopoiesis hi senescence. More broadly, these studies will further our understanding of the immune defects which accompany old age and their cellular and molecular mechanisms.