Regulation of E2A in Normal and Aged B Lymphopoiesis

描述（由申请人提供）：E2 A基因编码基础螺旋-环-螺旋蛋白（E47和E12），其对骨髓内B谱系细胞发育的调节至关重要。E2 A影响B淋巴细胞前体中的IG基因重排、增殖、存活和分化。在鼠衰老中，B淋巴细胞发育减少，特别是前B细胞数量通常减少。考虑到E2 A的重要性，我们假设在老年，E2 A的表达在B淋巴细胞生成过程中失调。这可能有助于减少B淋巴细胞在衰老。为了验证这一假设，我们提出了三个相互关联的具体目标。在具体目标1中，我们将评估在衰老中B细胞分化的不同阶段E2 A表达的相对水平，作为mRNA和蛋白质，以确定E2 A表达和/或功能的下降可能发生在何处。具体目标2询问是否转录或转录后机制导致衰老B细胞前体中E2 A表达降低。这个特定的目标将建立负责B细胞前体中E2 A失调的分子机制，特别强调泛素-蛋白酶体途径。具体目标3将确定骨髓内外在（微环境）信号传导以及内在信号传导（特别是通过前B细胞受体）的改变是否有助于衰老B细胞前体中E2 A表达的失调。特定骨髓辅助细胞群的功能（例如，基质）在支持衰老中的B细胞前体生长和发育中的作用。这些研究将有助于进一步了解E2 A在B淋巴细胞生成中的正常作用以及E2 A调节异常对衰老过程中B淋巴细胞生成的影响。更广泛地说，这些研究将进一步加深我们对伴随老年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.