Genetic analysis of forebrain patterning and neurogenesis

描述（由申请人提供）：成纤维细胞生长因子（FGF）对大量发育过程至关重要，包括大脑发育的许多方面。FGF如何在一种情况下诱导细胞命运，并在另一种情况下促进增殖，迁移，分化或存活尚不清楚。一种可能是不同的细胞内信号转导 不同细胞中的FGF激活了不同的信号通路。几乎完全基于生物化学和细胞培养数据，已经提出了几种FGF受体活化的细胞内转导物。其中最被接受的是FGF受体底物（FRS）蛋白，其中有两个家族成员。然而，体内任何FGF信号传导是否需要FRS仍然未知。令人惊讶的是，我们的初步数据表明，FRS是只需要某些方面的FGF信号在早期端脑发育。 因此，在目的1中，我们研究FRS在端脑发育过程中体内转导FGF信号的作用。我们正在关注两个端脑发育的过程，我们以前已经表明需要FGF。通过用三重FGF受体敲除废除FGF信号传导，我们发现FGF对于端脑细胞存活的早期和后来抑制皮质前体中干细胞向祖细胞的转变是必不可少的。在每种情况下，我们将确定FGF信号传导是否 取决于FRS。 细胞对FGF反应不同的另一种可能解释是其他细胞外因子调节其作用。例如，我们已经发现FGF、WNT和TGF β相互作用以调节早期端脑中的细胞存活和Cdkn1a转录。这些发现提供了一个体内背景，以破译细胞如何在决定采用命运之前整合多种信号。在目标2中，我们研究了细胞外信号对Cdkn1a的转录调控如何影响细胞命运。此外，FOXG1，其表达被FGF促进，可以抑制培养细胞中SMAD复合物与Cdkn1a启动子的结合。在目的3中，我们确定Foxg1是否以及如何参与调节Cdkn1a在早期端脑细胞在体内的转录，以及Foxg1，Smad4和Cdkn1a是否在遗传上相互作用。

DESCRIPTION (provided by applicant): Fibroblast Growth Factors (FGFs) are critical for a vast array of developmental processes, including many aspects of brain development. How FGFs induce cell fates in one context, and promote proliferation, migration, differentiation, or survival in another is unknown. One possibility is that different intracellular signal transduction pathways are activated by FGFs in different cells. Based almost exclusively on biochemical and cell culture data, several intracellular transducers of FGF receptor activation have been proposed. Most accepted among these are the FGF Receptor Substrate (FRS) proteins, of which there are two family members. However, whether FRS is required for any FGF signaling in vivo remains unknown. Surprisingly, our preliminary data indicate that FRS is only required for certain aspects of FGF signaling in early telencephalon development. Hence in Aim 1, we examine the role of FRS in transducing FGF signals in vivo during telencephalon development. We are focusing on two processes of telencephalon development that we have previously shown require FGFs. By abolishing FGF signaling with a triple FGF receptor knockout, we found that FGFs are essential early for telencephalic cell survival and later for inhibiting the stem to progenitor cell transition in cortical precursors. In each case, we will determine if FGF signaling depends on FRS. Another possible explanation for why cells respond differently to FGFs is that other extracellular factors modulate its effects. For example, we have found that FGFs, WNTs, and TGFbs interact to regulate cell survival and Cdkn1a transcription in the early telencephalon. These findings provide an in vivo context to decipher how a cell can integrate multiple signals before deciding to adopt a fate. In Aim 2, we examine how the transcriptional regulation of Cdkn1a by extracellular signals affects cell fate. Moreover, FOXG1, whose expression is promoted by FGFs, can inhibit the binding of a SMAD complex to the promoter of Cdkn1a in cultured cells. In Aim 3, we determine whether and how Foxg1 participates in regulating Cdkn1a transcription in early telencephalic cells in vivo and whether Foxg1, Smad4, and Cdkn1a genetically interact.