Genetic analysis of forebrain patterning and neurogenesis

说明(申请人提供)：成纤维细胞生长因子(FGFs)对许多发育过程至关重要，包括大脑发育的许多方面。FGFs如何在一种环境中诱导细胞命运，并在另一种环境中促进增殖、迁移、分化或存活尚不清楚。一种可能性是不同的细胞内信号转导 FGFs在不同的细胞中激活信号转导通路。几乎完全基于生化和细胞培养数据，已经提出了几种激活成纤维细胞生长因子受体的细胞内转导分子。其中最被接受的是成纤维细胞生长因子受体底物(FRS)蛋白，其中有两个家族成员。然而，目前尚不清楚体内的任何成纤维细胞生长因子信号是否需要FRS。令人惊讶的是，我们的初步数据表明，只有在端脑发育的早期，成纤维细胞生长因子信号的某些方面才需要FRS。因此，在目标1中，我们研究了在端脑发育过程中FRS在体内传递成纤维细胞生长因子信号中的作用。我们将重点放在端脑发育的两个过程上，这两个过程我们之前已经证明需要FGFs。通过通过敲除三重的成纤维细胞生长因子受体来取消成纤维细胞生长因子信号，我们发现成纤维细胞生长因子早期对于端脑细胞的存活是必不可少的，后来在皮质前体细胞中抑制干细胞向祖细胞的转变是必不可少的。在每种情况下，我们将确定成纤维细胞生长因子信号 这要看FRS了。细胞对FGFs反应不同的另一个可能解释是，其他细胞外因素调节了它的影响。例如，我们发现在早期端脑中，FGFs、WNTs和TGFbs相互作用，调节细胞生存和CDKN1A转录。这些发现为破译细胞在决定接受命运之前如何整合多个信号提供了活体背景。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的表达受FGFs的促进，在培养细胞中可以抑制SMAD复合体与CDKN1A启动子的结合。在目标3中，我们确定FOXG1是否以及如何参与调节体内早期端脑细胞中CDKN1A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.