Sillitoe Roy V, Stephen Daniel, Lao Zhimin, Joyner Alexandra L
Developmental Biology Program, Sloan-Kettering Institute, New York, New York 10021, USA.
J Neurosci. 2008 Nov 19;28(47):12150-62. doi: 10.1523/JNEUROSCI.2059-08.2008.
Underlying the seemingly uniform cellular composition of the adult mammalian cerebellum (Cb) are striking parasagittal stripes of gene expression along the medial-lateral (ML) axis that are organized with respect to the lobules that divide the Cb along the anterior-posterior (AP) axis. Although there is a clear correlation between the organization of gene expression stripes and Cb activity patterns, little is known about the genetic pathways that determine the intrinsic stripe molecular code. Here we establish that ML molecular code patterning is highly dependent on two homeobox transcription factors, Engrailed1 (En1) and En2, both of which are also required for patterning the lobules. Gene expression analysis of an allelic series of En1/2 mutant mice that have an intact Purkinje cell layer revealed severe patterning defects using three known components of the ML molecular code and a new marker of Hsp25 negative stripes (Neurofilament heavy chain, Nfh). Importantly, the complementary expression of ZebrinII/PhospholipaseC beta4 and Hsp25/Nfh changes in unison in each mutant. Furthermore, each En gene has unique as well as overlapping functions in patterning the ML molecular code and each En protein has dominant functions in different AP domains (subsets of lobules). Remarkably, in En1/2 mutants with almost normal foliation, ML molecular code patterning is severely disrupted. Thus, independent mechanisms that use En1/2 must pattern foliation and spatial gene expression separately. Our studies reveal that En1/2 are fundamental components of the genetic pathways that pattern the two intersecting coordinate systems of the Cb, morphological divisions and the molecular code.
成年哺乳动物小脑(Cb)看似均匀的细胞组成之下,是沿内侧-外侧(ML)轴排列的显著的基因表达矢状旁条纹,这些条纹是相对于沿前后(AP)轴划分小脑的小叶组织起来的。尽管基因表达条纹的组织与小脑活动模式之间存在明显的相关性,但对于决定内在条纹分子编码的遗传途径却知之甚少。在这里,我们确定ML分子编码模式高度依赖于两个同源盒转录因子,即 engrailed1(En1)和En2,这两个因子也是小叶模式形成所必需的。对具有完整浦肯野细胞层的En1/2突变小鼠等位基因系列进行的基因表达分析显示,使用ML分子编码的三个已知成分和Hsp25阴性条纹的一个新标记(神经丝重链,Nfh),存在严重的模式形成缺陷。重要的是,在每个突变体中,ZebrinII/磷脂酶Cβ4和Hsp25/Nfh的互补表达一致变化。此外,每个En基因在ML分子编码模式形成中具有独特以及重叠的功能,并且每个En蛋白在不同的AP结构域(小叶亚群)中具有主导功能。值得注意的是,在具有几乎正常叶状结构的En1/2突变体中,ML分子编码模式严重破坏。因此,使用En1/2的独立机制必须分别对叶状结构和空间基因表达进行模式化。我们的研究表明,En1/2是对小脑的两个相交坐标系(形态学划分和分子编码)进行模式化的遗传途径的基本组成部分。