Perea-Atienza E, Sprecher S G, Martínez P
1Departament de Genètica, Universitat de Barcelona, Av. Diagonal 643, 08028 Barcelona, Spain.
3Department of Biology, University of Fribourg, 10, ch. Du Musée, 1700 Fribourg, Switzerland.
Evodevo. 2018 Mar 29;9:8. doi: 10.1186/s13227-018-0097-y. eCollection 2018.
The basic helix-loop-helix (bHLH) family of transcription factors is one of the largest superfamilies of regulatory transcription factors and is widely used in eukaryotic organisms. They play an essential role in a range of metabolic, physiological, and developmental processes, including the development of the nervous system (NS). These transcription factors have been studied in many metazoans, especially in vertebrates but also in early branching metazoan clades such as the cnidarians and sponges. However, currently very little is known about their expression in the most basally branching bilaterian group, the xenacoelomorphs. Recently, our laboratory has characterized the full complement of bHLH in the genome of two members of the Xenacoelomorpha, the xenoturbellid and the acoel . Understanding the patterns of bHLH gene expression in members of this phylum (in space and time) provides critical new insights into the conserved roles of the bHLH and their putative specificities in this group. Our focus is on deciphering the specific roles that these genes have in the process of neurogenesis.
Here, we analyze the developmental expression of the whole complement of bHLH genes identified in the acoel Based on their expression patterns, several members of bHLH class A appear to have specific conserved roles in neurogenesis, while other class A genes (as well as members of other classes) have likely taken on more generalized functions. All gene expression patterns are described in embryos and early juveniles.
Our results suggest that the main roles of the bHLH genes of are evolutionarily conserved, with a specific subset dedicated to patterning the nervous system: SrAscA, SrAscB, SrHes/Hey, SrNscl, SrSrebp, SrE12/E47 and SrOlig.
转录因子的碱性螺旋-环-螺旋（bHLH）家族是调控转录因子中最大的超家族之一，广泛存在于真核生物中。它们在一系列代谢、生理和发育过程中发挥着重要作用，包括神经系统（NS）的发育。这些转录因子已在许多后生动物中得到研究，尤其是在脊椎动物中，但也在早期分支的后生动物类群中进行了研究，如刺胞动物和海绵动物。然而，目前对于它们在最基部分支的两侧对称动物类群——异涡虫类中的表达情况知之甚少。最近，我们实验室已经对异涡虫类的两个成员——异涡虫和无肠虫基因组中的bHLH进行了全面鉴定。了解该门成员中bHLH基因在空间和时间上的表达模式，为深入了解bHLH的保守作用及其在该类群中的假定特异性提供了关键的新见解。我们的重点是解读这些基因在神经发生过程中的具体作用。
在这里，我们分析了在无肠虫中鉴定出的整个bHLH基因家族的发育表达情况。基于它们的表达模式，A类bHLH的几个成员似乎在神经发生中具有特定的保守作用，而其他A类基因（以及其他类别的成员）可能具有更广泛的功能。所有基因表达模式均在胚胎和早期幼体中进行了描述。
我们的结果表明，无肠虫bHLH基因的主要作用在进化上是保守的，有一个特定的子集专门用于构建神经系统：SrAscA、SrAscB、SrHes/Hey、SrNscl、SrSrebp、SrE12/E47和SrOlig。
