Cserjesi P, Brown D, Lyons G E, Olson E N
Department of Biochemistry and Molecular Biology, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
Dev Biol. 1995 Aug;170(2):664-78. doi: 10.1006/dbio.1995.1245.
We employed the yeast two-hybrid technique to screen a mouse embryo cDNA library for novel tissue-specific Class B basic helix-loop-helix (bHLH) transcription factors, which heterodimerize with the ubiquitously expressed Class A bHLH protein E12. From this screen, we cloned a novel bHLH protein, which we named eHAND. Its low sequence identity with other bHLH family members and unique expression pattern during development suggest that eHAND defines a new subclass of Class B bHLH proteins. eHAND was expressed at high levels in trophoblast cells and extraembryonic membranes throughout development. The first site of eHAND expression in embryos was the heart, where it was expressed at high levels between 8.5 and 10.5 days post coitum (d.p.c.), after which transcript levels declined abruptly. By 13.5 d.p.c., eHAND expression in the heart was localized to regions of valve formation. Expression in other regions of the embryo was confined to tissues with a substantial neural crest component. eHAND was expressed in the first branchial arch and its derivatives, in the sympathoadrenal lineage, and in the enteric systems. The expression pattern of eHAND during development is distinct from that of other bHLH genes and suggests that it has a role in formation of extraembryonic tissues, heart, and neural crest derivatives.
我们运用酵母双杂交技术，从小鼠胚胎cDNA文库中筛选与广泛表达的A类碱性螺旋-环-螺旋（bHLH）蛋白E12异二聚化的新型组织特异性B类bHLH转录因子。通过该筛选，我们克隆了一种新型bHLH蛋白，将其命名为eHAND。它与其他bHLH家族成员的序列同一性较低，且在发育过程中具有独特的表达模式，这表明eHAND定义了B类bHLH蛋白的一个新亚类。在整个发育过程中，eHAND在滋养层细胞和胚外膜中高水平表达。胚胎中eHAND表达的第一个部位是心脏，在交配后8.5至10.5天（d.p.c.），它在心脏中高水平表达，之后转录水平急剧下降。到13.5 d.p.c.时，心脏中eHAND的表达定位于瓣膜形成区域。在胚胎的其他区域，其表达局限于具有大量神经嵴成分的组织。eHAND在第一鳃弓及其衍生物、交感肾上腺谱系和肠道系统中表达。eHAND在发育过程中的表达模式与其他bHLH基因不同，提示它在胚外组织、心脏和神经嵴衍生物的形成中发挥作用。
