Jiang Y, Tarzami S, Burch J B, Evans T
Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York, USA.
Dev Genet. 1998;22(3):263-77. doi: 10.1002/(SICI)1520-6408(1998)22:3<263::AID-DVG8>3.0.CO;2-4.
The GATA-4/5/6 genes encode transcription factors implicated previously in the regulation of cardiac-specific differentiation programs. However, recent analyses of mouse GATA-4 null mutations found evidence for function in endoderm development (in vitro) and embryonic morphogenesis (in vivo). Whether each of the three cardiac-associated GATA factors function within distinct or common developmental programs was previously untested; past studies defined specific and distinct roles for each of the GATA-1/2/3 genes in embryonic hematopoiesis. In this study, we compare the transcript patterns of cGATA-4/5/6 during chick embryogenesis. Each of the three GATA factors is expressed in a similar pattern within gastrulating cells of the primitive streak, prior to determination of the cardiomyocyte progenitors, and later within the lateral plate mesoderm and associated endoderm layer. The patterns overlap but extend beyond the presumptive cardiomyocyte population expressing cNkx-2.5. Later in development, cGATA-4/5/6 are all transcribed throughout the differentiating heart, in similar but not identical patterns, within the endocardium, myocardium, and great vessels. In order to test the function of GATA factors during chick cardiogenesis, embryos were cultured in vitro in the presence of antisense oligomers designed to deplete specifically transcripts encoding cGATA-4/5/6, beginning around stage 7. When oligomers are used to target transcripts for all three genes, a high percentage of the embryos develop abnormal hearts related to the failure to form a normal primitive heart tube. In the most severe phenotype, cardiac bifida results in two bilateral beating hearts. In some embryos, the paired heart primordia undergo partial fusion but fail to form a single looping heart tube. In all cases, cellular differentiation is not obviously affected, as the abnormal hearts form beating tissue. Depletion of transcripts encoding any single GATA factor, or any combination of two GATA factors, does not affect development. The partial depletion of all three genes in chick results in a remarkably similar phenotype compared to the null GATA-4 mutation in mouse. Therefore, in the chick, each of the GATA-4/5/6 genes functions in a common pathway, at the time of cardiac crescent formation, for regulating early embryonic cardiac morphogenesis, apparently associated with embryonic folding or the migration of primordia to form a primitive tube.
GATA - 4/5/6基因编码的转录因子先前被认为参与心脏特异性分化程序的调控。然而，最近对小鼠GATA - 4无效突变的分析发现了其在内胚层发育（体外）和胚胎形态发生（体内）中发挥作用的证据。此前尚未测试这三种与心脏相关的GATA因子是否在不同或共同的发育程序中发挥作用；过去的研究确定了GATA - 1/2/3基因在胚胎造血过程中各自特定且不同的作用。在本研究中，我们比较了鸡胚胎发育过程中cGATA - 4/5/6的转录模式。在确定心肌祖细胞之前，这三种GATA因子在原条的原肠胚形成细胞中以相似的模式表达，随后在侧板中胚层和相关的内胚层中表达。这些模式相互重叠，但延伸到了表达cNkx - 2.5的推定心肌细胞群体之外。在发育后期，cGATA - 4/5/6在整个分化中的心脏中都有转录，在内皮、心肌和大血管中呈现相似但不完全相同的模式。为了测试GATA因子在鸡心脏发生过程中的功能，从大约第7阶段开始，在体外培养胚胎时加入反义寡核苷酸，以特异性耗尽编码cGATA - 4/5/6的转录本。当使用寡核苷酸靶向所有三个基因的转录本时，很大比例的胚胎会发育出与无法形成正常原始心管相关的异常心脏。在最严重的表型中，心脏裂导致两个双侧跳动的心脏。在一些胚胎中，成对的心脏原基会部分融合，但无法形成单个环化的心管。在所有情况下，细胞分化并未受到明显影响，因为异常心脏形成了跳动的组织。耗尽编码任何单个GATA因子或任何两个GATA因子组合的转录本都不会影响发育。与小鼠中GATA - 4无效突变相比，鸡中所有三个基因的部分耗尽导致了非常相似的表型。因此，在鸡中，GATA - 4/5/6基因在心脏新月形成时，在一个共同的途径中发挥作用，以调节早期胚胎心脏形态发生，这显然与胚胎折叠或原基迁移以形成原始管有关。
