Alexander J, Stainier D Y, Yelon D
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0554, USA.
Dev Genet. 1998;22(3):288-99. doi: 10.1002/(SICI)1520-6408(1998)22:3<288::AID-DVG10>3.0.CO;2-2.
The genetic pathways underlying the induction and anterior-posterior patterning of the heart are poorly understood. The recent emergence of the zebrafish model system now allows a classical genetic approach to such challenging problems in vertebrate development. Two large-scale screens for mutations affecting zebrafish embryonic development have recently been completed; among the hundreds of mutations identified were several that affect specific aspects of cardiac morphogenesis, differentiation, and function. However, very few mutations affecting induction and/or anterior-posterior patterning of the heart were identified. We hypothesize that a directed approach utilizing molecular markers to examine these particular steps of heart development will uncover additional such mutations. To test this hypothesis, we are conducting two parallel screens for mutations that affect either the induction or the anterior-posterior patterning of the zebrafish heart. As an indicator of cardiac induction, we examine expression of nkx2.5, the earliest known marker of precardiac mesoderm; to assess anterior-posterior patterning, we distinguish ventricle from atrium with antibodies that recognize different myosin heavy chain isoforms. In order to expedite the examination of a large number of mutations, we are screening the haploid progeny of mosaic F1 females. In these ongoing screens, we have identified four mutations that affect nkx2.5 expression as well as 21 that disrupt either ventricular or atrial development and thus far have recovered several of these mutations, demonstrating the value of our approach. Future analysis of these and other cardiac mutations will provide further insight into the processes of induction and anterior-posterior patterning of the heart.
目前，人们对心脏诱导和前后模式形成的遗传途径了解甚少。斑马鱼模型系统的近期出现，使得我们能够采用经典遗传学方法来研究脊椎动物发育中此类具有挑战性的问题。最近已完成了两项针对影响斑马鱼胚胎发育的突变的大规模筛选；在鉴定出的数百个突变中，有几个影响心脏形态发生、分化和功能的特定方面。然而，鉴定出的影响心脏诱导和/或前后模式形成的突变非常少。我们推测，利用分子标记物来检查心脏发育这些特定步骤的定向方法，将发现更多此类突变。为了验证这一推测，我们正在进行两项平行筛选，以寻找影响斑马鱼心脏诱导或前后模式形成的突变。作为心脏诱导的指标，我们检测nkx2.5的表达，nkx2.5是已知最早的心脏前体中胚层标记物；为了评估前后模式形成，我们使用识别不同肌球蛋白重链异构体的抗体来区分心室和心房。为了加快对大量突变的检测，我们正在筛选嵌合F1雌性的单倍体后代。在这些正在进行的筛选中，我们已经鉴定出四个影响nkx2.5表达的突变以及21个破坏心室或心房发育的突变，并且到目前为止已经找回了其中一些突变，证明了我们方法的价值。对这些以及其他心脏突变的进一步分析，将为心脏诱导和前后模式形成过程提供更多见解。
