Tickle Cheryll
Department of Biology and Biochemistry, University of Bath, Bath, UK.
Dev Biol. 2017 Sep 15;429(2):374-381. doi: 10.1016/j.ydbio.2017.05.028. Epub 2017 Jun 15.
John Saunders was a highly skilled embryologist who pioneered the study of limb development. His studies on chick embryos provided the fundamental framework for understanding how vertebrate limbs develop. This framework inspired generations of scientists and formed the bridge from experimental embryology to molecular mechanisms. Saunders investigated how feathers become organized into tracts in the skin of the chick wing and also identified regions of programmed cell death. He discovered that a region of thickened ectoderm that rims the chick wing bud - the apical ectodermal ridge - is required for outgrowth and the laying down of structures along the proximo-distal axis (long axis) of the wing, identified the zone of polarizing activity (ZPA; polarizing region) that controls development across the anteroposterior axis ("thumb to little finger "axis) and contributed to uncovering the importance of the ectoderm in development of structures along the dorso-ventral axis ( "back of hand to palm" axis). This review looks in depth at some of his original papers and traces how he made the crucial findings about how limbs develop, considering these findings both in the context of contemporary knowledge at the time and also in terms of their immediate impact on the field.
约翰·桑德斯是一位技艺高超的胚胎学家，他开创了肢体发育的研究领域。他对鸡胚胎的研究为理解脊椎动物肢体的发育提供了基本框架。这个框架激励了一代又一代的科学家，并搭建起了从实验胚胎学到分子机制的桥梁。桑德斯研究了羽毛如何在鸡翅膀的皮肤中形成羽区，还确定了程序性细胞死亡的区域。他发现，鸡翅膀芽边缘增厚的外胚层区域——顶端外胚层嵴——对于翅膀沿近端 - 远端轴（长轴）的生长和结构形成是必需的，确定了控制前后轴（“拇指到小指”轴）发育的极化活性区（ZPA；极化区域），并为揭示外胚层在沿背腹轴（“手背到手掌”轴）结构发育中的重要性做出了贡献。这篇综述深入研究了他的一些原始论文，并追溯了他是如何得出关于肢体发育的关键发现的，既从当时的当代知识背景角度，也从这些发现对该领域的直接影响方面进行了考量。
