Sheldon Penman, "Rethinking cell structure," Proceedings of the National Academy of Sciences USA 92 (1995): 5251-57.
While his ideas of a complex cellular matrix are controversial (see, e.g., Science 268 (1995): 1564-65), Sheldon Penman doesn't apologize for them. Current cell biology is stuck on "solution biochemistry," he argues. When the field awakens, however, it will turn to "cell architecture," and realize that cytoskeletal structure can "illuminate that most vexing and refractory of puzzles--the nature and location of the genomic instructions dictating the form of cells, tissue, and, ultimately, organisms" (p. 5251). In this review, Penman (a member of the National Academy of Sciences and cell biologist at MIT) urges that conventional electronic microscopy has misled biologists, because it fails to reveal "most of cells' architectural components." This is critical, Penman is persuaded, to understanding the open questions surrounding the specification of biological form: "Form and structure are not natural subjects for biochemistry that, in the macroscopic world, deals with scalar quantities--i.e., amounts, rates, etc. Building the complex designs glimpsed in any anatomy or physiology text requires, at the very least, instructions that are vectorial--i.e., that specify direction and place. These instructions are encoded somewhere--it seems very likely that they reside in the heavily transcribed but "non-protein coding" DNA. Building staggeringly complex organs--e.g., brains or kidneys--by simply specifying the constituent protein components (as suggested by the more extreme formulations of molecular biology that genes are simply proteins) is unlikely. Such a strategy would be tantamount to trying to specify a bridge or an edifice by merely giving a list of parts. Indeed, Gray's Anatomy, seen with an engineer's eye, suggests that the complexity of the instruction sets for mammalian morphology require large regions of the genome: very likely much of most of the currently ignored, non-protein coding, 90% (or more) of the genome. I suspect that future cell scientists will marvel at the density and ingenuity of genome instructions for structure while wondering how we could overlook them for so long" (p. 5257).
Copyright © 1996 Paul Nelson. All rights reserved. International copyright
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File Date: 6.22.96