For better and for worse, human health depends on a cell's motility -- the ability to crawl from place to place. In every human body, millions of cells -are crawling around doing mostly good deeds -- though if any of those crawlers are cancerous, watch out. "This is not some horrible sci-fi movie come true but, instead, normal cells carrying out their daily duties," said Florida State University cell biologist Tom Roberts. For 35 years he has studied the mechanical and molecular1 means by which amorphous2(无定形的) single cells purposefully propel(推进,驱使) themselves throughout the body in amoeboid-like fashion --absent muscles, bones or brains.
Meanwhile, human cells don't give up their secrets easily. In the body, they use the millions of tiny filaments3(花丝,细丝) found on their front ends to push the front of their cytoskeletons forward. In rapid succession the cells then retract4 their rears in a smooth, coordinated5 extension-contraction manner that puts inchworms to shame. Yet take them out of the body and put them under a microscope and the crawling changes or stops.
But now Roberts and his research team have found a novel way around uncooperative human cells.
In a landmark6 study led by Roberts and conducted in large part by his then-FSU postdoctoral associate Katsuya Shimabukuro, researchers used worm sperm7 to replicate8 cell motility in vitro -- in this case, on a microscope slide.
Doing what no other scientists had ever successfully done before, Shimabukuro disassembled and reconstituted a worm sperm cell, then devised conditions to promote the cell's natural pull-push crawling motions even in the unnatural9 conditions of a laboratory. Once launched, the reconstituted machinery10 moved just like regular worm sperm do in a natural setting -- giving scientists an unprecedented11 opportunity to watch it move.
Roberts called his former postdoc's signal achievement "careful, clever work" -- and work it did, making possible new, revealing images of cell motility that should help to pinpoint12 with never-before-seen precision just how cells crawl.
"Understanding how cells crawl is a big deal," Roberts said. "The first line of defense13 against invading microorganisms, the remodeling of bones, healing wounds in the skin and reconnecting of neuronal circuits during regeneration of the nervous system -- all depend on the capacity of specialized14 cells to crawl.
"On the downside, the ability of tumor15 cells to crawl around is a contributing factor in the metastasis of malignancies(恶性肿瘤) ," he said. "But we believe our achievements in this latest round of basic research could eventually aid in the development of therapies that target cell motility in order to interfere16 with or block the metastasis of cancer."
Funding for Robert's worm-sperm study came from the National Institutes of Health. The findings are described in a paper "Reconstitution of Amoeboid Motility In Vitro Identifies a Motor-Independent Mechanism17 for Cell Body Retraction18" published online in the journal Current Biology.