"Long before it's in the papers"
June 04, 2013


Do sex cells hold the secret to long life?

June 7, 2009
World Science staff

The se­cret of long life may lurk with­in the ge­net­ic ac­ti­vity pro­file of sex cells—such as the sperm and eggs of hu­mans, a pa­per newly pub­lished in the re­search jour­nal Na­ture sug­gests. 

The round­worm Cae­nor­hab­di­tis el­e­gans, about 1 mm long. (Im­age cour­te­sy NIH)

Sex cells, and the line­age of cells that de­vel­op in­to them, are “im­mor­tal” in the sense that once they are used to cre­ate a new or­gan­ism, they don’t die. In­stead they br­ing about the pro­duc­tion of all the new crea­ture’s cells, in­clud­ing more sex cells. 

Only the non-sex cell­s—called so­mat­ic cells—are doomed to age and die, typ­ic­ally by ac­cu­mu­lating dam­age, de­bris and muta­t­ions.

Gary Ru­vkun, a ge­net­icist at Har­vard Med­i­cal School, and col­leagues found in the new study that the gene ac­ti­vity in so­mat­ic cells of long-lived nem­a­tode worm mu­tants re­sem­bles that of “germ­line,” or sex cells. Switch­ing to germline char­ac­ter­is­tics may there­fore con­fer health ben­e­fits and longe­vity to these mu­tant worms, ac­cord­ing to Ru­vkun’s team.

The si­m­i­lar­ity in the so­mat­ic cells’ gene ac­ti­vity pro­file to that of sex cells largely in­volved de­crease in a pat­tern of chem­i­cal ac­ti­vity known as insulin-like sig­nal­ling, ac­cord­ing to the re­search­ers.

The al­tered ge­net­ic ac­ti­vity al­so made the non-sex cells more re­sist­ant to tox­icity, the group re­ported. This makes sense, they added, be­cause some the­o­ries hold that ag­ing evolved as a trade-off in which or­gan­isms di­verted re­sources to­ward main­tain­ing and pro­tect­ing the re­pro­duc­tive cells at the ex­pense of the oth­ers.

“Given that pro­tec­tion of the germ line is an ev­o­lu­tionarily shared trait across spe­cies, it will be in­ter­est­ing to in­ves­t­i­gate wheth­er this is a broadly con­served mech­an­ism of mod­u­lat­ing life­span” for oth­er an­i­mals, in­clud­ing hu­mans, wrote the sci­en­tists.

“The idea that so­mat­ic cells main­tain the po­ten­tial to re­ac­quire path­ways lost dur­ing dif­fer­entia­t­ion [genera­t­ion of new cells] is tan­ta­liz­ing,” they added, and may help re­search­ers de­vel­op “ther­a­peu­tics to as­sist in cel­lu­lar re­pair and pos­sibly re­genera­t­ion.”

The paper appears in the June 8 ad­vance on­line issue of the jour­nal.

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The secret of long life may lurk within the genetic activity profile of sex cells—such as sperm and eggs, a paper newly published in the research journal Nature suggests. Sex cells, and the lineage of cells that develop into them, are “immortal” in the sense that once they are used to create a new organism, they don’t die. Instead they bring about the production of all the new organism’s cells, including more sex cells. Only the non-sex cells—called somatic cells—are doomed to age and die, typically by accumulating damage, debris and mutations. Gary Ruvkun, a geneticist at Harvard Medical School, and colleagues found in the new study that the gene activity in somatic cells of long-lived nematode worm mutants resembles that of “germline,” or sex cells. Switching to germline characteristics may therefore confer health benefits and longevity to these mutant worms, according to Ruvkun’s team. The similarity in the somatic cells’ gene activity profile to that of non-sex cells largely involved decrease in a pattern of chemical activity known as insulin-like signalling, according to the researchers. The altered genetic activity also made the non-sex cells more resistant to toxicity, the group reported. This makes sense, they added, because some theories hold that aging evolved as a trade-off in which organisms diverted resources toward maintaining and protecting the reproductive cells at the expense of the other cells, known as somatic cells. “Given that protection of the germ line is an evolutionarily shared trait across species, it will be interesting to investigate whether this is a broadly conserved mechanism of modulating lifespan” for other animals, including humans, wrote the scientists. “The idea that somatic cells maintain the potential to reacquire pathways lost during differentiation [generation of new cells] is tantalizing,” they added, and may help researchers develop “therapeutics to assist in cellular repair and possibly regeneration.”