Oct 29, 2010

Do sex cells hold the secret to long life?

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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