Embryonic telomeres go long

Telomeres go through a growth spurt early in embryonic development, as Lin Liu, David Keefe (University of South Florida, Tampa, FL), and colleagues report. The surge might help restore telomeres whittled down during oocytes' long quiescence.

Size is no issue for sperm, which maintain lengthy telomeres, and researchers assumed that eggs did the same. However, mammalian oocytes stall in meiosis, and for months or years they are besieged by reactive oxygen species that could wear down their telomeres. Supporting that idea, Keefe and coworkers recently reported that human oocytes have short telomeres. The researchers wanted to determine how these structures regrew.

Chromosome caps that were puny in mouse oocytes had stretched dramatically by the two-cell embryo stage, the team found. The stimulus for this growth didn't come from the sperm,...