Sex difference in leukocyte telomere length is ablated in opposite-sex co-twins

Athanase Benetos, Christine Dalgård, Carlos Labat, Jeremy D. Kark, Simon Verhulst, Kaare Christensen, Masayuki Kimura, Kent Horvath, Kirsten Ohm Kyvik, Abraham Aviv

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Background: In eutherian mammals and in humans, the female fetus may be masculinized while sharing the intra-uterine environment with a male fetus. Telomere length (TL), as expressed in leukocytes, is heritable and is longer in women than in men. The main determinant of leukocyte TL (LTL) is LTL at birth. However, LTL is modified by age-dependent attrition. Methods: We studied LTL dynamics (LTL and its attrition) in adult same-sex (monozygotic, n = 268; dizygotic, n = 308) twins and opposite-sex (n = 144) twins. LTL was measured by Southern blots of the terminal restriction fragments. Results: We observed that in same-sex (both monozygotic and dizygotic) twins, as reported in singletons, LTL was longer in females than in males [estimate ± standard error (SE):163 ± 63 bp, P < 0.01]. However, in opposite-sex twins, female LTL was indistinguishable from that of males (31 ± 52 bp, P = 0.6), whereas male LTL was not affected. Findings were similar when the comparison was restricted to opposite-sex and same-sex dizygotic twins (females relative to males: same-sex: 188 ± 90 bp, P < 0.05; other-sex: 32 ± 64 bp, P = 0.6).Conclusions: These findings are compatible with masculinization of the female fetus in opposite-sex twins. They suggest that the sex difference in LTL, seen in the general population, is largely determined in utero, perhaps by the intrauterine hormonal environment. Further studies in newborn twins are warranted to test this thesis.

Original languageEnglish (US)
Article numberdyu146
Pages (from-to)1799-1805
Number of pages7
JournalInternational journal of epidemiology
Issue number6
StatePublished - Dec 1 2014

All Science Journal Classification (ASJC) codes

  • Epidemiology


  • Men
  • Sex
  • Telomeres
  • Twins
  • Women

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    Benetos, A., Dalgård, C., Labat, C., Kark, J. D., Verhulst, S., Christensen, K., Kimura, M., Horvath, K., Kyvik, K. O., & Aviv, A. (2014). Sex difference in leukocyte telomere length is ablated in opposite-sex co-twins. International journal of epidemiology, 43(6), 1799-1805. [dyu146].