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Zygote

Table of Contents - 2000 - Volume 8, Issue 03  


Sperm decondensation during fertilisation in the mouse: presence of DNase I hypersensitive sites in situ and a putative role for topoisomerase II

Davide  Bizzaro a1c1, Giancarlo  Manicardi a1, Patrizia Grace  Bianchi a2 and Denny  Sakkas a3
a1 Department of Animal Biology, University of Modena and Reggio Emilia, Via Berengario 14, 41100 Modena, Italy.
a2 Clinic of Sterility, Department of Obstetrics and Gynaecology, University Hospital of Geneva, 20 rue Alcide Jentzer, 1211 Geneva 14, Switzerland.
a3 Assisted Conception Unit, Birmingham Women's Hospital, Birmingham B15 2TG, UK.

Abstract

In this study our aim was to characterise the presence and the role of DNA alterations during sperm decondensation in the mouse. To visualise the changes during decondensation we investigated for the presence of DNase I hypersensitive sites in situ and for a putative role for topoisomerase II by examining the effect of teniposide, a topoisomerase II inhibitor, during fertilisation. In situ nick translation without the previous addition of DNase I failed to reveal the presence of endogenous nicks in decondensing sperm and pronuclei whereas preincubation of fixed oocytes with DNase I indicated that decondensing sperm were sensitive to this enzyme. Addition of 100 μM teniposide did not completely inhibit pronuclei formation but its addition to the fertilisation medium did lead to the presence of endogenous DNA nicks in decondensing sperm. These observations suggest that DNase I hypersensitivity during sperm decondensation is related to the dramatic conformational changes that the chromatin undergoes during the decondensation process, in which topoisomerase II may be implicated.

(Received December 9 1999)
(Accepted January 21 2000)


Key Words: DNase I; Fertilisation; In situ nick translation; Sperm decondensation; Topoisomerase II.

Correspondence:
c1 Department of Animal Biology, University of Modena and Reggio Emilia, Via Berengario 14, 41100 Modena, Italy. Tel: +39 59 243566. Fax: +39 59 226769. e-mail: bizzaro@unimo.it

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