1. Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
2. Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia; and MRC Human Genetics Unit, Western General Hospital, Edinburgh, United Kingdom
3. Laboratoire de Biologie Moleculaire et Cellulaire, UMR 5161, Centre Nationale de la Recherche Scientifique, Ecole Normale Superieure de Lyon, Lyon, France