| Cloning of animals by nuclear transplantation has demonstrated that reprogramming of nuclear function is possible. However, low pregnancy rates, elevated pregnancy losses and lethal abnormalities in most cloned animals born argue that somatic cell reprogramming by nuclear transplantation is not always complete. Here, we report the identification of four nuclear markers of incomplete reprogramming in nuclear transplant mouse embryos. Nuclear transplant embryos exhibit (i) pronucleur assembly of A-type lamins, (ii) increased NuMA content, (iii) stronger anchoring of AKAP95 and (iv) a greater proportion of heterochromatin, compared to fertilized embryos. We propose that deficiencies in reprogramming through nuclear transplantation result from failure to morphologically remodel the somatic donor nucleus into a normal, fully functional pronucleus. |
