Transgenic twin lambs cloned by granulosa cells

[Somatic cell nuclear transfer and centrosome inheritance]

The developmental competence of embryos cloned from somatic cells depends on the cellular event and molecular process, such as separation of chromosomes and reorganization of spindle after nuclear transfer. Centrosome, the main microtubule organizing centers in a cell, is crucial for reorganization of spindle and normal separation of chromosomes during mitosis. Aberrant of centrosomes will lead to aneuploidy of blastomere and developmental failure of embryo. This paper expounded the situation of animal somatic cell nuclear transfer (SCNT) and biological functions of centrosome and analyzed the inheritance mechanism of centrosome during gametogenesis and fertilization. Additionally, the study condition of centrosome and its associated proteins in SCNT embryos were introduced, which provided a new clue to study the de-velopmental abnormality of cloned embryos and animals.

Fate of centrosomes following somatic cell nuclear transfer (SCNT) in bovine oocytes

Cloning mammalians by somatic cell nuclear transfer (SCNT) remains inefficient. A majority of clones produced by SCNT fail to develop properly and of those which do survive, some exhibit early aging, premature death, tumors, and other pathologies associated with aneuploidy. Alterations of centrosomes are linked to aberrant cell cycle progression, aneuploidy, and tumorigenesis in many cell types. It remains to be determined how centrosomes are remodeled in cloned bovine embryos. We show that abnormalities in either distribution and/or number of centrosomes were evident in approximately 50% of reconstructed embryos following SCNT. Moreover, centrosome abnormalities and failed ‘pronuclear’ migration which manifested during the first cell cycle coincided with errors in spindle morphogenesis, chromosome alignment, and cytokinesis. By contrast, nuclear mitotic apparatus protein (NuMA) exhibited normal expression patterns at metaphase spindle poles and in ‘pronucleus’ during interphase. The defects in centrosome remodeling and ‘pronuclear’ migration could lead to chromosome instability and developmental failures associated with embryo production by SCNT. Addressing these fundamental problems may enhance production of normal clones.