Abstract
BackgroundMicrocell-mediated chromosome transfer (MMCT) was developed to introduce a low number of chromosomes into a host cell. We have designed a novel technique combining part of MMCT with somatic cell nuclear transfer, which consists of injecting a somatic micronucleus into an enucleated oocyte, and inducing its cellular machinery to replicate such micronucleus. It would allow the isolation and manipulation of a single or a low number of somatic chromosomes.MethodsMicronuclei from adult bovine fibroblasts were produced by incubation in 0.05 μg/ml demecolcine for 46 h followed by 2 mg/ml mitomycin for 2 h. Cells were finally treated with 10 μg/ml cytochalasin B for 1 h. In vitro matured bovine oocytes were mechanically enucleated and intracytoplasmatically injected with one somatic micronucleus, which had been previously exposed [Micronucleus- injected (+)] or not [Micronucleus- injected (−)] to a transgene (50 ng/μl pCX-EGFP) during 5 min. Enucleated oocytes [Enucleated (+)] and parthenogenetic [Parthenogenetic (+)] controls were injected into the cytoplasm with less than 10 pl of PVP containing 50 ng/μl pCX-EGFP. A non-injected parthenogenetic control [Parthenogenetic (−)] was also included. Two hours after injection, oocytes and reconstituted embryos were activated by incubation in 5 μM ionomycin for 4 min + 1.9 mM 6-DMAP for 3 h. Cleavage stage and egfp expression were evaluated. DNA replication was confirmed by DAPI staining. On day 2, Micronucleus- injected (−), Parthenogenetic (−) and in vitro fertilized (IVF) embryos were karyotyped. Differences among treatments were determined by Fisher′s exact test (p≤0.05).ResultsAll the experimental groups underwent the first cell divisions. Interestingly, a low number of Micronucleus-injected embryos showed egfp expression. DAPI staining confirmed replication of micronuclei in most of the evaluated embryos. Karyotype analysis revealed that all Micronucleus-injected embryos had fewer than 15 chromosomes per blastomere (from 1 to 13), while none of the IVF and Parthenogenetic controls showed less than 30 chromosomes per spread.ConclusionsWe have developed a new method to replicate somatic micronuclei, by using the replication machinery of the oocyte. This could be a useful tool for making chromosome transfer, which could be previously targeted for transgenesis.
Highlights
Microcell-mediated chromosome transfer (MMCT) was developed to introduce a low number of chromosomes into a host cell
There are no previous reports of the generation of micronuclei in bovine cells, we assayed different treatments to induce a block in metaphase, on the basis of human or mouse protocols [7,10,26,51]
No differences were found between groups in percentages of cells that became micronucleated over total number of cells (Table 1), except for DMC 0.05 μg/ml + Mit, which showed a significantly higher value (21.75 vs. 3.25 to 10%) (p≤0.05)
Summary
Microcell-mediated chromosome transfer (MMCT) was developed to introduce a low number of chromosomes into a host cell. We have designed a novel technique combining part of MMCT with somatic cell nuclear transfer, which consists of injecting a somatic micronucleus into an enucleated oocyte, and inducing its cellular machinery to replicate such micronucleus It would allow the isolation and manipulation of a single or a low number of somatic chromosomes. In 1977, Fournier and Ruddle [7] designed the microcell-mediated chromosome transfer technique (MMCT) which is still used to introduce a low number of chromosomes into host somatic cells [8,9] This technique has been used in several ways, mainly for the mapping of genes, like tumor suppressor genes [10,11,12,13,14,15], telomerase suppressor genes [16,17,18,19], senescence inducing genes [20,21,22], and genes involved in DNA repair pathways [23,24,25]. It has been used to study the effect of genomic imbalances on chromosome- specific gene expression patterns and the behavior of polysomies in different cell lines [26,27], and for analysis of genomic imprinting [28,29,30]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
