Chemically assisted somatic cell nuclear transfer without micromanipulator in the goat: effects of demecolcine, cytochalasin-B, and MG-132 on the efficiency of a manual method of oocyte enucleation using a pulled Pasteur pipette

• A time- and cost-efficient method of SCNT was described without micromanipulator.
• Glass Pasteur pipette pulled over flame was used as enucleation device.
• Demecolcine was used for chemically assisted handmade oocyte enucleation.
• The technique allows large scale production of goat clones with high efficiency.

The present study aimed to facilitate widespread application of a previously described manual method of somatic cell nuclear transfer (SCNT) by investigating the effects of demecolcine (a microtubule-depolymerizing chemical), cytochalasin-B (a microfilament-depolymerizing chemical: 2.5 μg/ml for 15 min) and MG-132 (a proteasome inhibitor chemical) on the (i) incidence of cytoplasmic protrusion of MII chromosomes, (ii) improvement of manual oocyte enucleation, and (iii) in vitro and in vivo developmental competence of SCNT embryos in the goat. Following in vitro maturation, around 65% of goat oocytes contained a characteristic cytoplasmic protrusion of MII-chromosomes. Treatment with demecolcine (0.4 μg/ml for 30 min) significantly increased this rate to 92.2 ± 4.5%. Treatment with MG-132 (2 μM for 30 min) could not improve this rate when used alone (61.4 ± 11.5%), but when combined with demecolcine (86.4 ± 8.1%). Treatment with cytochalasin-B completely suppressed this rate whenever used, either alone (7.7 ± 5.1%) or in combination with demecolcine (3.9 ± 1.3%). In a direct comparison, there was no significant difference in quantity and quality of embryos propagated by the manual vs. micromanipulation-based methods of SCNT (cleavage: 85.3 ± 4.5 vs. 89.5 ± 8.9%, blastocyst: 19.5 ± 4.3 vs. 24.3 ± 4.4%, grade 1 and 2 blastocyst: 33.8 ± 7.1 vs. 29.5 ± 6.3%, total cell count: 125 ± 11.1 vs. 122 ± 10.5, respectively). Furthermore, development to live kids at term was not significant between the two SCNT methods. From both technical and economical points of view, the overall in vitro and in vivo efficiency of this manual method of SCNT proved it a simple, fast and efficient alternative for large scale production of cloned goats.