will remain in GV, some will be at MI and will reach MII
much later. The remaining 30% are those that have already
degenerated. In our experience, although the maturation
rate is similar in the two media, the developmental competence
to blastocyst is higher for DMEM/F12-based media
(Table 22.3).
The limited supply of horse ovaries and low efficiency
of maturation stimulated interest in using also metaphase
I (MI) oocytes, which are not normally used in cloning
laboratories. Choi et al. (2009) used a small number of
MI oocytes and found that blastocyst rates did not differ
between oocytes in metaphase I or II at the time of nuclear
transfer, and produced a healthy foal from two blastocysts
originated from MI oocytes. We, however, found a significantly
lower capacity of MI oocytes, compared with MII
oocytes, to support NT embryo cleavage and blastocyst
development (Table 22.4). The obtained MI blastocysts
were also smaller than their MII counterparts. Therefore,
the use of MI oocytes can only marginally improve the
outcome of horse cloning. A possibility that has been
investigated in order to compensate for the limited oocyte
supply is the use of oocytes from another species where
they are more abundant and easily available, such as cattle
and pigs. This approach has been studied for the cloning
of endangered species (Loi et al., 2011). In our laboratory
we used pig and bovine oocytes with horse somatic cell
for intergenera SCNT (Lagutina et al., 2011). The initial
stages of nuclear reprogramming of the horse nucleus were
more evident using porcine oocytes, with the formation
of nucleoli, which was not observed when bovine oocytes
were used. However, after initial cleavage these intergenera
embryos never developed to morula or blastocyst, indicating
a failure of embryonic genome activation.
will remain in GV, some will be at MI and will reach MIImuch later. The remaining 30% are those that have alreadydegenerated. In our experience, although the maturationrate is similar in the two media, the developmental competenceto blastocyst is higher for DMEM/F12-based media(Table 22.3).The limited supply of horse ovaries and low efficiencyof maturation stimulated interest in using also metaphaseI (MI) oocytes, which are not normally used in cloninglaboratories. Choi et al. (2009) used a small number ofMI oocytes and found that blastocyst rates did not differbetween oocytes in metaphase I or II at the time of nucleartransfer, and produced a healthy foal from two blastocystsoriginated from MI oocytes. We, however, found a significantlylower capacity of MI oocytes, compared with MIIoocytes, to support NT embryo cleavage and blastocystdevelopment (Table 22.4). The obtained MI blastocystswere also smaller than their MII counterparts. Therefore,the use of MI oocytes can only marginally improve theoutcome of horse cloning. A possibility that has beeninvestigated in order to compensate for the limited oocytesupply is the use of oocytes from another species wherethey are more abundant and easily available, such as cattleand pigs. This approach has been studied for the cloningof endangered species (Loi et al., 2011). In our laboratorywe used pig and bovine oocytes with horse somatic cellสำหรับ intergenera SCNT (Lagutina et al., 2011) เริ่มต้นขั้นตอนของการ reprogramming นิวเคลียร์ของนิวเคลียสม้าได้ชัดขึ้นด้วยช่วงแช่สารละลาย การก่อตัวของ nucleoli ซึ่งถูกตรวจสอบเมื่อวัวแช่สารละลายใช้ อย่างไรก็ตาม หลังจากเริ่มต้นปริ intergenera เหล่านี้โคลนไม่เคยพัฒนา morula หรืออดีต แสดงความล้มเหลวของการเปิดใช้งานกลุ่มตัวอ่อน
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