Activation method does not alter abnormal placental gene expression and development in cloned pigs

Area of Science:

• Reproductive biology
• Genomics
• Animal cloning

Background:

• Nuclear transfer (NT) efficiency in pigs is limited, often attributed to poor placental development.
• Understanding gene expression in NT-derived placentas is crucial for improving cloning success.

Purpose of the Study:

• To identify differentially expressed transcripts in pig placentas from in vivo fertilization (IVV), in vitro fertilization (IVF), and nuclear transfer (NT) at Day 30 of gestation.
• To compare gene expression profiles across different NT activation methods and assess their impact on placental development.

Main Methods:

• Extraembryonic membranes were collected from pigs at Day 30 of gestation.
• cDNA from these membranes was hybridized to a pig reproductive tissue-specific microarray.
• Gene expression analysis was performed using ANOVA, with validation by real-time PCR, Western blot, and protein localization studies.

Main Results:

• 227 differentially expressed transcripts were identified between the five treatment groups, with no significant differences among the three activation methods.
• Comparison of pooled NT groups to IVV samples revealed 34 up-regulated and 19 down-regulated transcripts (>2-fold change).
• Protein expression patterns for UPTI and PAG2 mirrored their mRNA abundance, and localization studies identified specific protein distributions.

Conclusions:

• Gene and protein expression differences in NT extraembryonic membranes indicate an impaired fetal-maternal interface.
• The activation method is unlikely to be the primary cause of defects observed in cloned pigs; placental development is the key factor.