Developmental and epigenetic anomalies in cloned cattle

Area of Science:

• Epigenetics
• Developmental Biology
• Animal Reproduction

Background:

• Large offspring syndrome (LOS) in cloned animals, characterized by fetal and placental overgrowth, is linked to epigenetic dysregulation.
• Imprinted genes, expressed in a parent-specific manner, are hypothesized to be central to LOS.
• Assisted reproductive technologies (ART), including in vitro culture (IVC) and somatic cell nuclear transfer (SCNT), may induce epigenetic alterations.

Purpose of the Study:

• To investigate epigenetic modifications in imprinted genes associated with ART in cattle.
• To identify genetic markers in Bos indicus for analyzing parental-specific gene expression in hybrid embryos.
• To compare methylation patterns of key imprinted genes (SNRPN, H19, IGF2R) between SCNT and in vivo-produced cattle embryos.

Main Methods:

• Analysis of single nucleotide polymorphisms (SNPs) in Bos indicus DNA.
• Hybrid embryo creation by crossing Bos indicus and Bos taurus.
• Differential methylation region (DMR) analysis of imprinted genes SNRPN, H19, and IGF2R.
• Comparison of methylation patterns and allelic expression in SCNT versus in vivo embryos.

Main Results:

• Generalized hypomethylation of the imprinted allele was observed in SCNT-derived embryos.
• Biallelic expression was detected in SCNT embryos for the analyzed imprinted genes.
• Significant differences in methylation patterns were found between SCNT and in vivo embryos.

Conclusions:

• Imprinting marks are erased during somatic cell nucleus reprogramming in early development.
• Epigenetic anomalies, specifically altered imprinting, likely contribute to the high mortality and morbidity rates in cloned animals.
• Understanding these epigenetic errors is crucial for improving the safety and efficiency of SCNT and other ARTs.