In vitro culture and somatic cell nuclear transfer affect imprinting of SNRPN gene in pre- and post-implantation stages of development in cattle.
BACKGROUND
Embryo in vitro manipulations during early development are thought to increase mortality by altering the epigenetic regulation of some imprinted genes. Using a bovine interspecies model with a single nucleotide polymorphism, we assessed the imprinting status of the small nuclear ribonucleoprotein polypeptide N (SNRPN) gene in bovine embryos produced by artificial insemination (AI), in vitro culture (IVF) and somatic cell nuclear transfer (SCNT) and correlated allelic expression with the DNA methylation patterns of a differentially methylated region (DMR) located on the SNRPN promoter.


RESULTS
In the AI group, SNRPN maternal expression is silenced at day 17 and 40 of development and a third of the alleles analyzed are methylated in the DMR. In the IVF group, maternal transcripts were identified at day 17 but methylation levels were similar to the AI group. However, day-40 fetuses in the IVF group showed significantly less methylation when compared to the AI group and SNRPN expression was mostly paternal in all fetal tissues studied, except in placenta. Finally, the SCNT group presented severe loss of DMR methylation in both day-17 embryos and 40 fetuses and biallelic expression was observed in all stages and tissues analyzed.


CONCLUSIONS
Together these results suggest that artificial reproductive techniques, such as prolonged in vitro culture and SCNT, lead to abnormal reprogramming of imprinting of SNRPN gene by altering methylation levels at this locus.
Suzuki
Joao
J
Centre de recherche en reproduction animale, Faculty of veterinary medicine, University of Montreal, Saint-Hyacinthe, Quebec, Canada. heihachi74@hotmail.com
Therrien
Jacinthe
J
Filion
France
F
Lefebvre
Rejean
R
Goff
Alan K
AK
Smith
Lawrence C
LC
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D019175:DNA Methylation; D010064:Embryo Implantation; D005260:Female; D018392:Genomic Imprinting / Q000235:genetics*; D007315:Insemination, Artificial; D008969:Molecular Sequence Data; D053652:Nuclear Transfer Techniques; D011247:Pregnancy; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D055517:snRNP Core Proteins / Q000235:genetics*
D055517:snRNP Core Proteins