Spontaneous and ART-induced large offspring syndrome: similarities and differences in DNA methylome

Abstract

Large/abnormal offspring syndrome (LOS/AOS) is a congenital overgrowth syndrome reported in ruminants produced by assisted reproduction (ART-LOS) which exhibit global disruption of the epigenome and transcriptome. LOS/AOS shares phenotypes and epigenotypes with the human congenital overgrowth condition Beckwith-Wiedemann syndrome. We have reported that LOS occurs spontaneously (SLOS), however, to date, no study has been conducted to determine if SLOS has the same methylome epimutations as ART-LOS. In this study, we performed whole genome bisulfite sequencing to examine global DNA methylation in SLOS and ART-LOS tissues. We observed unique patterns of global distribution of differentially methylated regions (DMRs) over different genomic contexts, such as promoters, CpG islands and surrounding regions, and repetitive sequences from different treatment groups. In addition, we identified hundreds of LOS-vulnerable DMRs across different cattle breeds when analyzing four idependent LOS experiments together. Specifically, there are 25 highly vulnerable DMRs that could potentially serve as molecular markers for the diagnosis of LOS, including at the promoters of DMRT2 and TBX18, at the imprinted gene bodies of IGF2R, PRDM8, and BLCAP/NNAT, and at multiple CpG islands. We also observed tissue-specific DNA methylation patterns between muscle and blood, and conservation of ART-induced DNA methylation changes between muscle and blood. We conclude that as in ART-LOS, alterations of the epigenome are involved in the etiology of SLOS. In addition, SLOS and ART-LOS share some similarities in methylome epimutations.

Identification of large offspring syndrome during pregnancy through ultrasonography and maternal blood transcriptome analyses

“…Enlarged tongue was also observed in D105 IVP-LOS which is similar to previous findings in our laboratory 2 , 64 and comparable to what has been observed in a similar congenital overgrowth condition in humans, namely Beckwith–Wiedemann Syndrome 65 . Large tongues can lead to difficulty in suckling and increase the chances of prenatal death 26 .…”

Identification of large offspring syndrome during pregnancy through ultrasonography and maternal blood transcriptome analyses

“…Enlarged tongue was also observed in D105 ART-LOS which is similar to previous findings in our laboratory 2,23 and comparable to what has been observed in a similar congenital overgrowth condition in humans, namely Beckwith-Wiedemann Syndrome 64 . Large tongues can lead to difficulty in suckling and increase the chances of prenatal death 26 .…”

Identification of large offspring syndrome during pregnancy through ultrasonography and maternal blood transcriptome analyses

“…Enlarged tongue was also observed in D105 ART-LOS which is similar to previous findings in our laboratory 2,23 and comparable to what has been observed in a similar congenital overgrowth condition in humans, namely Beckwith-Wiedemann Syndrome 63 . Large tongues can lead to difficulty in suckling and increase the chances of prenatal death 26 .…”

“…Serum has been experimentally determined to cause LOS in sheep [16][17][18] and bovine offspring derived from embryos cultured in serum containing medium can develop LOS 2 . In addition, the syndrome can also occur in fetuses and calves derived from embryos cultured without serum supplementation 19,20 and, more recently, we have documented that this syndrome occurs spontaneously in cattle produced by natural or artificial insemination [21][22][23] . The latter is of interest as there is a similar loss-of-imprinting overgrowth syndrome in humans, namely Beckwith-Wiedemann syndrome, which occurs naturally, and its incidence is increased in children conceived by ART 24 .…”