Integrated multiomics reveal the molecular characteristics of conjoined twin fetuses.

RESEARCH QUESTION:Are there any differences between conjoined twin fetuses at the molecular level? DESIGN:Skin tissues were collected from thoracopagus conjoined twins at 15+4 weeks of gestation. The skin tissues were collected from the thigh side of conjoined twins after the abortion procedure. All specimens were obtained after written informed patient consent and were fully anonymized. All relevant ethical regulations were followed. Every specimen underwent multiomics sequencing analysis to determine associations among the DNA methylome, transcriptome and mutations in the exon regions in the conjoined twins. RESULTS:The global methylation pattern was similar in the two fetuses of conjoined twins, while significant differences were seen in local regions such as CpG islands (P = 0.026), enhancers (P < 0.001) and various repetitive elements (P < 0.05), which showed significant differences. The conjoined twins also differed in genes related to growth and development, cellular component morphogenesis and cellular stress, both in terms of DNA methylation levels and gene expression levels. Exon data analysis revealed that the common mutations in conjoined twins mainly occurred in neural development, lipid metabolism and microtubule morphogenesis. Specific mutations were associated with cellular component biosynthesis, behaviour and germ cell development. CONCLUSION:Conjoined twins were similar to each other globally, but there were significant differences related to growth and development, cellular component morphogenesis and cellular stress. The current study reveals the molecular features of conjoined twins for the first time, laying the foundation for future exploration of the mechanism of conjoined twins.