Transcriptomic Profiling of Developing Human Paraxial Mesoderm from 4.5-5 Weeks of Gestation Human Embryos

Somites form during embryonic development and give rise to unique cell and tissue types, such as skeletal muscles and bones and cartilages of the vertebrae. Using somitogenesis stage human embryos, we performed the first ever transcriptomic profiling of human presomitic mesoderm as well as nascent and developed somites. Using this approach we uncovered novel regulators unique duing human somitogensis, and efficiently guided human pluripotent stem cells to differentiate to somite cells and downstream progeny. This work improves our understanding of human somite development and may enhance our ability to model and treat diseases affecting somite derivatives. Overall design: Human embryos of 4.5-5 weeks of gestation were obtained from electively aborted fetuses following informed consent and de-identification. After procurement, tissues were immediately washed in sterile PBS, placed in PBS supplemented with 5% fetal bovine serum, 1% Penicillin-Streptomycin and 2.5 µg/mL Amphotericin B, and shipped on ice. Within 48 hours, targeted tissues were micro-dissected from the embryos. Developed somites (SM Dev) included the two somite pairs at the forelimb bud level, nascent somites (SM) included the two somite pairs just anterior to the most caudal segmentation border that was visible, and presomitic mesoderm (PSM) included the tail region mesoderm posterior to SM. Duplicates were used for each sample type for RNA-seq.