Practice question

Embryonic stem cells derived from pre-implantation blastocyst inner cell mass ICM three point five days mouse development maintain naive pluripotency defined by capacity to contribute to all three germ layers ectoderm mesoderm endoderm forming teratoma containing differentiated tissues and chimeric mice after blastocyst injection including germ line transmission indicating functional pluripotency plus transcriptome expressing OCT4 SOX2 NANOG core triad forming feedforward loop activating pluripotency enhancers while repressing differentiation genes via recruiting Polycomb repressive complex 2 depositing H3K27me3 at lineage promoters. Maintenance in vitro requires external cytokine signal leukemia inhibitory factor LIF belonging to interleukin-6 family four helix bundle cytokine binding heterodimer gp130 signal transducer and LIF receptor beta LIFRβ activating associated Janus kinases JAK1 JAK2 cross phosphorylating receptor cytoplasmic tyrosine creating docking sites for SH2 domain containing STAT3 signal transducer and activator transcription three that is phosphorylated on tyrosine seven hundred five. This mechanistic insight supports diagnostic and therapeutic applications while reinforcing core immunological and cell biology principles taught in advanced curricula.