Practice question

Blastocyst inner cell mass is compact cluster of roughly twenty to thirty cells expressing characteristic pluripotency transcription factor network including Oct4, Sox2, Nanog, Klf2, and surface marker SSEA1 in mouse, TRA-1-60 in human. When microsurgically isolated and cultured, these cells establish embryonic stem cell lines that stably self-renew and differentiate into derivatives of three germ layers in teratomas and contribute to chimeric embryos including germline, confirming pluripotent classification. They are not totipotent because they cannot generate trophoblast autonomously, nor multipotent because not restricted to single germ layer, nor unipotent, highlighting intermediate potency crucial for development progression.