Practice question

ABp fate distinguishing dorsal versus ventral AB lineage derivatives depends on GLP-1 Notch receptor activation. GLP-1 protein segregates to all AB daughters but functionally active only in ABp due to contact with P2 ligands APX-1 and LAG-2. Activated GLP-1 ICD upregulates Notch target genes ref-1 family, promoting ABp-specific blastomere divisions generating dorsal epidermis and distinct pharyngeal cells. In glp-1 mutants ABp transforms to ABa, equalizing lineage. Therefore GLP-1 presence and selective activation is decisive intrinsic factor ensuring ABp identity, integrating positional signal from P2 to create anterior-posterior and dorsal-ventral pattern within early embryo ectoderm contribution.