Transcription factor. Binds to E-box motifs 5'-CANNTG-3' in the regulatory elements of target genes, probably as a heterodimer with another basic helix-loop-helix (bHLH) protein such as the transcription factor TCF3. May bind both open and closed chromatin, acting as a pioneer transcription factor to allow other factors to bind and activate lineage-specific genes. Required during post-implantation development for the generation of some differentiated trophoblast cell types. Transcriptional activity of ASCL2 may be antagonised in a subset of trophoblast cells by bHLH transcription factor HAND1, perhaps by competing for dimerization with other bHLH proteins. Involved in differentiation and function of follicular T-helper (Tfh) cells, thereby playing a role in germinal center responses; probably modulates expression of genes involved in Tfh cell function, such as BCL6. May also act as a suppressor of Th1-, Th2- and Th17-cell differentiation. Induces the formation of stem cells in intestinal crypts in vitro, synergistically activating transcription of target genes, such as SOX9, together with TCF4/beta-catenin. May form a bistable transcriptional switch, controlling expression of its own gene together with Wnt/R- spondin signaling, and thereby maintaining stem cell characteristics (By similarity). Modulates expression of target genes, including perhaps down-regulating EGR1/Krox24 and chemokine CXCL10/Mob-1 and up- regulating CXCR4 and CDKN1C/p57kip2, in Schwann cells. May play a role in reducing proliferation of Schwann cells, perhaps acting via modulation of expression of CDKN1C (By similarity). May be dispensable for blastocyst formation and later embryonic function (By similarity). May be involved in the determination of neuronal precursors (By similarity). {ECO:0000250|UniProtKB:O35885, ECO:0000250|UniProtKB:P19360}. This is the function of ENSG00000183734 (ASCL2, achaete-scute family bHLH transcription factor 2).