Myc Conditional Knockout mouse models

Myc, the mouse ortholog of human MYC, encodes a basic helix-loop-helix leucine zipper transcription factor that heterodimerizes with Max to occupy E-box CACGTG elements, recruiting Trrap, Gcn5, and P-TEFb to release paused RNA polymerase II and thereby amplifying the existing transcriptional program rather than imposing a single target signature; it also represses through Miz1. Protein stability is governed by a phosphodegron in which Erk-driven Ser62 phosphorylation primes Gsk3-mediated Thr58 phosphorylation, creating the Fbxw7 recognition site, while Aurora kinase A binding and Usp28 oppose turnover. Homozygous nulls die at mid-gestation, so conditional deletion is required, and allele class maps to distinct questions: a Thr58Ala knockin isolates degradation control, tetracycline-regulated or Lox-Stop-Lox overexpression tests reversibility and tumor maintenance, and humanization supports epitope-dependent reagents. Mycn and Mycl are paralogs with restricted expression that can substitute when knocked into the Myc locus, so dosage and driver choice determine the phenotype observed.

A floxed Myc allele paired with Cre gives spatial control that whole body knockouts cannot offer. People use it to separate developmental roles from adult homeostasis, to model somatic mutations, and to match disease that begins in one organ.