Erbb4 Conditional Knockout mouse — mammary specific context

Erbb4, mouse ortholog of human ERBB4, encodes the only ERBB member that is both a fully active tyrosine kinase and a regulated intramembrane proteolysis substrate, binding neuregulins 1 through 4 and heparin binding EGF. Alternative splicing generates JM-a isoforms that contain a TACE and ADAM17 cleavage site permitting ectodomain shedding followed by gamma-secretase release of a soluble intracellular domain that translocates to the nucleus and partners with YAP, STAT5A and ETO2, versus JM-b isoforms that are not cleavable, and CYT-1 isoforms that carry a PI3K p85 binding site versus CYT-2 isoforms that do not. This isoform architecture means a conventional null conflates four biologically distinct receptors, so isoform-selective knockins are the correct design for neurodevelopmental, cardiac and mammary questions. Null mice die at midgestation from cardiac trabeculation failure and cranial ganglion defects, requiring conditional alleles. Erbb2 is the obligate heterodimer partner, so pair alleles when testing whether phenotypes reflect receptor loss or dimer loss.

A floxed Erbb4 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. For mammary work, plan Cre specificity, reporter crosses, and baseline phenotyping before you scale.