The P2A-3xSV40 NLS-mScarlet cassette was inserted upstream of TGA stop codon. Nuclear-localized mScarlet is expressed under the regulatory control of Alpl gene elements in this mouse model, without impacting endogenous Alpl gene expression. This localization is achieved through the Nuclear Localization Signal (NLS), which efficiently targets mScarlet to the cell nucleus. This enables mScarlet fluorescence protein nuclear tracing studies.