Stearoyl-coenzyme A desaturase is an iron-containing enzyme that is crucial for the synthesis of unsaturated fatty acids. Four SCD isoforms, coded by Scd1 through Scd4, have been identified in the mouse. Scd1 is ubiquitously expressed in adipose tissues, Scd2 is primarily expressed in the brain, Scd3 expression is limited to sebaceous glands of the skin, while Scd4 is exclusively expressed in the heart. The full-length Scd3 gene has six exons, while a truncated variant has only 3 exons, with exons 2-3 of the short isoform being the same as exons 5-6 of the full-length gene. In normal mouse intestinal tissues, Scd3 expression is low; however, increased expression of the truncated Scd3 isoform is found in colon tumors. Scd3-icre/ERT2ex1-2 knock-in (KI) mice have an icre/ERT2-P2A cassette replacing exons 1-2 of the truncated form of the Scd3 gene, allowing for co-expression of endogenous SCD3 and an iCre/ERT2 fusion protein. This insertion is designed to have the endogenous promoter/enhancer elements direct icre/ERT2 expression to cells that express the truncated SCD3 isoform. When bred with mice containing a loxP-flanked sequence of interest, tamoxifen-inducible, Cre-mediated recombination will result in deletion of the floxed sequences in the Scd3-expressing cells of the offspring. Heterozygous and homozygous Scd3-icre/ERT2ex1-2 KI mice are viable and fertile. The donating investigator has not confirmed endogenous expression of the truncated Scd3 allele prior to tamoxifen exposure, nor have they evaluated iCre/ERT2 recombinase activity in the epidermis of these Scd3-icre/ERT2ex1-2 KI mice. The donating laboratory bred these Scd3-icre/ERT2ex1-2 mice to an Ai9 tdTomato reporter mouse line (<a href="https://www.jax.org/strain/007909">RRID:IMSR_JAX:007909</a>) and an <a href="https://www.informatics.jax.org/allele/MGI:3513416">Apc&Delta;14</a> cancer model. The resulting progeny demonstrated tdTomato fluorescence in the epididymis and colon tumor cells after exposure to tamoxifen. These mice may be useful when studying fatty acid synthesis and tumor progression in intestinal cancers. Of note, the donating laboratory also has a Scd3-iCreERT2 line available where the iCre/ERT2 cassette was inserted immediately after exon 6 of the full length Scd3 gene (<a href="https://www.mmrrc.org/catalog/sds.php?mmrrc_id=71741">RRID:MMRRC_071741-UNC</a>).

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Scd3-icre/ERT2ex1-2 knock-in mice have an icre/ERT2-P2A cassette replacing exons 1 and 2 of the truncated form of the Scd3 gene. When these mice are bred with mice containing a loxP-flanked sequence of interest, tamoxifen-inducible, Cre-mediated recombination will result in deletion of the floxed sequences in the Scd3-expressing cells of the offspring. These mice may be useful when studying fatty acid biosynthesis and tumor progression in intestinal cancers. Of note, the donating laboratory also has a&nbsp;Scd3-iCreERT2 line available where the iCre/ERT2 cassette was inserted immediately after exon 6 of the full length Scd3 gene (<a href="https://www.mmrrc.org/catalog/sds.php?mmrrc_id=71741">RRID:MMRRC_071741-UNC</a>).

This strain is hosted by NIH's MMRRC, which partners with JAX for the distribution of this and other strains. For additional information and to purchase, please visit the MMRRC site.