Cyp19a1-IRES-Cre Mice

The “IRES-Cre” cassette was inserted downstream of TGA stop codon with 20~30bp.

a. Method

The Cyp19a1-IRES-Cre mice were bred with Rosa26-LSL-tdTomato mice to generate double heterozygous offspring. Cre-mediated recombination will result in the expression of tdTomato protein in the Cre-positive cells of the offspring. The ovaries, testes, and brain tissue of 6-week-old offspring mice were collected and immunofluorescence was used to observe the expression of tdTomato protein to determine the activity of Cre recombinase.

b. Genotype

Cre+: Cyp19a1-IRES-Cre[KI/+]; Rosa26-LSL-tdTomato[CKI/+]
Cre-: Rosa26-LSL-tdTomato[CKI/+]

c. Result

1. Expression of Cre recombinase in the female gonads

Figure 1. Immunofluorescence staining of the ovaries in female mice. In Cre+ female mice, there was a large amount of red fluorescence from the tdTomato protein in the ovarian granulosa cells, indicating a large amount of Cre recombinase expression in this location. In contrast, no expression of tdTomato red fluorescence was detected in the control group (Cre-) mice, indicating the absence of Cre recombinase.

2. Expression of Cre recombinase in the male gonads

Figure 2. Immunofluorescence staining of the testis in male mice. In Cre+ male mice, there was red fluorescence in a small number of testicular cells, which partially overlapped with DAPI staining, indicating that these cells may be testicular support cells or other types of cells. In contrast, no expression of tdTomato red fluorescence was detected in the control group (Cre-) mice, indicating the absence of Cre recombinase.

3. Expression of Cre recombinase in the hippocampal region of the brain

Figure 3. Immunofluorescence staining of the hippocampal region of the brain. In Cre+ mice, there was partial red fluorescence in the hippocampal CA region* (as shown within the white box in the image), indicating that Cre recombination has occurred in this area. In contrast, no expression of tdTomato red fluorescence was detected in the control group (Cre-) mice, indicating the absence of Cre recombinase.

*The hippocampal CA region refers to the Cornu Ammonis region of the hippocampal formation, which includes areas CA1 and CA2.

4. Expression of Cre recombinase in the ventricles, fiber tracts, and nucleus accumbens regions of the brain

Figure 4. Immunofluorescence staining of the ventricles, fiber tracts, and nuclei of the brain. In Cre+ mice, there was partial red fluorescence in the lateral ventricles*, stria terminalis*, and caudoputamen structures*, indicating that Cre recombination has occurred in these areas. In contrast, no expression of tdTomato red fluorescence was detected in the control group (Cre-) mice, indicating the absence of Cre recombinase.

*The fiber tract region: stria terminalis (as shown by the left arrow in the image).
*The ventricular region: lateral ventricle (as shown by the middle arrow in the image).
*The brain nuclei region: caudoputamen (as shown by the right arrow in the image).

d. Summary

In the Cyp19a1-IRES-Cre mice, the expression of Cre recombinase is mainly localized in the ovarian granulosa cells. At the same time, recombination mediated by Cre recombinase can also occur in some cells in the hippocampus, ventricles, fiber tracts, and brain nuclei of the brain. The expression of Cre recombinase is similar to the expression pattern of the endogenous Cyp19a1 gene in mice and has good specificity.

The Cre recombinase gene is located on chromosome 9 in Cyp19a1-IRES-Cre mice. Please avoid using mice that have been targeted on the same chromosome for breeding.