The connective tissue growth factor protein encoded by the Ctgf gene is a mitogen that is secreted by vascular endothelial cells. CTGF plays a role in chondrocyte proliferation and differentiation, cell adhesion in many cell types, and is related to platelet-derived growth factor. In zebra fish, CTGF is necessary and sufficient to stimulate glial bridging and natural spinal cord regeneration.


The Ctgf-2A-dgCre-D knockin mutation has an in-frame insertion of a viral 2A oligopeptide (T2A) and a destabilized EGFP/Cre fusion gene (dgCre), all in place of the Ctgf translational STOP codon. This is designed to have both endogenous gene and dgCre expression directed to Ctgf-expressing cells by the endogenous promoter/enhancer elements.

The ecDHFR^R12Y/Y100I domain of dgCre leads to proteosomal degradation of the entire EGFP/Cre fusion protein, resulting in reduced overall Cre recombinase activity. Administration of the DHFR inhibitor, trimethoprim (TMP), prevents degradation of the dgCre fusion gene and results in increased Cre recombinase activity. The EGFP sequences included in the DHFR-Cre cassette contribute to the destabilization of the entire dgCre fusion protein in the absence of TMP.

When Ctgf-2A-dgCre-D mice are bred with mice containing loxP-flanked sequences, TMP-enhanced Cre recombination will result in deletion of floxed sequences in the Ctgf-expressing cells of the double mutant offspring.

Specifically, the donating investigator reports that Ctgf-2A-dgCre-D mice exhibit TMP-inducible Cre recombinase activity that is specific and efficient (largely recapitulates the endogenous Ctgf expression pattern with efficient inducibility). When induced, strong Cre recombinase activity is restricted to layer 6b of the cortex and in restricted populations within the cortical subplate (e.g., endopiriform nucleus). In the absence of TMP, Cre activity is only present in a few cortical layer 6b cells.
The donating investigator reports no EGFP fluorescence with or without TMP. Immunohistochemical detection of EGFP levels, if any, have not yet been evaluated in the presence or absence of TMP (December 2015).

Heterozygous mice are viable and fertile with no reported gross physical or behavioral abnormalities. The donating investigator did not examine dgCre activity in tissues other than brain. To date (December 2015), it has not been attempted to make this strain homozygous.

For characterization information, see images at the Allen Institute for Brain Science website (Ctgf-2A-dgCre images).

The dgCre fusion gene (also called destabilized EGFP/Cre, DHFR-EGFP-Cre, hDHFR/EGFP/Cre or ecDHFR^R12Y/Y100I/EGFP/Cre) is an enhanced green fluorescent protein/Cre recombinase fusion gene with an N terminal fusion of the first 159 amino acids of the Escherichia coli K-12 strain chromosomal dihydrofolate reductase gene (DHFR or folA) harboring the G67S mutation and modified to also include the R12Y/Y100I destabilizing domain mutations. The ecDHFR^R12Y/Y100I domain of dgCre leads to proteosomal degradation of the entire fusion protein, resulting in reduced Cre recombinase activity. The donating investigator reports that administration of the high affinity DHFR inhibitor trimethoprim (TMP; at a concentration of 0.25-0.30 mg/g body weight) prevents degradation of the dgCre fusion gene, resulting in increased Cre recombinase activity. The EGFP sequences included in the DHFR-Cre cassette contribute to the destabilization of the entire dgCre fusion protein in the absence of TMP. The donating investigator reports no EGFP fluorescence with or without TMP. Immunohistochemical detection of EGFP levels, if any, have not yet been evaluated in the presence or absence of TMP (December 2015).