FIG. 1.

Gene structure of the two SREBP-1 isoforms (SREBP-1a and SREBP-1c) and generation of SREBP-1a deficient mice. (A) Schematic diagram of SREBP-1a and SREBP-1c, indicating that the only difference is with different amino-terminal domains. (B) The β-geo gene-trap cassette was located between the unique 5′ first exons for SREBP-1a and SREBP-1c, as described in Materials and Methods. PCR genotyping, using the indicated oligonucleotide primers, yielded 120-bp fragments for wild-type alleles (+/+) and 750-bp fragments for targeted (DF/DF) alleles. (C) Frequency of different genotypes in the offspring of heterozygous offspring. Littermates were genotyped over a 2-year period. The first row reflects the actual number of viable mice by genotype. The second row reflects the theoretical number of mice for each group based on Mendelian genetics.