Exons 3 of Tsc2 which consists of 111 bp, encoding 37 amino acids near the N terminus of the protein (note that in some schemes this is counted as exon 4; however in accordance with human TSC2 gene, always denoted this as exon 3, labeling a 5' untranslated exon as 1a) was removed from the Tsc2tm2Djk locus by crossing with mice expressing Cre recombinase in the germline. This allele is hypomorphic allele. (J:149326)