Matr3^{Gt(RRR075)Byg}

The beta-geo cassette inserted into exon 13. 3' RACE analysis of mouse E14.5 brain and heart tissues showed that the long 3' RACE product (the only form detected in brain) is reduced in heterozygous brain, and that both long and short 3' RACE products are reduced in heterozygous heart. While interruption of the 3' end by the gene trap insertion reduced wild-type transcripts in heterozygotes, this was accompanied by the expression of a fusion transcript that may encode a functional or partly functional fusion protein. Western blot analyses of heterozygous heart and brain failed to detect a significant alteration in protein levels but did reveal the presence of the Matrin 3-beta-geo fusion protein in embryonic heart.