A 0.6kb region in length including Mir29a and Mir29b-1 pre-microRNAs was removed in this strain. Real-time PCR analysis demonstrated absence of mature Mir29a RNA in various tissues of homozygous mutant mice. Precursor RNA levels of pre-Mir29a or pre-Mir29a were reduced in heterozygous mice and nearly undetectable in homozygous mutant mice. (J:238766, J:324059)