Fbxl10^T mice have a gene trap cassette, consisting of a β-geo sequence (a β-galactosidase reporter (lacZ) fused to a neomycin resistance cassette), inserted downstream the exon encoding the CXXC motif of the lysine (K)-specific demethylase 2B (Kdm2b) gene (also termed Fbxl10). The trap cassette is inserted into exon 13 of Fbxl10-1 (corresponding to exon 2 of Fbxl10-2). The long form of FBXL10 (FBXL10-1) encodes a histone demethylase that demethylates Lys-4 and Lys-36 of histone H3. The short form, FBXL10-2 lacks the histone demethylase domain but has the same C-terminus of FBXL10-1 composed of CXXC, PHD, leucine rich and F-box domains. Both FBXL10 isoforms binds to all unmethylated CpG-dense promoters through their common CXXC motif. FBXL10 acts by binding to the transcribed region of ribosomal RNA and repressing the transcription of ribosomal RNA genes which inhibits cell growth and proliferation. FBXL10 has also been reported to be an oncogene and a tumor suppressor in leukemia. Complete inactivation of the Fbxl10 gene leads to methylation only of promoters that are co-occupied by both FBXL10 and Polycomb repressive complexes (PRCs). The targeted mutation in this strain results in the truncation of both Fbxl10-1 and Fbxl10-2 isoforms. The PHD, F-box and leucine-rich repeat domains that are crucial for the incorporation of FBXL10 into polycomb repressive complex (PRC1) are not detectable in homozygotes. Small amounts of RNA encoded by the two exons of Fbxl10-2 upstream of the insertion site are present and translated into an exclusively cytoplasmic peptide. FBXL10-1 and FBXL10-2 proteins are undetectable in the homozygous Fbxl10^T/T mutants.

Homozygotes are embryonic lethal before E10.5 due to open and malformed anterior neural tube, a kinked and tortuous posterior neural tube, abnormal somitogenesis, heart defects and reduced size. Heterozygous mice are viable and fertile and born at Mendelian ratios. Hypermethylation of DNA is targeted to the promoters of the large families of Hox, Tbx, and other genes whose products are involved in the regulation of early embryonic development. These mice exhibit extreme sexual dimorphism, with more severe gene dysregulation in mutant female embryos due to dysregulation of X-linked genes.