Fig. 7. Normal levels of p21, p19^ARF, p16^INK4a and p15^INK4b expression in Tbx2^tm1Pa/Tbx2^tm1Pa mutants (–/–), 9.5-10.5 dpc. (A) Results of semi-quantitative RT-PCR expression analysis demonstrating no evidence of elevated p21 transcription in homozygous mutants versus either wild-type (+/+) or heterozygous (+/–) controls at 9.5 dpc, 10.5 dpc, or in cases with dissected 10.5 dpc heart and trunk (h). Mandible from a 14.5 dpc mouse embryo (m-14) serves as the positive control. (B) Results of semi-quantitative RT-PCR expression analysis demonstrating no evidence of elevated p19^ARF or p16^INK4a transcription in homozygous mutants versus wild-type controls at 9.5 dpc, 10.5 dpc or in cases with dissected 10.5 dpc heart and trunk (h). Adult testis (t) serves as the positive control. (C) Results of semi-quantitative RT-PCR expression analysis demonstrating no evidence of elevated p15^INK4b transcription in homozygous mutants versus either wild-type or heterozygous controls at 9.5 dpc, 10.5 dpc, or in cases with dissected 10.5 dpc heart and trunk (h). Adult testis (t) serves as the positive control.