Figure 4. TFAM mutant epithelia harbor elongated crypts.

(A) Adult-onset loss of TFAM, using Villin-Cre^ERT2; Tfam^f/f mice, results in weight loss and death within 11 days after the initial tamoxifen treatment. (t-test, n= 7 controls, 5 mutants). (B) Consistent with efficient loss of TFAM, transcripts of Tfam and targets of TFAM in the mitochondrial genome are almost undetectable in the mutants (t-test, n=7 controls, 4 mutants). (C) Crypt lengths are noticeably longer in adult mice 10 days after TFAM inactivation, as observed in whole mount images, and histologically, longer crypts are also observed (D–E). Longer crypt length corresponds to an increase in total cell numbers in the crypts (F–G), and (E) elevated immunoreactivity for CD44, a crypt cell marker. Surprisingly longer crypts are not accompanied by an increased number of proliferating cells (D, H). BrdU pulse-chase analysis at 24 hours post-treatment suggests there is reduced migration rates of BrdU-labeled cells onto the villus of Tfam mutants (t-test, n= 3 controls, 3 mutants) (I–J). Taken together, these results suggest increased numbers of cells with crypt identity upon TFAM-loss. Histology is imaged and quantified from the duodenum. Scale bars = 50µm.