The RNA polymerase III subunit Polr3b is required for the maintenance of small intestinal crypts in mice.

BACKGROUND & AIMS: The continuously self-renewing mammalian intestinal epithelium, with high cellular turnover, depends on adequate protein synthesis for its proliferative capacity. RNA polymerase III activity is closely related to cellular growth and proliferation. Here, we studied the role of Polr3b, a large RNA polymerase III subunit, in the mammalian intestinal epithelium.

METHODS

We derived mice with an intestinal epithelium-specific hypomorphic mutation of the b gene, using VillinCre-mediated gene ablation. Phenotypic consequences of the mutation on the intestinal epithelium in mice were assessed using histological and molecular methodologies, including genetic lineage tracing.

RESULTS

The mutation severely reduced survival and growth in mice during the first postnatal week, the period when the expansion of the intestinal epithelium, and thus the requirement for protein synthesis, are highest. The neonatal intestinal epithelium of ; mice was characterized by areas with reduced proliferation, abnormal epithelial architecture, loss of Wnt signaling and a dramatic increase in apoptotic cells in crypts. Genetic lineage tracing using ; mice demonstrated that in surviving mutant mice, Polr3b-deficient dying crypts were progressively replaced by 'Cre-escaper' cells that had retained wild type Polr3b function. In addition, enteroids cultured from ; mice show reduced proliferative activity and increased apoptosis.

CONCLUSIONS

We provide evidence for an essential role of the Pol III subunit Polr3b in orchestrating the maintenance of the intestinal crypt during early postnatal development in mice.