The transcriptional repressor Blimp1/Prdm1 regulates postnatal reprogramming of intestinal enterocytes

Abstract

Female mammals produce milk to feed their newborn offspring before teeth develop and permit the consumption of solid food. Intestinal enterocytes dramatically alter their biochemical signature during the suckling-to-weaning transition. The transcriptional repressor Blimp1 is strongly expressed in immature enterocytes in utero, but these are gradually replaced by Blimp1(-) crypt-derived adult enterocytes. Here we used a conditional inactivation strategy to eliminate Blimp1 function in the developing intestinal epithelium. There was no noticeable effect on gross morphology or formation of mature cell types before birth. However, survival of mutant neonates was severely compromised. Transcriptional profiling experiments reveal global changes in gene expression patterns. Key components of the adult enterocyte biochemical signature were substantially and prematurely activated. In contrast, those required for processing maternal milk were markedly reduced. Thus, we conclude Blimp1 governs the developmental switch responsible for postnatal intestinal maturation.

Fig. 1.

Dynamic Blimp1 expression patterns during intestinal maturation. (A) At E16.5, c-Myc⁺ cells are restricted to the intervillus pockets but become confined to developing crypts from P0 onward. Blimp1 is broadly expressed throughout the fetal endoderm. At P0, individual Blimp1⁻ cells are detectable within the intervillus pockets (red arrow), and by P10 populate the entire maturing crypt (dashed red line). At approximately P13, Blimp1⁻ cells enter the proximal villi, displacing immature Blimp1⁺ enterocytes (red bar). By P18, Blimp1 expression becomes restricted to the distal tip cells and endothelial cells in the lamina propria. (B) Quantification of Blimp1 (green, 605-nm Qdot) and Ki67 (red, 655-nm Qdot) coexpression via multi spectral imaging with yellow mask reveals decreasing percentages of double positives during villus morphogenesis and postnatal crypt formation. By P14, colocalization is no longer detectable (0.01%). (C) qPCR analysis confirms decreasing Prdm1 expression levels in total intestinal tissue (box, mean; bar, ± SEM; n > 10 for each data point).

Fig. 2.

Blimp1 inactivation fails to disturb intestinal morphogenesis before birth. (A–H) Conditional loss of Blimp1 has no noticeable effect on expression of mature markers of enterocyte (alkaline phosphatase), goblet (mucin-2), and enteroendocrine cells (chromogranin), or Sox9, a marker of Paneth cell progenitors. (I–K) More than 20 completely intact villi from proximal sections stained for phosphohistone 3, mucin 2, or chromogranin were counted (box, interquartile range; horizontal line, median; vertical line, minimum to maximum values excluding outliers; cross, mean).

Fig. 3.

Loss of Blimp1 disrupts tissue architecture and causes postnatal lethality. (A) Blimp1 mutant offspring display significantly decreased body weights compared with control littermates. (B) Kaplan–Meier survival curve (n ≥ 35 for all genotypes). (C–H) Alkaline phosphatase, Ki67, and c-Myc staining at P3 reveals changed tissue architecture in mutant intestines. Mutants display reduced villus density and occupancy of intervillous regions by differentiated columnar epithelium. Intervillus regions show reduced proliferative potential as judged by Ki67 staining and fewer shallow crypt structures are evident. c-Myc expression is confined to the rare shallow crypts.

Fig. 4.

Summary of misregulated genes identified in transcriptional profiling experiments. Transcripts with greater than fivefold changes in expression with Illumina DiffScores of more than 100 are shown. Gene Ontology identifies highest enrichment scores for categories associated with metabolic processes, vacuole function, and molecular transport. Fold changes in individual samples are normalized to mean Prdm1^+/+ signal. The heat-map scale ranges from 10-fold reduced (green) to normal (black) and 10-fold increased (red).

Fig. 5.

Blimp1 regulates intestinal maturation during the suckling-to-weaning transition. (A) qPCR analysis of adult enterocyte markers reveals a dramatic shift in transcriptional profiles between P10 and P21. Mutant intestines obtained by crossing the conditional allele with Villin.Cre (red line) or the epiblast-specific Sox2.Cre (blue line) deleter strains acquire the adult biochemical signature at E16.5 as judged by dramatically up-regulated expression of Sis, (B), Treh (C), and Arg2 (D), and two RIKEN EST clones from an adult intestine library (E and F). (Symbol, mean; bar, ± SEM; n > 10 genotypes.)

Fig. 6.

Blimp1 loss causes the fetal intestinal epithelium to adopt an adult enterocyte phenotype. (A and B) WT enterocytes weakly express Myo1A and lack Sis expression at E18.5 and P3, whereas mutants strongly express both Sis and Myo1A. (C) qPCR analysis of developmentally regulated Afp and Ttr expression levels. (D and E) At E18.5 and P3, in contrast to WT, mutant enterocytes completely lack Afp and Ttr expression.