Dicer is required for maintaining adult pancreas - PubMed (original) (raw)

Dicer is required for maintaining adult pancreas

Sumiyo Morita et al. PLoS One. 2009.

Abstract

Dicer1, an essential component of RNA interference and the microRNA pathway, has many important roles in the morphogenesis of developing tissues. Dicer1 null mice have been reported to die at E7.5; therefore it is impossible to study its function in adult tissues. We previously reported that Dicer1-hypomorphic mice, whose Dicer1 expression was reduced to 20% in all tissues, were unexpectedly viable. Here we analyzed these mice to ascertain whether the down-regulation of Dicer1 expression has any influence on adult tissues. Interestingly, all tissues of adult (8-10 week old) Dicer1-hypomorphic mice were histologically normal except for the pancreas, whose development was normal at the fetal and neonatal stages; however, morphologic abnormalities in Dicer1-hypomorphic mice were detected after 4 weeks of age. This suggested that Dicer1 is important for maintaining the adult pancreas.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1

Figure 1. Body weight growth curves.

Male wild-type (+/+) and _Dicer1_-hypomorphic (−/−) mice were measured to determine the change in body weight from 10 to 80 days of age. *, P<0.05. n = 8–10 per group.

Figure 2

Figure 2. Comparison of Dicer1 expression in nine tissues between wild-type (+/+) and _Dicer1_-hypomorphic (−/−) mice.

The expression in the _Dicer1_-hypomorphic mice was normalized to that in the wild-type mice.

Figure 3

Figure 3. H&E-stained section of adult tissues of wild-type (+/+) (n = 2) and _Dicer1_-hypomorphic (−/−) mice (n = 4).

Figure 4

Figure 4. Comparison of the size of islets in wild-type and _Dicer1_-hypomorphic mice.

The islets mass was measured in wild-type (blue bar) and _Dicer1_-hypomorphic mice (pink bar). The numbers of islets were examined in wild-type (n = 6) and _Dicer1_-hypomorphic (n = 6) mice, with six sections from each animal. The graph shows the percentage of islets in each size category.

Figure 5

Figure 5. Pancreas morphology in adult (8–10 weeks of age) _Dicer1_-hypomorphic mice.

A, B: Hematoxylin-eosin (H & E)-stained islets of the pancreas from an 8-week-old wild-type (+/+) mouse and _Dicer1_-hypomorphic (−/−) mice (*400). A: Arrows indicate an irregular distribution of islet cells. B: Arrowheads indicate that the boundary of islets and ducts was not clearly defined in the pancreas of _Dicer1_-hypomorphic mice. C: Immunohistochemistry of duct cells of _Dicer1_-hypomorphic mice. (I) Insulin (green) and glucagon (red) double-expressing cells were detected in the duct. (II) Insulin-positive cells (brown) and glucagon-positive cells (blue) were observed in the duct. (III) Comparison of the number of epithelial cells stained with both insulin and glucagon, only insulin, and only glucagon in wild-type and _Dicer1_-hypomorphic mice. These numbers were averaged from 6 animals, with six sections from each animal. **, P<0.01. (IV) Comparison of the proportion of ducts containing epithelial cells stained with Pdx1 in wild-type and _Dicer1_-hypomorphic mice. Arrowheads indicate the Pdx1-positive cells. *, P<0.01. (V) Abnormal staining of Ki67 was observed in the pancreas of _Dicer1_-hypomorphic mice. D: (I) H & E-stained multinuclear atypical cells in the pancreas of _Dicer1_-hypomorphic mice. The black dotted line indicates atypical multinuclear cells. (II) Comparison of the number of multi-nucleated cells in wild-type and _Dicer1_-hypomorphic mice. These numbers were averaged from 6 animals, with six sections from each animal. **, P<0.01. E: Immunohistochemistry of multinuclear atypical cells of adjacent sections of the pancreas of _Dicer1_-hypomorphic mice using anti-insulin (I) and anti-glucagon (II) antibodies. F: H & E-stained acinar cells. The rectangular areas outlined in the upper panels are magnified in the lower panels. An abnormal structure of exocrine cells was observed in the pancreas of _Dicer1_-hypomorphic mice.

Figure 6

Figure 6. Histological and immunohistochemical analysis of the pancreas at E15.5 (A) and P1 (B) of wild-type and _Dicer1_-hypomorphic mice.

_Dicer1_-hypomorphic mice show normal insulin (brown) and glucagon (blue) staining at E15.5 and P1. C: Histological abnormalities found in the pancreas of 4-week-old _Dicer1_-hypomorphic mice. (I) The endocrinal distribution was slightly irregular. The dotted line indicates the abnormal region of the islet. (II) Multi-nucleated cells were observed. The dotted line indicates multi-nucleated cells, which were also found in the pancreas of adult _Dicer1_-hypomorphic mice.

Figure 7

Figure 7. Analysis of ActRIIA and ActRIIB expression.

Data are expressed relative (n-fold) to the wild-type pancreas and correspond to the means and standard errors for three independent experiments performed in triplicate. *, P<0.05. wild-type n = 9, _Dicer1_-hypomorphic mice n = 9.

Figure 8

Figure 8. The distribution of changes in miRNA levels in _Dicer1_-hypomorphic mice compared to wild-type mice.

Figure 9

Figure 9. Glucose metabolism and growth hormone levels in wild-type and _Dicer1_-hypomorphic mice.

A: Glucose tolerance test. Fasted 8-week-old mice received an intraperitoneal injection of glucose (2 mg/g body weight). B: Insulin concentration. Plasma insulin was measured before and after the intraperitoneal glucose injection. C: Growth hormone concentration. Plasma growth hormone concentrations were measured in wild-type and _Dicer1_-hypomorphic mice. A, B: Values are expressed as the means±S.D. (n = 20 per group). C: Values are expressed as the means±S.D. (n = 10 per group).*, P<0.05.

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