Expression and localization of microRNAs in perinatal rat pancreas: role of miR-21 in regulation of cholesterol metabolism.
OBJECTIVE
To investigate the expression of pancreatic microRNAs (miRNAs) during the period of perinatal beta-cell expansion and maturation in rats, determine the localization of these miRNAs and perform a pathway analysis with predicted target mRNAs expressed in perinatal pancreas.


METHODS
RNA was extracted from whole pancreas at embryonic day 20 (E20), on the day of birth (P0) and two days after birth (P2) and hybridized to miRNA microarrays. Differentially expressed miRNAs were verified by northern blotting and their pancreatic localization determined by in situ hybridization. Pathway analysis was done using regulated sets of mRNAs predicted as targets of the miRNAs. Possible target genes were tested using reporter-gene analysis in INS-1E cells.


RESULTS
Nine miRNAs were differentially expressed perinatally, seven were confirmed to be regulated at the level of the mature miRNA. The localization studies showed endocrine localization of six of these miRNAs (miR-21, -23a, -29a, -125b-5p, -376b-3p and -451), and all were expressed in exocrine cells at one time point at least. Pathways involving metabolic processes, terpenoid and sterol metabolism were selectively affected by concomitant regulation by miRNAs and mRNAs, and Srebf1 was validated as a target of miR-21.


CONCLUSIONS
The findings suggest that miRNAs are involved in the functional maturation of pancreatic exocrine and endocrine tissue following birth. Pathway analysis of target genes identify changes in sterol metabolism around birth as being selectively affected by differential miRNA expression during this period.
Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark.
Louise
L
Larsen
Maiken W
MW
Rosenstierne
Louise W
LW
Gaarn
Annika
A
Bagge
Lykke
L
Pedersen
Christina M
CM
Dahmcke
Jens H
JH
Nielsen
Louise T
LT
Dalgaard
D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D001665:Binding Sites; D015152:Blotting, Northern; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D053858:Metabolic Networks and Pathways / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010179:Pancreas / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D034443:RNA Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D051780:Sterol Regulatory Element Binding Protein 1 / Q000235:genetics / Q000378:metabolism
D035683:MicroRNAs; D012333:RNA, Messenger; C497389:Srebf1 protein, rat; D051780:Sterol Regulatory Element Binding Protein 1; C546082:mirn21 microRNA, rat; D002784:Cholesterol