Developmental regulation of elastin production. Expression of tropoelastin pre-mRNA persists after down-regulation of steady-state mRNA levels.
To assess the mechanisms controlling the developmental regulation of tropoelastin expression in vivo, we developed a reverse-transcription-polymerase chain reaction (RT-PCR) assay to detect tropoelastin pre-mRNA as an indicator of ongoing transcription in intact tissue. RNA was isolated from mid-fetal (early-elastogenic), neonatal (peak tropoelastin expression), and adult (very low tropoelastin expression) rat lungs and reverse transcribed, and the cDNA was amplified with intron specific primers. A weak hybridization signal for tropoelastin pre-mRNA was seen in mid-fetal samples, and paralleling the increase in steady-state mRNA levels, a strong signal for pre-mRNA was detected in neonatal samples, indicating transcriptional regulation. Stimulation of fetal lung tropoelastin expression by maternal administration of dexamethasone also led to an increase in pre-mRNA levels. However, signal for tropoelastin pre-mRNA in adult samples was equal to that detected in neonatal samples, even though mRNA levels had dropped about 80-fold. Persistence of tropoelastin transcription in adult tissue was also seen in cell culture models and was verified by nuclear runoff assay. In addition, an RT-PCR assay for alpha 1 (I) procollagen pre-mRNA accurately revealed the known transcriptional regulation of this gene. Our results demonstrate that the induction and maintenance of elastogenesis is controlled by a transcriptional mechanism, whereas, the cessation of tropoelastin expression is controlled by a post-transcriptional mechanism.
Swee
M H
MH
Department of Medicine (Dermatology), Jewish Hospital, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Parks
W C
WC
Pierce
R A
RA
D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D017931:DNA Primers; D004549:Elastin / Q000096:biosynthesis*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D008168:Lung / Q000254:growth & development / Q000378:metabolism*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011347:Procollagen / Q000096:biosynthesis*; D012322:RNA Precursors / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014333:Tropoelastin / Q000096:biosynthesis*
D017931:DNA Primers; D011347:Procollagen; D012322:RNA Precursors; D012333:RNA, Messenger; D014333:Tropoelastin; D004549:Elastin