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Embryonic and uterine expression patterns of peptidylglycine alpha-amidating monooxygenase transcripts suggest a
1Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway 08854, USA.
Insights
Peptidylglycine alpha-amidating monooxygenase (PAM) is crucial for peptide processing. Its widespread gene expression and cell-specific alternative splicing during development suggest a significant role in various developmental processes.
Area of Science:
- Developmental Biology
- Molecular Biology
- Biochemistry
Background:
- Posttranslational processing of peptide precursors often involves COOH-terminal amidation.
- This process is catalyzed by the bifunctional enzyme peptidylglycine alpha-amidating monooxygenase (PAM).
Purpose of the Study:
- To investigate the developmental expression patterns of PAM.
- To determine the specific PAM transcript isoforms expressed during embryonic development.
- To explore the functional implications of PAM expression and splicing in development.
Main Methods:
- In situ hybridization was used to examine PAM gene expression patterns.
- Probes distinguishing major PAM transcript subsets were employed to analyze alternative splicing.
- Expression analysis was conducted across various embryonic tissues and developmental stages.
Main Results:
- PAM gene expression was detected early in development in the cardiogenic region, uterine endometrium, and myometrial smooth muscle.
- Complex PAM expression patterns were observed in the central nervous system (CNS), with initial neuronal expression at embryonic day 13.
- Integral membrane PAM isoforms predominated in most developing cell types, while soluble isoforms were largely absent in specific CNS regions.
- High PAM expression was also noted in non-neural tissues like limb mesoderm and mesenchyme adjacent to fusing epithelia.
Conclusions:
- PAM exhibits widespread expression and cell-type-specific alternative splicing during development.
- The differential expression of PAM isoforms suggests region-specific amidation of substrates.
- This process may significantly contribute to various critical developmental events.
Abstract:
Posttranslational processing of peptide precursors frequently includes COOH-terminal amidation by the bifunctional enzyme peptidylglycine alpha-amidating monooxygenase (PAM). We examined the ontogeny of PAM gene expression using in situ hybridization and detected expression in the cardiogenic region beginning at embryonic day 9 (e9) and in decidualizing uterine endometrium and myometrial smooth muscle at even earlier postimplantation stages. PAM expression in the CNS at e10 was highest in the dorsal spinal cord and floor plate and exhibited complex patterning in several CNS regions, including the ventricular zone, over the next several days with PAM expression first detected in neurons at e13. High levels of PAM expression characterized several nonneural cell populations as well, including limb mesoderm and the mesenchyme immediately adjacent to nasal, maxillary, palatal, and dental epithelia during tissue fusion and remodeling. Since alternative splicing generates PAM transcripts encoding proproteins that are differentially localized and processed, we used probes that distinguish major subsets of PAM transcripts to determine that transcripts encoding integral membrane PAM isoforms predominate in most, if not all, PAM-expressing cell types throughout development. Further, transcripts that encode soluble and cleavable PAM isoforms are essentially absent from two CNS areas that are rich in transcripts encoding integral membrane, bifunctional PAM: the ependymal region of the spinal cord and the ventricular zone of the hippocampus. These results provide evidence for widespread expression and cell-type-specific alternative splicing of PAM during development and raise the possibility that region-specific amidation of PAM substrates contributes significantly to several developmental processes.