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Differential display protocol with selected primers that preferentially isolates mRNAs of moderate- to low-abundance
1Worcester Foundation for Biomedical Research, Shrewsbury, MA, USA.
Abstract:
A modified reverse transcription polymerase chain reaction (RT-PCR)-based differential display procedure with selected primers (SPR) was developed to increase the bias toward isolating moderate- to low-abundance transcripts that are differentially expressed during synapse formation in a microscopic neuronal system, the embryonic chicken ciliary ganglion. Major modifications, in comparison with available arbitrarily primed RT-PCR protocols, include the use of (i) experimentally selected primer pairs (50% GC-rich 15-21-mers) that avoid the amplification of highly abundant ribosomal and mitochondrial transcripts; (ii) a higher PCR annealing temperature (50 degrees C instead of 40 degrees C); (iii) selection of sequencing gel bands that are dependent on the two primers for amplification; (iv) tests for reproducibility by SPR amplification of independent sets of RNA extractions and Southern blot analysis of the products with an isolated radiolabeled clone; and (v) quantitative RT-PCR, instead of Northern blot analysis, to confirm the differential expression of individual cDNAs. Thirty-six cDNAs were isolated and sequenced using SPR. None showed significant homology to highly abundant transcripts. In contrast, when no criterion for primer or band selection was applied, 22% of 55 cDNAs were identical to ribosomal and mitochondrial transcripts. Reproducible amplification of 9 out of 10 SPR-isolated cDNAs was established by Southern blot analysis. Differential expression was then confirmed for 4 selected sequences by quantitative RT-PCR. Thus, SPR is a reproducible and efficient procedure for identifying differentially regulated transcripts of moderate- to low-abundance in microscopic biological systems.
Insights
A new method, selected primer pair (SPR) reverse transcription polymerase chain reaction (RT-PCR), efficiently identifies low-abundance gene transcripts. This technique improves the study of gene expression in microscopic neuronal systems.
Area of Science:
- Molecular Biology
- Neuroscience
- Genomics
Background:
- Differential gene expression is crucial for understanding cellular development and function.
- Identifying low-abundance transcripts presents a significant technical challenge in gene expression studies.
- Existing arbitrarily primed RT-PCR methods often amplify abundant housekeeping genes, masking low-abundance targets.
Purpose of the Study:
- To develop a modified RT-PCR technique for enhanced isolation of moderate- to low-abundance differentially expressed transcripts.
- To improve the efficiency and reproducibility of differential display in microscopic biological systems.
- To identify novel genes involved in synapse formation in the embryonic chicken ciliary ganglion.
Main Methods:
- Development of a modified RT-PCR technique termed Selected Primer Pair (SPR).
- Utilized experimentally selected, GC-rich primer pairs to avoid amplification of highly abundant transcripts.
- Employed higher PCR annealing temperatures and specific band selection criteria.
- Validated reproducibility using Southern blot analysis and confirmed differential expression via quantitative RT-PCR.
Main Results:
- SPR successfully isolated 36 unique cDNAs, none homologous to highly abundant transcripts.
- Compared to standard methods, SPR significantly reduced the amplification of ribosomal and mitochondrial transcripts (0% vs. 22%).
- Reproducible amplification was confirmed for 90% of SPR-isolated cDNAs, with differential expression verified for 4 sequences.
Conclusions:
- SPR is a reproducible and efficient method for identifying differentially regulated transcripts of moderate- to low-abundance.
- This technique is particularly valuable for gene expression analysis in microscopic biological systems.
- SPR offers a significant improvement over traditional RT-PCR methods for discovering novel, low-abundance transcripts.