Finding Gene's mRNA Sequence from RNA Seq Data

April 11, 2025

Identifying gene mRNA from RNA-Seq data involves isolating and analyzing the messenger RNA sequences from RNA molecules. Messenger RNA (mRNA) carries the coding information necessary for protein synthesis, making it essential for understanding cellular function. 

However, extracting these sequences is very challenging because the RNA-Seq dataset contains a mix of different RNA types, such as ribosomal RNA (rRNA) and non-coding RNA (ncRNA), which need to be filtered out to focus on mRNA. Therefore, accurate mapping and assembly methods are critical for aligning RNA fragments to a reference genome and reconstructing complete mRNA sequences. 

These precise techniques enable researchers to gain accurate insights into gene expression and regulation. Let's explore this concept briefly and understand how to find an RNA sequence, the full procedure, techniques, methods, and more.  

How to Find a Gene mRNA from RNA Seq Data?

How to Find a Gene mRNA from RNA Seq Data?

Source: Pixabay

Before we dive into how to find a gene's mRNA from RNA seq data, let's explore why RNA sequencing was developed. RNA sequencing was designed to determine which genomic regions are active in a cell population at a specific time.

Compared to traditional methods, RNA-seq can even detect lowly expressed transcripts while reducing false positives. Moreover, RNA-seq isn't just about measuring mRNA levels between conditions. It can also uncover non-coding RNAs, splice isoforms, novel transcripts, and protein-RNA interaction sites.  

As you understand the goal of this technology development, it is also crucial to know how to find an RNA sequence from RNA sequence data.

To find a gene's mRNA from RNA-Seq data, the process typically follows these steps:

How to Find a Gene mRNA from RNA Seq Data?
  1. Quality Control: Use specialized tools to check the quality of the raw sequencing reads.
  2. Read Alignment: Align these reads to a reference genome using alignment tools.
  3. Transcript Quantification: Quantify the transcripts to confirm they match the investigated gene.

The above gives a general idea of how to find a gene's mRNA from RNA-seq data. Now, let's explore the topic in more detail. This comprehensive guide is divided into clear sections for easy understanding.  

Data Access and Preparation

Data Access and Preparation

Source: NIH

The first step in finding a gene's mRNA sequence from RNA-Seq data is data preparation, including file management and preprocessing. The raw sequencing data—FASTQ, VCF, and BAM files—must be properly organized before analysis.

Preparing Input Data

  • FASTQ Files: Contain nucleotide sequences and quality scores.
  • Quality Control: Use tools like FastQC to assess sequence quality and detect adapter contamination.
  • Trimming & Cleaning: Remove low-quality bases to improve mapping accuracy.

At this stage, the RNA-Seq data is prepared, enabling further analysis. The next step is utilizing K-mer matching for quality control.

Utilizing K-mer Matching for Quality Control

K-mer matching is a fundamental step in RNA-Seq data analysis because it helps filter, classify, and assemble sequencing reads with high accuracy. It is essential for preprocessing the data and improving the quality of RNA-Seq reads. K-mer matching improves mapping accuracy.

Employing Tools Like BBDuk for K-mer Matching

BBDuk (BBMap's Deduper and K-mer Remover) is widely used for preprocessing sequencing reads. BBDuk is mainly used to clean up and remove contaminants and low-quality sequences.  

  1. Remove Contaminants: Eliminates adapter sequences, ribosomal RNA (rRNA), and other unwanted fragments.
  2. Filter Low-Quality Reads: Ensures high-quality bases remain for more accurate mapping and quantification.
  3. Enhance Downstream Analysis: Improves the efficiency of transcriptome assembly and gene expression quantification by providing cleaner data.

Although K-mer matching does not directly identify mRNA sequences, it is essential in generating high-quality sequencing reads that improve the accuracy of RNA-Seq analysis.

Mapping RNA Seq Reads

Mapping RNA-Seq is an essential step in RNA-Seq analysis. This process uses specialized mapping algorithms capable of handling splicing events. Outputs are often converted to formats like BAM (Binary Alignment Map) and BED (Browser Extensible Data) for further analysis.

Key Considerations in RNA-Seq Read Mapping

  • Challenges Due to Splicing: Since RNA-Seq reads originate from different parts of genes due to splicing, aligners must handle discontinuous alignments.
  • Splice-Aware Mapping Tools: Use STAR, HISAT2, or Salmon for highly accurate transcriptome alignment and expression quantification.
  • Reference Genome Quality: A well-annotated genome ensures accurate mapping and transcript identification.

Mapping and Format Conversion

Once the reads are aligned, they undergo post-processing, which includes filtering low-quality or ambiguous reads and converting data formats for analysis.

  • SAM/BAM Formats: Use SAMtools to convert the alignment file from SAM to BAM for efficient processing.
  • BED Format (Optional): Convert the BAM file to a BED format for easier visualization in genome browsers.

Expression Analysis

After mapping, the next steps include detecting splice junctions, quantifying gene expression, and performing differential expression analysis:

  • Splice Junction Detection: Detect known and novel splice sites using splice-aware aligners.
  • Gene Expression Quantification: Count aligned reads per gene to estimate transcript abundance.
  • Differential Expression: Use tools like DESeq2 or edgeR to compare gene expression levels between samples.

Variant Calling (VCF Generation): Relevant If The Goal Is To Identify Transcript-Specific Mutations

  • Detecting Variants: Tools like GATK HaplotypeCaller analyze BAM files to detect SNPs (single nucleotide polymorphisms) and INDELs (insertions/deletions), generating a VCF (Variant Call Format) file.
  • Filtering Variants: Apply allele depth, quality score, and frequency thresholds to remove low-quality variants.
  • Base Quality Recalibration: Optional but recommended for improving variant detection accuracy.

After mapping, the next step is de novo assembly. This approach builds transcripts directly from your RNA-Seq reads without needing a reference genome. Let's explore it below.

De Novo Transcriptome Assembly (Essential Only If No Reference Exists)

You might wonder why this "de novo transcriptome assembly" is included in this procedure. It is an essential step when studying organisms without a reference genome. De novo transcriptome assembly does not rely on a preexisting reference genome, essentially building the transcript sequences "from scratch" using only the information present in the RNA reads themselves.  

1. Key Points About De Novo Assembly

  • No Reference Genome Needed: De novo assembly doesn’t rely on a pre-existing reference genome. Instead, it uses algorithms to identify overlapping RNA-Seq reads and assemble them into contigs (transcript sequences).
  • Applications: Useful for studying non-model organisms, discovering novel transcripts, and exploring alternative splicing patterns.

2. Steps in De Novo Transcriptome Assembly

  • Experimental Design: Start with high-quality RNA and determine the appropriate sequencing depth and platform.
  • Data Processing: Clean up low-quality reads and contaminants.
  • Assembly: Use tools like Trinity, SOAPdenovo-Trans, or rnaSPAdes to assemble the reads into transcripts.
  • Annotation: Use tools like BUSCO and databases like BLAST for assembly validation and functional annotation.

Challenges

These challenges are highlighted to help you anticipate and mitigate potential issues in de novo transcriptome assembly. 

  • Assembly complexity: Without a reference, de novo assembly can be computationally intensive and prone to errors, particularly with short reads or highly complex transcriptomes with many splice variants. 
  • Annotation difficulty: Once assembled, the transcripts must be annotated by comparing them to known protein sequences or using homology searches to assign functional information. This paper compares reference-guided vs. de novo transcriptome assembly.

As you have uncovered the importance of de nova transcript assembly, now you’ll explore gene sequence quantification, which is also a critical step in finding a gene’s mRNA. 

Gene Sequence Quantification

Gene Sequence Quantification

Gene sequence quantification is critical in RNA-Seq analysis. It helps determine the abundance of mRNA transcripts in a given sample, which is necessary to identify and analyze a gene’s mRNA sequence accurately.

Gene sequence quantification involves aligning reads to a reference genome and counting the number of reads that map to a gene or transcript. This can be done using alignment-based or alignment-free tools.

1. Alignment-Based Methods

Tools like HISAT2 and STAR align reads to a reference genome, after which the number of reads mapping to each gene is counted.

2. Alignment-Free Methods

Alignment-free methods, such as Salmon and Kallisto, directly estimate transcript abundance without the need for aligning reads to a genome.

As you have explored the gene sequence quantification below, you’ll explore the last step, advanced techniques used in mRNA identification. 

Advanced Techniques in mRNA Identification

Do you know? A real-world contribution of RNA-Seq and mRNA sequence analysis is the finding of HER2-positive breast cancer, which is a well-known oncogene located on chromosome 17 (17q12-21). It encodes a transmembrane receptor tyrosine kinase involved in cell growth and survival.  

You have explored almost all the major steps that need to be followed on how to find a gene RNA sequence from RNA sequencing data. Now, you have landed on the last step, which is an advanced technique that should be used in mRNA identification. This involves identifying which genes are upregulated or downregulated under different conditions. Several methods are used for this:

  • Differential Expression Analysis: Tools like DESeq2 or edgeR allow you to analyze differential expression, identifying genes whose expression levels differ significantly between two or more conditions.
  • Visualization: Visual tools like heatmaps, volcano plots, or PCA (Principal Component Analysis) can help interpret and visualize gene expression patterns, making it easier to identify key genes involved in the biological processes you’re studying.

As mentioned above, you explored the full procedure of finding mRNA sequences from RNA-Seq data. This offered you an understanding of how you can seamlessly incorporate this procedure to accomplish your research goals. Below, you’ll find the recap of the whole content.

Conclusion

Identifying mRNA sequences from RNA-Seq data involves critical steps, from data preparation and quality control to alignment and variant detection. Researchers can ensure trustworthy results by following effective strategies such as assessing raw sequence quality, using reliable alignment tools, and employing techniques like K-mer matching for accuracy.  

As RNA-Seq technologies evolve, it is essential to stay updated on the latest advancements in tools and techniques. The field is constantly growing, offering more efficient ways to handle complex datasets, improve alignment accuracy, and uncover new insights into gene regulation. 

This is why new emerging projects like Biostate.ai are great options if you want complete RNA sequencing done for any sample at an affordable cost. The team handles everything from sample collection to final insights. Get Your Quote Today!

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