Best Practices for Choosing an mRNA Library Prep Kit

Studying gene expression provides important insights into cellular processes and biological changes across different cells and tissues. One of the most powerful approaches for investigating gene expression is mRNA sequencing. This technique has improved dramatically over the last two decades, and recent advancements have led to mRNA library prep kits that streamline workflows and enhance data quality. In this article, we’ll discuss the latest innovations in mRNA library prep, review leading kits and their features, and provide guidance on selecting the best method for specific research needs.

mRNA library prep process

The details of library preparation vary between kits and sequencing platforms, but the process generally follows several key steps. After isolating RNA, one of the initial steps is mRNA enrichment or rRNA depletion, which selectively captures mRNA or removes unwanted rRNA. This is particularly important since mRNA constitutes only a small percentage of total RNA, whereas rRNA is the predominant RNA type in a cell.¹ The next critical step is reverse transcription, which converts mRNA into cDNA. Unlike Oxford Nanopore Technologies, which can sequence RNA directly, most sequencing platforms require this conversion for sequencing.

After cDNA synthesis, the library prep process continues with variations of adapter ligation, PCR amplification, and size selection. These steps prepare cDNA fragments for sequencing by adding platform- and sample-specific adapters, as well as enriching desired fragments.

Due to the complexity of the library preparation process, selecting the right kit is essential for obtaining reliable results. While sequencing instrument providers offer a range of library prep solutions, groups like New England Biolabs (NEB) and Watchmaker Genomics stand out for their expertise in enzyme engineering and molecular biology, enabling them to develop some of the most advanced mRNA library prep kits in the industry.

How to select a kit

Choosing an mRNA library preparation kit can be difficult due to numerous available options. However, there are several factors that researchers should consider to help them make the decision. “The first step of planning for your library prep involves knowing the origin of your sample; its treatment, handling, and storage; and determining the amount of your sample that will be allocated to the workflow and what will remain,” explained Deyra N. Rodriguez, Ph.D., M.B.A., NEBNext Product Marketing Manager at NEB.

Along with these sample considerations, Rodriguez noted that researchers should assess the quality of their isolated RNA, as low-quality RNA could impact the library prep protocol. RNA quality is typically measured using RIN (RNA integrity number) or DV200 (the percentage of fragments greater than 200 nucleotides). Rodriguez added that it’s also important to choose library prep kits that have proven to deliver optimal results for samples comparable in integrity and input.

Kristina Giorda, Ph.D., Associate Director, NGS Product Management at Watchmaker Genomics, explained that generating high-quality sequencing data is a top priority for researchers. “That means the first consideration should be choosing a workflow that meets their data needs, particularly one that maximizes library complexity and gene detection sensitivity,” Giorda stated. Library prep workflows that preserve the original RNA diversity enable researchers to detect the full range of genes, including those expressed at very low levels.

Another helpful strategy is to understand if automation will be used in the library prep workflow. Both experts recommend choosing automation-compatible kits that enhance consistency, reduce errors, and streamline workflows. Scientists should also search for kit options with automation support, minimal hands-on steps, and features like reagent overages to accommodate liquid handler dead volumes.

“One aspect that researchers may not always consider is whether a prep can adapt to their evolving needs,” shared Giorda. For instance, it's important to consider whether the prep can accommodate lower inputs or scale up as sample volumes increase. Giorda emphasized that future-proofing workflows allows researchers to adapt to evolving project needs while maintaining long-term flexibility and efficiency for on-going sequencing processes.

Regardless of experience level, Rodriguez also advised choosing kits from companies that prioritize customer support and ensure researchers can get help when needed. This includes support from dedicated technical scientists and comprehensive online resources to assist users.

Latest innovations

Between enzyme innovations, simplified workflows, and the integration of automation, library preps for mRNA sequencing have seen significant improvements. These developments have been driven by the work of various industry leaders to make mRNA library preps faster, more efficient, and cost-effective.

“The newest and most impactful kit and workflow advance for mRNA library prep from NEB is, without question, the NEBNext UltraExpress RNA Library Prep Kit when used in concert with the NEBNext Poly(A) mRNA Enrichment Kit’s Express protocol,” stated Rodriguez. With the "Express" protocol, researchers can perform mRNA enrichment and fast RNA library prep in only 3.5 hours, using diverse total RNA inputs. Additionally, it pairs well with NEB’s upstream rRNA depletion, making mRNA library preparation from total RNA possible within a day.

“Our mRNA library prep solution is designed to save researchers time, reducing workflow duration by up to three hours compared to other commercial kits,” emphasized Giorda. Watchmaker's prep features a specially engineered reverse transcriptase for RNA sequencing, along with workflow and chemistry optimizations to enhance efficiency. The prep produces strong performance across a wide input range, from as little as 2.5 ng of RNA for enhanced library complexity and gene detection, to as much as 1 µg for robust results.

Another important development is the increased focus on multi-omics integration, which combines transcriptomics with techniques like DNA sequencing or epigenetic analyses to offer deeper biological insights. Giorda highlighted Watchmaker Genomics' methylation analysis using TET-assisted pyridine borane sequencing (TAPS), noting that this approach enables researchers to study gene regulation and epigenetic modifications alongside transcriptomic data. From the NEB side, the recent launch of NEBNext Enzymatic Methyl-seq v2 highlights this focus as the new kit is compatible with samples down to 100 pg of input DNA and the technology has been implemented in a variety of multi-omic settings.

Looking ahead

“The future of mRNA library prep is moving toward faster, more efficient, and increasingly automated workflows to better support the growing demands of transcriptomics research,” said Giorda. She emphasized that ongoing advances in enzymes and reaction optimization will reduce bias, improve sensitivity, and enhance transcript coverage to ensure more reliable data from every experiment.

Rodriguez explained that future developments will also include minimizing hands-on steps, enhancing compatibility, and enabling researchers to conduct larger and more consistent studies. Innovations in reagent chemistry will simplify the handling of challenging samples, such as FFPE and liquid biopsies, while pushing input requirements lower without losing data quality.

Finally, as NGS data continues to grow in complexity and scale, user-friendly analysis tools will become essential for integrating techniques like bulk and single-cell RNA-seq, as well as spatial transcriptomics. “This integration will be critical for achieving a more holistic view of biological systems,” concluded Rodriguez.

Factors to consider when selecting an mRNA library prep

• Sample compatibility: Ensure the library prep is suitable for your input type, sample concentration, and RNA quality.
• Data quality: Select kits that have been validated for your application, generate high-quality data, and maximize gene detection sensitivity.
• Workflow efficiency: Find a prep that simplifies protocols, reduces hands-on time, and minimizes reagents.
• Future-proofing and scalability: Choose a workflow that is flexible for when research requires change.
• Automation readiness: Opt for automation-compatible kits and features like reagent overages to support liquid handlers.
• Technical support: Utilize kits where the manufacturer provides support, such as troubleshooting assistance and detailed resources.

Reference

1. Wu, J., Xiao, J., Zhang, Z., Wang, X., Hu, S., & Yu, J. (2014). Ribogenomics: the science and knowledge of RNA. Genomics, Proteomics and Bioinformatics, 12(2), 57-63.