Context
Recently, scientists and researchers from various global institutes have reported that Extracellular RNA (ExRNA) derived from bacteria can surprisingly persist in disinfected drinking water, challenging the long-held belief that RNA is too fragile to survive outside a cellular environment for extended periods.
What is Extracellular RNA (ExRNA)?
Extracellular RNA refers to RNA molecules that exist outside the cells in which they were originally transcribed. While traditional biology focused on RNA’s role within the cell (Protein synthesis), ExRNA represents a paradigm shift in understanding intercellular communication.
- Presence in Body Fluids: It is found in almost all biological fluids, including blood (plasma/serum), saliva, urine, breast milk, and cerebrospinal fluid.
- Types of RNA involved: ExRNA is a heterogeneous population consisting of both coding RNA (mRNA) and non-coding RNA (miRNA, siRNA, lncRNA, and tRNA).
- Stability Mechanism: Since the extracellular environment is rich in RNases (enzymes that degrade RNA), ExRNA survives by traveling in “molecular containers.” These include:
- Extracellular Vesicles (EVs): Such as exosomes and microvesicles (lipid-bilayer enclosed).
- Lipoprotein Particles: Such as High-Density Lipoprotein (HDL).
- Protein Complexes: Binding with proteins like Argonaute2 (Ago2) which shield them from degradation.
Functions and Significance
- Intercellular Communication: ExRNA acts as a “long-distance” signaling messenger. Cells release ExRNA to deliver genetic instructions to recipient cells, thereby influencing their behavior, gene activation, and protein translation.
- Immune Response: It helps coordinate the body’s response to infections, tissue repair, and general development.
- Disease Biomarker: Because ExRNA patterns change during illness, they serve as “liquid biopsies.” They are being researched for the early detection of cancer, heart disease, and neurodegenerative disorders without the need for invasive tissue biopsies.
- Therapeutic Potential: Start-ups and research centers (like those collaborating with the University of Hyderabad) are exploring ExRNA to develop novel therapeutic agents for both communicable and non-communicable diseases.
Q1. With reference to Extracellular RNA (ExRNA), consider the following statements:
1. It refers to RNA molecules that remain stable outside the cell by being enclosed in lipid-based molecular containers.
2. ExRNA is exclusively composed of messenger RNA (mRNA) and does not include non-coding RNA varieties.
3. It can act as a signaling medium to mediate communication between distant cells in the human body.
Which of the statements given above is/are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2, and 3
Answer: (c)
Solution:
• STATEMENT 1 IS CORRECT: ExRNA survives in the extracellular milieu because it is protected by molecular containers like extracellular vesicles (exosomes) or lipoproteins that prevent enzymatic degradation.
• STATEMENT 2 IS INCORRECT: ExRNA is a heterogeneous population. It includes not only coding RNA (mRNA) but also various non-coding RNAs such as microRNA (miRNA), small interfering RNA (siRNA), and long non-coding RNA (lncRNA).
• STATEMENT 3 IS CORRECT: One of the primary biological functions of ExRNA is to serve as a sophisticated long-distance communication system, allowing donor cells to influence the gene expression of recipient cells.
