Understanding MPL Mutation in Myeloproliferative Neoplasms (MPNs)

Myeloproliferative neoplasms (MPNs), previously known as myeloproliferative disorders (MPDs), are a group of hematological diseases characterized by the excessive production of blood cells—red blood cells, white blood cells, or platelets—originating in the bone marrow. These disorders are commonly associated with genetic mutations that dysregulate tyrosine kinases, causing uncontrolled cell proliferation and survival.

MPNs are generally divided into two categories based on the presence or absence of the Philadelphia chromosome (BCR-ABL1 translocation). Philadelphia-positive MPNs include chronic myeloid leukemia (CML), whereas Philadelphia-negative MPNs include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). While CML is driven by the BCR-ABL1 fusion gene, Philadelphia-negative MPNs are often associated with mutations in genes such as JAK2, MPL, PDGFRA, PDGFRB, FGFR1, and KIT.

Role of MPL in MPN Pathogenesis

The MPL gene, located on chromosome 1p34, encodes the thrombopoietin (TPO) receptor—critical for the proliferation and survival of megakaryocytes. Mutations in MPL, particularly in exon 10, lead to constitutive activation of the JAK-STAT signaling pathway, promoting unregulated cell growth. The W515L mutation is the most frequently observed MPL mutation in MPNs and has been extensively studied in JAK2 V617F-negative patients.

Other clinically relevant MPL mutations include:

• W515K: Substitution of tryptophan with lysine

• W515A: Substitution of tryptophan with alanine (via two known transitions)

• S505N: Substitution of serine with asparagine

Identifying these mutations is vital for accurate diagnosis, prognosis, and potential therapeutic decisions in MPN patients.

About the TRUPCR® MPL Mutation Qualitative Kit

The TRUPCR® MPL Mutation Qualitative Kit is designed to detect the four most relevant MPL mutations using real-time PCR technology. It uses mutation-specific primers and probes to identify W515L, W515K, W515A, and S505N mutations in separate reaction tubes.

Each reaction is labeled with a FAM dye for mutation detection, while an internal endogenous human control (labeled with VIC) is multiplexed in every tube to confirm the presence of amplifiable human DNA and detect PCR inhibition. This dual-target system increases assay reliability and minimizes false negatives.

Kit Principle

The kit operates on the principle of fluorescence-based real-time PCR. During amplification, specific oligonucleotide probes bind to their target DNA sequences. The probes contain a fluorescent dye on the 5’ end and a quencher on the 3’ end. When DNA polymerase extends the primers and encounters the probe, its 5’-3’ exonuclease activity cleaves the probe, separating the dye and quencher. This results in a measurable increase in fluorescence, proportional to the amount of target DNA present.

Compatibility & Workflow

The assay runs four parallel reactions—one for each MPL mutation. Each reaction mix includes both mutation-specific and internal control primers/probes. The test is compatible with most commonly used real-time PCR systems that support FAM and VIC channels. The protocol is simple, and all reagents required are supplied in the kit, reducing the chance of user error and improving workflow efficiency in diagnostic labs.

Clinical Application

The TRUPCR® MPL Mutation Qualitative Kit is intended for use by trained professionals in clinical laboratories. It serves as a diagnostic aid for identifying MPL mutations in suspected cases of myeloproliferative neoplasms. The results should always be interpreted in the context of clinical presentation, patient history, and other laboratory findings.