The CALR gene gives cells instructions for calreticulin, a protein that helps fold newly made proteins and balance calcium inside the cell. If it does not work properly, cells may manage proteins less effectively, and blood-forming cells can start growing in abnormal ways. This gene plays an important role in the bone marrow, where certain acquired CALR variants are linked to essential thrombocythemia and primary myelofibrosis. These variants help doctors classify some blood conditions, rather than predict exactly how a person will feel.
What is a gene?
A gene is a stretch of DNA that carries instructions your cells use to make molecules or regulate activities in the body. Some genes hold the directions for producing proteins, the parts of cells that do much of the work. Others mainly help determine when certain processes happen, where they happen, and how strongly they run. Taken together, genes affect how the body develops and functions, and they can influence how you respond to food, stress, or medications. For a more detailed look at this topic, you can read more in the LearnHub.
Overview
CALRGene function
What if the gene works
The CALR gene helps cells fold newly made proteins and manage calcium inside the endoplasmic reticulum, the cell’s protein processing area. These routine jobs support stable cell signaling and everyday cell function.
Risk
What if the gene does not work
Some bone marrow variants in the CALR gene are linked to essential thrombocythemia and primary myelofibrosis. Milder and more severe variants can affect signaling differently, which may influence when disease appears and how marked blood count changes are.
Treatment
What does that mean for your treatment
No CALR-specific treatment or management approach is currently established in clinical guidelines. Mutant CALR is being studied as a treatment target and biomarker in myeloproliferative cancers, including vaccine-based and other immune-based approaches.
Conditions associated with CALR
Gene function
What if the gene works
Inside many cells, the CALR gene supports two steady housekeeping jobs: helping new proteins take shape and helping control calcium inside a cell compartment called the endoplasmic reticulum. These routines matter because proteins need the right shape and cells need stable calcium signals. Understanding what the CALR gene does in your cells helps show how everyday cell work stays organized.
The CALR gene helps newly made proteins fold into the right shape inside the endoplasmic reticulum, a cell compartment that processes proteins. This support helps proteins become ready for their usual jobs.
Through its protein, the CALR gene helps cells inspect certain sugar-tagged proteins as they are being made. It keeps them in the endoplasmic reticulum until they are properly prepared to move on.
The CALR gene also helps store and buffer calcium inside the endoplasmic reticulum. This gives cells a steady reserve they can use for signaling, protein processing, and other routine tasks.
What is a variant?
A genetic variant is a small alteration in the DNA sequence of a gene. These changes are common and help account for normal human diversity, including differences in appearance, metabolism, or how the body responds to environmental influences. Many variants do not have any noticeable effect and simply represent natural genetic variation. In some cases, though, a variant can change a gene’s function more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Most CALR gene variants linked to disease are exon 9 frameshift variants that replace the protein’s normal tail with an abnormal one. This often removes the signal that keeps it in the right part of the cell and changes its charge, so the altered protein can bind abnormally to the MPL receptor and keep growth signaling switched on. Different CALR exon 9 variants can disrupt the tail to different degrees, which may shape how strongly this signaling is altered.
How variants are linked to conditions
Variants in the CALR gene are most clearly linked to essential thrombocythemia and primary myelofibrosis, two blood conditions in which the bone marrow makes blood cells in an unbalanced way. These CALR gene variants are usually acquired in blood-forming cells during life rather than inherited from a parent. Some people carrying this gene change have a different pattern of blood counts and disease course than people with other gene variants, but it does not define exactly how the condition will affect one person.
A variant is not necessarily a diagnosis
Genetic variants are common in the general population and are a normal feature of human biology. Most do not have a direct effect on health and simply reflect natural human diversity. For many genes, carrying a variant associated with a condition indicates a possible link rather than a definite diagnosis, especially when several genes and environmental factors contribute. In some situations, though, a single well understood variant in a specific gene can be enough to confirm a diagnosis.
Are there things that can increase or change my risk?
There is not yet broadly confirmed evidence on specific lifestyle or environmental factors that clearly increase or reduce risk related to CALR. Most CALR changes linked to blood conditions happen during life in bone marrow cells rather than being inherited, so personal risk is usually not something people can estimate from family history alone.
Inheritance of CALR variants
For most health conditions linked to the CALR gene, there is not a broadly confirmed inherited pattern in families. Many well-known CALR gene changes are found only in blood-forming cells during a person’s lifetime rather than being passed from a parent, which is an important part of understanding how CALR variants are inherited. The CALR gene is located on chromosome 19, which is an autosome, so you inherit one copy from each parent.
What does my CALR result mean for my family?
There is not a broadly confirmed inherited pattern tied to CALR for most people. Many CALR changes linked to blood conditions happen during life in blood-forming cells rather than being passed down in a family, so they usually do not mean close relatives carry the same change. If you have a specific CALR result, its meaning for family members depends on whether it was found as an acquired change or as part of inherited testing.
Genetic information
Genetic testing
How you find out about variants
If you have unexplained high platelets, CALR genetic testing is usually done on a blood sample. A lab analyzes the CALR gene, often focusing on exon 9, to look for acquired variants such as insertions or deletions. Results can help doctors classify certain bone marrow conditions.
When should I consider getting a genetic test?
CALR testing may be considered when blood tests keep showing very high platelets or there are signs of certain blood-forming bone marrow conditions, such as unexplained clotting, bleeding, or an enlarged spleen. These CALR changes are usually acquired during life rather than inherited, so testing is most often used to help explain a current blood problem.
A genetic result is only one part of your health story
A genetic finding can provide useful information, but how much it reveals depends on the condition and the type of variant involved. Many factors, including lifestyle, environment, age, and medical history, shape how the body works over time. For some conditions, especially those influenced by many genes, genetic information offers context rather than certainty and is best understood together with other parts of care. In other situations, a genetic result can give a clear answer. In areas such as medication response, it can also help place individual experiences in context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how your body responds to medicines. Some people break down a drug more slowly or more quickly, while others may be more or less sensitive to its effects. This helps explain why the same treatment can work well for one person, have less benefit for another, or cause more side effects in someone else. These differences are common and are one part of how clinicians understand medication response.
What is Pharmacogenetics?
Pharmacogenetics examines how inherited genetic differences can affect the way someone responds to a medication. It focuses on links between genes and drugs to help explain why the same treatment may work differently in different people. With many medicines, genes can influence how powerful a drug’s effects are or how the body handles it. This information can help guide more informed, individualized treatment decisions. More detailed information on this topic is available in the LearnHub.
Drugs influenced by the CALR gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medication choice or dose, so questions about medicines or side effects are best discussed with your doctor. In people with CALR-related blood conditions, researchers have studied whether CALR changes may relate to response to some treatments, but this is not yet a standard part of routine prescribing.
History
The CALR gene entered medical genetics in a major way when researchers identified recurrent variants in 2013 in people with certain blood conditions, especially essential thrombocythemia and primary myelofibrosis. This discovery helped explain many cases that had not been accounted for by earlier findings in the JAK2 and MPL genes. From these first observations, research expanded steadily. Scientists soon recognized that CALR variants were especially important in people whose test results were negative for those other common gene changes. That finding changed diagnostic practice and sharpened how these conditions were classified. In recent years, CALR has remained an important part of research on blood cancers and how inherited versus acquired gene changes are interpreted in clinical care.