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SMN1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

SMN1 gene

The SMN1 gene provides instructions for making the survival motor neuron (SMN) protein, which is essential for the maintenance and function of specialized nerve cells called motor neurons.

Normal Function

The SMN1 gene provides instructions for making the survival motor neuron (SMN) protein. This protein is found throughout the body, with highest levels in the spinal cord. It is part of a group of proteins called the SMN complex, which is critical for the maintenance of motor neurons. These cells, located in the spinal cord and brainstem, transmit signals that tell skeletal muscles to contract, allowing for body movement.

Within cells, the SMN complex plays a vital role in processing messenger RNA (mRNA), the genetic blueprints for proteins. The complex helps assemble the cellular machinery needed to convert rough pre-mRNA into mature, functional forms. Additionally, the SMN complex supports the development of dendrites and axons, which are specialized outgrowths from nerve cells required for transmitting impulses between neurons and to muscles.

A similar gene, SMN2, produces a small amount of SMN protein. However, only one version of the protein produced by SMN2 is functional; other versions are smaller and quickly broken down.

Health Conditions Related to Genetic Changes

Amyotrophic lateral sclerosis

MedlinePlus Genetics provides information about Amyotrophic lateral sclerosis.

Spinal muscular atrophy

Many mutations in the SMN1 gene cause spinal muscular atrophy, a condition characterized by the loss of motor neurons, leading to progressive weakness and wasting (atrophy) of skeletal muscles. About 95 percent of individuals with this disorder have mutations that delete a piece of the SMN1 gene in both copies of the gene in each cell, impairing SMN protein production. In the remaining 5 percent, one copy of the gene is missing a section, while the other has a different mutation disrupting protein function.

  • Cellular impact: A shortage of SMN protein leads to inefficient assembly of pre-mRNA processing machinery. This lack of mature mRNA and necessary proteins damages motor neuron development and survival.
  • Variable severity: The number of SMN2 gene copies varies among individuals. Multiple copies of SMN2 are usually associated with less severe, later-onset features because the small amount of SMN protein produced by these genes can help compensate for the SMN1 deficiency.

Other Names for This Gene

  • BCD541
  • SMA1
  • SMA2
  • SMA3
  • SMA4
  • SMN_HUMAN
  • SMNT
  • T-BCD541
  • telomeric SMN

Frequently Asked Questions

Being a carrier means you have one normal copy and one mutated copy of the SMN1 gene. You typically do not have symptoms of spinal muscular atrophy (SMA). If both parents are carriers, there is a 25% chance with each pregnancy that their child will inherit two mutated copies of the SMN1 gene and develop SMA, a 50% chance the child will be a carrier, and a 25% chance the child will inherit two normal copies.
mutation in the SMN1 gene means the body cannot make enough of the survival motor neuron (SMN) protein. This protein is crucial for the health and function of motor neurons, which are nerve cells that send signals from the brain and spinal cord to muscles. Without enough SMN protein, motor neurons degenerate and die, leading to progressive muscle weakness and wasting, which are the hallmarks of SMA.
The SMN2 gene is very similar to SMN1 and can produce some SMN protein, but most of it is a shorter, less functional version. However, the number of SMN2 gene copies a person has can influence the severity of spinal muscular atrophy (SMA). More copies of SMN2 can lead to more functional SMN protein being produced, which may result in milder symptoms or a later onset of the disease.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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