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SOS1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

SOS1 gene

The SOS1 gene provides instructions for making a protein that regulates the RAS/MAPK signaling pathway, which is essential for controlling cell growth, division, and embryonic development.

Normal Function

The SOS1 gene provides instructions for making a protein that is involved in controlling (regulating) the activation of the RAS/MAPK signaling pathway, which helps control several important cell functions. Specifically, the pathway regulates the growth and division of cells (proliferation), the process by which cells mature to carry out specific functions (differentiation), cell movement (migration), and the self-destruction of cells (apoptosis). Within the RAS/MAPK signaling pathway, the SOS1 protein regulates a protein, called Ras, that stimulates cells to grow and divide. This regulation tightly controls the growth of cells and tissues, and is especially important for proper embryonic development.

Health Conditions Related to Genetic Changes

Noonan syndrome

More than 55 mutations causing Noonan syndrome have been identified in the SOS1 gene. Noonan syndrome is characterized by mildly unusual facial characteristics, short stature, heart defects, bleeding problems, skeletal malformations, and many other signs and symptoms. The SOS1 gene mutations change single protein building blocks (amino acids) in the SOS1 protein. The resulting protein is either continuously turned on (active) or has prolonged activation, rather than promptly switching on and off in response to other cellular proteins. This increase in protein activity disrupts the regulation of the RAS/MAPK signaling pathway that controls cell functions such as growth and division. This misregulation can result in the heart defects, growth problems, skeletal abnormalities, and other features of Noonan syndrome.

Other disorders

Mutations in the SOS1 gene can also cause hereditary gingival fibromatosis type 1. This disorder is characterized by a slowly progressive overgrowth of the tissue of the gums (gingiva). Too much of this tissue can impair teeth from emerging through the gums, which can cause difficulties in speech and chewing food. At least one mutation in the SOS1 gene has been shown to cause hereditary gingival fibromatosis type 1. This mutation is an addition of a single building block of DNA (nucleotide). The mutation inserts the nucleotide cytosine into an area of the gene called exon 21 (written 3248_3249insC) and disrupts the gene's instructions, resulting in a shortened protein. Unlike the normal SOS1 protein, the shortened protein is permanently active because it is missing areas that regulate its activity. Instead of triggering cell growth in response to particular signals from outside the cell, the overactive protein directs cells to grow and divide constantly. It is unclear why the overgrowth of tissue is seen only in the gums.

Other Names for This Gene

  • alternate SOS1
  • GF1
  • GGF1
  • GINGF
  • gingival fibromatosis
  • gingival fibromatosis, hereditary, 1
  • HGF
  • son of sevenless homolog 1
  • son of sevenless homolog 1 (Drosophila)
  • SOS1_HUMAN

Frequently Asked Questions

Management of SOS1-related Noonan syndrome is focused on addressing specific symptoms. Heart defects, such as pulmonary valve stenosis, may require medication or surgical intervention. Growth hormone therapy can be considered for short stature. Bleeding problems are managed with appropriate precautions and sometimes medication. Other issues like feeding difficulties, developmental delays, or skeletal problems are managed by a multidisciplinary team of specialists, including cardiologists, endocrinologists, and developmental pediatricians.
Noonan syndrome caused by an SOS1 mutation is typically inherited in an autosomal dominant pattern. This means that if one parent carries the mutation, there is a 50% chance for each child to inherit the condition. However, some cases can arise from new (de novo) mutations in the affected individual, meaning neither parent carries the mutation. Genetic counseling can help families understand their specific risk and reproductive options.
Noonan syndrome due to an SOS1 gene mutation often presents with characteristic facial features, such as widely spaced eyes, downward-sloping eyelids, low-set ears that are rotated backward, and a short neck with excess skin folds. Other common signs include short stature, heart defects (especially pulmonary valve stenosis), bleeding problems, and skeletal abnormalities like a sunken or protruding chest. These features can vary in severity among individuals.
Diagnosis of Noonan syndrome is often suspected based on the characteristic physical features. To confirm the diagnosis and identify the specific genetic cause, genetic testing is performed. This involves analyzing a blood sample to look for mutations in genes known to cause Noonan syndrome, including the SOS1 gene. Genetic counseling is also an important part of the diagnostic process.
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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