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SMAD3 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

SMAD3 gene

The SMAD3 gene provides instructions for a protein that transmits signals from the cell surface to the nucleus, playing a vital role in cell growth, movement, and apoptosis.

Normal Function

The SMAD3 gene provides instructions for making a protein that is a key component of the transforming growth factor-beta (TGF-β) signaling pathway. This pathway allows the environment outside the cell to influence internal cell functions. When TGF-β binds to a cell surface receptor, it activates SMAD proteins, including SMAD3, which combine to form a complex that moves to the cell nucleus. Once in the nucleus, this complex binds to DNA to regulate the activity of specific genes, influencing processes such as:

  • Cell growth and division (proliferation)
  • Cell movement (migration)
  • Controlled cell death (apoptosis)

Health Conditions Related to Genetic Changes

Loeys-Dietz syndrome

At least 35 mutations in the SMAD3 gene have been linked to Loeys-Dietz syndrome type III. This disorder affects connective tissue, which provides structure and support to blood vessels, the skeleton, and other body parts. Symptoms include:

  • Abnormal blood vessels
  • Skeletal and joint deformities
  • Skin abnormalities

These mutations lead to a nonfunctional SMAD3 protein. Paradoxically, this results in an overactive TGF-β pathway, likely due to compensatory mechanisms by other proteins. This overactive signaling leads to dysregulated cell proliferation and gene activation, causing the abnormalities associated with the syndrome.

Familial thoracic aortic aneurysm and dissection

Mutations in the SMAD3 gene are also associated with familial thoracic aortic aneurysm and dissection, a condition involving the weakening and potential tearing of the large blood vessel that carries blood from the heart to the rest of the body.

Other Names for This Gene

  • hMAD-3
  • hSMAD3
  • JV15-2
  • MAD homolog 3
  • MAD, mothers against decapentaplegic homolog 3
  • mad3
  • MADH3
  • mothers against decapentaplegic homolog 3
  • SMAD, mothers against DPP homolog 3
  • SMAD3_HUMAN

Frequently Asked Questions

Most experts recommend a baseline MRI or CT angiogram at diagnosis, followed by repeat imaging every 6‑12 months if the aorta is >4.0 cm or shows rapid growth (>0.5 cm/year). If the aorta is stable and <4.0 cm, annual imaging is usually sufficient, but the interval may be shortened based on family history or symptoms.
Several trials are evaluating TGF‑β antagonists (e.g., fresolimumab) and angiotensin‑II receptor blockers (losartan, irbesartan) for their ability to slow aortic dilation in Loeys‑Dietz and related syndromes. Patients can search clinicaltrials.gov for “SMAD3” or “Loeys‑Dietz” and discuss eligibility with their geneticist or cardiovascular specialist.
High‑impact sports, heavy weight lifting, and activities that cause sudden spikes in blood pressure (e.g., competitive sprinting) are generally discouraged because they can accelerate aortic stress. Non‑steroidal anti‑inflammatory drugs (NSAIDs) and certain stimulants may also raise blood pressure; discuss any new medication with a cardiologist familiar with connective‑tissue disorders.
Patients often present with aortic root dilation detectable on echocardiogram, arterial tortuosity, or a family history of aortic dissection. Other clues include joint hypermobility, bifid uvula or cleft palate, and skin striae. Routine blood pressure checks and a physical exam for a wide pulse pressure can help catch early changes.
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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