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MASP1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

MASP1 Gene

The MASP1 gene provides instructions for proteins involved in the lectin complement pathway, a process critical for cell migration during development and immune function after birth.

Normal Function

The MASP1 gene produces proteins that participate in the lectin complement pathway. This pathway is believed to direct the movement (migration) of cells during prenatal development to form the body's organs and systems. It is particularly important for directing the migration of neural crest cells, which give rise to various tissues, including:

  • Many tissues in the face and skull
  • Endocrine glands (glands that produce hormones)
  • Portions of the nervous system

After birth, the lectin complement pathway plays a role in the immune system.

Protein Variants

Depending on how the gene's instructions are assembled, the MASP1 gene can produce three different proteins: MASP-1, MASP-3, and MAp44. These proteins differ at one end of their structure:

  • MASP-1 and MASP-3 have different versions of regions called serine protease domains.
  • MAp44 has no serine protease domain.

Researchers are currently studying whether these distinct proteins play different roles within the lectin complement pathway.

Health Conditions Related to Genetic Changes

3MC Syndrome

At least 11 mutations in the MASP1 gene have been identified in individuals with 3MC syndrome. This disorder is characterized by unusual facial features and a variety of problems affecting other tissues and organs.

All identified MASP1 mutations that cause 3MC syndrome affect the MASP-3 protein. Consequently, alterations in MASP-3 function are thought to account for the signs and symptoms of the syndrome. Because parts of the three protein versions are identical, some MASP1 mutations also affect the other protein versions in addition to MASP-3.

These protein changes result in faulty control of cell migration during early development, leading to the abnormalities seen in this disorder. Researchers suggest that similar pathways in the immune system can compensate for issues in the lectin complement pathway, which explains why immune system abnormalities are not a feature of 3MC syndrome.

Other Names for This Gene

  • 3MC1
  • complement factor MASP-3
  • complement-activating component of Ra-reactive factor
  • CRARF
  • CRARF1
  • mannan-binding lectin serine peptidase 1 (C4/C2 activating component of Ra-reactive factor)
  • mannose-binding lectin-associated serine protease 1
  • mannose-binding protein-associated serine protease
  • MAP1
  • MAp44
  • MASP
  • MASP3
  • PRSS5
  • Ra-reactive factor serine protease p100
  • RaRF
  • serine protease 5

Genomic Location

The MASP1 gene is located on chromosome 3.

Frequently Asked Questions

Diagnosis is based on a combination of clinical features—such as distinctive facial traits, growth delays, and organ involvement—and laboratory findings. Genetic confirmation is obtained through sequencing of the MASP1 gene, focusing on exons that encode MASP‑3. A targeted MASP1 panel or whole‑exome sequencing can detect pathogenic variants. Genetic counseling is advised for families.
Common features include a broad nasal bridge, micrognathia (small jaw), ear anomalies, and sometimes cleft palate. Skeletal abnormalities such as short stature and limb malformations may also appear. These traits are usually evident in infancy or early childhood, and early imaging or ENT evaluation can identify associated airway or feeding issues.
Management is multidisciplinary. Surgical correction may be needed for cleft palate, ear malformations, or skeletal deformities. Early intervention programs for speech, feeding, and developmental delays improve outcomes. Regular monitoring of hearing, vision, and endocrine function is essential. While no cure exists for the underlying genetic defect, supportive care and timely surgeries can significantly improve quality of life.===
MASP‑3 is a serine protease that activates complement components during the lectin pathway, which is essential for proper cell migration during embryonic development. Mutations that reduce or eliminate MASP‑3 activity disrupt the normal signaling that guides neural crest cells, leading to the characteristic facial and organ abnormalities seen in 3MC syndrome. The loss of MASP‑3 also impairs the regulation of inflammation, contributing to the syndrome’s clinical features.
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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