Tyrosine-protein kinase that acts as a cell-surface receptor for fibroblast growth factors and plays an essential role in the regulation of cell proliferation, differentiation, migration and apoptosis, and in the regulation of embryonic development. Required for normal embryonic patterning, trophoblast function, limb bud development, lung morphogenesis, osteogenesis and skin development. Plays an essential role in the regulation of osteoblast differentiation, proliferation and apoptosis, and is required for normal skeleton development.

Promotes cell proliferation in keratinocytes and immature osteoblasts, but promotes apoptosis in differentiated osteoblasts. Phosphorylates PLCG1, FRS2 and PAK4. Ligand binding leads to the activation of several signaling cascades.

Activation of PLCG1 leads to the production of the cellular signaling molecules diacylglycerol and inositol 1,4,5-trisphosphate. Phosphorylation of FRS2 triggers recruitment of GRB2, GAB1, PIK3R1 and SOS1, and mediates activation of RAS, MAPK1/ERK2, MAPK3/ERK1 and the MAP kinase signaling pathway, as well as of the AKT1 signaling pathway. FGFR2 signaling is down-regulated by ubiquitination, internalization and degradation.

Mutations that lead to constitutive kinase activation or impair normal FGFR2 maturation, internalization and degradation lead to aberrant signaling. Over-expressed FGFR2 promotes activation of STAT1

Monomer. Homodimer after ligand binding. Interacts predominantly with FGF1 and FGF2, but can also interact with FGF3, FGF4, FGF6, FGF7, FGF8, FGF9, FGF10, FGF17, FGF18 and FGF22 (in vitro).

Ligand specificity is determined by tissue-specific expression of isoforms, and differences in the third Ig-like domain are crucial for ligand specificity. Isoform 1 has high affinity for FGF1 and FGF2, but low affinity for FGF7. Isoform 3 has high affinity for FGF1 and FGF7, and has much higher affinity for FGF7 than isoform 1 (in vitro).

Affinity for fibroblast growth factors (FGFs) is increased by heparan sulfate glycosaminoglycans that function as coreceptors. Likewise, KLB increases the affinity for FGF19 and FGF21. Interacts with PLCG1, GRB2 and PAK4.

Interacts with FLRT2 (By similarity)

The second and third Ig-like domains directly interact with fibroblast growth factors (FGF) and heparan sulfate proteoglycans. Alternative splicing events affecting the third Ig-like domain are crucial for ligand selectivity

• Crouzon syndrome (CS)

  An autosomal dominant syndrome characterized by craniosynostosis, hypertelorism, exophthalmos and external strabismus, parrot-beaked nose, short upper lip, hypoplastic maxilla, and a relative mandibular prognathism.

• Jackson-Weiss syndrome (JWS)

  An autosomal dominant craniosynostosis syndrome characterized by craniofacial abnormalities and abnormality of the feet: broad great toes with medial deviation and tarsal-metatarsal coalescence.

• Apert syndrome (APRS)

  A syndrome characterized by facio-cranio-synostosis, osseous and membranous syndactyly of the four extremities, and midface hypoplasia. The craniosynostosis is bicoronal and results in acrocephaly of brachysphenocephalic type. Syndactyly of the fingers and toes may be total (mitten hands and sock feet) or partial affecting the second, third, and fourth digits.

  Intellectual deficit is frequent and often severe, usually being associated with cerebral malformations.

• Pfeiffer syndrome (PS)

  A syndrome characterized by the association of craniosynostosis, broad and deviated thumbs and big toes, and partial syndactyly of the fingers and toes. Three subtypes are known: mild autosomal dominant form (type 1); cloverleaf skull, elbow ankylosis, early death, sporadic (type 2); craniosynostosis, early demise, sporadic (type 3).

• Beare-Stevenson cutis gyrata syndrome (BSTVS)

  An autosomal dominant disease characterized by craniofacial anomalies, particularly craniosynostosis, and ear defects, cutis gyrata, acanthosis nigricans, anogenital anomalies, skin tags, and prominent umbilical stump. The skin furrows have a corrugated appearance and are widespread. Cutis gyrata variably affects the scalp, forehead, face, preauricular area, neck, trunk, hands, and feet.

• Familial scaphocephaly syndrome (FSPC)

  An autosomal dominant craniosynostosis syndrome characterized by scaphocephaly, macrocephaly, hypertelorism, maxillary retrusion, and mild intellectual disability. Scaphocephaly is the most common of the craniosynostosis conditions and is characterized by a long, narrow head. It is due to premature fusion of the sagittal suture or from external deformation.

• Lacrimo-auriculo-dento-digital syndrome 1 (LADD1)

  A form of lacrimo-auriculo-dento-digital syndrome, an autosomal dominant disease characterized by aplastic/hypoplastic lacrimal and salivary glands and ducts, cup-shaped ears, hearing loss, hypodontia and enamel hypoplasia, and distal limb segments anomalies. In addition to these cardinal features, facial dysmorphism, malformations of the kidney and respiratory system and abnormal genitalia have been reported. Craniosynostosis and severe syndactyly are not observed.

• Antley-Bixler syndrome, without genital anomalies or disordered steroidogenesis (ABS2)

  A rare syndrome characterized by craniosynostosis, radiohumeral synostosis present from the perinatal period, midface hypoplasia, choanal stenosis or atresia, femoral bowing and multiple joint contractures. Arachnodactyly and/or camptodactyly have also been reported.

• Bent bone dysplasia syndrome 1 (BBDS1)

  A perinatal lethal skeletal dysplasia characterized by poor mineralization of the calvarium, craniosynostosis, dysmorphic facial features, prenatal teeth, hypoplastic pubis and clavicles, osteopenia, and bent long bones. Dysmorphic facial features included low-set ears, hypertelorism, midface hypoplasia, prematurely erupted fetal teeth, and micrognathia.

• Saethre-Chotzen syndrome (SCS)

  A craniosynostosis syndrome characterized by coronal synostosis, brachycephaly, low frontal hairline, facial asymmetry, hypertelorism, broad halluces, and clinodactyly.