Meta-Biol

• Pathways

Autosomal dominant mutations in FGFR2 are associated with the development of a range of skeletal disorders including Beare-Stevensen cutis gyrata syndrome, Pfeiffer syndrome, Jackson-Weiss syndrome, Crouzon syndrome and Apert Syndrome (reveiwed in Burke, 1998; Webster and Donoghue 1997; Cunningham, 2007). Mutations that give rise to Crouzon, Jackson-Weiss and Pfeiffer syndromes tend to cluster in the third Ig-like domain of the receptor, either in exon IIIa (shared by the IIIb and the IIIc isoforms) or in the FGFR2c-specific exon IIIc. These mutations frequently involve creation or removal of a cysteine residue, leading to the formation of an unpaired cysteine residue that is thought to promote intramolecular dimerization and thus constitutive, ligand-independent activation (reviewed in Burke, 1998; Webster and Donoghue, 1997; Cunningham, 2007). Mutations in FGFR2 that give rise to Apert Syndrome cluster to the highly conserved Pro-Ser dipeptide in the IgII-Ig III linker; mutations in the paralogous residues of FGFR1 and 3 give rise to Pfeiffer and Muenke syndromes, respectively (Muenke, 1994; Wilkie, 1995; Bellus, 1996). Development of Beare-Stevensen cutis gyrata is associated with mutations in the transmembrane-proximal region of the receptor (Przylepa, 1996), and similar mutations in FGFR3 are linked to the development of thanatophoric dysplasia I (Tavormina, 1995a). These mutations all affect FGFR2 signaling without altering the intrinsic kinase activity of the receptor.


Activating point mutations have also been identified in FGFR2 in ~15% of endometrial cancers, as well as to a lesser extent in ovarian and gastric cancers (Dutt, 2008; Pollock, 2007; Byron, 2010; Jang, 2001). These mutations are found largely in the extracellular region and in the kinase domain of the receptor, and parallel activating mutations seen in autosomal dominant disorders described above.


Activating mutations in FGFR2 are thought to contribute to receptor activation through diverse mechanisms, including constitutive ligand-independent dimerization (Robertson, 1998), expanded range and affinity for ligand (Ibrahimi, 2004b; Yu, 2000) and enhanced kinase activity (Byron, 2008; Chen, 2007).

Signaling processes are central to human physiology (e.g., Pires-da Silva & Sommer 2003), and their disruption by either germ-line and somatic mutation can lead to serious disease. Here, the molecular consequences of mutations affecting visual signal transduction and signaling by diverse growth factors are annotated.

Biological processes are captured in Reactome by identifying the molecules (DNA, RNA, protein, small molecules) involved in them and describing the details of their interactions. From this molecular viewpoint, human disease pathways have three mechanistic causes: the inclusion of microbially-expressed proteins, altered functions of human proteins, or changed expression levels of otherwise functionally normal human proteins.

The first group encompasses the infectious diseases such as influenza, tuberculosis and HIV infection. The second group involves human proteins modified either by a mutation or by an abnormal post-translational event that produces an aberrant protein with a novel function. Examples include somatic mutations of EGFR and FGFR (epidermal and fibroblast growth factor receptor) genes, which encode constitutively active receptors that signal even in the absence of their ligands, or the somatic mutation of IDH1 (isocitrate dehydrogenase 1) that leads to an enzyme active on 2-oxoglutarate rather than isocitrate, or the abnormal protein aggregations of amyloidosis which lead to diseases such as Alzheimer's.

Infectious diseases are represented in Reactome as microbial-human protein interactions and the consequent events. The existence of variant proteins and their association with disease-specific biological processes is represented by inclusion of the modified protein in a new or variant reaction, an extension to the 'normal' pathway. Diseases which result from proteins performing their normal functions but at abnormal rates can also be captured, though less directly. Many mutant alleles encode proteins that retain their normal functions but have abnormal stabilities or catalytic efficiencies, leading to normal reactions that proceed to abnormal extents. The phenotypes of such diseases can be revealed when pathway annotations are combined with expression or rate data from other sources.

Depending on the biological pathway/process immediately affected by disease-causing gene variants, non-infectious diseases in Reactome are organized into diseases of signal transduction by growth factore receptors and second messengers, diseases of mitotic cell cycle, diseases of cellular response to stress, diseases of programmed cell death, diseases of DNA repair, disorders of transmembrane transporters, diseases of metabolism, diseases of immune system, diseases of neuronal system, disorders of developmental biology, disorders of extracellular matrix organization, and diseases of hemostatis.