FGF23 signaling in hypophosphatemic rickets and related disorders (Homo sapiens)

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Taken from FGF23 and its role in X-linked hypophosphatemia-related morbidity by Signe Sparre Beck-Nielsen, Zulf Mughal, Dieter Haffner, Ola Nilsson, Elena Levtchenko, Gema Ariceta, Carmen de Lucas Collantes, Dirk Schnabel, Ravi Jandhyala and Outi Mäkitie [1].

X-linked hypophosphatemia (XLH) is an inherited disease of phosphate metabolism in which inactivating mutations of the Phosphate Regulating Endopeptidase Homolog, X-Linked (PHEX) gene lead to local and systemic effects including impaired growth, rickets, osteomalacia, bone abnormalities, bone pain, spontaneous dental abscesses, hearing difficulties, enthesopathy, osteoarthritis, and muscular dysfunction. Patients with XLH present with elevated levels of fibroblast growth factor 23 (FGF23), which is thought to mediate many of the aforementioned manifestations of the disease. Elevated FGF23 has also been observed in many other diseases of hypophosphatemia, and a range of animal models have been developed to study these diseases, yet the role of FGF23 in the pathophysiology of XLH is incompletely understood.

Regulation of FGF23 expression and secretion in XLH. Inactivating mutations in PHEX increase fibroblast growth factor 23 (FGF23) expression by increasing levels of acidic serine aspartate-rich-MEPE-associated protein (ASARM) peptide. This leads to increased release of FGF23 into the serum, and increased levels of FGF23-mediated signalling.

The pathway illustrates hypophosphatemic and autocrine/paracrine molecular pathways that have been proposed to link FGF23 to bone abnormalities in XLH.

Linked with a dotted arrow to the GeneProduct nodes are diseases caused by mutation in the respective gene.