The FGD1 gene provides instructions for making a protein that turns on (activates) another protein called Cdc42, which transmits signals that are important for various aspects of development before and after birth.Mutations in the FGD1 gene lead to the production of an abnormally functioning protein. These mutations disrupt Cdc42 signaling, leading to the wide variety of abnormalities that occur in people with Aarskog-Scott syndrome.Only about 20 percent of people with this disorder have identifiable mutations in the FGD1 gene. The cause of Aarskog-Scott syndrome in other affected individuals is unknown. Pathophysiology
The Aarskog–Scott syndrome is due to mutation in the FGD1 gene. FGD1 encodes a guanine nucleotide exchange factor (GEF) that specifically activates Cdc42, a member of the Rho (Ras homology) family of the p21 GTPases. By activating Cdc42, FGD1 protein stimulates fibroblasts to form filopodia, cytoskeletal elements involved in cellular signaling, adhesion, and migration. Through Cdc42, FGD1 protein also activates the c-Jun N-terminal kinase (JNK) signaling cascade, a pathway that regulates cell growth, apoptosis, and cellular differentiation.Within the developing mouse skeleton, FGD1 protein is expressed in precartilaginous mesenchymal condensations, the perichondrium and periosteum, proliferating chondrocytes, and osteoblasts. These results suggest that FGD1 signaling may play a role in the biology of several different skeletal cell types including mesenchymal prechondrocytes, chondrocytes, and osteoblasts.
Smiths Recognizable Patterns of Human Malformation (6th ed.). Philadelphia: WB Saunders. ISBN 978-0-7216-2359-7. Orrico A.; Galli L.; Cavaliere ML. ;  et al. (2004). "Phenotypic and molecular characterisation of the Aarskog–Scott syndrome: a survey of the clinical variability in light of FGD1 mutation analysis in 46 patients". Eur. J. Hum. Genet. 12 (1): 16–23. doi:10.1038/sj.ejhg.5201081. PMID 14560308. External links
Aarskog–Scott syndrome, detailed up-to-date information in OMIM (Online Mendelian Inheritance in Man)
Aarskogs syndrome at Who Named It?