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Abstract

Aarskog-Scott Syndrome (AAS) is an X-linked disorder characterised by short stature and multiple facial, Limb and genital abnormalities. A gene, FGD1, altered in a patient with AAS phenotype, has been identified and found to encode a protein with homology to Rho/Rac guanine nucleotide exchange factors (Rho/Rac GEF), However, since this original report on identification of a mutated FGD1 gene in an AAS patient, no additional mutations in the FGD1 gene have been described. We analysed 13 independent patients with clinical diagnosis of AAS. One patient presented a mutation that results in a nucleotide change in exon TO of the FGD1 gene (G2559 > A) substituting a Gin for Arg in position 610, The mutation was found to segregate with the AAS phenotype in affected males and carrier females in the family of this patient. Interestingly, Arg-610 is located within one of the two pleckstrin homology (PH) domains of the FGD1 gene and it corresponds to a highly conserved residue which has been involved in InsP binding in PH domains of other proteins, The same residue is often mutated in the Bruton's tyrosine kinase (Btk) gene in patients with an X-linked agammaglobulinemia. The Arg610Gln mutation represents the first case of a mutation in the PII domain of the FGD1 gene and additional evidence that mutations in PH domains can be associated to human diseases. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.