The molecular basis of familial hemolytic uremic syndrome: mutation analysis of factor H gene reveals a hot spot in short consensus repeat 20.
The aim of the present study was to clarify whether factor H mutations were involved in genetic predisposition to hemolytic uremic syndrome, by performing linkage and mutation studies in a large number of patients from those referred to the Italian Registry for Recurrent and Familial HUS/TTP. PCR and Western blot analyses were conducted to characterize the biochemical consequences of the mutations. Five mutations in the factor H gene were identified. Three, identified in two families and in a sporadic case, are heterozygous point mutations within the most C-terminal short consensus repeat 20 (SCR20) of factor H, resulting in single amino acid substitutions. The other two mutations introduce premature stop codons that interrupt the translation of factor H. A heterozygous nonsense mutation was identified in SCR8 in one family, and a homozygous 24-bp deletion within SCR20 was identified in a Bedouin family with a recessive mode of inheritance. Reverse transcription-PCR analysis of cDNA from peripheral blood leukocytes from the Bedouin family showed that the deletion lowered factor H mRNA levels. Although heterozygous mutations were associated with normal factor H levels and incomplete penetrance of the disease, the homozygous mutation in the Bedouin family resulted in severe reduction of factor H levels accompanied by very early disease onset. These data provide compelling molecular evidence that genetically determined deficiencies in factor H are involved in both autosomal-dominant and autosomal-recessive hemolytic uremic syndrome and identify SCR20 as a hot spot for mutations in the disease. The mutations identified here give an important hint to the relevance of the C-terminus of factor H in the control of the alternative complement activation pathway.
Caprioli
Jessica
J
Mario Negri Institute for Pharmacological Research, Clinical Research Center for Rare Diseases, Aldo e Cele Daccò, Villa Camozzi-Ranica, Italy.
Bettinaglio
Paola
P
Mario Negri Institute for Pharmacological Research, Clinical Research Center for Rare Diseases, Aldo e Cele Daccò, Villa Camozzi-Ranica, Italy.
Zipfel
Peter F
PF
Hans-Knöll-Institute for Natural Products Research, Jena, Germany.
Amadei
Barbara
B
Mario Negri Institute for Pharmacological Research, Clinical Research Center for Rare Diseases, Aldo e Cele Daccò, Villa Camozzi-Ranica, Italy.
Daina
Erica
E
Mario Negri Institute for Pharmacological Research, Clinical Research Center for Rare Diseases, Aldo e Cele Daccò, Villa Camozzi-Ranica, Italy.
Gamba
Sara
S
Mario Negri Institute for Pharmacological Research, Clinical Research Center for Rare Diseases, Aldo e Cele Daccò, Villa Camozzi-Ranica, Italy.
Skerka
Christine
C
Hans-Knöll-Institute for Natural Products Research, Jena, Germany.
Marziliano
Nicola
N
PE Applied Biosystems, Monza, Italy.
Remuzzi
Giuseppe
G
Mario Negri Institute for Pharmacological Research, Clinical Research Center for Rare Diseases, Aldo e Cele Daccò, Villa Camozzi-Ranica, Italy.|Unit of Nephrology and Dialysis, Azienda Ospedaliera, Ospedali Riuniti di Bergamo, Italy.
Noris
Marina
M
Mario Negri Institute for Pharmacological Research, Clinical Research Center for Rare Diseases, Aldo e Cele Daccò, Villa Camozzi-Ranica, Italy.
D000595:Amino Acid Sequence; D001483:Base Sequence; D017242:Complement Factor H / Q000737:chemistry / Q000235:genetics*; D020022:Genetic Predisposition to Disease; D006463:Hemolytic-Uremic Syndrome / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010375:Pedigree; D018807:Polymorphism, Single-Stranded Conformational; D020449:Repetitive Sequences, Amino Acid
C493495:CFH protein, human; D017242:Complement Factor H