Detection of mutations in theCOL4A5gene by SSCP in X-linked Alport syndrome

Abstract

Alport syndrome is a progressive renal disease leading to chronic renal failure, which often is accompanied by sensorineural deafness and ophthalmological signs in the form of anterior lenticonus. The X-linked form of the disease is caused by mutations in the COL4A5 gene encoding the alpha5-chain of type IV-collagen. We performed mutation analysis of the COL4A5 gene by PCR-SSCP analysis of each of the 51 exons with flanking intronic sequences in 81 patients suspected of X-linked Alport syndrome including 29 clear X-linked cases, 37 cases from families with a pedigree compatible with X-linked inheritance, and 15 isolated cases. We found a mutation detection rate of 52% (42/81) (58% in males and 21% in females), and 69% (20/29) in families who clearly demonstrated X-linked inheritance. Thirty-six different mutations were found in 42 patients comprising 16 missense mutations, seven frameshifts, three in-frame deletions, four nonsense mutations, and six splice site mutations. Twenty-two of the mutations have not previously been reported. Furthermore, we found one non-pathogenic amino acid substitution, one rare variant in a non-coding region, and one polymorphism with a heterozygosity of 28%. Three de novo mutations were found, two of which were paternal and one of maternal origin.

X-Linked Alport Syndrome

“…The lowest rate of progression to ESRD is associated with missense mutations, as in related boys and men; however, the association is not statistically significant. Similarly, the 11 girls and women with X-linked AS who developed ESRD in the recent study of Hertz et al (27) bore different types of mutations from missense to frameshift, and in the series of Inoue et al (22), the two girls with heavy proteinuria at, respectively, 13 and 15 yr of age had missense mutation. No genotype-phenotype correlation was detected regarding the occurrence of hearing loss.…”

Mild Forms of Alport Syndrome: Hereditary Nephropathy in the Absence of Extra-Renal Features

“…A previous study classified X-linked Alport syndrome patients caused by mutations involving the NC1 domain into Type S (severe) phenotype (Gross et al, 2002). Mutations involving other cysteine residues in the NC1 domain have also been reported and include C1486S (Zhou et al, 1991), C1567R (Knebelmann et al, 1996) and C1586R (Hertz et al, 2001) and others (see Figure 7). Using the proposed classification suggested by Gross and colleagues, the New Zealand family would be placed in 'type S' on the basis of the mutant genotype involving the NC1 domain.…”

“…In general, substitution and missense mutations in the NC1 domain, as in other regions of COL4A5, lead to hematuria, proteinuria, ESRF and sensorineural hearing loss with an overwhelming predominance in males (Barker et al, 1996, Barker et al, 1997, Gross et al, 2002, Hertz et al, 2001, Inoue et al, 1999, Knebelmann et al, 1996, Nakanishi et al, 1994, Netzer et al, 1996, Zhou et al, 1991. A previous study classified X-linked Alport syndrome patients caused by mutations involving the NC1 domain into Type S (severe) phenotype (Gross et al, 2002).…”

“…Further to the New Zealand family, there have been 7 other mutations involving cysteine residues in the NC1 domain (Bekheirnia et al, 2010, Gross et al, 2002, Hertz et al, 2001, Inoue et al, 1999, Knebelman et al, 1996., Wilson et al, 1997, Zhou et al, 1991 affecting males and females ( Figure 7). These mutations are shown together with information of age at the time of diagnosis.…”

“…M, male, F, female. Refs; 1 (Zhou et al, 1991); 2 (Knebelmann et al, 1996); 3 (Hertz et al, 2001);4 (Bekheirnia et al, 2010); 5 (Wilson et al, 1997);6 (Gross et al, 2002), 7 (Inoue et al, 19998 (Wang et al, 2005).…”