Mutations in the COL4A5 gene in Alport syndrome: A possible mutation in primordial germ cells

Abstract

Using a combination of gene amplification with single strand conformation polymorphisms analysis and sequencing, we examined the COL4A5 gene in 37 patients with Alport syndrome. In patient A8, a single base insertion was noted at codon 1,597 tyrosine in exon 49. The premature terminal signal appeared and 89 amino acids (approximately one-third) of the non-collagenous domain were lost. The mutation was present in the mother, hence she is heterozygous. In patient A12, the nucleotide changed from C to T at codon 1,679 glutamine in exon 51, which created a termination codon, and 7 amino acids at the carboxyl terminus were lost. Gene tracking using peripheral leukocytes revealed that the parents did not carry the mutant allele, while the sister was heterozygous. DNA samples from hair roots and skin fibroblasts of the mother were normal and immunological examination of the epidermis of the mother indicated that the alpha 5(IV) chain was normally expressed. As these results suggest that somatic cells of the mother do not carry the mutant allele, the primordial germ cells possibly carry a fresh mutation in the mother of patient A12.

Meta-analysis of genotype-phenotype correlation in X-linked Alport syndrome: impact on clinical counselling

“…In contrast, the present study also includes publications after 1997 leaving only a minority of identical mutations being analysed in both studies. Additionally, more than 100 mutations from the US and Japan were included [5,12,23,26,31,33,34,36,37,[40][41][42][43][44]. The previous study by Jais et al [49] reports the genotype-phenotype correlation with regard to large rearrangements, missense, splicing and 'small' mutations, focusing on the differences between major rearrangements and small mutations.…”

Expert consensus guidelines for the genetic diagnosis of Alport syndrome

“…Deep intronic variants that introduce splicing defects often require whole genomic sequencing or a splicing assay for their detection. Deep intronic variants have been detected by sequencing [46], but splice site testing is typically performed using hair root cDNA [47][48][49][50] to confirm COL4A5 variants, or lymphocyte cDNA [51] for COL4A3/COL4A4 variants. The hair roots are stable for days at room temperature, but must be of sufficient number, and the nested primer design is critical.…”

Sporadic case of X-chromosomal Alport syndrome in a consanguineous family

“…The NC 1-domain is essential for the assembly and folding of three alpha chains into a triple helix, and is involved in the formation of head-to-head crosslinks between individual type IV collagen molecules [29]. germline mosaicism, which has been reported once in AS [31].…”