title: Next generation sequencing as a useful tool in the diagnostics of mosaicism in Alport syndrome.
abstract: Alport syndrome (ATS) is a progressive hereditary nephropathy characterized by hematuria and/or proteinuria with structural defects of the glomerular basement membrane. It can be associated with extrarenal manifestations (high-tone sensorineural hearing loss and ocular abnormalities). Somatic mutations in COL4A5 (X-linked), COL4A3 and COL4A4 genes (both autosomal recessive and autosomal dominant) cause Alport syndrome. Somatic mosaicism in Alport patients is very rare. The reason for this may be due to the difficulty of detection. We report the case of a boy and his mother who presented with Alport syndrome. Mutational analysis showed the novel hemizygote pathogenic mutation c.2396-1G>A (IVS29-1G>A) at the splice acceptor site of the intron 29 exon 30 boundary of the COL4A5 gene in the boy. The mutation in the mother would not have been detected by Sanger sequencing without the knowledge of the mutational analysis result of her son. Further investigation of the mother using next generation sequencing showed somatic mosaicism and implied potential germ cell mosaicism. The mutation in the mother has most likely occurred during early embryogenesis. Analysis of tissue of different embryonic origin in the mother confirmed mosaicism in both mesoderm and ectoderm. Low grade mosaicism is very difficult to detect by Sanger sequencing. Next generation sequencing is increasingly used in the diagnostics and might improve the detection of mosaicism. In the case of definite clinical symptoms of ATS and missing detection of a mutation by Sanger sequencing, mutational analysis should be performed by next generation sequencing.
authors.affiliation: Center for Human Genetics and Laboratory Medicine Dr. Klein, Dr. Rost and Colleagues, Martinsried, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Beicht
authors.forename: Gertrud
authors.initials: G
authors.lastname: Strobl-Wildemann
authors.forename: Sabine
authors.initials: S
authors.lastname: Rath
authors.forename: Oliver
authors.initials: O
authors.lastname: Wachter
authors.forename: Martin
authors.initials: M
authors.lastname: Alberer
authors.forename: Elke
authors.initials: E
authors.lastname: Kaminsky
authors.forename: Lutz T
authors.initials: LT
authors.lastname: Weber
authors.forename: Tanja
authors.initials: T
authors.lastname: Hinrichsen
authors.forename: Hanns-Georg
authors.initials: HG
authors.lastname: Klein
authors.forename: Julia
authors.initials: J
authors.lastname: Hoefele
mesh_terms: D000328:Adult; D001483:Base Sequence; D024141:Collagen Type IV / Q000737:chemistry / Q000235:genetics; D005091:Exons; D005260:Female; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007223:Infant; D008297:Male; D009030:Mosaicism; D009154:Mutation; D009394:Nephritis, Hereditary / Q000175:diagnosis* / Q000235:genetics*
chemical_list: C478159:COL4A5 protein, human; D024141:Collagen Type IV
keywords: ATS; Alport syndrome; DNA; ESRD; GBM; Germline mutations; NGS; PCR; Somatic mosaicism; TBMN; deoxyribonucleic acid; end-stage renal disease; glomerular basement membrane; mRNA; messenger ribonucleic acid; next generation sequencing; polymerase chain reaction; thin basement membrane nephropathy