title: Analysis of CTNS gene transcripts in nephropathic cystinosis.
abstract: Nephropathic cystinosis (NC) is an autosomal recessive disorder caused by mutations of the CTNS gene that encodes for a cystine transmembrane transporter. Several mutations have been described in the coding and promoter regions of the CTNS gene in affected individuals. We selected three patients with NC from two unrelated families, in whom sequence analysis of the CTNS gene detected only one or no mutations. Total RNA was isolated from peripheral blood mononuclear cells or fibroblasts and CTNS transcripts were analyzed. We observed a skipping of exon 5 (85 bp) in two siblings and an intron 9 retention of 75 bp associated with partial replication of exon 9 in the third patient. Genomic DNA analysis of intron regions surrounding exon 5 showed a point mutation in the hypothetical lariat branch site of intron 4 at position -24 (c.141-24 T > C) in the first two patients and a duplication of 266 bp including a part of exon and intron 9 in the third patient. Analysis of CTNS gene transcripts allowed identification of mutations in patients in whom CTNS mutations could not be detected by traditional DNA sequencing. These results support the hypothesis that cystinosis is a monogenic disorder.
authors.affiliation: Department of Nephrology and Urology, Division of Nephrology, Bambino Gesù Children's Hospital and Research Institute, Piazza S. Onofrio, 4, 00165, Rome, Italy. taranta@opbg.net
authors.forename: Anna
authors.initials: A
authors.lastname: Taranta
authors.forename: Martijn J
authors.initials: MJ
authors.lastname: Wilmer
authors.forename: Lambert P
authors.initials: LP
authors.lastname: van den Heuvel
authors.forename: Paola
authors.initials: P
authors.lastname: Bencivenga
authors.forename: Francesco
authors.initials: F
authors.lastname: Bellomo
authors.forename: Elena N
authors.initials: EN
authors.lastname: Levtchenko
authors.forename: Francesco
authors.initials: F
authors.lastname: Emma
mesh_terms: D017398:Alternative Splicing; D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics*; D002675:Child, Preschool; D003554:Cystinosis / Q000235:genetics* / Q000473:pathology; D004247:DNA / Q000032:analysis; D004252:DNA Mutational Analysis; D005260:Female; D005347:Fibroblasts / Q000737:chemistry / Q000473:pathology; D020440:Gene Duplication; D006801:Humans; D007223:Infant; D007668:Kidney / Q000473:pathology*; D007963:Leukocytes, Mononuclear / Q000737:chemistry / Q000473:pathology; D008297:Male; D017354:Point Mutation
chemical_list: D026921:Amino Acid Transport Systems, Neutral; C111445:CTNS protein, human; D004247:DNA