title: Analysis of the CTNS gene in nephropathic cystinosis Mexican patients: report of four novel mutations and identification of a false positive 57-kb deletion genotype with LDM-2/exon 4 multiplex PCR assay.
abstract: OBJECTIVE
  Identify CTNS gene mutations in nephropathic cystinosis Mexican patients.
  
  
  METHODS
  Eleven patients were included, nine presenting infantile nephropathic cystinosis and two siblings with the juvenile phenotype. The common 57-kb deletion was detected by multiplex PCR using large deletion marker-2 (LDM-2)/exon 4 set primers. Those alleles negative for 57-kb deletion were screened by single strand confirmation polymorphism (SSCP) and subsequent direct sequencing.
  
  
  RESULTS
  In our sample, five mutations previously reported are identified: 57-kb deletion, EX4_EX5del, c.985_986insA, c.357_360delGACT, and c.537_557del. We detect a false assignation of 57-kb deletion homozygous genotype by using the LDM-2/exon 4 primers. In addition, four novel and severe mutations are identified: c.379delC, c.1090_1093delACCAinsCG, c.986C>G (p.T216R), and c.400+5G>A.
  
  
  CONCLUSIONS
  Our sample of Mexican patients display allelic heterogeneity as compared to European or North American cystinosis cases. The identification of novel mutations might suggest the presence of exclusive American CTNS alleles in Mexican population. In order to prevent the false positive assignation of 57-kb deletion genotype, as caused by the presence of another type of intragenic CTNS gross deletion, we propose to analyze a different control CTNS exon to those originally reported in both LDM multiplex PCR assays, especially when parental DNA samples are not available.
authors.affiliation: Departamento de Genética Humana, Instituto Nacional de Pediatría, México City, Distrito Federal, México.
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: Alcántara-Ortigoza
authors.forename: Leticia
authors.initials: L
authors.lastname: Belmont-Martínez
authors.forename: Marcela
authors.initials: M
authors.lastname: Vela-Amieva
authors.forename: Ariadna
authors.initials: A
authors.lastname: González-Del Angel