title: Molecular genetic analysis of the PLP1 gene in 38 families with PLP1-related disorders: identification and functional characterization of 11 novel PLP1 mutations.
abstract: BACKGROUND
  The breadth of the clinical spectrum underlying Pelizaeus-Merzbacher disease and spastic paraplegia type 2 is due to the extensive allelic heterogeneity in the X-linked PLP1 gene encoding myelin proteolipid protein (PLP). PLP1 mutations range from gene duplications of variable size found in 60-70% of patients to intragenic lesions present in 15-20% of patients.
  
  
  METHODS
  Forty-eight male patients from 38 unrelated families with a PLP1-related disorder were studied. All DNA samples were screened for PLP1 gene duplications using real-time PCR. PLP1 gene sequencing analysis was performed on patients negative for the duplication. The mutational status of all 14 potential carrier mothers of the familial PLP1 gene mutation was determined as well as 15/24 potential carrier mothers of the PLP1 duplication.
  
  
  CONCLUSIONS
  PLP1 gene duplications were identified in 24 of the unrelated patients whereas a variety of intragenic PLP1 mutations were found in the remaining 14 patients. Of the 14 different intragenic lesions, 11 were novel; these included one nonsense and 7 missense mutations, a 657-bp deletion, a microdeletion and a microduplication. The functional significance of the novel PLP1 missense mutations, all occurring at evolutionarily conserved residues, was analysed by the MutPred tool whereas their potential effect on splicing was ascertained using the Skippy algorithm and a neural network. Although MutPred predicted that all 7 novel missense mutations would be likely to be deleterious, in silico analysis indicated that four of them (p.Leu146Val, p.Leu159Pro, p.Thr230Ile, p.Ala247Asp) might cause exon skipping by altering exonic splicing elements. These predictions were then investigated in vitro for both p.Leu146Val and p.Thr230Ile by means of RNA or minigene studies and were subsequently confirmed in the case of p.Leu146Val. Peripheral neuropathy was noted in four patients harbouring intragenic mutations that altered RNA processing, but was absent from all PLP1-duplication patients. Unprecedentedly, family studies revealed the de novo occurrence of the PLP1 duplication at a frequency of 20%.
authors.affiliation: SSD Lab, Diagnosi Pre-Postnatale Malattie Metaboliche, IRCCS G, Gaslini, Genova, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: Grossi
authors.forename: Stefano
authors.initials: S
authors.lastname: Regis
authors.forename: Roberta
authors.initials: R
authors.lastname: Biancheri
authors.forename: Matthew
authors.initials: M
authors.lastname: Mort
authors.forename: Susanna
authors.initials: S
authors.lastname: Lualdi
authors.forename: Enrico
authors.initials: E
authors.lastname: Bertini
authors.forename: Graziella
authors.initials: G
authors.lastname: Uziel
authors.forename: Odile
authors.initials: O
authors.lastname: Boespflug-Tanguy
authors.forename: Alessandro
authors.initials: A
authors.lastname: Simonati
authors.forename: Fabio
authors.initials: F
authors.lastname: Corsolini
authors.forename: Ercan
authors.initials: E
authors.lastname: Demir
authors.forename: Valentina
authors.initials: V
authors.lastname: Marchiani
authors.forename: Antonio
authors.initials: A
authors.lastname: Percesepe
authors.forename: Franco
authors.initials: F
authors.lastname: Stanzial
authors.forename: Andrea
authors.initials: A
authors.lastname: Rossi
authors.forename: Catherine
authors.initials: C
authors.lastname: Vaurs-Barrière
authors.forename: David N
authors.initials: DN
authors.lastname: Cooper
authors.forename: Mirella
authors.initials: M
authors.lastname: Filocamo
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004247:DNA / Q000235:genetics; D020440:Gene Duplication; D006801:Humans; D007223:Infant; D008297:Male; D018991:Myelin Proteolipid Protein / Q000235:genetics*; D020371:Pelizaeus-Merzbacher Disease / Q000235:genetics*; D015419:Spastic Paraplegia, Hereditary / Q000235:genetics*; D055815:Young Adult
chemical_list: D018991:Myelin Proteolipid Protein; C472930:PLP1 protein, human; D004247:DNA