title: Further genotype-phenotype correlation emerging from two families with PLP1 exon 4 skipping.
abstract: Proteolipid protein 1 (PLP1) gene-related disorders due to mutations in the PLP1 include a wide spectrum of X-linked disorders ranging from severe connatal Pelizaeus-Merzbacher disease (PMD) to spastic paraplegia 2 (SPG2). Duplications, deletions or point mutations in coding and noncoding regions of the PLP1 gene may occur. We report the clinical, neuroradiologic and molecular findings in six patients from two unrelated families. The affected males showed severe mental retardation, spastic tetraparesis, inability of walking and pes cavus at onset in early infancy. Brain magnetic resonance imaging (MRI) showed hypomyelination and brain atrophy. Nystagmus was never observed. The affected females showed adult-onset progressive spastic paraparesis leading to wheel-chair dependency and subtle white matter changes on brain MRI. Molecular studies in the two families identified two different intronic mutations, the novel c.622+2T>C and the known c.622+1G>A, leading to the skipping of PLP1-exon 4. The clinical presentation of the affected males did not consistently fit in any of the PLP1-related disorder subtypes (i.e., connatal or classic PMD, SPG2 and 'PLP1 null syndrome'), and in addition, the carrier females were symptomatic despite the severe clinical picture of their respective probands. This study provides new insight into the genotype-phenotype correlations of patients with PLP1 splice-site mutations.
authors.affiliation: Child Neurology and Psychiatry Unit.
authors.forename: Roberta
authors.initials: R
authors.lastname: Biancheri
authors.forename: Serena
authors.initials: S
authors.lastname: Grossi
authors.forename: Stefano
authors.initials: S
authors.lastname: Regis
authors.forename: Andrea
authors.initials: A
authors.lastname: Rossi
authors.forename: Fabio
authors.initials: F
authors.lastname: Corsolini
authors.forename: Daniela Paola
authors.initials: DP
authors.lastname: Rossi
authors.forename: Pietro
authors.initials: P
authors.lastname: Cavalli
authors.forename: Mariasavina
authors.initials: M
authors.lastname: Severino
authors.forename: Mirella
authors.initials: M
authors.lastname: Filocamo
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology; D004252:DNA Mutational Analysis; D005091:Exons; D005260:Female; D056726:Genetic Association Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D018991:Myelin Proteolipid Protein / Q000235:genetics*; D010375:Pedigree; D020371:Pelizaeus-Merzbacher Disease / Q000175:diagnosis / Q000235:genetics; D017354:Point Mutation; D022821:RNA Splice Sites; D055815:Young Adult
chemical_list: D018991:Myelin Proteolipid Protein; C472930:PLP1 protein, human; D022821:RNA Splice Sites
keywords: Pelizaeus-Merzbacher disease; magnetic resonance imaging; molecular genetics