L1 disease is a group of overlapping clinical phenotypes including X-linked hydrocephalus, MASA syndrome, spastic paraparesis type 1, and X-linked agenesis of corpus callosum. The patients are characterized by hydrocephalus, agenesis or hypoplasia of corpus callosum and corticospinal tracts, mental
Intronic mutations in the L1CAM gene may cause X-linked hydrocephalus by aberrant splicing
✍ Scribed by Christian A. Hübner; Barbara Utermann; Sigrid Tinschert; Gabriele Krüger; Bernadette Ressler; Cordula Steglich; Albert Schinzel; Andreas Gal
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 36 KB
- Volume
- 23
- Category
- Article
- ISSN
- 1059-7794
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✦ Synopsis
Communicated by Mark H. Paalman L1 disease is a clinically heterogeneous X-chromosomal neurodevelopmental disorder that is frequently associated with mental retardation and congenital hydrocephalus in males. It is caused by mutations in L1CAM that encodes a multifunctional transmembrane neuronal cell adhesion molecule. We report our findings on 6 novel intronic L1CAM sequence variants (c.523+5G>A, c.1123+1G>A, c.1547-13delC, c.3323-17dupG, c.3457+3A>T, and c.3457+18C>T), and a recurrent one (c.523+12C>T). While the pathogenic potential of nucleotide changes w ithin the evolutionarily well-conserved splice consensus sequence (c.523+5G>A, c.1123+1G>A, and c.3457+3A>T) is widely accepted, it is not always straight forward to assess the disease relevance of intronic mutations, if they lie outside the consensus. The c.523+12C>T variant co-segregated with X-linked hydrocephalus in two unrelated families. In the mutated allele, a preferentially used novel splice donor site is generated that results in a frame shift due to insertion of the first 10 bp of intron 5 in the mature mRNA, a largely truncated protein, and most likely a functional null allele. The c.1547-13delC mutation creates a new acceptor site resulting in the insertion of 4 additional amino acids at the end of the immunoglobulin like domain 5. In contrast, c.3323-17dupG and c.3457+18C>T seem to be non-pathogenic L1CAM variants.
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Eight novel mutations were identified in the gene encoding L1CAM, a neural cell adhesion protein, in patients/families with Xlinked hydrocephalus (XHC) providing additional evidence for extreme allelic heterogeneity of the trait. The two nonsense mutations (Gln440Ter and Gln1042Ter) result most like