X-linked partial corpus callosum agenesis with mild intellectual disability: identification of a novel L1CAM pathogenic variant.
Neurogenetics
; 22(1): 43-51, 2021 03.
Article
in En
| MEDLINE
| ID: mdl-33415589
ABSTRACT
Pathogenic variants in L1CAM, the gene encoding the L1 cell adhesion molecule, are responsible for a wide clinical spectrum including X-linked hydrocephalus with stenosis of the Sylvius aqueduct, MASA syndrome (mental retardation, aphasia, shuffling gait, adducted thumbs), and a form of spastic paraplegia (SPG1). A moderate phenotype with mild intellectual disability (ID) and X-linked partial corpus callosum agenesis (CCA) has only been related to L1CAM in one family. We report here a second family, including 5 patients with mild to moderate ID and partial CCA without signs usually associated with L1CAM pathogenic variations (such as hydrocephalus, pyramidal syndrome, thumb adductus, aphasia). We identified a previously unreported c.3226A > C transversion leading to a p.Thr1076Pro amino acid substitution in the fifth fibronectin type III domain (FnIII) of the protein which co-segregates with the phenotype within the family. We performed in vitro assays to assess the pathogenic status of this variation. First, the expression of the novel p.Thr1076Pro mutant in COS7 cells resulted in endoplasmic reticulum (ER) retention and reduced L1CAM cell surface expression, which is expected to affect both L1CAM-mediated cell-cell adhesion and neurite growth. Second, immunoblotting techniques showed that the immature form of the L1CAM protein was increased, indicating that this variation led to a lack of maturation of the protein. ID associated with CCA is not a common clinical presentation of L1CAM pathogenic variants. Genome-wide analyses will identify such variations and it is important to acknowledge this atypical phenotype.
Key words
Full text:
1
Database:
MEDLINE
Main subject:
Cerebral Aqueduct
/
Genetic Diseases, X-Linked
/
Neural Cell Adhesion Molecule L1
/
Agenesis of Corpus Callosum
/
Hydrocephalus
/
Intellectual Disability
/
Mutation
Type of study:
Diagnostic_studies
/
Prognostic_studies
Limits:
Adult
/
Female
/
Humans
Language:
En
Journal:
Neurogenetics
Journal subject:
GENETICA
/
NEUROLOGIA
Year:
2021
Type:
Article
Affiliation country:
France