Exome sequencing reveals SPG11 mutations causing juvenile ALS

Area of Science:

• Genetics and Molecular Biology
• Neuroscience
• Rare Diseases

Background:

• Juvenile motor neuron diseases are a group of rare, inherited neurological disorders affecting motor function.
• The SPG11 gene is known to be associated with hereditary spastic paraplegia, but its role in other juvenile motor neuron diseases is less understood.
• Understanding the genetic basis of these conditions is crucial for diagnosis and potential therapeutic strategies.

Purpose of the Study:

• To investigate the genetic cause of recessively inherited juvenile motor neuron disease in a nonconsanguineous family.
• To identify novel mutations in the SPG11 gene and analyze their impact on protein function.
• To explore the phenotypic variability associated with SPG11 mutations within a single family.

Main Methods:

• Exome sequencing was performed on two affected individuals from the family.
• Identification and characterization of compound heterozygous deletions in the SPG11 gene.
• Clinical evaluation of affected individuals to document phenotypic presentation.

Main Results:

• Two novel compound heterozygous deletions in the SPG11 gene were identified, leading to frameshift and premature stop codons.
• One identified deletion, c.5199delA in exon 30, was previously unreported.
• The family exhibited intrafamilial phenotypic heterogeneity, with one individual presenting atypical juvenile amyotrophic lateral sclerosis (ALS) and the other classical hereditary spastic paraplegia with thin corpus callosum.

Conclusions:

• The findings confirm SPG11 as a genetic cause of juvenile amyotrophic lateral sclerosis (ALS).
• SPG11 mutations can manifest as distinct clinical phenotypes, including hereditary spastic paraplegia and juvenile ALS, within the same family.
• This study expands the mutational spectrum of SPG11 and highlights its role in diverse juvenile motor neuron disorders.