Exome sequencing in congenital ataxia identifies two new candidate genes and highlights a pathophysiological link between some congenital ataxias and early infantile epileptic encephalopathies

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To investigate the genetic basis of congenital ataxias (CAs), a unique group of cerebellar ataxias with a nonprogressive course, in 20 patients from consanguineous families, and to identify new CA genes.


Singleton -exome sequencing on these 20 well-clinically characterized CA patients. We first checked for rare homozygous pathogenic variants, then, for variants from a list of genes known to be associated with CA or very early-onset ataxia, regardless of their mode of inheritance. Our replication cohort of 180 CA patients was used to validate the new CA genes.


We identified a causal gene in 16/20 families: six known CA genes (7 patients); four genes previously implicated in another neurological phenotype (7 patients); two new candidate genes (2 patients). Despite the consanguinity, 4/20 patients harbored a heterozygous de novo pathogenic variant.


Singleton exome sequencing in 20 consanguineous CA families led to molecular diagnosis in 80% of cases. This study confirms the genetic heterogeneity of CA and identifies two new candidate genes (PIGS and SKOR2). Our work illustrates the diversity of the pathophysiological pathways in CA, and highlights the pathogenic link between some CA and early infantile epileptic encephalopathies related to the same genes (STXBP1, BRAT1, CACNA1A and CACNA2D2).

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Fig. 1: Magnetic resonance image (MRI) features of the patients with identified causal or strongly candidate pathogenic variants.
Fig. 2: Identification of likely pathogenic variants in PIGS.
Fig. 3: SKOR2 pathogenic variant in patient 15.


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Correspondence to Lydie Burglen MD, PhD.

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  • Congenital ataxia
  • exome sequencing,
  • Cerebellar atrophy
  • Early infantile epileptic encephalopathies
  • Pathophysiology

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