A novel intronic GAA repeat expansion in<i>FGF14</i>causes autosomal dominant adult-onset ataxia (SCA50, ATX-FGF14) release_r3lemacirzgyfmtaufdfgvfft4

by Haloom Rafehi, Justin Read, David J Szmulewicz, Kayli C. Davies, Penny Snell, Liam G Fearnley, Liam Scott, Mirja Thomsen, Greta Gillies, Kate Pope, Mark F Bennett, Jacob E Munro (+19 others)

Released as a post by Cold Spring Harbor Laboratory.



<jats:title>ABSTRACT</jats:title>Adult-onset cerebellar ataxias are a group of neurodegenerative conditions that challenge both genetic discovery and molecular diagnosis. In this study, we identified a novel intronic GAA repeat expansion in the gene encoding Fibroblast Growth Factor 14 (<jats:italic>FGF14</jats:italic>). Genetic analysis identified 4/95 previously unresolved Australian affected individuals (4.2%) with (GAA)<jats:sub>&gt;335</jats:sub>and a further nine individuals with (GAA)<jats:sub>&gt;250</jats:sub>. Notably, PCR and long-read sequence analysis revealed these were pure GAA repeats. In comparison, no controls had (GAA)<jats:sub>&gt;300</jats:sub>and only 2/311 control individuals (0.6%) encoded a pure (GAA)<jats:sub>&gt;250</jats:sub>. In a German validation cohort 9/104 (8.7%) of affected individuals had (GAA)<jats:sub>&gt;335</jats:sub>and a further six had (GAA)<jats:sub>&gt;250</jats:sub>. In comparison no controls had (GAA)<jats:sub>&gt;335</jats:sub>and 10/190 (5.3%) encoded (GAA)<jats:sub>&gt;250</jats:sub>. The combined data suggests (GAA)<jats:sub>&gt;335</jats:sub>are disease-causing and fully penetrant [P-value 6.0×10<jats:sup>−8</jats:sup>, OR 72 (95% CI=4.3-1227)], while (GAA)<jats:sub>&gt;250</jats:sub>is likely pathogenic, albeit with reduced penetrance. Affected individuals had an adult-onset, slowly progressive cerebellar ataxia with a clinical phenotype that may include vestibular impairment, hyper-reflexia and autonomic dysfunction. A negative correlation between age at onset and repeat length was observed (R2=0.44 p=0.00045, slope = -0.12). This study demonstrates the power of genome sequencing and advanced bioinformatic tools to identify novel repeat expansion loci via model free, genome-wide analysis and identifies SCA50/ATX-FGF14 is a frequent cause of adult-onset ataxia.
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Date   2022-10-25
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