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Supportive evidence for the DYX3 dyslexia susceptibility gene in Canadian families
  1. T L Petryshen1,
  2. B J Kaplan2,
  3. M L Hughes1,
  4. J Tzenova3,
  5. L L Field1,3
  1. 1Department of Medical Genetics, University of Calgary, Calgary, Canada
  2. 2Department of Paediatrics, University of Calgary, and Alberta Children's Hospital, Calgary, Canada
  3. 3Department of Medical Genetics, University of British Columbia and British Columbia Research Institute for Women's and Children's Health, Vancouver, Canada
  1. Correspondence to:
 Dr L L Field, Department of Medical Genetics, British Columbia Research Institute for Women's and Children's Health, 950 West 28th Avenue, Vancouver, British Columbia, Canada V5Z 4H4;
 llfield{at}interchange.ubc.ca

https://doi.org/10.1136/jmg.39.2.125

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    A previous report in the Journal by Fagerheim et al1 identified a dyslexia locus (DYX3) on chromosome 2p15-p16 in a large Norwegian family with autosomal dominant inheritance of dyslexia. Parametric linkage analyses using three diagnostic schemes found significant evidence for linkage in this family (maximum lod = 4.3 at D2S378), which was supported by non-parametric linkage analysis (p=0.0009 between D2S2352 and D2S1337). Furthermore, identification of a three marker haplotype cosegregating with dyslexia in the family defined a 2 cM region between D2S2352 and D2S1337 that probably harbours the DYX3 gene. Replication of this linkage in other families would confirm the existence of the locus. We therefore examined our independent sample of dyslexia families and found preliminary evidence for linkage to the DYX3 locus.2 Here, we report the results of more comprehensive analyses, which provide further evidence for the chromosome 2p dyslexia locus.

    METHODS

    As described in detail elsewhere,3,4 our sample consists of 96 Canadian families (877 subjects), each containing two or more sibs diagnosed with phonological coding dyslexia (PCD). This diagnosis was used since the key problem in most reading disabled subjects is a specific difficulty in the phonological coding component of reading, where written words are sounded out using grapheme-phoneme (letter-sound) rules. The PCD diagnosis (affected, unaffected, or uncertain) was determined for all subjects primarily based on psychometric test results for phonological coding. Test …

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