Proxy Molecular Diagnosis from Whole-Exome Sequencing Reveals Papillon-Lefevre Syndrome Caused by a Missense Mutation in <i>CTSC</i>

<div><p>Papillon-Lefevre syndrome (PLS) is an autosomal recessive disorder characterised by severe early onset periodontitis and palmoplantar hyperkeratosis. A previously reported missense mutation in the <i>CTSC</i> gene (NM_001814.4:c.899G>A:p.(G300D)) was identified in a homozygous state in two siblings diagnosed with PLS in a consanguineous family of Arabic ancestry. The variant was initially identified in a heterozygous state in a PLS unaffected sibling whose whole exome had been sequenced as part of a previous Primary ciliary dyskinesia study. Using this information, a proxy molecular diagnosis was made on the PLS affected siblings after consent was given to study this second disorder found to be segregating within the family. The prevalence of the mutation was then assayed in the local population using a representative sample of 256 unrelated individuals. The variant was absent in all subjects indicating that the variant is rare in Saudi Arabia. This family study illustrates how whole-exome sequencing can generate findings and inferences beyond its primary goal.</p></div

Validation of NM_001814.4:c.899G>A:p.(G300D) in all family members using ARMS-PCR.

<p>For primers, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121351#pone.0121351.s004" target="_blank">S2 Table</a>. L1-L6: using AS primer for wild type. L7-L12: using AS primer for mutant. L1/7: Mother. L2/8: Father. L3/9: PLS Proband. L4/10: PLS Affected brother. L5/11: Unaffected sibling—homozygous for <i>CTSC</i> wild type allele. L6/12: PCD affected sibling who is a carrier for PLS. Ladder’s three bands are 100bp (bottom), 200bp and 300bp (top).</p

Reads (from PCD affected sibling) mapped to the human genome hg19 at the p.(G300D) mutation.

<p>The read depth is 46 (not all shown due to space restrictions) with twenty six of the reads having a G at the loci and twenty having an A. The image was created using IGV [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121351#pone.0121351.ref020" target="_blank">20</a>]. NB: The <i>CTSC</i> gene is oriented the reverse strand, therefore the codon change p.G300D (GGC>GAC) is exhibiting as C>T.</p