Mild recessive epidermolytic hyperkeratosis associated with a novel keratin 10 donor splice-site mutation in a family of Norfolk terrier dogs

Authors

  • K.M. Credille,

    1. Comparative Dermatology Laboratory, Texas A&M University, College Station, TX, U.S.A.
      *Pfizer Global Research and Development, Ann Arbor, MI, U.S.A.
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  • K.F. Barnhart,

    1. Comparative Dermatology Laboratory, Texas A&M University, College Station, TX, U.S.A.
      *Pfizer Global Research and Development, Ann Arbor, MI, U.S.A.
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  • J.S. Minor,

    1. Comparative Dermatology Laboratory, Texas A&M University, College Station, TX, U.S.A.
      *Pfizer Global Research and Development, Ann Arbor, MI, U.S.A.
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  • R.W. Dunstan

    1. Comparative Dermatology Laboratory, Texas A&M University, College Station, TX, U.S.A.
      *Pfizer Global Research and Development, Ann Arbor, MI, U.S.A.
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  • Conflicts of interest: None declared.

  • This work was performed at Michigan State University in East Lansing, MI, U.S.A. and Texas A&M University, College Station, TX, U.S.A.

Kelly Credille, Eli Lilly and Co., 2001 West Main Street GL44, Greenfield, IN 46160, U.S.A.
E-mail:credillekm@lilly.com

Summary

Background  Epidermolytic hyperkeratosis in humans is caused by dominant-negative mutations in suprabasal epidermal keratins 1 and 10. However, spontaneous keratin mutations have not been confirmed in a species other than human.

Objectives  To describe an autosomal recessive, mild, nonpalmar/plantar epidermolytic ichthyosis segregating in an extended pedigree of Norfolk terrier dogs due to a splice-site mutation in the gene encoding keratin 10 (KRT10).

Methods  Dogs were evaluated clinically, and skin samples were examined by light and electron microscopy. Genomic DNA samples and cDNA from skin RNA were sequenced and defined a mutation in KRT10. Consequences of the mutation were evaluated by assessing protein expression with immunohistochemistry and Western blotting and gene expression with real-time RT-PCR (reverse transcriptase-polymerase chain reaction).

Results  Adult dogs with the disease had generalized, pigmented hyperkeratosis with epidermal fragility. Light microscopic examination defined epidermolysis with hyperkeratosis; ultrastructural changes included a decrease in tonofilaments and abnormal filament aggregation in upper spinous and granular layer keratinocytes. Affected dogs were homozygous for a single base GT→TT change in the consensus donor splice site of intron 5 in KRT10. Keratin 10 protein was not detected with immunoblotting in affected dogs. Heterozygous dogs were normal based on clinical and histological appearance and keratin 10 protein expression. The mutation caused activation of at least three cryptic or alternative splice sites. Use of the cryptic sites resulted in transcripts containing premature termination codons. One transcript could result in shortening of the proximal portion of the 2B domain before the stutter region. Quantitative real-time PCR indicated a significant decrease in KRT10 mRNA levels in affected dogs compared with wild-type dogs.

Conclusions  This disease is the first confirmed spontaneous keratin mutation in a nonhuman species and is the first reported recessive form of epidermolytic hyperkeratosis.

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