Deficiency of the human cysteine protease inhibitor cystatin M/E causes hypotrichosis and dry skin

  • Genet Med. 2019 Jul;21(7):1559-1567. doi: 10.1038/s41436-018-0355-3.
Ellen H J van den Bogaard  1 ,  Michel van Geel  2  3  4 ,  Ivonne M J J van Vlijmen-Willems  1 ,  Patrick A M Jansen  1 ,  Malou Peppelman  1 ,  Piet E J van Erp  1 ,  Selma Atalay  1 ,  Hanka Venselaar  5 ,  Marleen E H Simon  6 ,  Marieke Joosten  7 ,  Joost Schalkwijk  1 ,  Patrick L J M Zeeuwen  8
Affiliations
  • 1. Department of Dermatology, Radboud Institute for Molecular Life Sciences (RIMLS), Radboud University Nijmegen Medical Center (Radboudumc), Nijmegen, The Netherlands.
  • 2. Department of Dermatology, Maastricht University Medical Centre, Maastricht, The Netherlands.
  • 3. Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, The Netherlands.
  • 4. GROW Research Institute for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands.
  • 5. Center for Molecular and Biomolecular Informatics, RIMLS, Radboudumc, Nijmegen, The Netherlands.
  • 6. Department of Medical Genetics, University Medical Centre Utrecht, Utrecht, The Netherlands.
  • 7. Department of Clinical Genetics, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
  • 8. Department of Dermatology, Radboud Institute for Molecular Life Sciences (RIMLS), Radboud University Nijmegen Medical Center (Radboudumc), Nijmegen, The Netherlands. [email protected].
PMID: 30425301 DOI: 10.1038/s41436-018-0355-3
Abstract

Purpose: We aimed to assess the biological and clinical significance of the human cysteine protease inhibitor Cystatin M/E, encoded by the CTS6 gene, in diseases of human hair and skin.

Methods: Exome and Sanger Sequencing was performed to reveal the genetic cause in two related patients with hypotrichosis. Immunohistochemical, biophysical, and biochemical measurements were performed on patient skin and 3D-reconstructed skin from patient-derived keratinocytes.

Results: We identified a homozygous variant c.361C>T (p.Gln121*), resulting in a premature stop codon in exon 2 of CST6 associated with hypotrichosis, eczema, blepharitis, photophobia and impaired sweating. Enzyme assays using recombinant mutant Cystatin M/E protein, generated by site-directed mutagenesis, revealed that this p.Gln121* variant was unable to inhibit any of its three target proteases (Legumain and cathepsins L and V). Three-dimensional protein structure prediction confirmed the disturbance of the protease/inhibitor binding sites of Legumain and cathepsins L and V in the p.Gln121* variant.

Conclusion: The herein characterized autosomal recessive hypotrichosis syndrome indicates an important role of human Cystatin M/E in epidermal homeostasis and hair follicle morphogenesis.

Keywords
3D-reconstructed epidermis; hair follicle; proteases; skin barrier.