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Molecular analysis and characterization of nine novel CTSK mutations in twelve patients affected by pycnodysostosis
Author(s) -
Donnarumma Michela,
Regis Stefano,
Tappino Barbara,
Rosano Camillo,
Assereto Stefania,
Corsolini Fabio,
Di Rocco Maja,
Filocamo Mirella
Publication year - 2007
Publication title -
human mutation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 162
eISSN - 1098-1004
pISSN - 1059-7794
DOI - 10.1002/humu.9490
Subject(s) - biology , missense mutation , mutant , cathepsin k , microbiology and biotechnology , mutation , genetics , gene , mutation testing , osteoclast , in vitro
Molecular characterization of twelve unrelated patients affected by the autosomal recessive osteosclerotic skeletal dysplasia, Pycnodysostosis (cathepsin k deficiency), revealed 11 different genotypes. The mutational profile consisted of 12 different mutations, including nine previously unreported ones, spread throughout the whole gene. One mutation occurred in regions coding predomain, two affected the prodomain and nine others occurred in the mature domain. The novel lesions consisted in six missense mutations c.20T>C (p.L7P), c.494A>G (p.Q165R), c.580G>A (p.G194S), c.746T>C (p.I249T), c.749A>G (p.D250G), c.955G>T (p.G319C), two frameshifts c.60_61dupGA (p.I21RfsX29), c.282dupA (p.S95VfsX9) and a splicing mutation c.890G>A (r.785_890del). The six new missense mutations were examined by western blots of COS‐7 cells transfected with mutant CTSK genes. The L7P, occurring within the predicted hydrophobic domain of signal peptide, showed a significantly reduced expression level compared to the wild type control. These findings suggested that the mutation affected targeting and translocation of the nascent lysosomal protein across the endoplasmatic reticulum membrane. The novel amino acid changes were also modeled into the three‐dimensional structure that predicted incorrect protein folding for all of them. Molecular characterization of the patients is of particular value for genetic counseling of patients and their families as diagnosis of Pycnodysostosis based on enzyme assay is unpractical and thus not offered routinely. © 2007 Wiley‐Liss, Inc.