Cathepsin-C mutation in an individual with phenotypic features of Haim-Munk syndrome: a case report

Haim–Munk syndrome and Papillon–Lefèvre syndrome are rare genodermatoses caused by mutations in CTSC, which encodes cathepsin C. Both syndromes cause palmoplantar keratoderma and are associated with periodontitis. We report a variant in CTSC that has previously been described in Papillon–Lefèvre syndrome but has not previously been reported in Haim–Munk syndrome. We suggest that Papillon–Lefèvre syndrome and Haim–Munk syndrome are a spectrum of diseases, caused by CTSC mutations, with significant overlap in their phenotypic features.

A novel missense variant in cathepsin C gene leads to PLS in a Chinese patient: A case report and literature review

BACKGROUND

Papilon-Lefevre syndrome (PLS; OMIM 245000) is a rare autosomal recessive disease characterized by aggressive periodontitis and palmoplantar keratoderma. The prevalence of PLS in the general population is one to four cases per million. Although the etiology and pathogenic mechanisms underlying PLS remain largely unclear, existing evidence shows loss-of-function mutations of the cathepsin C gene (CTSC; OMIM 602365) could cause PLS. Here we found a novel variant of the CTSC gene in a Chinese PLS family and predicted the effect of the variant on the physic-chemical characters and tertiary structure of the protein.

METHODS

The 1-7 coding exons and exon-intron boundaries of CTSC gene of the proband and her family were amplified and sequenced directly, and Chromas was used to read sequencing files. Furthermore, the PolyPhen-2, PROVEAN, and Mutation Taster were utilized to predict the pathogenicity of the variant. Besides, the physic-chemical and structural characters of the protein were analyzed by ProtParam, ProtScale, and SWISS-MODEL.

RESULTS

Our study identified a novel homozygous variant c.763T>C (p.Cys255Arg) in exon 6 of the CTSC gene, and it was a likely pathogenic variant as predicted by PolyPhen-2, PROVEAN, and Mutation Taster. Moreover, ProtParam and Protscale revealed the variant increased the isoelectric point and hydrophilicity of the protein, and the SWISS-MODEL analysis suggested the variant was located in a critical domain for protein activity.

CONCLUSION

Our study analyzed a Chinese family with PLS and identified a novel missense variant in the CTSC gene. Besides, this study retrospectively summarized 113 variants of CTSC in the world and highlighted the features of 27 CTSC variants in Chinese PLS patients. In addition, this study paid much particular attention to the relationship between CTSC variants and different phenotypes.

Identification of putative genetic modifying factors that influence the development of Papillon-Lefévre or Haim-Munk syndrome phenotypes

BACKGROUND

Papillon-Lefévre syndrome (PLS; OMIM 245000) and Haim-Munk syndrome (HMS; OMIM 245010), which are both characterized by palmoplantar hyperkeratosis and periodontitis, are phenotypic variants of the same disease caused by mutations of the cathepsin C (CTSC) gene.

AIM

To identify putative genetic modifying factors responsible for the differential development of the PLS or HMS phenotypes, we investigated two Hungarian patients with different phenotypic variants (PLS and HMS) but carrying the same homozygous nonsense CTSC mutation (c.748C/T; p.Arg250X).

METHODS

To gain insights into phenotype-modifying associations, whole exome sequencing (WES) was performed for both patients, and the results were compared to identify potentially relevant genetic modifying factors.

RESULTS

WES revealed two putative phenotype-modifying variants: (i) a missense mutation (rs34608771) of the SH2 domain containing 4A (SH2D4A) gene encoding an adaptor protein involved in intracellular signalling of cystatin F, a known inhibitor of the cathepsin protein, and (ii) a missense variant (rs55695858) of the odorant binding protein 2A (OBP2A) gene, influencing the function of the cathepsin protein through the glycosyltransferase 6 domain containing 1 (GLT6D1) protein.

CONCLUSION

Our study contributes to the accumulating evidence supporting the clinical importance of phenotype-modifying genetic factors, which have high potential to aid the elucidation of genotype-phenotype correlations and disease prognosis.

Palmoplantar keratoderma, oral involvement, and homozygous CTSC mutation in two brothers from Cambodia

Haim-Munk syndrome (HMS) and Papillon-Lefevre syndrome (PLS) are phenotypic variants of palmoplantar keratoderma (PPK) with progressive early-onset periodontitis and dental caries. HMS and PLS have been associated with homozygous or compound heterozygous mutations in the lysosomal protease gene Cathepsin C (CTSC). There have been only a few documented cases of CTSC mutations in patients from South-East Asia. We report the clinical findings of two Cambodian brothers who presented with diffuse, demarcated PPK with transgrediens extending to the elbows and knees, as well as pachyonychia and dental caries. Arachnodactyly and periodontitis were also found in the older brother. Next-generation sequencing unveiled a homozygous missense variant in CTSC (NM_001814.5: c.1337AC: p.(Asp446Ala)) in both brothers. Both parents were heterozygous for the variant, while an unaffected older brother was homozygous for the wild-type allele. Our study adds to the spectrum of mutations and associated clinical presentations for this rare genodermatosis.

Exome sequencing identifies a novel missense variant in CTSC causing nonsyndromic aggressive periodontitis

Cathepsin C (CatC) is a cysteine protease involved in a variety of immune and inflammatory pathways such as activation of cytotoxicity of various immune cells. Homozygous or compound heterozygous variants in the CatC coding gene CTSC cause different conditions that have in common severe periodontitis. Periodontitis may occur as part of Papillon-Lefèvre syndrome (PLS; OMIM#245000) or Haim-Munk syndrome (HMS; OMIM#245010), or may present as an isolated finding named aggressive periodontitis (AP1; OMIM#170650). AP1 generally affects young children and results in destruction of the periodontal support of the primary dentition. In the present study we report exome sequencing of a three generation consanguineous Turkish family with a recessive form of early-onset AP1. We identified a novel homozygous missense variant in exon 2 of CTSC (NM_148170, c.G302C, p.Trp101Ser) predicted to disrupt protein structure and to be disease causing. This is the first described CTSC variant specific to the nonsyndromic AP1 form. Given the broad phenotypic spectrum associated with CTSC variants, reporting this novel variant gives new insights on genotype/phenotype correlations and might improve diagnosis of patients with early-onset AP1.

Periodontal and other oral manifestations of immunodeficiency diseases

The list of immunodeficiency diseases grows each year as novel disorders are discovered, classified, and sometimes reclassified due to our ever-increasing knowledge of immune system function. Although the number of patients with secondary immunodeficiencies (SIDs) greatly exceeds those with primary immunodeficiencies (PIDs), the prevalence of both appears to be on the rise probably because of scientific breakthroughs that facilitate earlier and more accurate diagnosis. Primary immunodeficiencies in adults are not as rare as once thought. Globally, the main causes of secondary immunodeficiency are HIV infection and nutritional insufficiencies. Persons with acquired immune disorders such as AIDS caused by the human immunodeficiency virus (HIV) are now living long and fulfilling lives as a result of highly active antiretroviral therapy (HAART). Irrespective of whether the patient's immune-deficient state is a consequence of a genetic defect or is secondary in nature, dental and medical practitioners must be aware of the constant potential for infections and/or expressions of autoimmunity in these individuals. The purpose of this review was to study the most common conditions resulting from primary and secondary immunodeficiency states, how they are classified, and the detrimental manifestations of these disorders on the periodontal and oral tissues.

Salivary Tick Cystatin OmC2 Targets Lysosomal Cathepsins S and C in Human Dendritic Cells

To ensure successful feeding tick saliva contains a number of inhibitory proteins that interfere with the host immune response and help to create a permissive environment for pathogen transmission. Among the potential targets of the salivary cystatins are two host cysteine proteases, cathepsin S, which is essential for antigen- and invariant chain-processing, and cathepsin C (dipeptidyl peptidase 1, DPP1), which plays a critical role in processing and activation of the granule serine proteases. Here, the effect of salivary cystatin OmC2 from Ornithodoros moubata was studied using differentiated MUTZ-3 cells as a model of immature dendritic cells of the host skin. Following internalization, cystatin OmC2 was initially found to inhibit the activity of several cysteine cathepsins, as indicated by the decreased rates of degradation of fluorogenic peptide substrates. To identify targets, affinity chromatography was used to isolate His-tagged cystatin OmC2 together with the bound proteins from MUTZ-3 cells. Cathepsins S and C were identified in these complexes by mass spectrometry and confirmed by immunoblotting. Furthermore, reduced increase in the surface expression of MHC II and CD86, which are associated with the maturation of dendritic cells, was observed. In contrast, human inhibitor cystatin C, which is normally expressed and secreted by dendritic cells, did not affect the expression of CD86. It is proposed that internalization of salivary cystatin OmC2 by the host dendritic cells targets cathepsins S and C, thereby affecting their maturation.

[Gene mutational analyses of the cathepsin C gene in families with Papillon-Lefèvre syndrome]

OBJECTIVE

This study aims to investigate the gene mutational characteristics of cathepsin C (CTSC) gene in a Chinese patient with Papillon-Lefèvre syndrome (PLS), then further confirm the genetic basis for the phenotype of PLS, and obtain genetic information that can be used as guide in the diagnosis and treatment of PLS.

METHODS

With their consent, peripheral blood samples were obtained from the proband and his family members (his parents and older sister) for genomic DNA extraction. The coding region and exon/intron boundaries of the CTSC gene were amplified and sequenced using poly-merase chain reaction and direct sequencing of DNA.

RESULTS

Compound heterozygous mutations of CTSC gene were iden-tified in the patient. The proband carries one heterozygous nonsense mutation c.754C>T in exon 5 and one heterozygous missense mutation c.1040A>G in exon 7. Both parents were heterozygous carriers without the clinical symptoms of PLS. None of the mutations were detected in the proband's sister.

CONCLUSIONS

The study proves that mutations of CTSC gene are responsible for the phenotype of Papillon-Lefèvre syndrome.
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Inherited diseases caused by mutations in cathepsin protease genes

Lysosomal cathepsins are proteolytic enzymes increasingly recognized as prognostic markers and potential therapeutic targets in a variety of diseases. In those conditions, the cathepsins are mostly overexpressed, thereby driving the respective pathogenic processes. Although less known, there are also diseases with a genetic deficiency of cathepsins. In fact, nowadays 6 of the 15 human proteases called 'cathepsins' have been linked to inherited syndromes. However, only three of these syndromes are typical lysosomal storage diseases, while the others are apparently caused by defective cleavage of specific protein substrates. Here, we will provide an introduction on lysosomal cathepsins, followed by a brief description of the clinical symptoms of the various genetic diseases. For each disease, we focus on the known mutations of which many have been only recently identified by modern genome sequencing approaches. We further discuss the effect of the respective mutation on protease structure and activity, the resulting pathogenesis, and possible therapeutic strategies.

Palmoplantar keratodermas: clinical and genetic aspects

Palmoplantar keratodermas comprise a diverse group of acquired and hereditary disorders marked by excessive thickening of the epidermis of palms and soles. Early onset and positive family history suggest a genetic cause. While hereditary forms of palmoplantar keratoderma (PPK) may represent the sole or dominant clinical feature, they may also be associated with other ectodermal defects or extracutaneous manifestations. In recent years, much progress has been made in deciphering the genetic basis of PPK, which has led to the emergence of new disorders and syndromes. The elucidation of disease mechanisms has opened new avenues for specific therapies, increasingly sparking interest in this field. Given the high heterogeneity with respect to clinical features, genetic defects, and disease mechanisms, the classification of PPK is based on various criteria. These include extent of disease manifestations, morphology of palmoplantar skin involvement, inheritance patterns, and molecular pathogenesis. Though not always feasible, the clinical distinction of various PPK entities is based on fine-tuned criteria or clues. Remarkably, apparently distinct disorders have been shown to be allelic, as they are caused by mutations in the same gene. By contrast, similar clinical pictures may result from mutations in different genes. Because of this complexity, mutation analysis is required to determine the precise type of PPK. The best-defined entities are described in this review.