Identification of cathepsin C mutations in ethnically diverse papillon-Lefèvre syndrome patients

INTRODUCTION—Papillon-Lefèvre syndrome (PLS) is an autosomal recessive disorder characterised by palmoplantar keratoderma and severe, early onset periodontitis, which results from deficiency of cathepsin C activity secondary to mutations in the cathepsin C gene. To date, 13 different cathepsin C mutations have been reported in PLS patients, all of which are homozygous for a given mutation, reflecting consanguinity.
AIM—To evaluate the generality of cathepsin C mutations in PLS, we studied an ethnically diverse group of 20 unrelated families.
METHODS—Mutations were identified by direct automated sequencing of genomic DNA amplified for exonic regions and associated splice site junctions of the cathepsin C gene. Long range PCR was performed to determine the genomic structure of the cathepsin C gene.
RESULTS—The cathepsin C gene spans over 46 kb, with six introns ranging in size from 1.6 to 22.4 kb. Eleven novel mutations and four previously reported mutations were identified in affected subjects from 14 families. Missense mutations were most common (9/15), followed by nonsense mutations (3/15), insertions (2/15), and deletions (1/15). Among these 14 probands, two were compound heterozygotes. Affected subjects with transgressions of the dermal lesions onto the knees or elbows or both had mutations in both the pro- and mature regions of the enzyme, although most were in the mature region.
CONCLUSION—Mutations in the mature region of cathepsin C were more likely to be associated with the transgressions of the dermatological lesions, although the results were not statistically significant. A comprehensive list of all cathepsin C mutations described to date, representing 25 mutations from 32 families with PLS and related conditions, is also presented.


Keywords: cathepsin C; genetics; severe early onset periodontitis; hyperkeratosis     

A novel C202F mutation in the connexin26 gene (GJB2) associated with autosomal dominant isolated hearing loss

Mutations in the GJB2 gene encoding connexin26 (CX26) account for up to 50% of cases of autosomal recessive hearing loss. In contrast, only one GJB2 mutation has been reported to date in an autosomal dominant form of isolated prelingual hearing loss. We report here a novel heterozygous 605G→T mutation in GJB2 in all affected members of a large family with late childhood onset of autosomal dominant isolated hearing loss. The resulting C202F substitution, which lies in the fourth (M4) transmembrane domain of CX26, may impair connexin oligomerisation. Finally, our study suggests that GJB2 should be screened for heterozygous mutations in patients with autosomal dominant isolated hearing impairment, whatever the severity of the disease.


Keywords: C202F mutation; connexin26 gene (GJB2); autosomal dominant hearing loss     

Evidence of a founder effect for four cathepsin C gene mutations in Papillon-Lefèvre syndrome patients

We describe a mutation and haplotype analysis of Papillon-Lefèvre syndrome probands that provides evidence of a founder effect for four separate cathepsin C mutations. A total of 25 different cathepsin C mutations have been reported in 32 families with Papillon-Lefèvre syndrome (PLS) and associated conditions. A characteristic of these findings is the diversity of different cathepsin C mutations that have been identified. To evaluate the generality of cathepsin C mutations, PLS probands representative of five reportedly unrelated Saudi Arabian families were evaluated by mutational and haplotype analyses. Sequence analysis identified two cathepsin C gene mutations: a novel exon 7 G300D mutation was found in the proband from one family, while probands from four families shared a common R272P mutation in exon 6. The R272P mutation has been previously reported in two other non-Saudi families. The presence of the R272P mutation in probands from these four Saudi families makes this the most frequently reported cathepsin C mutation. To distinguish between the presence of a possible founder effect or a mutational hot spot for the R272P mutation, we performed haplotype analysis using six novel DNA polymorphisms that span a 165 kb interval containing the cathepsin C gene. Results of haplotype analysis for genetic polymorphisms within and flanking the cathepsin C gene are consistent with inheritance of the R272P mutation "identical by descent" from a common ancestor in these four Saudi families. Haplotype analysis of multiple PLS probands homozygous for other cathepsin C mutations (W249X, Q286X, and T153I) also supports inheritance of each of these mutations from common ancestors. These data suggest that four of the more frequently reported cathepsin C mutations have been inherited from common ancestors and provide the first direct evidence for a founder effect for cathepsin C gene mutations in PLS. Identification of these six short tandem repeat polymorphisms that span the cathepsin C gene will permit haplotype analyses to determine other founder haplotypes of cathepsin C mutations in additional PLS families.


Keywords: Papillon-Lefèvre syndrome; cathepsin C; founder effect; chromosome 11q14     

Mutations of the cathepsin C gene are responsible for Papillon-Lefèvre syndrome

Papillon-Lefèvre syndrome (PLS) is an autosomal recessive disorder characterised by palmoplantar hyperkeratosis and severe early onset periodontitis that results in the premature loss of the primary and secondary dentitions. A major gene locus for PLS has been mapped to a 2.8 cM interval on chromosome 11q14. Correlation of physical and genetic maps of this interval indicate it includes at least 40 ESTs and six known genes including the lysosomal protease cathepsin C gene (CTSC). The CTSC message is expressed at high levels in a variety of immune cells including polymorphonuclear leucocytes, macrophages, and their precursors. By RT-PCR, we found CTSC is also expressed in epithelial regions commonly affected by PLS, including the palms, soles, knees, and oral keratinised gingiva. The 4.7 kb CTSC gene consists of two exons. Sequence analysis of CTSC from subjects affected with PLS from five consanguineous Turkish families identified four different mutations. An exon 1 nonsense mutation (856C-->T) introduces a premature stop codon at amino acid 286. Three exon 2 mutations were identified, including a single nucleotide deletion (2692delA) of codon 349 introducing a frameshift and premature termination codon, a 2 bp deletion (2673-2674delCT) that results in introduction of a stop codon at amino acid 343, and a G-->A substitution in codon 429 (2931G-->A) introducing a premature termination codon. All PLS patients were homozygous for cathepsin C mutations inherited from a common ancestor. Parents and sibs heterozygous for cathepsin C mutations do not show either the palmoplantar hyperkeratosis or severe early onset periodontitis characteristic of PLS. A more complete understanding of the functional physiology of cathepsin C carries significant implications for understanding normal and abnormal skin development and periodontal disease susceptibility.     

Familial neonatal Marfan syndrome due to parental mosaicism of a missense mutation in the FBN1 gene

We present a family in which three siblings were born with neonatal Marfan syndrome (MFS) to unaffected parents. The clinical findings included joint contractures, large ears, loose skin, ectopia lentis, muscular hypoplasia, aortic root dilatation, mitral and tricuspid valve insufficiency, and pulmonary emphysema. All three siblings died due to cardiorespiratory insufficiency by 2-4 months of age. Screening of the FBN1 gene showed the heterozygous c.3257G > A (p.Cys1086Tyr) mutation in the proband. Mosaicism of the mutation was demonstrated in the somatic cells and in the germ line of the father. Although three examples of parental mosaicism for classical MFS were demonstrated previously, this is the first report of familial occurrence of neonatal MFS due to a heterozygous mutation in FBN1. In conclusion, the p.Cys1086Tyr mutation in FBN1 is consistently associated with neonatal MFS. Parental mosaicism should always be kept in mind when counseling families with MFS.     

Clinical and molecular analysis in Papillon–Lefèvre syndrome

Papillon–Lefèvre syndrome (PLS; MIM#245000) is a rare recessive autosomal disorder characterized by palmar and plantar hyperkeratosis, and aggressively progressing periodontitis leading to premature loss of deciduous and permanent teeth. PLS is caused by loss‐of‐function mutations in the CTSC gene, which encodes cathepsin C. PLS clinical expressivity is highly variable and no consistent genotype–phenotype correlation has been demonstrated yet. Here we report the clinical and genetic features of five PLS patients presenting a severe periodontal breakdown in primary and permanent dentition, hyperkeratosis over palms and soles, and recurrent sinusitis and/or tonsillitis. Mutation analysis revealed two novel homozygous recessive mutations (c.947T>C and c.1010G>C) and one previous described homozygous recessive mutation (c.901G>A), with parents carrying them in heterozygous, in three families (four patients). The fourth family presented with the CTSC c.628C>T mutation in heterozygous, which was inherited maternally. Patient carrying the CTSC c.628C>T mutation featured classical PLS phenotype, but no PLS clinical characteristics were found in his carrier mother. All mutations were found to affect directly (c.901G>A, c.947T>C, and c.1010G>C) or indirectly (c.628C>T, which induces a premature termination) the heavy chain of the cathepsin C, the region responsible for activation of the lysosomal protease. Together, these findings indicate that both homozygous and heterozygous mutations in the cathepsin C heavy chain domain may lead to classical PLS phenotype, suggesting roles for epistasis or gene–environment interactions on determination of PLS phenotypes.     

Mutational analysis of the cathepsin C gene in a family of Han nationality with Papillon-Lefevre syndrome

OBJECTIVE: To investigate the mutational characteristics of the cathepsin C gene (CTSC, also known as dipeptidyl-peptidase I gene, DPP I) in a family of Han nationality with Papillon-Lefevre syndrome, and to provide the molecular basis for the phenotype. METHODS: Genomic DNAs were extracted from the proband, his parents and younger sister after informed consent. Polymerase chain reaction and direct DNA sequencing were carried out to screen the mutations of the cathepsin C gene. RESULTS: Compound heterozygous mutations of the cathepsin C gene were identified in the patient. The patient carried one frameshift mutation 116delG in exon 1, one heterozygous mutation C255S in exon 6, one missense mutation F314S and one sense mutation E335E in exon 7. The four changes were novel mutations of the cathepsin C gene, which had not been reported previously. None of the mutations were detected in normal controls.CONCLUSION: Mutations of the cathepsin C gene are probably responsible for the phenotype of Papillon-Lefevre syndrome in this family.     

一个掌跖角化牙周病变综合征家系的组织蛋白酶C基因突变分析

目的 探讨中国汉族掌跖角化牙周病变综合征[又称帕-勒氏综合征(Papillon-Lefevre syndrome,PIS)]的组织蛋白酶C(cathepsin C,CISC)[又称二肽肽酶I(dipeptidyl-peptidase I,DPPl)]基因的突变特点,为该基因的突变在PLS疾病的表型中所起的作用提供科学资料.方法 分析临床诊断为PIS的1例患者及其家庭成员的组织蛋白酶C基因的突变,分别提取患者和其父母、妹妹的基因组DNA,应用PCR和DNA直接测序的方法对该家族成员进行组织蛋白酶C基因突变的检测.结果 该例PIS患者存在组织蛋白酶C基因的复合型杂合突变,突变为:第1外显子的第116位碱基G缺失(P.V40S),并使随后的第40～50位氨基酸发生了移码改变;第6外显子的C255S杂合突变突变;第7外显子的F314S错义突变和E335E同义突变.这4个突变均为新的突变位点,健康对照组未发现基因突变.结论 组织蛋白酶C基因的突变是引起PLS临床显型的病因.     

一个中国耳聋家系的SLC26A4基因分析

目的 确定一个非综合征型耳聋家系的致病基因。方法 应用聚合酶链反应-直接测序方法，对溶质转运蛋白家族26，成员4（solute carrier family 26，member 4；SLC26A4）基因的所有外显子及其与内含子交界处进行测序寻找突变。结果 在该家系先证者发现SLC26A4基因的N392Y、S448X复合杂合突变，其父亲为S448X的杂合突变，其母亲为N392Y的杂合突变。结论 SLC26A4基因的N392Y、S448X复合杂合突变是导致该先证者耳聋发生的原因。     

A novel mutation in the mitochondrial tRNA(Ser(UCN)) gene in a family with non-syndromic sensorineural hearing impairment

We describe a family with non-syndromic sensorineural hearing impairment inherited in a manner consistent with maternal transmission. Affected members were found to have a novel heteroplasmic mtDNA mutation, T7510C, in the tRNA^Ser(UCN) gene. This mutation was not found in 661 controls, is well conserved between species, and disrupts base pairing in the acceptor stem of the tRNA, making it the probable cause of hearing impairment in this family. Sequencing of the other mitochondrial tRNA genes did not show any other pathogenic mutations. Four other mutations causing hearing impairment have been reported in the tRNA^Ser(UCN) gene, two having been shown to affect tRNA^Ser(UCN) levels. With increasing numbers of reports of mtDNA mutations causing hearing impairment, screening for such mutations should be considered in all cases unless mitochondrial inheritance can be excluded for certain.


Keywords: hearing impairment; mtDNA mutation; tRNA^Ser(UCN)     

Loss-of-function mutations in cathepsin C in two families with Papillon-Lefèvre syndrome are associated with deficiency of serine proteinases in PMNs

Papillon-Lefèvre syndrome (PLS) is a rare autosomal recessive disease that involves severe periodontitis and hyperkeratosis of the hand palms and foot soles. Recently it was found that PLS patients carry loss-of-function mutations in the gene encoding cathepsin C (CTSC). In the present study we have analyzed the CTSC gene in two unrelated families with PLS. In the first non-consanguineous family, mutation analysis revealed the previously reported c.815G>C/p.R272P mutation. The second consanguineous family displayed a c.1213C>A mutation which resulted in the novel mutation p.H405N and is the first mutation described in the active site of the enzyme. The PLS patients had, next to the absence of cathepsin C activity in polymorphonuclear leukocytes (PMNs), no activity of the three serine proteinases elastase, cathepsin G and proteinase 3. Serine proteinases are supposed to be important in both the innate and adaptive immune systems. Their absence in PLS patients could explain the inadequate defense to periodontal infection.     

Haim-Munk syndrome and Papillon-Lefèvre syndrome are allelic mutations in cathepsin C

Of the many palmoplantar keratoderma (PPK) conditions, only Papillon-Lefèvre syndrome (PLS) and Haim-Munk syndrome (HMS) are associated with premature periodontal destruction. Although both PLS and HMS share the cardinal features of PPK and severe periodontitis, a number of additional findings are reported in HMS including arachnodactyly, acro-osteolysis, atrophic changes of the nails, and a radiographic deformity of the fingers. While PLS cases have been identified throughout the world, HMS has only been described among descendants of a religious isolate originally from Cochin, India. Parental consanguinity is a characteristic of many cases of both conditions. Although autosomal recessive transmission of PLS is evident, a more "complex" autosomal recessive pattern of inheritance with phenotypic influences from a closely linked modifying locus has been hypothesised for HMS. Recently, mutations of the cathepsin C gene have been identified as the underlying genetic defect in PLS. To determine if a cathepsin C mutation is also responsible for HMS, we sequenced the gene in affected and unaffected subjects from the Cochin isolate in which both the PLS and HMS phenotypes appear. Here we report identification of a mutation of cathepsin C (exon 6, 2127A--> G) that changes a highly conserved amino acid in the cathepsin C peptide. This mutation segregates with HMS in four nuclear families. Additionally, the existence of a shared common haplotype for genetic loci flanking the cathepsin C gene suggests that affected subjects descended from the Cochin isolate are homozygous for a mutation inherited "identical by descent" from a common ancestor. This finding supports simple autosomal recessive inheritance for HMS in these families. We also report a mutation of the same exon 6 CTSC codon (2126C-->T) in a Turkish family with classical PLS. These findings provide evidence that PLS and HMS are allelic variants of cathepsin C gene mutations.     

Molecular diagnosis of HFE mutations in routine laboratories. Results of a survey from reference laboratories in France

HFE-related hemochromatosis (HFE hemochromatosis) or type 1 hemochromatosis is an autosomal recessive disease characterized by progressive iron overload usually expressed in adulthood. The HFE gene, located on the short arm of chromosome 6 (6p21.3), encodes a protein that plays a crucial role in iron metabolism by modulating hepcidin synthesis in the liver. Homozygosity for the p.Cys282Tyr mutation accounts for nearly 80% of cases of hemochromatosis in France. Genetic testing is the key investigation to confirm the diagnosis of HFE hemochromatosis. A survey on routine practices was carried out among the eight reference laboratories of the French national network on genetic iron disorders. The main findings from this survey are as follows: 1) the p.Cys282Tyr mutation must be searched for as an initial step to establish the diagnosis of HFE hemochromatosis. This is in agreement with the recommendations of the French Health Authority (HAS) published in 2005. In these recommendations, homozygosity for the p.Cys282Tyr mutation with at least elevated transferrin saturation, is considered the only genotype that confirms of the diagnosis of HFE hemochromatosis; 2) in combination with the p.Cys282Tyr mutation (compound heterozygous genotypes), the p.Ser65Cys and the p.His63Asp variants may contribute to the occurrence of mild iron overload; 3) family screening is mandatory following the detection of homozygous individuals for the p.Cys282Tyr mutation.     

Localisation of a gene for an autosomal recessive syndrome of macrocephaly, multiple epiphyseal dysplasia, and distinctive facies to chromosome 15q26

BACKGROUND—We have previously described an autosomal recessive syndrome of macrocephaly, multiple epiphyseal dysplasia (MED), and distinctive facies in a large, extended Omani family. The MED observed seems to be part of a larger malformation syndrome, since both craniofacial and central nervous system changes were present in the family. We performed a whole genome scan in this family in order to identify the gene locus for this malformation syndrome.
METHODS AND RESULTS—Using homozygosity mapping, we show linkage to the telomeric region of the long arm of chromosome 15. The position of both the disease gene and the principal glycoprotein, chondroitin sulphate proteoglycan (aggrecan, AGC1) on chromosome 15q26, suggested that the aggrecan gene is a candidate for the disease in this family. However, three of the four affected children were heterozygous for a polymorphism at position 831 of the coding sequence of AGC1, providing strong evidence against its involvement.
CONCLUSION—We have identified a gene locus for a recessive syndrome of macrocephaly, MED, and distinctive facies in a large Omani family. Aggrecan located on chromosome 15q26, within the critical region determined for this syndrome in this family, was excluded as a candidate gene.


Keywords: macrocephaly; multiple epiphyseal dysplasia; distinctive facies; chromosome 15q26     

Novel missense mutation resulting in the substitution of tyrosine by cysteine at codon 597 of the type X collagen gene associated with Schmid metaphyseal chondrodysplasia

Schmid metaphyseal chondrodysplasia (SMCD) is one of the most common forms of the osteochondrodysplasias. Mutations or deletions in the COL10A1 gene that encodes type X collagen have been shown to cause this disorder. Most of the gene mutations and deletions are located in the non-collagenous carboxy (C)-terminal (NC1) domain. We describe a novel missense mutation in a patient with SMCD that leads to the substitution of Tyr at codon 597 by Cys in the NC1 domain. Sequence analysis indicated that the proband was heterozygous for the mutation. Her parents were homozygous for the normal sequence, indicating the de-novo occurrence of this mutation. Received: April 27, 1998 / Accepted: June 24, 1998     

Report of two unrelated families with Jalili syndrome and a novel nonsense heterozygous mutation in CNNM4 gene

Jalili syndrome (JS) is an autosomal recessive disease characterized by a combination of cone-rode retinal dytrophy (CRD) and amelogenesis imperfect (AI). Mutations in cyclin and CBS domain divalent metal cation transport mediator 4 (CNNM4) gene cause JS. Here we described 2 families (3 members) affected by JS. In the first family, JS was caused by the homozygous p.Leu324Pro (c.971T > C) missense mutation and the affected patient developed both CRD and AI. In the second family, a specific combination of a compound heterozygous mutation was found – the p.Leu324Pro (c.971T > C) missense transition and the novel p.Tyr581* (c.1743C > G) nonsense mutation. The proband showed CRD and AI, but her father just developed eye alterations. Together, these findings suggest that the p.Leu324Pro mutation in homozygosis induces a complete phenotype with both CRD and AI, but in heterozygosis and in composition with the novel p.Tyr581* nonsense mutation in CNNM4 promotes variable clinical expressivity, particularly with lack of dental phenotypes. These different phenotypes could be explained by deletions affecting the proband's homologous allele, epistasia or interactions with environmental factors leading to residual activity of protein.     

线粒体糖尿病家系基因突变的遗传学筛查

目的 探索与糖尿病发病相关的线粒体基因突变位点。方法 采用PCR、DNA直接测序技术对28个临床疑似线粒体基因突变糖尿病家系(mitochondrial diabetes mellitus，MDM)进行线粒体基因突变高发区域(tRNA^Leu(UUR)基因及NADH脱氢酶1基因)的筛查。结果 两个家系发现与糖尿病发病有关的突变位点。其中1个家系(16号)同时携带nt3243A→G突变和16S rRNA3205C→T突变。该家系两例患者均有消瘦、耳聋、β细胞功能低下、发病年龄低的特点，先证者血乳酸水平在正常高限。在另1先证者患耳聋的家系(28号)发现NDl基因3434A→G突变，导致氨基酸改变，与家系中糖尿病呈共同分离。上述突变均未在正常人中检测到。结论 3243位点突变在本组家系中的发现率为3．08％。16S rRNA3205C→T突变可能与糖尿病发病有关或与nt3243A→G突变协同作用。NDl基因3434A→G突变与28号家系糖尿病的发生有关。     

Five familial hypercholesterolemic kindreds in Japan with novel mutations of the LDL receptor gene

In the course of investigations of familial coronary artery disease in Hokkaido, the northern island of Japan, we identified five families in which multiple members showed elevated plasma levels of low-density lipoprotein (LDL) cholesterol. To determine the genetic etiology of their lipoprotein abnormalities, we screened DNA samples from these families for mutations in all 18 exons and the exon-intron boundaries of the LDL receptor (LDLR) gene. Novel point mutations were identified in each family: (1) a C-to-A transversion at nucleotide 285, causing a nonsense mutation at codon 74, in eight members of family A; (2) a G-to-A transition at nucleotide 1136, causing substitution of Tyr for Cys at codon 358, in six members of family B; (3) a C-to-T transition at nucleotide 1822, causing substitution of Ser for Pro at codon 587, in five members of family C; (4) a one-base insertion of G to a five-G stretch at nucleotides 1774–1778 (codons 571–572), causing a frameshift, in six members of family D; and (5) a one-base deletion of T at nucleotide 1963–1964 (codon 634), causing a frameshift, in three members of family E. Through the molecular genetic approach a total of 28 individuals in these families were diagnosed unequivocally as heterozygous for the respective LDLR mutations. This method also helped us to diagnose familial hypercholesterolemia, or to exclude from carrier status, 11 children with borderline high cholesterol levels. Received: May 20, 1998 / Accepted: June 30, 1998     

Familial neurohypophyseal diabetes insipidus associated with a novel mutation in the vasopressin-neurophysin II gene

Familial neurohypophyseal diabetes insipidus (FNDI) is an autosomal dominant disorder of renal water conservation due to deficiency of arginine vasopressin as the result of mutations in the arginine vasopressin-neurophysin II (AVP-NPII) gene that encodes the hormone or its carrier protein. Thirty-one different mutations have been reported. In this study, we evaluated the AVP-NPII gene in a family with FNDI and identified a new mutation (1911Gright curved arrow A) in the coding sequence for NPII in affected family members. This mutation substitutes Tyr for 74 Cys in the NPII moiety. NPII is an intracellular carrier protein for AVP during the axonal transport from the hypothalamus to the posterior pituitary and contains 14 conserved cysteine residues forming 7 disulfide bonds. Because the mutation cosegregates with the phenotype, it is possible that this mutation causes neurohypophyseal diabetes insipidus in this family.     

Different ocular abnormalities in individuals of a three-generation family caused by a new nonsense mutation in the PST domain of the PAX6 gene

PAX6 is a candidate gene for familial aniridia. We have carried out a mutational analysis of the PAX6 gene in a three-generation family from Germany, containing 5 individuals affected with ocular abnormalities. In all affected individuals, a heterozygous mutation was detected in the PAX6 gene, exchanging tyrosine 369 by a stop codon. The mutation is located in the 3′ moiety of the PST domain, at the C terminus of the PAX6 protein. In the affected family members, the same heterozygous mutation leads to distinct phenotypes of varying severity. Most notably, s of varying severity. Most notably, no aniridia was observed in one of the family members carrying the mutation, although other ocular abnormalities (underdeveloped iris and cataracts) were present. We discuss the possibility that small C terminal truncations of the PAX6 protein might lead to less severe or more divergent phenotypes than truncations at internal positions. © 1998 Wiley-Liss, Inc.