[Clinical analysis of four patients with Schwartz-Jampel syndrome]

OBJECTIVE

To analyze the clinical manifestation, diagnosis and treatment of Schwartz-Jampel syndrome (SJS).

METHOD

The clinical data, including demographic, laboratory tests (creatase, creatine kinase, etc.) and electromyography of 4 children with SJS were analyzed.

RESULT

All the 4 patients were male. The age of onset was from 0.5 to 1.25 years (average 0.83 years). The onset of 4 patients was insidious, the age to see doctor was from 2.17 to 10 years (average 5.92 years), body height was less than the third percentile rank in the children of same age and gender, they presented with facial expression stiffness, microstomia, difficult in opening mouth, blepharophimosis, limbs stiffness and, so formed a characteristic phenotype. Investigations showed the creatase in serum increased, creatine kinase (CK): 229 - 1039 U/L (normal value < 200 U/L), Creatine Kinase MB (CK-MB): 30 - 45 U/L (normal value < 25 U/L), lactate dehydrogenase (LDH): 455 - 716 U/L (normal value < 240 U/L). General myotonia potential was found in electromyography, osteoarticular deformities in medical imaging, and muscle biopsy in 2 patients showed type I muscle fibers differed in size and were disproportionate. All the patients took oral vitamin B, and received rehabilitation training, 1 patient took carbamazepine for 1 month, blepharophimosis and limbs stiffness was improved.

CONCLUSION

SJS is a rare autosomal recessive inherited disease. Clinical manifestations of SJS are characteristic facies, skeletal abnormalities, generous myotonia and short stature. Carbamazepine is effective for treatment.

Transcriptional profiling of chondrodysplasia growth plate cartilage reveals adaptive ER-stress networks that allow survival but disrupt hypertrophy

Metaphyseal chondrodysplasia, Schmid type (MCDS) is characterized by mild short stature and growth plate hypertrophic zone expansion, and caused by collagen X mutations. We recently demonstrated the central importance of ER stress in the pathology of MCDS by recapitulating the disease phenotype by expressing misfolding forms of collagen X (Schmid) or thyroglobulin (Cog) in the hypertrophic zone. Here we characterize the Schmid and Cog ER stress signaling networks by transcriptional profiling of microdissected mutant and wildtype hypertrophic zones. Both models displayed similar unfolded protein responses (UPRs), involving activation of canonical ER stress sensors and upregulation of their downstream targets, including molecular chaperones, foldases, and ER-associated degradation machinery. Also upregulated were the emerging UPR regulators Wfs1 and Syvn1, recently identified UPR components including Armet and Creld2, and genes not previously implicated in ER stress such as Steap1 and Fgf21. Despite upregulation of the Chop/Cebpb pathway, apoptosis was not increased in mutant hypertrophic zones. Ultrastructural analysis of mutant growth plates revealed ER stress and disrupted chondrocyte maturation throughout mutant hypertrophic zones. This disruption was defined by profiling the expression of wildtype growth plate zone gene signatures in the mutant hypertrophic zones. Hypertrophic zone gene upregulation and proliferative zone gene downregulation were both inhibited in Schmid hypertrophic zones, resulting in the persistence of a proliferative chondrocyte-like expression profile in ER-stressed Schmid chondrocytes. Our findings provide a transcriptional map of two chondrocyte UPR gene networks in vivo, and define the consequences of UPR activation for the adaptation, differentiation, and survival of chondrocytes experiencing ER stress during hypertrophy. Thus they provide important insights into ER stress signaling and its impact on cartilage pathophysiology.

Tracheobronchopathia osteochondroplastica presenting as a single dominant tracheal mass

Tracheobronchopathia osteochondroplastica is a rare, benign disorder of upper airways characterized by multiple submucosal metaplastic cartilaginous and bony nodules arising from the tracheal cartilage. We report an unusual presentation of tracheobronchopathia osteochondroplastica as a single dominant nodule arising from the anterior tracheal rings in a young adult man who presented with wheezing and symptoms of airway obstruction. The differential diagnosis of cartilaginous and bony endotracheal lesions is discussed.

Increased basal activity is a key determinant in the severity of human skeletal dysplasia caused by TRPV4 mutations

TRPV4 is a mechanically activated Ca²⁺-passing channel implicated in the sensing of forces, including those acting on bones. To date, 33 mutations are known to affect human bone development to different extents. The spectrum of these skeletal dysplasias (SD) ranges from dominantly inherited mild brachylomia (BO) to neonatal lethal forms of metatropic dysplasia (MD). Complexities of the results from fluorescence and electrophysiological studies have led to questions on whether channel activity is a good predictor of disease severity. Here we report on a systematic examination of 14 TRPV4 mutant alleles covering the entire SD spectrum. Expressed in Xenopus oocyte and without any stimulation, the wild-type channel had a ∼1% open probability (Po) while those of most of the lethal MD channels approached 100%. All mutant channels had higher basal open probabilities, which limited their further increase by agonist or hypotonicity. The magnitude of this limitation revealed a clear correlation between the degree of over-activity (the molecular phenotype) and the severity of the disease over the entire spectrum (the biological phenotype). Thus, while other factors are at play, our results are consistent with the increased TRPV4 basal activity being a critical determinant of the severity of skeletal dysplasia. We discuss how the channel over-activity may lead to the “gain-of-function” phenotype and speculate that the function of wild-type TRPV4 may be secondary in normal bone development but crucial in an acute process such as fracture repair in the adult.

The jumping SHOX gene--crossover in the pseudoautosomal region resulting in unusual inheritance of Leri-Weill dyschondrosteosis

CONTEXT

During meiosis I, the recombination frequency in the pseudoautosomal region on Xp and Yp (PAR1) in males is very high. As a result, mutated genes located within the PAR1 region can be transferred from the Y-chromosome to the X-chromosome and vice versa.

PATIENTS

Here we describe three families with SHOX abnormalities resulting in Leri-Weill dyschondrosteosis or Langer mesomelic dysplasia.

RESULTS

In about half of the segregations investigated, a transfer of the SHOX abnormality to the alternate sex chromosome was demonstrated.

CONCLUSIONS

Patients with an abnormality of the SHOX gene should receive genetic counseling as to the likelihood that they may transmit the mutation or deletion to a son as well as to a daughter.

New phenotype with generalized platyspondyly, large mandible, hypoplastic teeth, strabismus, hyperopia and low cholesterol levels

A sporadic, adult male patient with generalized platyspondyly, large mandible, hypoplastic teeth, strabismus, and low serum cholesterol levels is presented. Some of the patient's features resemble brachyolmia, Spondylo-epiphyseal dysplasia tarda, Kenny-Caffey and Stickler syndromes. Based on literature review, possible diagnoses are discussed. In conclusion, this patient can have a variant of brachyolmia or Spondylo-epiphyseal dysplasia tarda. However, we cannot exclude that this constellation of clinical features may represent a new syndrome.

Fibrochondrogenesis results from mutations in the COL11A1 type XI collagen gene

Fibrochondrogenesis is a severe, autosomal-recessive, short-limbed skeletal dysplasia. In a single case of fibrochondrogenesis, whole-genome SNP genotyping identified unknown ancestral consanguinity by detecting three autozygous regions. Because of the predominantly skeletal nature of the phenotype, the 389 genes localized to the autozygous intervals were prioritized for mutation analysis by correlation of their expression with known cartilage-selective genes via the UCLA Gene Expression Tool, UGET. The gene encoding the α1 chain of type XI collagen (COL11A1) was the only cartilage-selective gene among the three candidate intervals. Sequence analysis of COL11A1 in two genetically independent fibrochondrogenesis cases demonstrated that each was a compound heterozygote for a loss-of-function mutation on one allele and a mutation predicting substitution for a conserved triple-helical glycine residue on the other. The parents who were carriers of missense mutations had myopia. Early-onset hearing loss was noted in both parents who carried a loss-of-function allele, suggesting COL11A1 as a locus for mild, dominantly inherited hearing loss. These findings identify COL11A1 as a locus for fibrochondrogenesis and indicate that there might be phenotypic manifestations among carriers.

An unfolded protein response is the initial cellular response to the expression of mutant matrilin-3 in a mouse model of multiple epiphyseal dysplasia

Multiple epiphyseal dysplasia (MED) can result from mutations in matrilin-3, a structural protein of the cartilage extracellular matrix. We have previously shown that in a mouse model of MED the tibia growth plates were normal at birth but developed a progressive dysplasia characterised by the intracellular retention of mutant matrilin-3 and abnormal chondrocyte morphology. By 3 weeks of age, mutant mice displayed a significant decrease in chondrocyte proliferation and dysregulated apoptosis. The aim of this current study was to identify the initial post-natal stages of the disease. We confirmed that the disease phenotype is seen in rib and xiphoid cartilage and, like tibia growth plate cartilage is characterised by the intracellular retention of mutant matrilin-3. Gene expression profiling showed a significant activation of classical unfolded protein response (UPR) genes in mutant chondrocytes at 5 days of age, which was still maintained by 21 days of age. Interestingly, we also noted the upregulation of arginine-rich, mutated in early stage of tumours (ARMET) and cysteine-rich with EGF-like domain protein 2 (CRELD2) are two genes that have only recently been implicated in the UPR. This endoplasmic reticulum (ER) stress and UPR did not lead to increased chondrocyte apoptosis in mutant cartilage by 5 days of age. In an attempt to alleviate ER stress, mutant mice were fed with a chemical chaperone, 4-sodium phenylbutyrate (SPB). SPB at the dosage used had no effect on chaperone expression at 5 days of age but modestly decreased levels of chaperone proteins at 3 weeks. However, this did not lead to increased secretion of mutant matrilin-3 and in the long term did not improve the disease phenotype. We performed similar studies with a mouse model of Schmid metaphyseal chondrodysplasia, but again this treatment did not improve the phenotype.

Mutations causing Greenberg dysplasia but not Pelger anomaly uncouple enzymatic from structural functions of a nuclear membrane protein

The lamin B receptor (LBR) is an inner nuclear membrane protein with a structural function interacting with chromatin and lamins, and an enzymatic function as a sterol reductase. Heterozygous LBR mutations cause nuclear hyposegmentation in neutrophils (Pelger anomaly), while homozygous mutations cause prenatal death with skeletal defects and abnormal sterol metabolism (Greenberg dysplasia). It has remained unclear whether the lethality in Greenberg dysplasia is due to cholesterol defects or altered nuclear morphology.To answer this question we characterized two LBR missense mutations and showed that they cause Greenberg dysplasia. Both mutations affect residues that are evolutionary conserved among sterol reductases. In contrast to wildtype LBR, both mutations failed to rescue C14 sterol reductase deficient yeast, indicating an enzymatic defect. We found no Pelger anomaly in the carrier parent excluding marked effects on nuclear structure. We studied Lbr in mouse embryos and demonstrate expression in skin and the developing skeletal system consistent with sites of histological changes in Greenberg dysplasia. Unexpectedly we found in disease-relevant cell types not only nuclear but also cytoplasmatic LBR localization. The cytoplasmatic LBR staining co-localized with ER-markers and is thus consistent with the sites of endogeneous sterol synthesis. We conclude that LBR missense mutations can abolish sterol reductase activity, causing lethal Greenberg dysplasia but not Pelger anomaly. The findings separate the metabolic from the structural function and indicate that the sterol reductase activity is essential for human intrauterine development.

An inducible cartilage oligomeric matrix protein mouse model recapitulates human pseudoachondroplasia phenotype

Cartilage oligomeric matrix protein (COMP) is a pentameric extracellular protein expressed in cartilage and other musculoskeletal tissues. Mutations in the COMP gene cause pseudoachondroplasia (PSACH), a severe dwarfing condition that has a growth plate chondrocyte pathology. PSACH is characterized by intracellular retention of COMP and other extracellular matrix (ECM) proteins, which form an ordered matrix within large rough endoplasmic reticulum cisternae. This accumulation is cytotoxic and causes premature chondrocyte cell death, thereby depleting chondrocytes needed for normal long bone growth. Research to define the underlying molecular mechanisms of PSACH has been hampered by the lack of a suitable model system. In this study, we achieved robust expression of human mutant (MT) or wild-type (WT) COMP in mice by using a tetracycline-inducible promoter. Normal growth plate distribution of ECM proteins was observed in 1-month-old WT-COMP and C57BL\6 control mice. In contrast, the structure of the MT-COMP growth plate recapitulated the findings of human PSACH growth plate morphology, including (1) retention of ECM proteins, (2) intracellular matrix formation in the rER cisternae, and (3) increased chondrocyte apoptosis. Therefore, we have generated the first mouse model to show extensive intracellular retention of ECM proteins recapitulating the human PSACH disease process at the cellular level.

Identification of novel mutations in WISP3 gene in two unrelated Chinese families with progressive pseudorheumatoid dysplasia

INTRODUCTION

Progressive pseudorheumatoid dysplasia (PPD) is an autosomal recessive genetic disease and it has been reported that PPD is caused by mutations of the Wnt1-inducible signaling pathway protein 3 (WISP3) gene which is located on chromosome 6q22. Up to date, 16 different mutations in the WISP3 have been identified in patients with PPD in different countries previously, but only two mutations in exon 5 were previously identified from Asian origin. Our study aimed to characterize the clinical manifestations and features of PPD and screen the mutations of the disease causing WISP3, and try to elucidate the molecular pathogenesis of PPD.

MATERIALS AND METHODS

Altogether, 153 persons, including 4 affected individuals, 49 unaffected individuals from two unrelated Chinese families, and 100 healthy donors were recruited and genomic DNA was extracted. PPD was diagnosed based on the clinical manifestations, physical examination, characteristics of their bones on X-ray and laboratory results. All 5 exons and their exon-intron boundaries of the WISP3 gene were amplified by polymerase chain reaction (PCR) and sequenced directly.

RESULTS

In family 1, we identified that the proband (IV4) carried a novel non-sense mutation (G46X) which consisted of a homozygous C to T transition at c.8004 in exon 3. This mutation changed codon CAG to TAG and resulted in a subsequent change of the glutamine codon to stop codon and truncation at p. 46. In family 2, a novel missense mutation (C114Y) was found in the three patients (IV6, IV7, IV8), namely, a homozygous G to A transition at c.8209 in exon 3, which resulted in a cysteine (TGT) to tyrosine (TAT) substitution at p.114. Neither G46X nor C114Y was found in 100 normal controls. Meanwhile, we found that these patients had some different phenotypes, compared with the affected individuals with PPD from cases reported previously.

CONCLUSIONS

Our study suggests that the novel G46X and C114Y mutations in exon 3 in WISP3 gene are responsible for PPD in Chinese patients. Furthermore, many heterozygous carriers (c.8004C>T and c.8209G>A) are found in the two families, suggesting the existence of a founder effect in the locality where they live, respectively.

[Lethal osteo-chondro-dysplasia: feto-pathological study of 32 cases]

BACKGROUND

The lethal osteochondrodysplasias are rare, their prevalence is estimated at 1 per 10 000 births. Mostly have genetic determinism.

AIMS

To describe the malformations and dysmorphic features in lethal osteochondrodysplasias

METHODS

Our study involved 32 cases of lethal fetal Osteochondrodysplasias, collected over a period of 14 years in the pathological department of Sousse.

RESULTS

Our series consisted of 23 foetuses from a medical termination of pregnancy, 6 newborns and 3 stillbirths. The mean age of mothers was 28 years old, consanguinity was observed in 61%. 3 cases of recurrence of the disease in three families were noted. The bone abnormalities were detected in antenatal ultrasonography in 25 cases (87%) and at birth in 7 cases. Ultrasound showed micromelia in all cases, a narrow chest in 5 cases and spina bifida in 3 cases. The feto-pathological exam, including a macroscopic examination, radiological and histological samples of bone, has allowed us, based on the International Classification of 2001 to classify the 32 cases of Osteochondrodysplasias in: 8 cases of Achondrogenesis type I (type Parenti-Fraccaro), 3 cases of Achondrogenesis type II (Langer Saldino), 9 cases of lethal osteogenesis imperfecta, 8 cases of thanatophoric dysplasia, 4 cases of Schneckenbecken dysplasia, 2 cases of Short rib polydactyly syndrome, Majewski type and 1 case of asphyxiating thoracic dysplasia.

[Jeune syndrome (asphyxiating thoracic dystrophy): a case report]

Jeune syndrome or asphyxiating thoracic dystrophy is a rare autosomal recessive skeletal dysplasia characterized by a small thorax, short-limbed dwarfism, renal and hepatic anomalies. It is estimated to occur in 1 per 100.000-130.000 live births. Radiological confirmation of diagnosis is essential. Prognosis of the disease is due to the severity of chest deformities and most of the patients are lost in their first year because of respiratory problems. We presented a 19-month-old female patient who admitted to our clinic because of recurrent lower respiratory tract infections and diagnosed as Jeune syndrome and reported due to its rarity.

Demonstration of the interaction of transforming growth factor beta 2 and type X collagen using a modified tandem affinity purification tag

Like other members of the transforming growth factor beta (TGF-beta) family of growth factors, the biological activity of TGF-beta2 is believed to be regulated by the formation and dissociation of multiprotein complexes. To isolate the molecular complex formed by TGF-beta2 secreted by hypertrophic chondrocytes we have used expression of TGF-beta2 fused with the humanized, tandem affinity purification (hTAP) tag and mass spectrometry for the identification of interacting proteins. The hTAP synthetic gene was assembled by systematically replacing the rare codons of the original TAP tag with codons most preferred in highly expressed human genes to circumvent the poor translation efficiency of the original TAP tag in animal cells. TGF-beta2 was shown to interact with Type X collagen and this interaction confirmed using V5 tagged TGF-beta2. Functional interaction was suggested by the inhibition of TGF-beta2 activity by type X collagen in culture and the influence of a mutation in type X collagen on the distribution of TGF-beta2 in growth cartilage.

A novel mutation in the sulfate transporter gene SLC26A2 (DTDST) specific to the Finnish population causes de la Chapelle dysplasia

BACKGROUND

Mutations in the sulfate transporter gene SLC26A2 (DTDST) cause a continuum of skeletal dysplasia phenotypes that includes achondrogenesis type 1B (ACG1B), atelosteogenesis type 2 (AO2), diastrophic dysplasia (DTD), and recessive multiple epiphyseal dysplasia (rMED). In 1972, de la Chapelle et al reported two siblings with a lethal skeletal dysplasia, which was denoted "neonatal osseous dysplasia" and "de la Chapelle dysplasia" (DLCD). It was suggested that DLCD might be part of the SLC26A2 spectrum of phenotypes, both because of the Finnish origin of the original family and of radiographic similarities to ACG1B and AO2.

OBJECTIVE

To test the hypothesis whether SLC26A2 mutations are responsible for DLCD.

METHODS

We studied the DNA from the original DLCD family and from seven Finnish DTD patients in whom we had identified only one copy of IVS1+2T>C, the common Finnish mutation. A novel SLC26A2 mutation was found in all subjects, inserted by site-directed mutagenesis in a vector harbouring the SLC26A2 cDNA, and expressed in sulfate transport deficient Chinese hamster ovary (CHO) cells to measure sulfate uptake activity.

RESULTS

We identified a hitherto undescribed SLC26A2 mutation, T512K, homozygous in the affected subjects and heterozygous in both parents and in the unaffected sister. T512K was then identified as second pathogenic allele in the seven Finnish DTD subjects. Expression studies confirmed pathogenicity.

CONCLUSIONS

DLCD is indeed allelic to the other SLC26A2 disorders. T512K is a second rare "Finnish" mutation that results in DLCD at homozygosity and in DTD when compounded with the milder, common Finnish mutation.

[A novel mutation in the SEDL gene leading to X-linked spondyloepiphyseal dysplasia tarda in a large Chinese pedigree]

OBJECTIVE

To identify the genetic defect in a four-generation pedigree with X-linked recessive spondyloepiphyseal dysplasia tarda (SEDT) from Southwest China.

METHODS

Linkage analysis with one panel of fluorescently labeled microsatellite markers on chromosome X and mutation screening of SEDL gene by direct sequencing were performed.

RESULTS

Linkage between SEDT and Xp22.2-Xp23.1 was established with maximum LOD score of 3.82 (theta = 0) between DXS987 and DXS8051. Upon sequence analysis, a point mutation within exon 4 of the SEDL gene (c.239A to G) was found which resulted in substitution of histidine with arginine at codon 80 (His80Arg).

CONCLUSION

A novel missense mutation (H80R) was identified for SEDL gene in the large Chinese SEDT pedigree.

Metatropic dysplasia in children

Metatropic dysplasia is a rare genetic condition characterized by progressive dwarfism. Metatropic dysplasia is defined as a short limb skeletal dysplasia characterized by dumbell like configuration of long bones, a narrow but normal length of thorax and occasionally a coccygeal appendage similar to a tail. Children born with this condition show different signs and symptoms throughout the childhood. An eight years old boy was admitted in the Paediatric ward of Bangbandhu Sheikh Mujib Medical University (BSMMU), Dhaka with the complain of swelling in the back for 7 1/2 years. On examination the boy had features suggestive of Metatropic dysplasia. Radiological findings included exaggerated curvature of the spine which was different at the different levels giving rise to "S" shaped deformity, pectus carinatum and flattening of the vertebral bodies which were variable at different levels. From the history, clinical examination and radiological findings the boy was diagnosed as a case of metatropic dysplasia.

Tibial dyschondroplasia 40 years later

Tibial dyschondroplasia is a disease of rapid growth rate that occurs in many avian species. It is characterized by an avascular lesion in which the life span of the growth plate chondrocyte is essentially doubled. A characteristic pattern of gene expression and gene product localization has emerged that mimics the pattern observed with endoplasmic reticulum (ER) stress in growth plate chondrocytes. This activates a cell-survival mechanism called autophagy. The initial phases of this mechanism appear to originate in the avascular transition zone of the growth plate. Because specific genes and gene products are associated with autophagy and ER stress, it should now be possible to identify the mechanisms involved in the development of this cartilage abnormality. The potential biochemical pathways responsible for initiating ER stress are discussed.

Effect of temperature during the incubation period on tibial growth plate chondrocyte differentiation and the incidence of tibial dyschondroplasia

Tibial dyschondroplasia (TD) is one of the most prevalent skeletal abnormalities in avian species, causing enormous economic losses and major animal welfare problems. Irregular cell differentiation of the chondrocytes that populate the growth plate has been hypothesized to be involved in the etiology of the disease. We evaluated the effect of incubation temperature at various stages of embryo development and bone formation on growth plate chondrocyte differentiation and the incidence of TD. Eggs were incubated either at a control temperature of 37.8 degrees C, or at 36.9 or 39 degrees C, each for 6 h/ d, during early (0 to 8 d) or late (10 to 18 d) embryo development. At 14 d of incubation and at hatch, tibias were collected and weighed, and their ash and calcium contents were determined. Growth plate chondrocyte differentiation was evaluated by alkaline phosphatase activity and collagen type II and osteopontin gene expression. In addition, the level of the heat-shock protein 90 (Hsp90) was evaluated by immunohistochemistry. The rest of the chicks were raised to 49 d and the incidence of TD was recorded. The incidence of TD increased only when the temperature was altered at the early stages of embryo development, and it was correlated with an increase in tibia ash but not with tibia weight or calcium content. Moreover, increased TD incidence was correlated with delayed chondrocyte differentiation. Early changes in incubation temperature caused an increase in the level of Hsp90 in articular and differentiated chondrocytes of the hypertrophic zone and in the numbers of distinct undifferentiated chondrocytes arranged in columns in the proliferative zone of the growth plate. In summary, the early stages of embryo development and bone formation are of utmost importantance for appropriate growth plate chondrocyte differentiation, and any temperature deviation will increase the subsequent incidence of TD. The increase in TD incidence is probably the result of delayed Hsp90-driven chondrocyte differentiation, supporting the hypothesis that TD is the result of abnormal chondrocyte differentiation.