Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)

Mucopolysaccharidosis VII (MPS VII; Sly syndrome) is an autosomal recessive disorder caused by a deficiency of β‐glucuronidase (GUS, EC 3.2.1.31; GUSB). GUS is required to degrade glycosaminoglycans (GAGs), including heparan sulfate (HS), dermatan sulfate (DS), and chondroitin‐4,6‐sulfate (CS). Accumulation of undegraded GAGs in lysosomes of affected tissues leads to mental retardation, short stature, hepatosplenomegaly, bone dysplasia, and hydrops fetalis. We summarize information on the 49 unique, disease‐causing mutations determined so far in the GUS gene, including nine novel mutations (eight missense and one splice‐site). This heterogeneity in GUS gene mutations contributes to the extensive clinical variability among patients with MPS VII. One pseudodeficiency allele, one polymorphism causing an amino acid change, and one silent variant in the coding region are also described. Among the 103 analyzed mutant alleles, missense mutations accounted for 78.6%; nonsense mutations, 12.6%; deletions, 5.8%; and splice‐site mutations, 2.9%. Transitional mutations at CpG dinucleotides made up 40.8% of all the described mutations. The five most frequent mutations (accounting for 44/103 alleles) were exonic point mutations, p.L176F, p.R357X, p.P408S, p.P415L, and p.A619 V. Genotype/phenotype correlation was attempted by correlating the effects of certain missense mutations or enzyme activity and stability within phenotypes. These were in turn correlated with the location of the mutation in the tertiary structure of GUS. A total of seven murine, one feline, and one canine model of MPS VII have been characterized for phenotype and genotype. Hum Mutat 0,1–10, 2009, © 2009 Wiley‐Liss, Inc.     

Pathogenesis of lumbar spine disease in mucopolysaccharidosis VII

Mucopolysaccharidosis type VII (MPS VII) is characterized by deficient β-glucuronidase (GUSB) activity, which leads to accumulation of chondroitin, heparan and dermatan sulfate glycosaminoglycans (GAGs), and multisystemic disease. MPS VII patients can develop kypho-scoliotic deformity and spinal cord compression due to disease of intervertebral disks, vertebral bodies, and associated tissues. We have previously demonstrated in MPS VII dogs that intervertebral disks degenerate, vertebral bodies have irregular surfaces, and vertebral body epiphyses have reduced calcification, but the pathophysiological mechanisms underlying these changes are unclear. We hypothesized that some of these manifestations could be due to upregulation of destructive proteases, possibly via the binding of GAGs to Toll-like receptor 4 (TLR4), as has been proposed for other tissues in MPS models. In this study, the annulus fibrosus of the intervertebral disk of 6-month-old MPS VII dogs had cathepsin B and K activities that were 117- and 2-fold normal, respectively, which were associated with elevations in mRNA levels for these cathepsins as well as TLR4. The epiphyses of MPS VII dogs had a marked elevation in mRNA for the cartilage-associated gene collagen II, consistent with a developmental delay in the conversion of the cartilage to bone in this region. The spine obtained at autopsy from a young man with MPS VII exhibited similar increased cartilage in the vertebral bodies adjacent to the end plates, disorganization of the intervertebral disks, and irregular vertebral end plate morphology. These data suggest that the pathogenesis of destructive changes in the spine in MPS VII may involve upregulation of cathepsins. Inhibition of destructive proteases, such as cathepsins, might reduce spine disease in patients with MPS VII or related disorders.     

Mental retardation,obesity, mandibular prognathism with eye and skin anomalies (MOMES Syndrome): A newly recognized autosomal recessive syndrome

We report two daughters of a Thai family affected with mental retardation, delayed speech, obesity, craniofacial manifestations, and ocular anomalies. Craniofacial manifestations included macrocephaly, maxillary hypoplasia, mandibular prognathism, and crowding of teeth. Ocular anomalies consisted of blepharophimosis, blepharoptosis, decreased visual acuity, abducens palsy, hyperopic astigmatism, and accommodative esotropia. Chronic atopic dermatitis, lateral deviation of the great toes, and cone‐shaped epiphyses of the toes were observed. The disorder is suggested to be autosomal recessive. The combination of findings found in our patients has not hitherto been described. © 2001 Wiley‐Liss, Inc.     

Mental retardation, obesity, mandibular prognathism with eye and skin anomalies (MOMES syndrome): a newly recognized autosomal recessive syndrome.

We report two daughters of a Thai family affected with mental retardation, delayed speech, obesity, craniofacial manifestations, and ocular anomalies. Craniofacial manifestations included macrocephaly, maxillary hypoplasia, mandibular prognathism, and crowding of teeth. Ocular anomalies consisted of blepharophimosis, blepharoptosis, decreased visual acuity, abducens palsy, hyperopic astigmatism, and accommodative esotropia. Chronic atopic dermatitis, lateral deviation of the great toes, and cone-shaped epiphyses of the toes were observed. The disorder is suggested to be autosomal recessive. The combination of findings found in our patients has not hitherto been described.     

Two-dimensional NMR spectroscopy of urinary glycosaminoglycans from patients with different mucopolysaccharidoses

Patients with different types of mucopolysaccharidoses (MPS) lack specific lysosomal enzymes, which leads to tissue accumulation and urinary excretion of glycosaminoglycans (GAGs). Since little is known about the molecular composition of the excreted GAG fragments, we used two-dimensional [1H,13C]-correlation nuclear magnetic resonance (NMR) spectroscopy for a detailed analysis of the urinary GAGs of patients with MPS types I, II, IIIA, IVA and VI. The method revealed that the molecular structures of the excreted GAGs, i.e. heparan sulfate (HS), dermatan sulfate (DS), chondroitin sulfate (CS), and keratan sulfate (KS) are clearly distinct for the different MPS types. The chain terminal residues that are the normal substrates for the defective enzymes constitute characteristic sets of signals for each MPS type. The GAG chains show variations in carbohydrate composition and sulfation patterns that can be related to the different MPS types and clinical features. For example, two patients with MPS IIIA (M. Sanfilippo) with signs of CNS degeneration but only mild somatic features excrete a highly sulfated variant of HS, resembling HS in porcine brain, whereas a patient with MPS I (M. Scheie) and two patients with MPS II (M. Hunter), who present primarily with coarse facial features, joint contractures and skeletal deformities excrete a different type of HS with lower sulfation. In another case study, a patient with MPS IVA (M. Morquio), who presented mainly with skeletal dysplasia, excreted not only excessive amounts of KS but also a highly sulfated CS variant, resembling CS in articular cartilage. The high-resolution NMR analysis of urinary GAGs presented here for the first time provides a solid basis for future studies with a larger number of patients to further explore pathogenesis and course of the MPS diseases.     

Morphologic determinants in the etiology of class III malocclusions: A review

Morphospatial disharmony of the craniomaxillary and mandibular complexes may yield apparent mandibular prognathism, but Class III malocclusions can exist with any number of aberrations of the craniofacial complex. Deficient orthocephalization of the cranial base allied with a smaller anterior cranial base component has been implicated in the etiology of Class III malocclusions. Whereas the more acute cranial base angle may affect the articulation of the condyles resulting in their forward displacement, the reduction in anterior cranial size may affect the position of the maxilla. As well, intrinsic skeletal elements of the maxillary complex may be responsible for maxillary hypoplasia that may exacerbate the anterior crossbite seen in the Class III condition. Conversely, with an orthognathic maxilla, condylar hyperplasia and anterior positioning of the condyles at the temporo‐mandibular joint may produce an anterior crossbite. Aside from the skeletal components, soft tissue matrices, particularly labial pressure from the circumoral musculature, may influence the final outcome of craniofacial growth of a child skeletally predisposed to Class III conditions. Indeed, as some Asian ethnic groups demonstrate an increased prevalence of Class III malocclusions, it is likely that the skeletal components and soft tissues matrices are genetically determined. Presumably, the co‐morphologies of the craniomaxillary and mandibular complexes are likely dependent upon candidate genes that undergo gene‐environmental interactions to yield Class III malocclusions. The identification of such genes is a desirable step in unraveling the complexity of Class III malocclusions. With this knowledge, the clinician may elect an early course of dentofacial orthopedic and orthodontic treatments aimed at preventing the development of Class III malocclusions. Clin. Anat. 12:382–405, 1999. © 1999 Wiley‐Liss, Inc.     

Effect of neonatal gene therapy on lumbar spine disease in mucopolysaccharidosis VII dogs

Mucopolysaccharidosis VII (MPS VII) is due to deficient β-glucuronidase (GUSB) activity, which leads to accumulation of chondroitin, heparan, and dermatan sulfate glycosaminoglycans in various tissues including those of the spine. Associated spine disease can be due to abnormalities in the vertebrae, the intervertebral disks, or other spine tissues. The goal of this study was to determine if neonatal gene therapy could prevent lumbar spine disease in MPS VII dogs. MPS VII dogs were injected intravenously with a retroviral vector (RV) expressing canine GUSB at 2 to 3days after birth, which resulted in transduction of hepatocytes that secreted GUSB into blood. Expression was stable for up to 11years, and mean survival was increased from 0.4years in untreated dogs to 6.1years in treated dogs. Despite a profound positive clinical effect, 6-month-old RV-treated MPS VII dogs still had hypoplastic ventral epiphyses with reduced calcification in the lumbar spine, which resulted in a reduced stiffness and increased range of motion that were not improved relative to untreated MPS VII dogs. At six to 11years of age, ventral vertebrae remained hypoplastic in RV-treated MPS VII dogs, and there was desiccation of the nucleus pulposus in some disks. Histochemical staining demonstrated that disks did not have detectable GUSB activity despite high serum GUSB activity, which is likely due to poor diffusion into this relatively avascular structure. Thus, neonatal gene therapy cannot prevent lumbar spine disease in MPS VII dogs, which predicts that enzyme replacement therapy (ERT) will similarly be relatively ineffective even if started at birth.     

Ultrastructural analysis of different skeletal cell types in mucopolysaccharidosis dogs at the onset of postnatal growth

The mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders characterized by deficient activity of enzymes that degrade glycosaminoglycans (GAGs). Abnormal development of the vertebrae and long bones is a hallmark of skeletal disease in several MPS subtypes; however, the underlying cellular mechanisms remain poorly understood. The objective of this study was to conduct an ultrastructural examination of how lysosomal storage differentially affects major skeletal cell types in MPS I and VII using naturally occurring canine disease models. We showed that both bone and cartilage cells from MPS I and VII dog vertebrae exhibit significantly elevated storage from early in postnatal life, with storage generally greater in MPS VII than MPS I. Storage was most striking for vertebral osteocytes, occupying more than forty percent of cell area. Secondary to storage, dilation of the rough endoplasmic reticulum (ER), a marker of ER stress, was observed most markedly in MPS I epiphyseal chondrocytes. Significantly elevated immunostaining of light chain 3B (LC3B) in MPS VII epiphyseal chondrocytes suggested impaired autophagy, while significantly elevated apoptotic cell death in both MPS I and VII chondrocytes was also evident. The results of this study provide insights into how lysosomal storage differentially effects major skeletal cell types in MPS I and VII, and suggests a potential relationship between storage, ER stress, autophagy, and cell death in the pathogenesis of MPS skeletal defects.     

Neonatal retroviral vector-mediated hepatic gene therapy reduces bone, joint, and cartilage disease in mucopolysaccharidosis VII mice and dogs

Mucopolysaccharidosis VII (MPS VII) is a lysosomal storage disease caused by deficient beta-glucuronidase (GUSB) activity. Accumulation of glycosaminoglycans (GAGs) in bone, cartilage, and synovium likely contributes to reduced mobility in untreated MPS VII individuals. We previously reported that neonatal intravenous injection of a retroviral vector (RV) expressing canine GUSB resulted in hepatocyte transduction in mice and dogs, and secreted GUSB was taken up from blood by other organs. Here we report the effect of this therapy on bone, cartilage, and joint disease. Osteocytes and bone-lining cells from RV-treated MPS VII mice had GUSB activity, resulting in a marked reduction, as compared with untreated MPS VII mice, in lysosomal storage in bone and at the bone:growth plate interface where bone elongation occurs. Although chondrocytes did not have detectable GUSB activity and had little reduction in lysosomal storage, the thickness of the growth plate was reduced toward normal. These pathological changes were likely responsible for improvements in facial morphology and long bone lengths. The synovium had reduced hyperplasia and lysosomal storage, and the thickness of the articular cartilage was reduced. Similarly, RV-treated MPS VII dogs had improved facial morphology and reduced lysosomal storage in osteocytes and synovium, but not chondrocytes. Nevertheless, the internal area of the trachea was increased, and erosions of the femoral head were reduced. We conclude that neonatal gene therapy can improve bone and joint disease in MPS VII mice and dogs. However, better delivery of GUSB to chondrocytes will be necessary to achieve more profound effects in cartilage.     

Radiographic evaluation of bones and joints in mucopolysaccharidosis I and VII dogs after neonatal gene therapy

Mucopolysaccharidosis I (MPS I) and MPS VII are due to deficient activity of the glycosaminoglycan-degrading lysosomal enzymes alpha-L-iduronidase and beta-glucuronidase, respectively, and result in abnormal bones and joints. Here, the severity of skeletal disease in MPS I and MPS VII dogs and the effects of neonatal gene therapy were evaluated. For untreated MPS VII dogs, the lengths of the second cervical vertebrae (C2) and the femur were only 56% and 84% of normal, respectively, and bone dysplasia and articular erosions, and joint subluxation were severe. Previously, we reported that neonatal intravenous injection of a retroviral vector (RV) with the appropriate gene resulted in expression in liver and blood cells, and high serum enzyme activity. In this study, we demonstrate that C2 and femurs of RV-treated MPS VII dogs were longer at 82% and 101% of normal, respectively, and there were partial improvements of qualitative abnormalities. For untreated MPS I dogs, the lengths of C2 and femurs (91% and 96% of normal, respectively) were not significantly different from normal dogs. Qualitative changes in MPS I bones and joints were generally modest and were partially improved with RV treatment, although cervical spine disease was severe and was difficult to correct with gene therapy in both models. The greater severity of skeletal disease in MPS VII than in MPS I dogs may reflect accumulation of chondroitin sulfate in cartilage in MPS VII, or could relate to the specific mutations. Neonatal RV-mediated gene therapy ameliorates, but does not prevent, skeletal disease in MPS I and MPS VII dogs.     

Evaluation of growth hormone axis and responsiveness to growth stimulation of short children with osteogenesis imperfecta

We present four individuals with Gerodermia Osteodysplastica in a Jewish family from Morocco confirming the autosomal recessive inheritance of the disorder. Three previously unreported findings are described: (a) enlarged funnel-shaped mandibular lingula; (b) extension of the mandibular premolar and molar roots below the inferior dental canal, and of the second molars into the lower border of mandibular cortical bone; and (c) hypercementosis of the maxillary incisors and mandibular molars surrounded by a radiolucent halo in several teeth. The facial deformity resulting from maxillary hypoplasia and mandibular prognathism was corrected by orthognathic surgery: Le Fort I maxillary osteotomy and vertical mandibular osteotomy. © 1993 Wiley-Liss, Inc.     

伴偏斜对下颌前突患者颞下颌关节应力分布的影响

目的探究伴偏斜对下颌前突患者颞下颌关节(temporomandibular joint,TMJ)应力分布的影响。方法在Mimics中建立4名下颌前突伴偏斜患者和4名下颌前突不伴偏斜患者的三维颌面部模型,在ABAQUS中赋予模型偏侧咬合(单侧磨牙咀嚼)的肌肉力与边界条件,分析偏侧咬合工况下患者TMJ的最大和最小主应力。结果偏侧咬合工况下,伴偏斜患者髁突的平均最大应力显著大于不伴偏斜患者(P<0.05),伴偏斜会使髁突处应力增加2~3倍,关节窝应力增加5~7倍,且伴偏斜患者中颞下颌关节紊乱综合征(temporomandibular disorder,TMD)患者同侧TMJ处的应力高于无TMD患者。结论伴偏斜会增大患者髁突和关节窝的应力,TMD会引起伴偏斜患者同侧TMJ的高应力。建议根据偏斜与否考虑下颌前突的治疗。     

Molecular genetics of mucopolysaccharidosis type IIIA and IIIB: Diagnostic,clinical, and biological implications

Mucopolysaccharidosis (MPS) types IIIA, B, C, and D are a group of autosomal recessive lysosomal storage diseases caused by mutations in one of four genes which encode enzyme activities required for the lysosomal degradation of heparan sulfate. The progressive lysosomal storage of heparan sulfate eventually results in the clinical onset of disease, which is predominantly characterized by severe central nervous system degeneration. MPS‐IIIA and MPS‐IIIB involve deficiencies of heparan sulfate sulfamidase (SGSH) and α‐N‐acetylglucosaminidase (NAGLU), respectively. Both the SGSH and NAGLU genes have been cloned and characterized, thereby permitting mutation analysis of MPS‐IIIA and MPS‐IIIB patients. A total of 62 mutations have now been defined for MPS‐IIIA consisting of 46 missense/nonsense mutations, 15 small insertions/deletions, and one splice site mutation. A total of 86 mutations have been identified in the NAGLU gene of MPS‐IIIB patients; 58 missense/nonsense mutations, 27 insertions/deletions, and one splice site mutation. Most of the identified mutations in the SGSH and NAGLU genes are associated with severe clinical phenotypes. Many of the missense, nonsense, and insertion/deletion mutations have been expressed in mammalian cell lines to permit the characterization of their effects on SGSH and NAGLU activity and intracellular processing and trafficking. For MPS‐IIIA and MPS‐IIIB many of the reported mutations are unique making screening the general population difficult. However, molecular characterization of MPS‐IIIA patients has revealed a high incidence of particular mutations of different geographical origins, which will be beneficial for the molecular diagnosis of MPS‐IIIA. Hum Mutat 18:264–281, 2001. © 2001 Wiley‐Liss, Inc.     

Hypoplastic occipital condyle and third occipital condyle: Review of their dysembryology

Disruption or embryologic derailment of the normal bony architecture of the craniovertebral junction (CVJ) may result in symptoms. As studies of the embryology and pathology of hypoplasia of the occipital condyles and third occipital condyles are lacking in the literature, the present review was performed. Standard search engines were accessed and queried for publications regarding hypoplastic occipital condyles and third occipital condyles. The literature supports the notion that occipital condyle hypoplasia and a third occipital condyle are due to malformation or persistence of the proatlas, respectively. The Pax‐1 gene is most likely involved in this process. Clinically, condylar hypoplasia may narrow the foramen magnum and lead to lateral medullary compression. Additionally, this maldevelopment can result in transient vertebral artery compression secondary to posterior subluxation of the occiput. Third occipital condyles have been associated with cervical canal stenosis, hypoplasia of the dens, transverse ligament laxity, and atlanto‐axial instability causing acute and chronic spinal cord compression. Treatment goals are focused on craniovertebral stability. A better understanding of the embryology and pathology related to CVJ anomalies is useful to the clinician treating patients presenting with these entities. Clin. Anat. 26:928–932, 2013. © 2013 Wiley Periodicals, Inc.     

Recombinant encapsulated cells overexpressing alpha-L-iduronidase correct enzyme deficiency in human mucopolysaccharidosis type I cells

Mucopolysaccharidosis I (MPS I) is an autosomal recessive lysosomal storage disease due to deficient α-L-iduronidase (IDUA) activity. It results in the accumulation of the glycosaminoglycans (GAGs) heparan and dermatan sulfate and leads to several clinical manifestations. Available treatments are limited in their efficacy to treat some aspects of the disease. Thus, new approaches have been studied for the treatment of MPS I. Here, we tested the ability of recombinant baby hamster kidney cells transfected with human IDUA cDNA in correcting skin fibroblasts from MPS I patients in vitro. Our results showed an increase in IDUA activity in MPS I fibroblasts after 15, 30 and 45 days of coculture with the capsules. Cytological analysis showed a marked reduction in GAG storage within MPS I cells. Enzyme uptake by the fibroblasts was blocked in a dose-dependent manner with mannose-6-phosphate (M6P), indicating that cells use the M6P receptor to internalize the recombinant enzyme. Capsules were effective in correcting MPS I cells even after a 12-month period of cryopreservation. Taken together, our results indicate that cell encapsulation is a potential approach for treatment of MPS I. This approach becomes particularly interesting as a complementary approach, since the capsules could be implanted in sites which current treatments available are not able to reach. Future studies will focus on the efficacy of this approach in vivo.     

Efficient analysis of urinary glycosaminoglycans by LC-MS/MS in mucopolysaccharidoses type I, II and VI

Mucopolysaccharidoses (MPSs) are complex storage disorders caused by specific lysosomal enzyme deficiencies, resulting in the accumulation of glycosaminoglycans (GAGs) in urine, plasma, as well as in various tissues. We devised and validated a straightforward, but accurate and precise tandem mass spectrometry methodology coupled to high performance liquid chromatography (LC-MS/MS) for the quantification of GAGs in urine. The method is applicable to the investigation of patients with MPS I, II, and VI, by quantifying dermatan sulfate (DS) and heparan sulfate (HS) in urine. We analyzed urine samples from 28 MPS patients, aged 1 to 42 years, and 55 control subjects (41 days to 18 years old). Levels of DS and HS in urine from healthy controls of all ages were below the limit of quantification. The levels of DS and HS in urine from 6 treated patients with MPS I were lower than in 6 untreated patients in DS (0.7-45 vs 9.3-177 mg/mmol creat) and HS (0-123 mg/mmol creatinine vs 38-418 mg/mmol creatinine); similar results were obtained for 9 patients with MPS II and 7 patients with MPS VI. Analyses were performed on as little as 250 μL of urine. Methanolysis took 75 min per sample; the total analysis run time for each LC-MS/MS injection was 8 min. Results indicate that the method is applicable to a wide variety of situations in which high accuracy and precision are required, including the evaluation of the effectiveness of existing and emerging treatments.     

Putative Biological Mechanisms of Efficiency of Substrate Reduction Therapies for Mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are inherited metabolic diseases caused by mutations in genes coding for lysosomal enzymes involved in the degradation of glycosaminoglycans (GAGs). Dysfunction of any of these enzymes results in the accumulation of GAGs, which leads to severe clinical symptoms and significantly shortened life span. Several kinds of therapies have been proposed to treat MPS, including bone marrow or stem cell transplantation, enzyme replacement therapy, and gene therapy. Another option is substrate reduction therapy (SRT), in which synthesis of GAGs is inhibited. Recent studies employing in vitro and animal models suggested that this therapy may be efficient in decreasing levels of GAGs in MPS cells, including those bearing two null alleles of the affected gene. Results of behavioral tests in animals as well as some preliminary clinical observations with pediatric patients corroborated the suggestions about possible efficacy of SRT in MPS treatment, including brain functions. Efficient reduction of GAG levels in MPS cells homozygous for null mutations may be intriguing in the commonly accepted scheme of SRT mode of action. In this paper, we propose an explanation of this phenomenon, based on already known facts. Thus, we suggest that SRT may lead to reduction of GAG levels in MPS cells due to inhibition of efficiency of GAG synthesis combined with (a) any readthrough of the stop codon, (b) dilution of already accumulated GAGs due to cell growth followed by cell divisions, and (c) action of endoglycosidases degrading GAGs, e.g., heparanase, in combination with functional GAG-specific hydrolases.     

Left ventricular aneurysm in an adult patient with mucopolysaccharidosis type I: comment on pathogenesis of a novel complication

Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disease caused by deficiency of the lysosomal enzyme alpha-L-iduronidase. This enzyme is involved in the degradation of the glycosaminoglycans (GAGs) dermatan and heparan sulphate and its deficiency results in the accumulation of GAGs and a progressive multisystem disease. Cardiac involvement is common in MPS patients and usually consists of progressive valvular thickening with incompetence and cardiomyopathy. We present an attenuated MPS I patient with a primary apical left ventricular aneurysm not associated with ischemia. We speculate that the defect in GAG catabolism leads not only to the storage of GAGs but also to alterations of the myocardial extracellular matrix. The latter ultimately being responsible for the formation of the aneurysm. This case emphasizes the importance of careful surveillance for cardiac lesions in MPS patients.