Study Of Clinic,Pathology,Genetic Mutation And Abnormal Proteins Accumulation On The Patients With Hereditary Inclusion Body Myopathy

Background and Objective:The hereditary inclusion body myopathies (h-IBM) are a heterogeneous group of autosomal-dominant (AD) or autosomal-recessive (AR) adult-onset muscle disorders with variable clinical phenotypes and special myopathological presentation, including rimmed vacuoles (RV) and intracytoplasmic and intranuclear tubulofilamentous inclusions. Although the classification of h-IBM still was not clear, myopathological presentation, muscle weakness and family history are essential for the diagnosis. Immunohistochemistry and ultrastructure observation indicated abnormal proteins accumulation in inclusion bodys.h-IBM may have similar pathogenic mechanisms with Alzheimer's disease (AD) and Parkinson's disease(PD). China has a large population and relatively few reported cases of this disorder. From 1986 to 2010, we performed muscle biopsies on more than 4200 suspected myopathy individuals in our department. To investigate the common ground and differences in h-IBM between Chinese and other descent, we systematically analyzed the clinical, pathological and genetic heterogeneity of Chinese h-IBM patients.And we further discussed the possible mechanisms of abnormal proteins accumulation in h-IBM.Methods:1. In part 1,112 h-IBM patients from our department or other Chinese hospitals between 1986-2011.They were divided into 4 groups:DMRV(n=66),OPDM (n=22,WDM(n=12)and uncertained subtype(n=12); In part 2,25 cases were divided into 2 groups:AR (n=19) and AD (n=6); In part 3, there were three groups:h-IBM (n=4), s-IBM (n=4) and normal (n=4).2. To investsgate the muscular pathological feartures, cryostat sections of muscle were prepared and stained with standard histochemical stains.3. Profile of reported Chinese h-IBM cases and current cases in our department were analyzed by retrospective study.4. Procedure of molecular genetic testing included DNA extraction, polymerase chain reaction (PCR), SNaPshot and TAclone.5. By using Real-time fluorescent quantitative PCR and Western Blot, we identified the mRNA and protein levels of APP, tissue inhibitors of metalloproteinase 3(TIMP-3), insulin-degrading enzyme (IDE).6. Using SPSS 13.0 for statistical analysis.Results:Part 1:1. A total of 112 h-IBM cases were reviewed (48 reported cases from 11 literitures, 64 current cases from our hospital).①66 DMRV cases (50 sporadic cases and 16 familial cases).Mean age of onset was 21.6±8.8 years.②22 OPDM cases (7 sporadic cases and 15 familial cases). Mean age of onset was 22.1±11.2 years.③One reported WDM family was included (12 members affected).④1 sporadic case was reported with uncertained classification; our department reported an AD h-IBM family with oculopharyngeal symptoms, mental retardation and central nervous system involvement.2.①Sporadic DMRV cases showed onset in childhood.Anterior tibial muscles were usually the first muscles affected. In contrast to familial DMRV, sporadic cases had more dysmorphic signs, including winged scapula, pseudohypertrophy of calf muscles and talipes cavus.②Weakness of extremities, rather than oculopharyngeal weakness, was the prominent initial symptom for OPDM. Pharyngeal symptoms showed more serious than oculorotary symptoms. Oculopharyngeal weakness revealed relatively complete in familial cases.③WDM family showed onset of distal weakness at 30 years.④Patients with uncertained classification have common symptoms as weakness, demencia, oculopharyngeal affection and deafness.3. The majority of atrophic fibers in h-IBM appeared to be mixtures of small-angular and small-round (79%). Primary shapes of RV were round or oval (81%) and 65% of inclusion bodies were coarse particles. Typical mononuclear cell invasion of non-necrotic muscle fiber could be observed in few cases.Part 2---section 1 1. GNE mutation were indetified in all 10 DMRV patients and their 8 family members in our department.Case 1-5,case 8,9 were compound heterozygous and case cases 6,7,9 were homozygous.8 mutations were indenyified:1 nonsense p.R8X and seven missense (p.C13S,p.D176V,p.I298T, p.H509Y,p.A591T, p.A631V, p.V696M).Two novel mutations were identified:one missense mutation c.317T>C(p.I106T),one deletion with frameshift mutation c.1543-1544delGA (p.D515QfsX2).2. Up to now, a total of 29 DMRV cases were performed GNE mutation testing (10 cases from our department,16 cases were reported) in China.Eighteen GNE mutions were identified. The allelic frequency of p.D176V, p.L508S and p.A631 V was 21%,17% and 15% respectively in the Chinese DMRV patients.3. The number of GCG repeats in the PABPN1 gene was within normal range (GCG6GCA3GCG1) and no mutations in other exons were indentified in our AR OPDM family.Part 2---section 21. All exons of VCP, MYH2, PABPN1 and GNE genes were performed in four DNA samples from AD h-IBM family with uncertained classification, and no mutation were indentified.2. Extra genentic analysis were performed on 2 probands of oculopharyngeal muscular dystrophy (OPMD) families.Abnormal repeat of GCN in exon 1 of PABPN1 were indentified.Case 1 showed GCN14(GCG10GCA3 GCG1),case 2 showed GCN15(GCG11GCA3GCG1), no mutation were indentified in other exons.Part 3:1. The levels of mRNA and protein of APP and TIMP-3 in h-IBM, s-IBM group were higher than that of normal group, but no significant difference (P>0.05).There was no significant difference between h-IBM and s-IBM group (P>0.05).2. The levels of mRNA and protein of IDE in h-IBM, s-IBM group were significantly decreased than that of normal group (P<0.05).There was no significant difference between h-IBM and s-IBM group (P>0.05).Conclusions:1. The main types of h-IBM in China were DMRV and OPDM, others were rare.The syptoms showed relatively comparable with Japanese patients, but some unique features actually existed among Chinese h-IBM patients.2. Rimmed vacuoles and coarse inclusion bodys in atrophic mucle fibers was the morphological features of h-IBM. Mononuclear cell invasion of necrotic muscle fibers was rare.3. Two novle mutations were indentified. p.D176V, p.L508S and p.A631V may be the hotspots of GNE mutation in Chinese decent.4. A rare family with uncertained classification of h-IBM was reported in our department.5. OPDM is a distinct genetic entity from OPMD.6. Abnormal expression of IDE maybe participate the pathological process of abnormal amyloid-p accumulation in IBM.