Med, The Psach Two Pathogenic Genes And Gene Mutation Analysis

Multiple epiphyseal dysplasia (MED) is a common skeletal dysplasia with a significant locus heterogeneity. EDM1 is the most common type which is an autosomal dominant disorder caused by mutations in the gene encoding cartilage oligomeric matrix protein (COMP), the area 19p13.1 harbors the gene for cartilage oligomeric matrix protein. COMP gene is also characterized by allele heterogeneous, mutations in this gene arose pseudoachondroplasia (PSACH), another skeletal dysplasia.Short stature is generally the cause of patients go to the hospital, the disease sometimes misdiagnosed by the doctors as achondroptasia (ACH) which is characterized by short stature. Additionly, some MED patients which have mild short stature were referred to the Rheumatology clinic for its osteoarthritis (OA), doctors generally diagnosed and treated as immunology-related disorder.Pseudoachondroplasia (PSACH) is another type of short-limb dwarfism. It is a genetic autosomal dominant disorder disease and is generally not diagnosed until 2 years of age, since growth is normal at first and at 2 years, begins to lag behind the growth rate of the standard growth curve.The adult height is usually 82-130cm.PSACH is usually first detected when the child has a delay in walking or presents with a waddling gait. Children with PSACH often experience joint pain, especially in the lower extremities.As a young adult, one may experience osteoarthritis of the upper extremities and spine. Joints continue to degenerate over time and approximately half of those with PSACH eventually require hip replacement surgery. In addition, patients often experience ligamentous laxity and joint over-extension. X-ray examination of an individual with PSACH generally exhibits the following signs:bilateral short and thick femoral neck, flattened femoral head, small epiphysis, irregular acetabulum, genua varus, bilateral short and thick phalanges, markedly delayed ossification of carpal bones, significant brachydactyly, short metacarpals and phalanges, and anterior beaking of the vertebral bodies on lateral view. The COMP gene, encoding the cartilage oligomeric matrix protein, is the only pathogenic gene known to be associated with PSACH. All mutations characterized, to date, have been structural mutations found in exons 8-14.So far, the study of MED and PSACH in mainland are limited and there is no report about the molecular pathogenesis study in mainland China. Aimed at definituding the disease-caused gene of the MED family, linkage analysis was conducted in the origination of this work. Finally, all 19 exons and the flanking intronic sequence of the COMP gene of the proband were amplified, DNA sequencing date revealed a G to T transition at nucleotide position 1552 of cDNA implying substitution of a aspartic acid residue by an tyrosine residue at position 518 of the COMP protein, the same mutation was detected in the mother and the mutation has not been report previously. Restrictive analysis of exon 14 of COMP gene in the MED family and 50 control was conducted which proved mutation in the family is disease-caused mutation. The blood samples of PSACH patients family and the normal control was collected to extract its DNA; this was followed by the PCR (polymerase chain reaction) to amplify the COMP gene exon 8-19. Direct DNA sequencing of amplified PCR products was performed to determine the mutation site. After the sequencing of the proband's COMP gene, exon 8-19 and the flanking intron sequences, we discovered the proband's abnormal point mutation at exon 8 of c.815T> C. It is a known mutation. The same mutation was found in his brother and father.To elucidate the mechanism more definitely, plasam concentration of cartilage oligomeric matrix protein of all member in the family were measured. Use the ELISA method to measure the serum COMP level of the 8 cases of patients with MED and PSACH in these two families and the 20 normal control cases. Results:All data, in form ofθx±s, were analyzed using SAS statistical software and differences were compared using t-tests. The results showed that the MED, PSACH serum COMP level was (3.16±0.42) U/L among cases which was significantly higher than that of the controls(10.86±2.26)U/L (P<0.05).