Study On The ARIX Gene Polymorphisms And Changes Of Extracellular Matrix Molecules In The Resected Medial Rectus Muscle In Patients With Concomitant Exotropia

Purpose: To investigate the ARIX gene polymorphism and the amounts of extracellularmatrix molecules (fibronectin and proteoglycan) in the resected medial rectus muscles of patients with concomitant exotropia, and to have a better understanding about the role of the hereditary factor and the pathomorpholosical change of extraocular muscles in the genesis and development of concomitant exotropia.Materials and methodsTwenty-two patients with concomitant exotropia and 20 normal individuals were involved in this study. The patients were divided into congenital (3 patients) and acquired (19 patients) exotropia. Among the total, 7 patients with positive family history of strabismus were found. The peripheral leucocytes were isolated from 5 ml blood and the genomic DNA were extracted in all cases. Two pairs of PCR primers were designed by DNA Star software, the gene fragments coding for the exon 1 and 2 of ARIX gene were amplified by PCR respectively, the PCR products were purified by QIA quick PCR kit and cloned into plasmid pMD18-T for DNA sequencing. DNA sequences were aligned with the human ARIX gene sequences registered in GenBank. The correlation of the nucleotide changes between patients and normal individuals, congenital and acquired concomitant exotropia, as well as those patients with positive and negative family history was statistical analysis.Thirty-one concomitant exotropic patients were chosen as exotropic group and 21 normals were selected: as control group. In exotropic group, there were 7 cases withpositive family history. Exotropic patients were divided into intermittent exotropic group 17 cases and constant exotropic group 14 cases. All the resected tissues of the medial rectus muscles were obtained from patients with concomitant exotropia during resection surgery and normal persons were weighted, and then pulverized to obtained supernatant. Fibronectin and proteoglycan were measured by competitive binding assay using Human Fibronectin ELISA KIT and Human Proteoglycan EASIA ELISA KIT. The total amounts of fibronectin and proteoglycan were calculated and normoalized by the weight of the medial rectus fragenent. The amounts of fibronectin and proteoglycan in unit weight (g) of resected muscle of patients were compared with normals, as well as correlated clinical data of patients such as different types of exotropia, age, gender and positive family history.ResultsThe DNA sequences of 19 patients (3 with congenital and 16 with acquired), and 20 normal individuals indicated that three kinds of nucleotide changes in the exon 1 of the ARIX gene were found in 8 of 19 patients with concomitant exotropia. Six patients had a nucleotide change of G153A in the 5-untranslated region (UTR) of the exon 1 of the ARIX gene. The nucleotide change of C-37A and T8G of the exon 1 of the ARIX gene were also found in one patient separately. And the nucleotide change of G1S3A was only found in 2 of 16 normal individuals. The total nucleotide changes and G153A in the exon 1 of the ARIX gene in concomitant exotropic patients were all significantly more than those of normal individuals(/>=0.0310,P=0.0436). Five of 7 patients with positive family history of strabismus had nucleotide changes, and 4 of 6 patients had the nucleotide change of G153A. The patients with positive family history of strabismus showed more, although not significantly, nucleotide changes including total nucleotide changes and G153A change than those of ones with negitive (P=0.0739, />=(). 1287) . The nucleotide changes had no significant difference between congenital' and acquired concomitant exotropic patients (7M)5459, />=0.2219) . ";?'~~ ^^Tb â– â–  IThe amounts of fibronectin in the resected medial rectus muscle of patients with concomitant exotropia were significantly lower than those of normal (P=0.0000), and the difference of proteoglycan amounts between patients and the normal was no significant (/>=0.0915). Patients with intermittent exotropia showed significantly larger amounts of fibronectin than those with constant exotropia ( P=0.0011 ) , and the amounts of proteoglycan had no significant difference between two groups (P=0.4999). The amounts of proteoglycan decreased significantly with the advance of age (r=-0.8712, P<0.01), while the amounts of fibronectin had no correction with age( r=-0.1718, P>0.05). Neither gender nor positive family was correlated with the amounts of proteoglycan and fibronectin (P>0.05) .Conclusion: The ARIX gene polymorphisms, especially the nucleotide change of G153A in the 5-untranslated region ( UTR) of the exon 1, may be one of the genetic risk factors for the genesis of concomitant exotropia. The amounts of fibronectin were correlated with the course of development from the intermittent exotropia to constant one.Postgraduate student: Gui-xiang Liu (Ophthalmology) Directed by Prof. Cong Hu...