Exclusion of pituitary homeobox 2 gene polymorphism in vertical mandibular asymmetry patients: A preliminary study

Abstract

Pituitary Homeobox 2 (PITX2), is an active gene as a paired-related homeobox gene that encodes multiple isoforms. Its Nodal pathway in determination of left-right patterning during embryogenesis has been reported in satellite cells and expressed in adult human skeletal muscle. PITX2A and PITX2B are produced by alternative splicing and used of different promoters. PITX2C uses an alternative promoter located upstream of exon 4. PITX2D is produced by PITX2C alternative promoter and differential splicing. The 5'-primers and 3'- antisense primer were unique for each isoforms. Variability measurement in vertical dimension showed stronger genetic component than sagittal. This study aims to obtain the genotype marker of vertical mandibular asymmetry related to PITX2A and PITX2D isoform by visualization of the amplified product on stained gel to allele specific oligonucleotide between the case and control with Restriction Fragment Length Polymorphism (RFLP). Determination of vertical mandibular asymmetry based on condylar height asymmetry index of pre-treatment panoramic radiograph using Kjellberg's technique whilst vertical mandibular growth pattern using lateral cephalogram. The differences of condylar height asymmetry in case-control based on vertical growth pattern was compared using Pearson's chi-squared test. DNA extraction of 129 out-coming orthodontic patients in Universitas Sumatera Utara Dental Hospital were obtained from Buccal swab. Then DNA samples were amplified by Polymerase chain reaction (PCR) and digested with NciI restriction enzyme prior to electrophoresis visualization. There was no significant statistical difference in vertical mandibular asymmetry compared to vertical mandibular growth pattern. The RFLP analysis did not show any polymorphism for PITX2A and PITX2D isoform. All of the samples showed wild type homozygote. Further analysis method, except RFLP, were required to understand the genetic factor in the variance of vertical mandibular asymmetry.