title: Enhancement of microtubule-associated protein-1 Alpha gene expression in osteoblasts by low level laser irradiation.
abstract: BACKGROUND
  Low level laser irradiation (LLLI) stimulates bone regeneration. However, the molecular mechanisms leading to this is not yet understood. The stepwise subtractive cDNA cloning technology has been developed, coupled with DNA homology searched in DNA database is useful to identify the certain gene.
  
  
  OBJECTIVE
  In order to understand the mechanism, we attempted to identify genes whose expressions are enhanced by LLLI. MC3T3-E1 osteoblastic cells were irradiated with an 830 nm Ga-Al-As diode laser, and a cDNA library was constructed using subtractive gene cloning.
  
  
  METHODS
  The cDNA library of osteoblasts which was treated by LLLI was constructed. Nucleotide sequences were analyzed and homology searched in a DNA database using BLASTN program to identify the gene with altered expression. Altered mRNA levels by LLLI were confirmed by reverse transcription polymerase chain reaction (RT-PCR) and real-time PCR.
  
  
  RESULTS
  The DNA sequence of a subtracted gene clone MCL129 indicated high homology (99%) with the microtubule-associated protein 1A (MAP1A) gene. Increase in MAP-1A mRNA level by LLLI was successfully confirmed by RT-PCR and real-time PCR.
  
  
  CONCLUSIONS
  MAP1A has been shown to promote microtubule assembly and its functional expression. Microtubules play an important role in cell division, cell shape and polarity, cell movement, intracellular transport, signal transduction, and synthesis and secretion of collagen. Thus, enhancement of MAP1A gene expression by LLLI may be one of the molecular mechanisms involved in accelerating bone formation by LLLI.
  
  
  CONCLUSIONS
  LLLI irradiation enhances MAP1A gene expression and modulates microtubule assembly and the functional structure of microtubules, in turn, stimulates osteoblastic proliferation and differentiation.
authors.affiliation: Department of Biochemistry and Molecular Biology, Nihon University School of Dentistry at Matsudo, Chiba 271, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kanenari
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Abiko
keywords: gene expression; low level laser; microtubule associated protein; osteoblasts