LOW-DOSE OF SODIUM ARSENITE CAUSES DELAYED DIFFERENTIATION IN C2C12 MOUSE MYOBLAST CELLS THROUGH THE REPRESSION OF THE TRANSCRIPTION FACTOR MYOGENIN

A number of epidemiological studies have correlated arsenic exposurwith cancer, skin diseases, cardiovascular diseases, and adverse developmental outcomes such as stillbirths, spontaneous abortions, neonatal mortality, low birth weight, and delays in the use of musculature. The current study used C2C12 mouse myoblast cells to examine whether low concentrations of arsenic could alter their differentiation into myotubes, which would indicate that arsenic has the ability to act as a developmental toxicant. Myoblast cells were exposed to 20nM sodium arsenite and allowed to differentiate into myotubes and expression of the muscle-specific transcription factor myogenin, along with the expression of myosin light chain 2, and tropomyosin were investigated using real time PCR and immunofluorescence. Exposing C2C12 cells to 20nM sodium arsenite delayed the differentiation process, as evidenced by a significant reduction in the number of multinucleated myotubes. Additionally, arsenic exposure caused a time-dependant decrease in myogenin mRNA expression, as compared to the control cells, starting on day two of the differentiation process. Arsenic reduced myogenin mRNA levels by 1.4-fold on day two, 2.7-fold on day three, and 5.1-fold on day four of differentiation. This reduction in transcript number was confirmed by immunofluorescence, which also showed a decrease in the total number of nuclei expressing myogenin protein. Interestingly, myosin light chain 2 mRNA was significantly upregulated in the arsenic-exposed cells, although this did not translate into altered protein expression. This study demonstrated that low concentrations of arsenic are able to disturb the differentiation process of myoblasts without causing overt toxicity