Final answer:
MyoD expression, when introduced to fibroblasts in culture, is sufficient for their differentiation into muscle cells. This is supported by the experiment where fibroblasts transformed after being induced to express MyoD, but it's not definitively stated that MyoD is necessary, as other factors might also contribute to the differentiation process.
Step-by-step explanation:
Understanding MyoD in Cell Differentiation
Fibroblasts are a type of cell found in connective tissue and play a significant role in producing extracellular matrix components, like collagen and elastin. Muscle tissue, on the other hand, develops from myoblasts, which are embryonic cells that differentiate into muscle cells. This differentiation process is heavily influenced by various transcription factors, including MyoD, which is crucial for the formation of muscle cells. When fibroblasts in culture are forced to express the MyoD gene, they differentiate and take on the characteristics of muscle cells.
The statement 'MyoD expression is sufficient to cause fibroblasts to differentiate to muscle cells in culture' suggests that the presence and expression of MyoD alone can cause the fibroblasts to undergo differentiation into muscle cells. However, it is not clear whether MyoD is also necessary for this process, meaning that without it, differentiation would not occur.
The most accurate option, based on the experiment mentioned, is (a) 'MyoD expression is sufficient to cause fibroblasts to differentiate to muscle cells in culture'. Though MyoD is crucial, stating it is necessary and sufficient without ruling out the potential involvement of other factors could be presumptive. Therefore, without further evidence that MyoD is required (i.e., that in its absence fibroblasts cannot differentiate into muscle cells), we cannot confidently claim option (c) or (d).