The MyoD transcriptional regulator is normally found in differentiating muscle c
ID: 203339 • Letter: T
Question
The MyoD transcriptional regulator is normally found in differentiating muscle cells and participates in the transcription of genes that produse fic proteins, such as those needed in contractile tissue. Amazingly. expression of MyoD in fibroblasts causes these cells n connective tissue to produce proteins normally only seen in muscles. However, some other cell types do not transcribe muscle-specific genes when MyoD is expressed in them. Which of the following statements below is the best explanation of why MyoD can cause fibroblasts to express muscle-specific genes? Unlke some other cell types, muscle-specific genes are still active in fibroblasts The muscle-specific genes must be in heterochromatin in fibroblasts Fibroblasts have accumulated some transcriptional regulators inew genes) during development. O The transcriptional activators belong to a positively regulated operonExplanation / Answer
Answer: Option A is correct.
Explanation:
Even though all cells contain almost identical DNA sequence, each cell type exhibits specific gene expression profile. This is achieved by epigenetic regulation. In fibroblasts, muscle-specific genes are silenced by an epigenetic mechanism (heterochromatinization). When MyoD is ectopically expressed in these cells, it will lead to euchromatinization of muscle-specific genes.This is accomplished by additional factors that are expressed specifically in fibroblast lineage cells.
Fibroblasts and muscle cells arise from the same lineage of progenitor cells. So, fibroblasts still show some similarities in gene expression with respect to muscle cells. In other words, they are more similar to muscle cells.