​Several extracellular mechanisms lead to intracellular changes to regulate stem cell behavior during development. Based on this, which one of the following statements is NOT true?

Correct option is C

​Explanation:

1. Understanding Asymmetric Division in Stem Cells
• Stem cells can divide asymmetrically to generate:
• One self-renewing stem cell.
• One differentiating daughter cell.
• During asymmetric division, cytoplasmic determinants (mRNA, proteins, organelles) are distributed unequally, leading to different cell fates.
2. Statement (3) is Incorrect
• It states that cytoplasmic determinants are distributed "evenly" during asymmetric division.
• However, asymmetric division involves unequal distribution, where only one daughter cell inherits specific determinants that drive differentiation.
• This incorrect claim contradicts the fundamental principle of asymmetric cell fate decisions in stem cells.

Evaluation of Other Statements:

• Statement (1) - Correct
• Extracellular matrix (ECM) components (collagen, laminins, fibronectins) play a crucial role in stem cell adhesion, signaling, and niche architecture.
• The stem cell niche provides structural support and signaling cues essential for maintaining stem cell function.
• Statement (2) - Correct
• Chromatin accessibility determines which genes are accessible for transcription, regulating stem cell differentiation vs. self-renewal.
• Epigenetic modifications (e.g., histone acetylation, DNA methylation) alter chromatin structure and control stem cell fate.
• Statement (4) - Correct
• Stem cells receive signals from neighboring cells via:
• Autocrine signaling (self-produced signals).
• Paracrine signaling (local diffusible factors).
• Juxtacrine signaling (direct cell-to-cell contact).
• These signals help maintain stem cells in an undifferentiated/pluripotent state until differentiation is required.

Information Booster:

1. Stem Cell Niche:
• The microenvironment where stem cells reside, providing physical support and regulatory signals.
• Examples: Hematopoietic stem cell niche (bone marrow), Neural stem cell niche (brain).
2. Asymmetric vs. Symmetric Stem Cell Division:
• Asymmetric Division: Produces one self-renewing stem cell and one committed daughter cell.
• Symmetric Division: Produces either two stem cells or two differentiated cells.
3. Cytoplasmic Determinants in Asymmetric Division:
• Includes mRNAs, proteins (e.g., Numb, Prospero in Drosophila), and organelles (e.g., mitochondria).
• These factors are preferentially inherited by one daughter cell, influencing differentiation.
4. Epigenetic Regulation of Stem Cells:
• Histone modifications: Acetylation (active genes), Methylation (silencing).
• DNA methylation: Silences differentiation genes in pluripotent stem cells.