Epithelia 3

Question 1

1. Describe how epithelial tissues are maintained and regulated, and describe the properties, functions, regulation and development of epithelial stem cells.

Answer 1

• Epithelial stem cells are capable of division and serve to self-renew (create more stem cells) and produce differentiated cell types specific to each epithelia/tissue.
• Stem cells replace the cells that die and can regulate/change the form/function of tissues.
• Some daughter cells are stem cells, some are differentiated cell types.
• Some daughter cells proliferate faster = transitional intermediates = transit amplifying cells –> produce differentiated cells.
• Specific stem cell type + intermediate progeny + differentiated progeny = cell lineage.
• Stem cells are very tightly regulated –> divide very slowly or infrequently and are less abundant.
• Signaling pathway has: extracellular ligand, a receptor for the ligand, a downstream effector protein(s), numerous modulator proteins that promote/suppress pathway.
• Cell signaling of epithelial stem cells can be local or happen over small distances. (Or long if endocrine).
• Signaling pathways are generally Wnt, sonic hedgehog, TGF-beta, Notch, and RTK family, and FGF receptor pathways.
• Each pathway is used by multiple, very distinct stem cell systems in different organs/tissues.
• Some individual proteins may be unique in different stem cell sets, but overall pathway share big components.
• A single signaling pathway often yields different developmental outcomes in different stem cell lineages. -Differences are result of: developmental histories, environments stem cells reside in, and differences in the levels of extracellular ligands/receptors/downstream components.

Question 2

2. State the general terms for epithelial-derived cancer, and describe how defects in epithelial cell regulation can contribute to cancer.

Answer 2

• Defects in regulation, expression, or structure of signaling components (ligands, receptors, effectors) –> disease/cancer.
• Good targets for drug therapies.
• Most cancers are epithelial (and adenocarcinomas if glandular).

Question 3

3. Describe how tissue sections are made and visualized for histological (microscope) examination, both for general staining and for specific staining of specific proteins and RNAs. Distinguish what general stains visualize from what immuno-staining or nucleic acid-staining techniques visualize. NOTE: Information on this objective is presented in the Intro-Epithelia Histo PDF (Histology lab material), and will also be presented in class.

Answer 3

yes.