CSB329H1 Lecture Notes - Lecture 3: Homeobox, Gsk3B, Hermaphrodite
9 May 2018
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Lecture 3(b): Flatworms and Roundworm Stem Cells
Spermatogenesis:
• Germ cells will undergo mitosis until they reach the
germline transition zone
o Mitotic to meiotic transition
ð L2-L4:
o Distal tip cell will signal spermatogenesis and
spermatozoa will undergo amoeboid movement till it gets to the spermatheca
ð We do not have the production of oocytes and spermatozoa at the same time
o Spermatozoa is produced first and stored in the spermatheca
o Later, oocytes production will occur moving through the spermatheca where it will
be fertilized and exported via the vulva
Germline Stem Cell:
• C. Elegans have ECM molecules that are required for maintaining the stem cell potential of
the germline => contact with ECM is essential
o Hemicentin – forms a thick ECM in intimate contact with the germline stem cells
ð Whether we are looking at a worm, or mammals – all stem cells require contact with the ECM
Structure & Signaling Mechanisms of C. Elegans GSC Niche:
• Germline stem cells are self-renewal that require a niche
o Central to the niche is the distal tip cell that functions to
support germline cell maintenance and proliferation
Digital Cell:
• Wnt signaling is essential to form the niche of the stem cell
o Communication between the distal tip cell and germline
stem cell occurs via notch delta signaling
ð Notch Delta Signaling:
o Delta is expressed by the distal tip cell
o Notch (GLP-1 [in C. Elegans]) is found in the germline
stem cell
§ Ligand-Ligand signaling
• Delta – signaling cell
• Notch – receiving cell
o Downstream of Delta-Notch signaling is activating the expression of a few RNA
binding proteins
§ Notch (GLP-1) signaling is necessary and sufficient to maintain germline
stem cells and mitotic zone
ð RNA binding proteins will function to inhibit the expression of Gld proteins which usually
function to inhibit self-renewal in germline stem cells
Document Summary
Spermatogenesis: germ cells will undergo mitosis until they reach the germline transition zone, mitotic to meiotic transition. L2-l4: distal tip cell will signal spermatogenesis and spermatozoa will undergo amoeboid movement till it gets to the spermatheca. Whether we are looking at a worm, or mammals all stem cells require contact with the ecm. Structure & signaling mechanisms of c. elegans gsc niche: germline stem cells are self-renewal that require a niche, central to the niche is the distal tip cell that functions to support germline cell maintenance and proliferation. Digital cell: wnt signaling is essential to form the niche of the stem cell, communication between the distal tip cell and germline stem cell occurs via notch delta signaling. Notch delta signaling: delta is expressed by the distal tip cell, notch (glp-1 [in c. elegans]) is found in the germline stem cell.
