May 1, 2012 journal club

• When: Tuesday, May 1, 12:15 PM
• Where: Room E6519, BSPH

Jenn Wang (Seydoux lab) will be presenting two complementary papers, published back-to-back in the March 15 issue of Developmental Cell: 

MITOPLD Is a Mitochondrial Protein Essential for Nuage Formation and piRNA Biogenesis in the Mouse Germline. 
Watanabe et al. 
Dev Cell 20:364

piRNA-Associated Germline Nuage Formation and Spermatogenesis Require MitoPLD Profusogenic Mitochondrial-Surface Lipid Signaling. 
Huang et al. [Frohman lab website]
Dev Cell 20:376.  

Jenn's comments on her paper choices . . . 
(with a little bold font, done by me for emphasis on keywords): 

"These papers revolve around the conserved, membrane-less, electron-dense RNA-protein aggregates in germ cells known as germ granules or nuage. These structures have been found to be crucial for the production of piRNAs, small RNAs that are required for maintaining genome integrity in the germline.  The mechanisms by which germ granules assemble in germ cells is not fully understood and is actively studied.  It has been known for many years that they are associated with mitochondria, (one of the many names for this structure in mammals is "intermitochondrial cement," or IMC) but the functional significance of mitochondrial association is not known. 

In this set of papers, the authors show that MITOPLD, a mitochondrial enzyme, is required for IMC assembly and function.  In the absence of MITOPLD, male mice are sterile, with spermatocytes arrested in meiosis due to retrotransposon derepression.  MITOPLD is the mitochondrial phospholipase D and generates phosphatidic acid, a signaling molecule.  The authors propose that phosphatidic acid may act to signal IMC component assembly or activation.  I picked these papers because they bring up the intriguing cell biology of interorganellar dynamics, with important consequences to the germ cells.  Moreover, these papers are a good example of evolutionary conservation, as zucchini, the Drosophila ortholog of MITOPLD, also acts in piRNA biogenesis. Finally, germ granule assembly is close to the center of my heart (and at the center of my thesis work)."

April 17, 2012 journal club

• When: Tuesday, April 17, 12:15 PM
• Where: Room E6519, BSPH

Lauren McGinnis will be presenting:
Calcium influx-mediated signaling is required for complete mouse egg activation
PNAS 2012, 109: 4169-4174
Miao et al. (Carmen Williams' research group website)

Lauren's comments about this paper:
"Cytosolic calcium oscillations are characteristic of the egg-to-embryo transition. It has been thought that the intracellular calcium that drives egg activation comes from the endoplasmic reticulum, but this paper looks into the necessity for calcium influx across the plasma membrane as a requirement for egg activation, in addition to a function of influx in restoring intercellular calcium stores that are depleted as a consequence of fertilization. I was interested in this paper because the experimental findings potentially provide insight into my project on post-ovulatory aging, and specifically why aged eggs commonly undergo spontaneous egg activation. The Evans lab has found that aged eggs have reduced cortical tension compared to young eggs and this decrease in membrane rigidity may allow additional calcium to enter the cell across the plasma membrane thereby initiating critical signaling pathways to activate the egg."

RBJC schedule for rest of spring 2012

We have a line-up for these upcoming Tuesdays:

April 17 - Lauren McGinnis (Evans lab)
May 1 - Jenn Wang (Seydoux lab)
May 15 - Shaina Palmere (Drummond-Barbosa lab)
May 29 - Melvin Rouse (Ball lab)

Time and place as per usual -- 12:15 in Room E6519 in the School of Public Health.