Yang, C.-R. | Search bioRxiv

bioRxiv2018

Cyclin B2 is required for progression through meiosis in mouse oocytes

Cyclins associate with CDK1 to generate the M-phase-promoting factor (MPF) essential for progression through mitosis and meiosis. Previous studies concluded that CCNB2 is dispensable for cell cycle progression. Given our findings of high translation rates of CcnB2 mRNA in prophase-arrested oocytes, we have reevaluated its role during meiosis. CcnB2-/- oocytes undergo delayed germinal vesicle breakdown followed by a defective M-phase due to reduced pre-MPF activity. This disrupted maturation is associated with compromised CcnB1 and Mos mRNA translation and delayed spindle assembly. Given these defects, a significant population of oocytes fail to complete meiosis I because SAC remains activated and APC function is inhibited. In vivo, CCNB2 depletion leads to decreased oocyte developmental competence, compromised fecundity, and premature ovarian failure. These findings demonstrate that CCNB2 is required to assemble sufficient pre-MPF for timely meiosis reentry and progression. Although endogenous cyclins cannot compensate, overexpression of CCNB1 rescues the meiotic phenotypes, demonstrating similar molecular properties but divergent modes of regulation of these cyclins.

developmental biology↗

bioRxiv2018

RNA-Seq and Protein Mass Spectrometry in Microdissected Kidney Tubules Reveal Signaling Processes that Initiate Lithium-Induced Diabetes Insipidus

ABSTRACT1Lithium salts, used for treatment of bipolar disorder, frequently induce nephrogenic diabetes insipidus (NDI), limiting therapeutic success. NDI is associated with loss of expression of the molecular water channel, aquaporin-2, in the renal collecting duct (CD). Here, we use the methods of systems biology in a well-established rat model of lithium-induced NDI to identify signaling pathways activated at the onset of polyuria. Using single-tubule RNA-Seq, full transcriptomes were determined in microdissected cortical CDs of rats 72 hrs after initiation of lithium chloride (LiCl) administration (vs. time-controls without LiCl). Transcriptome-wide changes in mRNA abundances were mapped to gene sets associated with curated canonical signaling pathways, showing evidence for activation of NF-{kappa}B signaling with induction of genes coding for multiple chemokines as well as most components of the Major Histocompatibility Complex (MHC) Class I antigen-presenting complex. Administration of antiinflammatory doses of dexamethasone to LiCl-treated rats countered the loss of aquaporin-2 protein. RNA-Seq also confirmed prior evidence of a shift from quiescence into the cell cycle with arrest. Time course studies demonstrated an early (12 hrs) increase in multiple immediate early genes including several transcription factors. Protein mass spectrometry in microdissected cortical CDs provided corroborative evidence but also identified decreased abundance of several anti-oxidant proteins. Integration of new data with prior data about lithium effects at a molecular level leads to a signaling model in which lithium increases ERK activation leading to induction of NF-{kappa}B signaling and an inflammatory-like response that represses Aqp2 gene transcription.

systems biology↗