Biology subjects

Licatalosi, D. D.

Publications and source records attributed to Licatalosi, D. D..

5 recordsLinked to original sources

bioRxiv2020

Adaptive translational pausing is a hallmark of the cellular response to severe environmental stress

Mammalian cells have to adapt to environmental challenges that range from mild to severe stress. While the cellular response to mild stress has been widely studied, how cells respond to severe stress remains unclear. We show here that under severe stress conditions, cells induce a transient hibernation-like mechanism that anticipates recovery. We demonstrate that this Adaptive Pausing Response (APR) is a coordinated cellular response that limits ATP supply and consumption though mitochondrial fragmentation and widespread pausing of mRNA translation. This pausing is accomplished by ribosome stalling at translation initiation codons, which keeps mRNAs poised to resume translation upon recovery from severe stress. We further show that recovery from severe stress involves adaptive ISR (Integrated Stress Response) signaling that in turn permits cell cycle progression, resumption of growth, and reversal of mitochondria fragmentation. Our findings indicate that cells can respond to severe stress through the APR, a mechanism that preserves vital elements of cellular function under harsh environmental conditions.

molecular biology↗

bioRxiv2018

PTBP2-dependent alternative splicing regulates protein transport and mitochondria morphology in post-meiotic germ cells.

The RNA binding protein PTBP2 (polypyrimidine tract binding protein 2) is a key regulator of tissue-specific alternative RNA splicing. In the testis, PTBP2 is expressed in meiotic and post-meiotic germ cells (spermatocytes and spermatids, respectively). In these cells, PTBP2 is required for proper alternative mRNA splicing for over 200 genes, disproportionately affecting genes encoding proteins involved in protein trafficking via transport vesicles. In this study, we used electron microscopy to test the hypothesis that protein trafficking is impaired in the absence of PTBP2, and to further investigate why spermatogenesis abruptly ceases in PTBP2-deficienct spermatids. Ultrastructural analysis shows that protein trafficking in spermatids is aberrant in the absence of PTBP2. Unexpectedly, we also found that mitochondria morphology and number are significantly altered in PTBP2-deficient spermatids, consistent with increased mitochondria fission. Furthermore, we show that genes with key roles in mitochondria dynamics and function are post-transcriptionally regulated by PTBP2 and in different stages of spermatogenesis. Collectively, the data provide ultrastructural evidence that alternative splicing regulation by PTBP2 during spermatogenesis is critical for proper regulation of protein trafficking and mitochondria morphology.

developmental biology↗

bioRxiv2018

Efficient GFP-labeling and analysis of spermatogenic cells using the IRG transgene and flow cytometry

Spermatogenesis is a highly ordered developmental program that produces haploid male germ cells. The study of male germ cell development in the mouse has provided unique perspectives into the molecular mechanisms that control cell development and differentiation in mammals, including tissue-specific gene regulatory programs. An intrinsic challenge in spermatogenesis research is the heterogeneity of germ and somatic cell types present in the testis. Techniques to separate and isolate distinct mouse spermatogenic cell types have great potential to shed light on molecular mechanisms controlling mammalian cell development, while also providing new insights into cellular events important for human reproductive health. Here, we detail a versatile strategy that combines Cre-lox technology to fluorescently label germ cells, with flow cytometry to discriminate and isolate germ cells in different stages of development for cellular and molecular analyses.

developmental biology↗

bioRxiv2018

Dazl regulates germ cell survival through a network of polyA proximal mRNA interactions

The RNA binding protein Dazl is essential for gametogenesis, but its direct in vivo functions, RNA targets, and the molecular basis for germ cell loss in DAZL null mice are unknown. Here, we mapped transcriptome-wide Dazl-RNA interactions in vivo, revealing Dazl binding to thousands of mRNAs via polyA-proximal 3UTR interactions. In parallel, fluorescence activated cell sorting and RNA-Seq identified mRNAs sensitive to Dazl deletion in male germ cells. Despite binding a broad set of mRNAs, integrative analyses indicate that Dazl post-transcriptionally controls only a subset of its mRNA targets, namely those corresponding to a network of genes critical for germ cell proliferation and survival. Additionally, we provide evidence that polyA sequences have key roles in specifying Dazl-RNA interactions across the transcriptome. Altogether, our results reveal a mechanism for Dazl-RNA binding, and illustrate that Dazl functions as a master regulator of a post-transcriptional mRNA program essential for germ cell survival.

molecular biology↗

bioRxiv2018

Neuron-specific cTag-CLIP reveals cell-specific diversity of functional RNA regulation in the brain

RNA-binding proteins (RBPs) regulate genetic diversity, but the degree to which they do so in individual cell-types in vivo is unknown. We employed NOVA2 cTag-CLIP to generate functional RBP-RNA maps from single neuronal populations in the mouse brain. Combining cell-type specific data from Nova2-cTag and Nova2 conditional knock-out mice revealed differential NOVA2 regulatory actions (e.g. alternative splicing) on the same transcripts in different neurons, including in cerebellar Purkinje cells, where NOVA2 acts as an essential factor for proper motor coordination and synapse formation. This also led to the discovery of a mechanism by which NOVA2 action leads to different outcomes in different cells on the same transcripts: NOVA2 is able to regulate retained introns, which subsequently serve as scaffolds for another trans-acting splicing factor, PTBP2. Our results describe differential roles and mechanisms by which RBPs mediate RNA diversity in different neurons and consequent functional outcomes within the brain.

neuroscience↗