Person: Pop, Ramona
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Pop
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Ramona
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Pop, Ramona
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Publication A mutation creating an upstream initiation codon in the SOX9 5′ UTR causes acampomelic campomelic dysplasia(John Wiley and Sons Inc., 2017) von Bohlen, Anna E.; Böhm, Johann; Pop, Ramona; Johnson, Diana S.; Tolmie, John; Stücker, Ralf; Morris‐Rosendahl, Deborah; Scherer, GerdAbstract Background: Campomelic dysplasia (CD) is a semilethal developmental disorder caused by mutations in and around SOX9. CD is characterized by multiple skeletal malformations including bending (campomelia) of long bones. Surviving patients frequently have the acampomelic form of CD (ACD). Methods: This is a single case report on a patient with clinical and radiological features of ACD who has no mutation in the SOX9 protein‐coding sequence nor a translocation with breakpoint in the SOX9 regulatory domain. We include functional studies of the novel mutant protein in vitro and in cultured cells. Results: The patient was found to have a de novo heterozygous mutation c.‐185G>A in the SOX9 5′UTR. The mutation creates an upstream translation start codon, uAUG, with a much better fit of its flanking sequence to the Kozak consensus than the wild‐type AUG. By in vitro transcription‐translation and transient transfection into COS‐7 cells, we show that the uAUG leads to translation of a short peptide from a reading frame that terminates just after the wild‐type AUG start codon. This results in reduced translation of the wild‐type protein, compatible with the milder phenotype of the patient. Conclusion: Findings support the notion that more mildly affected, surviving CD/ACD patients carry mutant SOX9 alleles with residual expression of SOX9 wild‐type protein. Although rarely described in human genetic disease and for the first time here for CD, mutations creating upstream AUG codons may be more common than generally assumed.Publication In vivo Monitoring of Transcriptional Dynamics After Lower-Limb Muscle Injury Enables Quantitative Classification of Healing(Nature Publishing Group, 2015) Aguilar, Carlos A.; Shcherbina, Anna; Ricke, Darrell O.; Pop, Ramona; Carrigan, Christopher T.; Gifford, Casey A.; Urso, Maria L.; Kottke, Melissa A.; Meissner, AlexanderTraumatic lower-limb musculoskeletal injuries are pervasive amongst athletes and the military and typically an individual returns to activity prior to fully healing, increasing a predisposition for additional injuries and chronic pain. Monitoring healing progression after a musculoskeletal injury typically involves different types of imaging but these approaches suffer from several disadvantages. Isolating and profiling transcripts from the injured site would abrogate these shortcomings and provide enumerative insights into the regenerative potential of an individual’s muscle after injury. In this study, a traumatic injury was administered to a mouse model and healing progression was examined from 3 hours to 1 month using high-throughput RNA-Sequencing (RNA-Seq). Comprehensive dissection of the genome-wide datasets revealed the injured site to be a dynamic, heterogeneous environment composed of multiple cell types and thousands of genes undergoing significant expression changes in highly regulated networks. Four independent approaches were used to determine the set of genes, isoforms, and genetic pathways most characteristic of different time points post-injury and two novel approaches were developed to classify injured tissues at different time points. These results highlight the possibility to quantitatively track healing progression in situ via transcript profiling using high- throughput sequencing.Publication An improved ScoreCard to assess the differentiation potential of human pluripotent stem cells(2015) Tsankov, Alexander M.; Akopian, Veronika; Pop, Ramona; Chetty, Sundari; Gifford, Casey A.; Daheron, Laurence; Melton, Douglas; Tsankova, Nadejda M.; Meissner, AlexanderResearch on human pluripotent stem cells has been hampered by the lack of a standardized, quantitative, scalable assay of pluripotency. We have previously described an assay called ScoreCard that used gene expression signatures to quantify differentiation efficiency. Here we report an improved version of the assay based on qPCR that enables faster, more quantitative assessment of functional pluripotency. We provide an in-depth characterization of the revised signature panel through embryoid body and directed differentiation experiments as well as a detailed comparison to the teratoma assay. We also show that the improved ScoreCard enables applications such as screening of small molecules, genetic perturbations and assessment of culture conditions. Beyond stem cell applications, this approach can in principle be extended to other cell types and lineages.Publication Targeted disruption of DNMT1, DNMT3A and DNMT3B in human embryonic stem cells(2015) Liao, Jing; Karnik, Rahul; Gu, Hongcang; Ziller, Michael; Clement, Kendell; Tsankov, Alexander M.; Akopian, Veronika; Gifford, Casey A.; Donaghey, Julie; Galonska, Christina; Pop, Ramona; Reyon, Deepak; Tsai, Shengdar Q.; Mallard, William; Joung, J. Keith; Rinn, John; Gnirke, Andreas; Meissner, AlexanderDNA methylation is a key epigenetic modification involved in regulating gene expression and maintaining genomic integrity. Here we inactivated all three catalytically active DNA methyltransferases in human embryonic stem cells (ESCs) using CRISPR/Cas9 genome editing to further investigate their roles and genomic targets. Disruption of DNMT3A or DNMT3B individually, as well as of both enzymes in tandem, creates viable, pluripotent cell lines with distinct effects on their DNA methylation landscape as assessed by whole-genome bisulfite sequencing. Surprisingly, in contrast to mouse, deletion of DNMT1 resulted in rapid cell death in human ESCs. To overcome the immediate lethality, we generated a doxycycline (DOX) responsive tTA-DNMT1* rescue line and readily obtained homozygous DNMT1 mutant lines. However, DOX-mediated repression of the exogenous DNMT1* initiates rapid, global loss of DNA methylation, followed by extensive cell death. Our data provide a comprehensive characterization of DNMT mutant ESCs, including single base genome-wide maps of their targets.Publication Transcriptional and Chromatin Dynamics of Muscle Regeneration after Severe Trauma(Elsevier, 2016) Aguilar, Carlos A.; Pop, Ramona; Shcherbina, Anna; Watts, Alain; Matheny, Ronald W.; Cacchiarelli, Davide; Han, Woojin M.; Shin, Eunjung; Nakhai, Shadi A.; Jang, Young C.; Carrigan, Christopher T.; Gifford, Casey A.; Kottke, Melissa A.; Cesana, Marcella; Lee, Jackson; Urso, Maria L.; Meissner, AlexanderSummary Following injury, adult skeletal muscle undergoes a well-coordinated sequence of molecular and physiological events to promote repair and regeneration. However, a thorough understanding of the in vivo epigenomic and transcriptional mechanisms that control these reparative events is lacking. To address this, we monitored the in vivo dynamics of three histone modifications and coding and noncoding RNA expression throughout the regenerative process in a mouse model of traumatic muscle injury. We first illustrate how both coding and noncoding RNAs in tissues and sorted satellite cells are modified and regulated during various stages after trauma. Next, we use chromatin immunoprecipitation followed by sequencing to evaluate the chromatin state of cis-regulatory elements (promoters and enhancers) and view how these elements evolve and influence various muscle repair and regeneration transcriptional programs. These results provide a comprehensive view of the central factors that regulate muscle regeneration and underscore the multiple levels through which both transcriptional and epigenetic patterns are regulated to enact appropriate repair and regeneration.