Pearl Esther J.

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Pearl
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Esther J.
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  • Article
    Transgenic Xenopus laevis line for in vivo labeling of nephrons within the kidney
    (MDPI AG, 2018-04-06) Corkins, Mark E. ; Hanania, Hannah L. ; Krneta-Stankic, Vanja ; DeLay, Bridget D. ; Pearl, Esther J. ; Lee, Moonsup ; Ji, Hong ; Davidson, Alan J. ; Horb, Marko E. ; Miller, Rachel K.
    Xenopus laevis embryos are an established model for studying kidney development. The nephron structure and genetic pathways that regulate nephrogenesis are conserved between Xenopus and humans, allowing for the study of human disease-causing genes. Xenopus embryos are also amenable to large-scale screening, but studies of kidney disease-related genes have been impeded because assessment of kidney development has largely been limited to examining fixed embryos. To overcome this problem, we have generated a transgenic line that labels the kidney. We characterize this cdh17:eGFP line, showing green fluorescent protein (GFP) expression in the pronephric and mesonephric kidneys and colocalization with known kidney markers. We also demonstrate the feasibility of live imaging of embryonic kidney development and the use of cdh17:eGFP as a kidney marker for secretion assays. Additionally, we develop a new methodology to isolate and identify kidney cells for primary culture. We also use morpholino knockdown of essential kidney development genes to establish that GFP expression enables observation of phenotypes, previously only described in fixed embryos. Taken together, this transgenic line will enable primary kidney cell culture and live imaging of pronephric and mesonephric kidney development. It will also provide a simple means for high-throughput screening of putative human kidney disease-causing genes.
  • Article
    An optimized method for cryogenic storage of Xenopus sperm to maximise the effectiveness of research using genetically altered frogs
    (Elsevier, 2017-01-17) Pearl, Esther J. ; Morrow, Sean ; Noble, Anna ; Lerebours, Adelaide ; Horb, Marko E. ; Guille, Matthew
    Cryogenic storage of sperm from genetically altered Xenopus improves cost effectiveness and animal welfare associated with their use in research; currently it is routine for X. tropicalis but not reliable for X. laevis. Here we compare directly the three published protocols for Xenopus sperm freeze-thaw and determine whether sperm storage temperature, method of testes maceration and delays in the freezing protocols affect successful fertilisation and embryo development in X. laevis. We conclude that the protocol is robust and that the variability observed in fertilisation rates is due to differences between individuals. We show that the embryos made from the frozen-thawed sperm are normal and that the adults they develop into are reproductively indistinguishable from others in the colony. This opens the way for using cryopreserved sperm to distribute dominant genetically altered (GA) lines, potentially saving travel-induced stress to the male frogs, reducing their numbers used and making Xenopus experiments more cost effective.
  • Preprint
    Development of xenopus resource centers : the national xenopus resource and the european xenopus resource center
    ( 2011-07) Pearl, Esther J. ; Grainger, Robert M. ; Guille, Matthew ; Horb, Marko E.
    Xenopus is an essential vertebrate model system for biomedical research that has contributed to important discoveries in many disciplines, including cell biology, molecular biology, physiology, developmental biology and neurobiology. However, unlike other model systems no central repository/stock center for Xenopus had been established until recently. Similar to mouse, zebrafish and fly communities, which have established stock centers, Xenopus researchers need to maintain and distribute rapidly growing numbers of inbred, mutant and transgenic frog strains, along with DNA and protein resources, and individual laboratories struggle to accomplish this efficiently. In the last five years two resource centers were founded to address this need: the European Xenopus Resource Center (EXRC) at the University of Portsmouth in England, and the National Xenopus Resource (NXR) at the Marine Biological Laboratory (MBL) in Woods Hole, MA, USA. These two centers work together to provide resources and support to the Xenopus research community. The EXRC and NXR serve as stock centers and acquire, produce, maintain and distribute mutant, inbred and transgenic X. laevis and X. tropicalis lines. Independently, the EXRC is a repository for Xenopus cDNAs, fosmids and antibodies; it also provides oocytes and wild type frogs within the UK. The NXR will complement these services by providing research training and promoting intellectual interchange through hosting minicourses and workshops and offering space for researchers to perform short-term projects at the MBL. Together the EXRC and NXR will enable researchers to improve productivity by providing resources and expertise to all levels, from graduate students to experienced PIs. These two centers will also enable investigators that use other animal systems to take advantage of Xenopus’ unique experimental features to complement their studies.
  • Preprint
    Transcriptomic insights into genetic diversity of protein-coding genes in X. laevis
    ( 2017-03) Savova, Virginia ; Pearl, Esther J. ; Boke, Elvan ; Nag, Anwesha ; Adzhubei, Ivan ; Horb, Marko E. ; Peshkin, Leonid
    We characterize the genetic diversity of Xenopus laevis strains using RNA-seq data and allele- specific analysis. This data provides a catalogue of coding variation, which can be used for improving the genomic sequence, as well as for better sequence alignment, probe design, and proteomic analysis. In addition, we paint a broad picture of the genetic landscape of the species by functionally annotating different classes of mutations with a well-established prediction tool (PolyPhen-2). Further, we specifically compare the variation in the progeny of four crosses: inbred genomic (J)- strain, outbred albino (B)-strain, and two hybrid crosses of J and B strains. We identify a subset of mutations specific to the B strain, which allows us to investigate the selection pressures affecting duplicated genes in this allotetraploid. From these crosses we find the ratio of non-synonymous to synonymous mutations is lower in duplicated genes, which suggests that they are under greater purifying selection. Surprisingly, we also find that function-altering ("damaging") mutations constitute a greater fraction of the non-synonymous variants in this group, which suggests a role for subfunctionalization in coding variation affecting duplicated genes.