Lasser M et al. (2019), The Many Faces of Xenopus: Xenopus laevis as a ...

XB-ART-56118

Front Physiol 2019 Jan 01;10:817. doi: 10.3389/fphys.2019.00817.

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The Many Faces of Xenopus: Xenopus laevis as a Model System to Study Wolf-Hirschhorn Syndrome.

Lasser M , Pratt B , Monahan C , Kim SW , Lowery LA .

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Wolf-Hirschhorn syndrome (WHS) is a rare developmental disorder characterized by intellectual disability and various physical malformations including craniofacial, skeletal, and cardiac defects. These phenotypes, as they involve structures that are derived from the cranial neural crest, suggest that WHS may be associated with abnormalities in neural crest cell (NCC) migration. This syndrome is linked with assorted mutations on the short arm of chromosome 4, most notably the microdeletion of a critical genomic region containing several candidate genes. However, the function of these genes during embryonic development, as well as the cellular and molecular mechanisms underlying the disorder, are still unknown. The model organism Xenopus laevis offers a number of advantages for studying WHS. With the Xenopus genome sequenced, genetic manipulation strategies can be readily designed in order to alter the dosage of the WHS candidate genes. Moreover, a variety of assays are available for use in Xenopus to examine how manipulation of WHS genes leads to changes in the development of tissue and organ systems affected in WHS. In this review article, we highlight the benefits of using X. laevis as a model system for studying human genetic disorders of development, with a focus on WHS.

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Species referenced: Xenopus laevis
Genes referenced: cplx1 ctbp1 fgfr3 fgfrl1 letm1 msx1 nelfa pigg slbp slc12a3 tacc3 twist1

???displayArticle.disOnts??? Wolf-Hirschhorn syndrome
???displayArticle.omims??? WOLF-HIRSCHHORN SYNDROME; WHS

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	FIGURE 1. Chromosome 4 and WHS-associated genes. All genes are represented in their order from left to right, telomeric to centromeric orientation, located on the distal arm of chromosome 4p16.3. Brackets delineate WHS critical region 1 (WHSCR1), comprised of LETM1 and WHSC1, and WHS critical region 2 (WHSCR2), comprised of WHSC1 and WHSC2. Genes that are also mutated in WHS patients consist of PIGG, CPLX1, FGFRL1, CTBP1, SLBP, TACC3, and FGFR3, which flank the WHS critical regions.
	FIGURE 2. Xenopus one-sided injections allow for side-by-side comparison to wild-type gene expression following genetic manipulation. (A) Xenopus embryos can be injected in one cell at the 2-cell stage with genetic manipulation macromolecules and fluorescent mRNA. At stage 21, embryos can be sorted depending on the side that was injected (left vs. right) and used for various assays throughout development. (B) Representative image of stage 47 X. laevis tadpole immunolabeled for acetylated tubulin. Asterisk represents the side that was injected with MO and fluorescent mRNA. Brain morphology, such as forebrain size (red outline), midbrain size (yellow outline), and hindbrain size (orange outline), of the manipulated side can be compared to the unaltered, wild-type side. Scale bar: 500 μm.
	FIGURE 3. Analysis of in vivo NCC migration using whole-mount in situ hybridization. Representative image of stage 30 X. laevis embryo labeled for xTWIST, a marker for NCCs. Measurements of the length (orange line) and area (red dotted line) of each individual pharyngeal arch can be done using ImageJ. Pharyngeal arch length is measured from the most dorsal point to the most ventral point of each individual arch. Pharyngeal arch area is measured as the area around the periphery of each individual arch. cg, cement gland; pa, pharyngeal arches. Scale bar: 500 μm.
	FIGURE 4. Measurements of Xenopus craniofacial features. (A) Representative frontal view image of stage 42 X. laevis tadpole. Measurements of facial features include facial height (blue line), facial width (orange line), facial area (red dotted line), facial angle (green line), and mouth roundness (yellow dotted line). Facial height is measured from the top of the middle of the eyes to the top of the cement gland. Facial width is measured from the middle of one eye to the middle of the opposite eye. Facial area is measured as the area around the top of the eyes to the top of the cement gland. Facial angle is measured as the angle between the middle of the eyes and the top of the cement gland. Mouth roundness is measured as the area around the periphery of the mouth. (B) Representative lateral view image of stage 42 X. laevis tadpole. Measurements of facial features include eye area (red dotted line) and snout length (orange line). Eye area is measured as the area around the periphery of the eye. Snout length is measured from the most anterior part of the face to the bottom of the eye. All measurements can be performed using ImageJ. cg, cement gland. Scale bar: 100 μm.
	FIGURE 5. Measurements of Xenopus cartilage elements. (A) Xenopus cartilage anatomy with all major cartilage elements labeled in various colors. (B) Representative ventral view image of stage 45 X. laevis tadpole stained for Alcian blue. Measurements of cartilage elements include branchial arch length (orange line) and ceratohyal area (red dotted line), which can be performed using ImageJ. Scale bar: 300 μm.

References [+] :

Alkobtawi, Characterization of Pax3 and Sox10 transgenic Xenopus laevis embryos as tools to study neural crest development. 2018, Pubmed, Xenbase