320
Xenopus
components. This experimental design can be further
manipulated by partially removing endogenous components
to simplify the analysis using CRISPR/Cas9 or morpholino
antisense oligonucleotides (Blum et al., 2015; Tandon et al.,
2017). These have already demonstrated the usefulness of
Xenopus embryos and oocytes to explore the contribution
of genetic polymorphisms to human disease and the spectrum of severities encountered among patients.
22.4. FUTURE OUTLOOK
It is well established that different human ethnic groups
display differential disease susceptibility and variable
responses to environmental factors and medical therapies.
Likewise, mutations in a given gene produce highly variable
dysmorphologies in several congenital syndromes. A signif -
cant factor in these differential responses is the underlying
genetic diversity of the population. Inbred lines of various
animal experimental models have been an invaluable tool for
examining the specifc role of single genes in development,
cell biology, and physiology; they also are commonly used
to explore medical treatments and drug responses. However,
the variable responses common in human populations may
not be observed in a given inbred line because it has a f xed
set of polymorphisms. Accordingly, these responses are best
examined in animal models that remain outbred and continue to be genetically polymorphic. We posit that an ideal
animal model for these studies is Xenopus. Although inbred
Xenopus lines are being used for specialized purposes, outbred Xenopus remains one of the common research models
and offers many experimental advantages to establish disease models and study the effects of genetic variability.
These advantages enable outbred Xenopus to elucidate the
important relationship between genetic variation and disease
and provide disease models to study possible treatments.
ACKNOWLEDGMENTS
We thank Dan Brattlie from Nasco and Rob Weymouth
from Xenopus 1 for sharing the history of their breeding
colonies and their maintenance practices. We also thank
Martin Blum, Dale Frank, and Graciela Pillemer for critically reading this chapter.
FUNDING
This work was funded in part by grants from the United StatesIsrael Binational Science Foundation (2013422 and 2017199)
to SM and AF, The Israel Science Foundation (668/17) to AF,
and the Wolfson Family Chair in Genetics to AF.
REFERENCES
Au, S., Cohen, S., Panté, N., 2010. Microinjection of Xenopus
laevis oocytes as a system for studying nuclear transport of viruses. Methods 51, 114–120. doi:10.1016/j.
ymeth.2010.02.001
Bachtiar, M., Ooi, B.N.S., Wang, J., Jin, Y., Tan, T.W., Chong, S.S.,
Lee, C.G.L., 2019. Towards precision medicine: interrogating
the human genome to identify drug pathways associated with
potentially functional, population-differentiated polymorphisms. Pharmacogenomics J. 19, 516–527. doi:10.1038/
s41397-019-0096-y
Baker, B.W., Dougherty, D.A., Lummis, S.C.R., 2020. Proline
residues contribute to effcient gabap receptor function. ACS
Chem. Neurosci. doi:10.1021/acschemneuro.0c00483
Balik-Meisner, M., Truong, L., Scholl, E.H., Tanguay, R.L.,
Reif, D.M., 2018. Population genetic diversity in zebraf sh
lines. Mamm. Genome 29, 90–100. doi:10.1007/s00335018-9735-x
Ballouz, S., Dobin, A., Gillis, J.A., 2019. Is it time to change the
reference genome? Genome Biol. 20, 159. doi:10.1186/
s13059-019-1774-4
Barton, H.J., Zeng, K., 2018. New methods for inferring the distribution of f tness effects for indels and snps. Mol. Biol. Evol.
35, 1536–1546. doi:10.1093/molbev/msy054
Bidwell, J., Keen, L., Gallagher, G., Kimberly, R., Huizinga, T.,
McDermott, M.F., Oksenberg, J., McNicholl, J., Pociot, F.,
Hardt, C., D’Alfonso, S., 1999. Cytokine gene polymorphism in human disease: on-line databases. Genes Immun. 1,
3–19. doi:10.1038/sj.gene.6363645
Biémont, C., Vieira, C., 2006. Genetics: Junk DNA as an evolutionary force. Nature 443, 521–524. doi:10.1038/443521a
Blackshear, P.J., Lai, W.S., Thorn, J.M., Kennington, E.A., Staffa,
N.G., Moore, D.T., Bouffard, G.G., Beckstrom-Sternberg,
S.M., Touchman, J.W., Bonaldo, M.F., Soares, M.B., 2001.
The NIEHS Xenopus maternal EST project: Interim analysis
of the frst 13,879 ESTs from unfertilized eggs. Gene 267,
71–87. doi:10.1016/s0378-1119(01)00383-3
Blair, K., Wray, J., Smith, A., 2011. The liberation of embryonic
stem cells. PLoS Genet. 7, e1002019. doi:10.1371/journal.
pgen.1002019
Blay, V., Tolani, B., Ho, S.P., Arkin, M.R., 2020. High-throughput
screening: Today’s biochemical and cell-based approaches.
Drug Discov. Today. doi:10.1016/j.drudis.2020.07.024
Blum, M., De Robertis, E.M., Wallingford, J.B., Niehrs, C., 2015.
Morpholinos: Antisense and sensibility. Dev. Cell 35, 145–
149. doi:10.1016/j.devcel.2015.09.017
Bryant, C.D., 2011. The blessings and curses of C57BL/6 substrains in mouse genetic studies. Ann. N. Y. Acad. Sci. 1245,
31–33. doi:10.1111/j.1749-6632.2011.06325.x
Bukowski, R., 2010. Stillbirth and fetal growth restriction. Clin.
Obstet. Gynecol. 53, 673–680. doi:10.1097/GRF.0b013e
3181eba0db
Choudhury, A., Hazelhurst, S., Meintjes, A., Achinike-Oduaran, O.,
Aron, S., Gamieldien, J., Jalali Sefd Dashti, M., Mulder, N.,
Tiffn, N., Ramsay, M., 2014. Population-specif c common
SNPs refect demographic histories and highlight regions of
genomic plasticity with functional relevance. BMC Genomics
15, 437. doi:10.1186/1471-2164-15-437
Cox, P., Marton, T., 2009. Pathological assessment of intrauterine
growth restriction. Best Pract. Res. Clin. Obstet. Gynaecol.
23, 751–764. doi:10.1016/j.bpobgyn.2009.06.006
Eberhart, J.K., Parnell, S.E., 2016. The genetics of fetal alcohol
spectrum disorders. Alcohol. Clin. Exp. Res. 40, 1154–1165.
doi:10.1111/acer.13066
Fainsod, A., Bendelac-Kapon, L., Shabtai, Y., 2020. Fetal alcohol
spectrum disorder: embryogenesis under reduced retinoic
acid signaling conditions. Subcell Biochem 95, 197–225.
doi:10.1007/978-3-030-42282-0_8
Fierro, A.C., Thuret, R., Coen, L., Perron, M., Demeneix, B.A.,
Wegnez, M., Gyapay, G., Weissenbach, J., Wincker, P.,
Xenopus
components. This experimental design can be further
manipulated by partially removing endogenous components
to simplify the analysis using CRISPR/Cas9 or morpholino
antisense oligonucleotides (Blum et al., 2015; Tandon et al.,
2017). These have already demonstrated the usefulness of
Xenopus embryos and oocytes to explore the contribution
of genetic polymorphisms to human disease and the spectrum of severities encountered among patients.
22.4. FUTURE OUTLOOK
It is well established that different human ethnic groups
display differential disease susceptibility and variable
responses to environmental factors and medical therapies.
Likewise, mutations in a given gene produce highly variable
dysmorphologies in several congenital syndromes. A signif -
cant factor in these differential responses is the underlying
genetic diversity of the population. Inbred lines of various
animal experimental models have been an invaluable tool for
examining the specifc role of single genes in development,
cell biology, and physiology; they also are commonly used
to explore medical treatments and drug responses. However,
the variable responses common in human populations may
not be observed in a given inbred line because it has a f xed
set of polymorphisms. Accordingly, these responses are best
examined in animal models that remain outbred and continue to be genetically polymorphic. We posit that an ideal
animal model for these studies is Xenopus. Although inbred
Xenopus lines are being used for specialized purposes, outbred Xenopus remains one of the common research models
and offers many experimental advantages to establish disease models and study the effects of genetic variability.
These advantages enable outbred Xenopus to elucidate the
important relationship between genetic variation and disease
and provide disease models to study possible treatments.
ACKNOWLEDGMENTS
We thank Dan Brattlie from Nasco and Rob Weymouth
from Xenopus 1 for sharing the history of their breeding
colonies and their maintenance practices. We also thank
Martin Blum, Dale Frank, and Graciela Pillemer for critically reading this chapter.
FUNDING
This work was funded in part by grants from the United StatesIsrael Binational Science Foundation (2013422 and 2017199)
to SM and AF, The Israel Science Foundation (668/17) to AF,
and the Wolfson Family Chair in Genetics to AF.
REFERENCES
Au, S., Cohen, S., Panté, N., 2010. Microinjection of Xenopus
laevis oocytes as a system for studying nuclear transport of viruses. Methods 51, 114–120. doi:10.1016/j.
ymeth.2010.02.001
Bachtiar, M., Ooi, B.N.S., Wang, J., Jin, Y., Tan, T.W., Chong, S.S.,
Lee, C.G.L., 2019. Towards precision medicine: interrogating
the human genome to identify drug pathways associated with
potentially functional, population-differentiated polymorphisms. Pharmacogenomics J. 19, 516–527. doi:10.1038/
s41397-019-0096-y
Baker, B.W., Dougherty, D.A., Lummis, S.C.R., 2020. Proline
residues contribute to effcient gabap receptor function. ACS
Chem. Neurosci. doi:10.1021/acschemneuro.0c00483
Balik-Meisner, M., Truong, L., Scholl, E.H., Tanguay, R.L.,
Reif, D.M., 2018. Population genetic diversity in zebraf sh
lines. Mamm. Genome 29, 90–100. doi:10.1007/s00335018-9735-x
Ballouz, S., Dobin, A., Gillis, J.A., 2019. Is it time to change the
reference genome? Genome Biol. 20, 159. doi:10.1186/
s13059-019-1774-4
Barton, H.J., Zeng, K., 2018. New methods for inferring the distribution of f tness effects for indels and snps. Mol. Biol. Evol.
35, 1536–1546. doi:10.1093/molbev/msy054
Bidwell, J., Keen, L., Gallagher, G., Kimberly, R., Huizinga, T.,
McDermott, M.F., Oksenberg, J., McNicholl, J., Pociot, F.,
Hardt, C., D’Alfonso, S., 1999. Cytokine gene polymorphism in human disease: on-line databases. Genes Immun. 1,
3–19. doi:10.1038/sj.gene.6363645
Biémont, C., Vieira, C., 2006. Genetics: Junk DNA as an evolutionary force. Nature 443, 521–524. doi:10.1038/443521a
Blackshear, P.J., Lai, W.S., Thorn, J.M., Kennington, E.A., Staffa,
N.G., Moore, D.T., Bouffard, G.G., Beckstrom-Sternberg,
S.M., Touchman, J.W., Bonaldo, M.F., Soares, M.B., 2001.
The NIEHS Xenopus maternal EST project: Interim analysis
of the frst 13,879 ESTs from unfertilized eggs. Gene 267,
71–87. doi:10.1016/s0378-1119(01)00383-3
Blair, K., Wray, J., Smith, A., 2011. The liberation of embryonic
stem cells. PLoS Genet. 7, e1002019. doi:10.1371/journal.
pgen.1002019
Blay, V., Tolani, B., Ho, S.P., Arkin, M.R., 2020. High-throughput
screening: Today’s biochemical and cell-based approaches.
Drug Discov. Today. doi:10.1016/j.drudis.2020.07.024
Blum, M., De Robertis, E.M., Wallingford, J.B., Niehrs, C., 2015.
Morpholinos: Antisense and sensibility. Dev. Cell 35, 145–
149. doi:10.1016/j.devcel.2015.09.017
Bryant, C.D., 2011. The blessings and curses of C57BL/6 substrains in mouse genetic studies. Ann. N. Y. Acad. Sci. 1245,
31–33. doi:10.1111/j.1749-6632.2011.06325.x
Bukowski, R., 2010. Stillbirth and fetal growth restriction. Clin.
Obstet. Gynecol. 53, 673–680. doi:10.1097/GRF.0b013e
3181eba0db
Choudhury, A., Hazelhurst, S., Meintjes, A., Achinike-Oduaran, O.,
Aron, S., Gamieldien, J., Jalali Sefd Dashti, M., Mulder, N.,
Tiffn, N., Ramsay, M., 2014. Population-specif c common
SNPs refect demographic histories and highlight regions of
genomic plasticity with functional relevance. BMC Genomics
15, 437. doi:10.1186/1471-2164-15-437
Cox, P., Marton, T., 2009. Pathological assessment of intrauterine
growth restriction. Best Pract. Res. Clin. Obstet. Gynaecol.
23, 751–764. doi:10.1016/j.bpobgyn.2009.06.006
Eberhart, J.K., Parnell, S.E., 2016. The genetics of fetal alcohol
spectrum disorders. Alcohol. Clin. Exp. Res. 40, 1154–1165.
doi:10.1111/acer.13066
Fainsod, A., Bendelac-Kapon, L., Shabtai, Y., 2020. Fetal alcohol
spectrum disorder: embryogenesis under reduced retinoic
acid signaling conditions. Subcell Biochem 95, 197–225.
doi:10.1007/978-3-030-42282-0_8
Fierro, A.C., Thuret, R., Coen, L., Perron, M., Demeneix, B.A.,
Wegnez, M., Gyapay, G., Weissenbach, J., Wincker, P.,