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Divergent mechanisms regulate conserved cardiopharyngeal development and gene expression in distantly related ascidians.

Stolfi A, Lowe EK, Racioppi C, Ristoratore F, Brown CT, Swalla BJ, Christiaen L - Elife (2014)

Bottom Line: Ascidians present a striking dichotomy between conserved phenotypes and divergent genomes: embryonic cell lineages and gene expression patterns are conserved between distantly related species.Much research has focused on Ciona or Halocynthia spp. but development in other ascidians remains poorly characterized.In this study, we surveyed the multipotent myogenic B7.5 lineage in Molgula spp.

View Article: PubMed Central - PubMed

Affiliation: Center for Developmental Genetics, Department of Biology, New York University, New York, United States.

ABSTRACT
Ascidians present a striking dichotomy between conserved phenotypes and divergent genomes: embryonic cell lineages and gene expression patterns are conserved between distantly related species. Much research has focused on Ciona or Halocynthia spp. but development in other ascidians remains poorly characterized. In this study, we surveyed the multipotent myogenic B7.5 lineage in Molgula spp. Comparisons to the homologous lineage in Ciona revealed identical cell division and fate specification events that result in segregation of larval, cardiac, and pharyngeal muscle progenitors. Moreover, the expression patterns of key regulators are conserved, but cross-species transgenic assays uncovered incompatibility, or 'unintelligibility', of orthologous cis-regulatory sequences between Molgula and Ciona. These sequences drive identical expression patterns that are not recapitulated in cross-species assays. We show that this unintelligibility is likely due to changes in both cis- and trans-acting elements, hinting at widespread and frequent turnover of regulatory mechanisms underlying otherwise conserved aspects of ascidian embryogenesis.

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Aldh1a expression in M. occidentalis embryo.In situ hybridization for Moocci.Aldh1a showing expression in TVCs and ATMs in a mid-tailbud embryo.DOI:http://dx.doi.org/10.7554/eLife.03728.012
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fig2s4: Aldh1a expression in M. occidentalis embryo.In situ hybridization for Moocci.Aldh1a showing expression in TVCs and ATMs in a mid-tailbud embryo.DOI:http://dx.doi.org/10.7554/eLife.03728.012

Mentions: Notably, the ATMs appear to be specified in M. occulta, as revealed by expression of Aldh1a (also known as Raldh2,Figure 2—figure supplement 3G–I), which encodes the rate-limiting enzyme for retinoic acid (RA) synthesis. Therefore, although the larval muscles of M. occulta do not differentiate (Swalla and Jeffery, 1990; Kusakabe et al., 1996), their ATMs may still be required for RA-mediated embryonic patterning like in C. intestinalis (Nagatomo and Fujiwara, 2003) and probably also in M. occidentalis (Figure 2—figure supplement 4).


Divergent mechanisms regulate conserved cardiopharyngeal development and gene expression in distantly related ascidians.

Stolfi A, Lowe EK, Racioppi C, Ristoratore F, Brown CT, Swalla BJ, Christiaen L - Elife (2014)

Aldh1a expression in M. occidentalis embryo.In situ hybridization for Moocci.Aldh1a showing expression in TVCs and ATMs in a mid-tailbud embryo.DOI:http://dx.doi.org/10.7554/eLife.03728.012
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4356046&req=5

fig2s4: Aldh1a expression in M. occidentalis embryo.In situ hybridization for Moocci.Aldh1a showing expression in TVCs and ATMs in a mid-tailbud embryo.DOI:http://dx.doi.org/10.7554/eLife.03728.012
Mentions: Notably, the ATMs appear to be specified in M. occulta, as revealed by expression of Aldh1a (also known as Raldh2,Figure 2—figure supplement 3G–I), which encodes the rate-limiting enzyme for retinoic acid (RA) synthesis. Therefore, although the larval muscles of M. occulta do not differentiate (Swalla and Jeffery, 1990; Kusakabe et al., 1996), their ATMs may still be required for RA-mediated embryonic patterning like in C. intestinalis (Nagatomo and Fujiwara, 2003) and probably also in M. occidentalis (Figure 2—figure supplement 4).

Bottom Line: Ascidians present a striking dichotomy between conserved phenotypes and divergent genomes: embryonic cell lineages and gene expression patterns are conserved between distantly related species.Much research has focused on Ciona or Halocynthia spp. but development in other ascidians remains poorly characterized.In this study, we surveyed the multipotent myogenic B7.5 lineage in Molgula spp.

View Article: PubMed Central - PubMed

Affiliation: Center for Developmental Genetics, Department of Biology, New York University, New York, United States.

ABSTRACT
Ascidians present a striking dichotomy between conserved phenotypes and divergent genomes: embryonic cell lineages and gene expression patterns are conserved between distantly related species. Much research has focused on Ciona or Halocynthia spp. but development in other ascidians remains poorly characterized. In this study, we surveyed the multipotent myogenic B7.5 lineage in Molgula spp. Comparisons to the homologous lineage in Ciona revealed identical cell division and fate specification events that result in segregation of larval, cardiac, and pharyngeal muscle progenitors. Moreover, the expression patterns of key regulators are conserved, but cross-species transgenic assays uncovered incompatibility, or 'unintelligibility', of orthologous cis-regulatory sequences between Molgula and Ciona. These sequences drive identical expression patterns that are not recapitulated in cross-species assays. We show that this unintelligibility is likely due to changes in both cis- and trans-acting elements, hinting at widespread and frequent turnover of regulatory mechanisms underlying otherwise conserved aspects of ascidian embryogenesis.

Show MeSH
Related in: MedlinePlus