Details

Autor(en) / Beteiligte

• Nishida, Hiroki

Titel

The maternal muscle determinant in the ascidian egg

Ist Teil von

• Wiley interdisciplinary reviews. Developmental biology, 2012-05, Vol.1 (3), p.425-433

Ort / Verlag

Hoboken, USA: John Wiley & Sons, Inc

Erscheinungsjahr

2012

Quelle

MEDLINE

Beschreibungen/Notizen

• Muscle formation in ascidian embryos has been investigated for more than a century as a representative example of cell fate specification by localized maternal factors within the egg cytoplasm. Observations of colored cytoplasm in combination with micromanipulation techniques have suggested the presence of a muscle‐forming factor. The molecular basis has been elucidated with the discovery of macho‐1. macho‐1 mRNA is already present in the unfertilized egg, and translocates to the posterior region of the egg during ooplasmic movements. It encodes a zinc‐finger transcription factor that positively regulates the expression of target genes. macho‐1‐binding cis‐elements have been identified in muscle‐specific zygotic genes. Maternally localized macho‐1 appears to have originated in the ascidian lineage, but it activates a muscle‐forming developmental program that is shared by the vertebrates. macho‐1 is also involved in establishment of the anterior–posterior axis as a competence factor in mesenchyme induction in the posterior region. It is suggested that translation of the macho‐1 protein is initiated at the eight‐cell stage, and that the protein is inherited by all descendant blastomeres of the posterior‐vegetal region. The macho‐1 activities in nonmuscle descendants are suppressed or modified by cell interactions during the cleavage stages. In addition to the primary muscle specified by maternal macho‐1, ascidian embryos develop secondary muscle, whose fate is determined by cell interactions. Dozens of maternal mRNAs show similar localization to macho‐1, and these are known as postplasmic/PEM RNAs, being also involved in various posterior‐specific developmental events. Evolutionary aspects relevant to macho‐1 and tail muscle formation are also discussed in this article. WIREs Dev Biol 2012, 1:425–433. doi: 10.1002/wdev.22 This article is categorized under: Establishment of Spatial and Temporal Patterns > Cytoplasmic Localization Early Embryonic Development > Fertilization to Gastrulation Comparative Development and Evolution > Body Plan Evolution