Comparative Analysis of Bivalve and Sea Urchin Genetics and Development: Investigating the Dichotomy in Bilateria

Abstract

This comprehensive review presents a comparative analysis of early embryogenesis in Protostomia and Deuterostomia, the first of which exhibit a mosaic pattern of development, where cells are fated deterministically, while Deuterostomia display a regulatory pattern of development, where the fate of cells is indeterminate. Despite these fundamental differences, there are common transcriptional mechanisms that underline their evolutionary linkages, particularly in the field of functional genomics. By elucidating both conserved and unique regulatory strategies, this review provides essential insights into the comparative embryology and developmental dynamics of these groups. The objective of this review is to clarify the shared and distinctive characteristics of transcriptional regulatory mechanisms. This will contribute to the extensive areas of functional genomics, evolutionary biology and developmental biology, and possibly lay the foundation for future research and discussion on this seminal topic.

Keywords: chromatin landscape; deuterostomia; genome; mollusks; non-coding RNA (ncRNA); protostomia; sea urchin; transcription; transposable elements (TE).

Figure 1

Truncated phylogenetic tree representing major taxa of the Protostomia and Deuterostomia, derived from combined analyses of molecular and morphological data [12,13,14]. Branch lengths do not correspond with time.

Figure 2

The percent content of transposable elements (TE) in genomes of the sea urchins and bivalves. TE classes are marked with a color: DNA transposons—red; LTR TE—ochre; nonLTR: LINE—yellow; SINE—green; other TE—blue; unclassified repeats—gray.