Single-Cell Transcriptomics Reveals Evolutionary Reconfiguration of Embryonic Cell Fate Specification in the Sea...

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Genomics

Background:

• Phenotypic diversity arises from altered regulatory interactions during development.
• Identifying specific evolutionary changes in developmental mechanisms is challenging.
• Single-cell developmental transcriptomes offer a powerful framework for unbiased analysis.

Purpose of the Study:

• To identify evolutionary changes in embryonic patterning using comparative single-cell RNA sequencing.
• To investigate developmental evolution in sea urchins, focusing on a lineage with a recent life history switch.
• To correlate changes in embryonic patterning with larval morphology evolution.

Main Methods:

• Comparative analysis of single-cell RNA sequencing (scRNA-seq) developmental time courses.
• Studied two sea urchin species: Heliocidaris erythrogramma (derived) and Lytechinus variegatus (ancestral).
• Analyzed regulator-target gene co-expression to infer changes in gene regulatory networks.

Main Results:

• Numerous evolutionary changes in embryonic patterning were identified between the two species.
• In H. erythrogramma, early cell fate specification and signaling centers are spatially and temporally separated, unlike in L. variegatus.
• Fate specification and differentiation are generally delayed in H. erythrogramma, with some conserved or accelerated processes.
• Many gene interactions are preserved but delayed, while some conserved interactions appear lost in H. erythrogramma.
• Specific patterning events correlate directly with evolutionary changes in larval morphology.

Conclusions:

• Comparative scRNA-seq developmental time courses effectively reveal diverse evolutionary changes in embryonic patterning.
• This approach efficiently identifies candidate regulatory interactions for experimental validation.
• Changes in embryonic patterning are directly linked to the sea urchin life history shift.