The mid-developmental transition and the evolution of animal body plans
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA287810 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR1552740.fastq.gz | Fastqsanger.gz | |||
| SRR1552750.fastq.gz | Fastqsanger.gz | |||
| SRR1552760.fastq.gz | Fastqsanger.gz | |||
| SRR1552770.fastq.gz | Fastqsanger.gz | |||
| SRR1552780.fastq.gz | Fastqsanger.gz |
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Project description:Animals are grouped into ~35 'phyla' based upon the notion of distinct body plans. Morphological and molecular analyses have revealed that a stage in the middle of development--known as the phylotypic period--is conserved among species within some phyla. Although these analyses provide evidence for their existence, phyla have also been criticized as lacking an objective definition, and consequently based on arbitrary groupings of animals. Here we compare the developmental transcriptomes of ten species, each annotated to a different phylum, with a wide range of life histories and embryonic forms. We find that in all ten species, development comprises the coupling of early and late phases of conserved gene expression. These phases are linked by a divergent 'mid-developmental transition' that uses species-specific suites of signalling pathways and transcription factors. This mid-developmental transition overlaps with the phylotypic period that has been defined previously for three of the ten phyla, suggesting that transcriptional circuits and signalling mechanisms active during this transition are crucial for defining the phyletic body plan and that the mid-developmental transition may be used to define phylotypic periods in other phyla. Placing these observations alongside the reported conservation of mid-development within phyla, we propose that a phylum may be defined as a collection of species whose gene expression at the mid-developmental transition is both highly conserved among them, yet divergent relative to other species.
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Project description:In mammals, a key transition in spermatogenesis is the exit from spermatogonial differentiation and mitotic proliferation and the entry into spermatocyte differentiation and meiosis. Although several genes that regulate this transition have been identified, how it is controlled and coordinated remains poorly understood. Here we examine the role in male gametogenesis of the Doublesex-related gene Dmrt6 (Dmrtb1) and find that Dmrt6 plays a critical role in directing germ cells through the mitotic to meiotic germ cell transition. DMRT6 protein is expressed in late mitotic spermatogonia. In mice of the C57BL/6J strain a null mutation in Dmrt6 disrupts spermatogonial differentiation, causing expression in inappropriate cell types of spermatogonial differentiation factors including SOHLH1, SOHLH2 and DMRT1 and the meiotic initiation factor STRA8 and causing most late spermatogonia to undergo apoptosis. In mice of the 129Sv background, most Dmrt6 mutant spermatogonia can complete differentiation and enter meiosis, but they show defects in chromosome pairing, establishment of the XY body, and processing of recombination foci, and mainly arrest in mid-pachynema. mRNA profiling of Dmrt6 mutant testes together with DMRT6 ChIP-seq suggest that DMRT6 represses genes involved in spermatogonial differentiation and activates genes required for meiotic prophase. Our results indicate that Dmrt6 plays a key role in coordinating the transition in gametogenic programs from spermatogonial differentiation and mitosis to spermatocyte development and meiosis.
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