scholarly journals Conserved Temporal Patterns of MicroRNA Expression in Drosophila Support a Developmental Hourglass Model

2014 ◽  
Vol 6 (9) ◽  
pp. 2459-2467 ◽  
Author(s):  
Maria Ninova ◽  
Matthew Ronshaugen ◽  
Sam Griffiths-Jones
Keyword(s):  
Temporal Patterns ◽  
Microrna Expression ◽  
Hourglass Model ◽  
Developmental Hourglass

scholarly journals The developmental hourglass model: a predictor of the basic body plan?

Development ◽  
2014 ◽  
Vol 141 (24) ◽  
pp. 4649-4655 ◽  
Author(s):  
N. Irie ◽  
S. Kuratani
Keyword(s):  
Body Plan ◽  
Basic Body ◽  
Hourglass Model ◽  
Developmental Hourglass

scholarly journals The hourglass model of evolutionary conservation during embryogenesis extends to developmental enhancers with signatures of positive selection

2020 ◽  
Author(s):  
Jialin Liu ◽  
Rebecca R. Viales ◽  
Pierre Khoueiry ◽  
James P. Reddington ◽  
Charles Girardot ◽  
...  
Keyword(s):  
Gene Expression ◽  
Positive Selection ◽  
Evolutionary Conservation ◽  
Animal Evolution ◽  
Species Comparisons ◽  
Underlying Mechanisms ◽  
Hourglass Model ◽  
Late Stages ◽  
Developmental Hourglass

Inter-species comparisons of both morphology and gene expression within a phylum have revealed a period in the middle of embryogenesis with more similarity between species compared to earlier and later time-points. This developmental hourglass pattern has been observed in many phyla, yet the evolutionary constraints on gene expression, and underlying mechanisms of how this is regulated, remains elusive. Moreover, the role of positive selection on gene regulation in the more diverged earlier and later stages of embryogenesis remains unknown. Here, using DNase-seq to identify regulatory regions in two distant Drosophila species (D. melanogaster and D. virilis), we assessed the evolutionary conservation and adaptive evolution of enhancers throughout multiple stages of embryogenesis. This revealed a higher proportion of conserved enhancers at the phylotypic period, providing a regulatory basis for the hourglass expression pattern. Using an in silico mutagenesis approach, we detect signatures of positive selection on developmental enhancers at early and late stages of embryogenesis, with a depletion at the phylotypic period, suggesting positive selection as one evolutionary mechanism underlying the hourglass pattern of animal evolution.

Somite number and vertebrate evolution

Development ◽  
1998 ◽  
Vol 125 (2) ◽  
pp. 151-160 ◽  
Author(s):  
M.K. Richardson ◽  
S.P. Allen ◽  
G.M. Wright ◽  
A. Raynaud ◽  
J. Hanken
Keyword(s):  
Expression Patterns ◽  
Vertebrate Evolution ◽  
Pharyngeal Arches ◽  
Evolution And Development ◽  
Evolutionary Changes ◽  
Phylotypic Stage ◽  
Tailbud Stage ◽  
Hourglass Model ◽  
Somite Number ◽  
Developmental Hourglass

Variation in segment number is an important but neglected feature of vertebrate evolution. Some vertebrates have as few as six trunk vertebrae, while others have hundreds. We examine this phenomenon in relation to recent models of evolution and development. Surprisingly, differences in vertebral number are foreshadowed by different somite counts at the tailbud stage, thought to be a highly conserved (phylotypic) stage. Somite number therefore violates the ‘developmental hourglass’ model. We argue that this is because somitogenesis shows uncoupling or dissociation from the conserved positional field encoded by genes of the zootype. Several other systems show this kind of dissociation, including limbs and feathers. Bmp-7 expression patterns demonstrate dissociation in the chick pharyngeal arches. This makes it difficult to recognise a common stage of pharyngeal development or ‘pharyngula’ in all species. Rhombomere number is more stable during evolution than somite number, possibly because segmentation and positional specification in the hindbrain are relatively interdependent. Although developmental mechanisms are strongly conserved, dissociation allows at least some major evolutionary changes to be generated in phylotypic stages.

scholarly journals The developmental hourglass model is applicable to the spinal cord

2021 ◽  
Author(s):  
Katsuki Mukaigasa ◽  
Chie Sakuma ◽  
Hiroyuki Yaginuma
Keyword(s):  
Spinal Cord ◽  
Regulatory Elements ◽  
Spinal Neurons ◽  
Upstream Gene ◽  
Spinal Cord Development ◽  
Neuronal Progenitor ◽  
Before And After ◽  
Hourglass Model ◽  
Fate Determinants ◽  
Developmental Hourglass

SummaryThe developmental hourglass model predict that embryonic morphology is most conserved at mid-embryonic stage and diverge at early and late stage. This model is generally considered by whole embryonic level. Here, we demonstrate that the hourglass model is also applicable to the more reduced element, the spinal cord. In the middle of the spinal cord development, dorsoventrally arrayed neuronal progenitor domains are established, which is conserved among vertebrates. We found that, by comparing the single-cell transcriptomes between mice and zebrafish, V3 interneurons, a subpopulation of the post-mitotic spinal neurons, display the divergent molecular profiles. We also found non-conservation of cis-regulatory elements located around the progenitor fate determinants, indicating the rewiring of the upstream gene regulatory network. These results demonstrate that, despite the conservation of the progenitor domains, processes before and after the progenitor domain specification has diverged. This study may help understand the molecular basis of the developmental hourglass model.

Gene expression divergence recapitulates the developmental hourglass model

Nature ◽  
2010 ◽  
Vol 468 (7325) ◽  
pp. 811-814 ◽  
Author(s):  
Alex T. Kalinka ◽  
Karolina M. Varga ◽  
Dave T. Gerrard ◽  
Stephan Preibisch ◽  
David L. Corcoran ◽  
...  
Keyword(s):  
Gene Expression ◽  
Expression Divergence ◽  
Gene Expression Divergence ◽  
Hourglass Model ◽  
Developmental Hourglass
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