Biology subjects

Munsterberg, A.

Publications and source records attributed to Munsterberg, A..

4 recordsLinked to original sources

bioRxiv2023

A transcriptional and regulatory map of mouse somitogenesis

The mammalian body plan is shaped by rhythmic segmentation of mesoderm into somites, which are transient embryonic structures consisting of hundreds of cells that form down each side of the neural tube. We have systematically analysed the genome-wide transcriptional and chromatin dynamics occurring within nascent somites, from early inception of somitogenesis to the latest stages of body plan establishment. We created matched gene expression and open chromatin maps for the three leading pairs of somites at six time points during embryonic development. Here we show that the rate of somite differentiation accelerates as development progresses. We identified a conserved maturation programme followed by all somites after segmentation, but somites from more developed embryos concomitantly switch on differentiation programmes from derivative cell lineages soon after segmentation. Integrated analysis of the somitic transcriptional and chromatin activities revealed opposing regulatory modules controlling the onset of differentiation. We identified transcription factors expressed during early development that inhibit the activity of proteins required for commitment and differentiation of skeletal cell populations. Our results provide a powerful, high-resolution view of the molecular genetics underlying somitic development in mammals.

developmental biology↗

bioRxiv2020

Fine-tuning of the PAX-SIX-EYA-DACH network by multiple microRNAs controls embryo myogenesis

MicroRNAs (miRNAs), short non-coding RNAs, which act post-transcriptionally to regulate gene expression, are of widespread significance during development and disease, including muscle disease. Advances in sequencing technology and bioinformatics led to the identification of a large number of miRNAs in vertebrates and other species, however, for many of these miRNAs specific roles have not yet been determined. LNA in situ hybridisation has revealed expression patterns of somite-enriched miRNAs, here we focus on characterising the functions of miR-128. We show that antagomir-mediated knock-down (KD) of miR-128 in developing chick somites has a negative impact on skeletal myogenesis. Computational analysis identified the transcription factor EYA4 as a candidate target consistent with the observation that miR-128 and EYA4 display similar expression profiles. Luciferase assays confirmed that miR-128 interacts with the EYA4 3UTR. Furthermore, in vivo experiments suggest that EYA4 is regulated by miR-128, as EYA4 expression is derepressed after antagomir-mediated inhibition of miR-128. EYA4 is a member of the PAX-SIX-EYA-DACH (PSED) network of transcription factors. Therefore, we identified additional candidate miRNA binding sites in the 3UTR of SIX1/4, EYA1/2/3 and DACH1. Using the miRanda algorithm, we found sites for miR-128, as well as for other myogenic miRNAs, miR-1a, miR-206 and miR-133a, some of these were experimentally confirmed as functional miRNA-target sites. Our results reveal that miR-128 is involved in regulating skeletal myogenesis by targeting EYA4 transcripts and moreover that the PSED network of transcription factors is co-regulated by multiple muscle-enriched microRNAs.

developmental biology↗

bioRxiv2020

Characterising open chromatin identifies novel cis-regulatory elements important for paraxial mesoderm formation and axis extension

The development of multicellular organisms is exquisitely regulated through differential gene activity, which governs cell differentiation programs. However, many details of spatiotemporal control of gene regulation are still poorly understood. We used the accessibility of chick embryos to examine genome-wide signatures characterizing the progressive differentiation of paraxial mesoderm along the head-to-tail axis. Paraxial mesoderm becomes organized into repetitive units, termed somites, the hallmark of the segmented vertebrate body plan. New somite pairs form periodically as the axis extends at the posterior end. This process generates a developmental gradient within a single embryo, with anterior somites more advanced in their differentiation compared to posterior somites. Following somite formation, cell rearrangements generate compartments, comprising lineages of the musculoskeletal system, including cartilage of the vertebral column and ribs, and skeletal muscle cells of the trunk and limbs. To examine how paraxial mesoderm becomes regionalized and patterned to eventually generate these discrete lineages, we investigated dynamic changes of the transcriptome and of chromatin accessibility using RNA-seq and ATAC-seq across a spatiotemporal series along the embryonic axis. Footprint analysis uncovers differential coverage of binding sites for a number of key transcription factors known to be involved in axial patterning and differentiation, including HOX genes. Furthermore, associating accessible chromatin with nearby expressed genes identifies candidate cis-regulatory elements (CRE). As exemplars we use TCF15 and MEOX1, which are crucial for somite formation and differentiation, to experimentally validate CREs in vivo using fluorescent reporters. Time-lapse microscopy reveals CRE spatiotemporal activity and mutation analysis uncovers necessary upstream regulators. The CRE for MEOX1 is conserved and recognized in Xenopus. In addition, a human element is active in chicken. In vivo epigenome editing of TCF15 and MEOX1 CREs disrupts gene expression regulation and recapitulates phenotypic abnormalities of anterior-posterior axis extension.

developmental biology↗

bioRxiv2018

4D imaging reveals stage dependent random and directed cell motion during somite morphogenesis

Somites are paired embryonic segments that form in a regular sequence from unsegmented mesoderm during vertebrate development. Of fundamental importance, they are transient structures that generate cell lineages of the musculoskeletal system in the trunk such as cartilage, tendon, bone, endothelial cells and skeletal muscle. Surprisingly, very little is known about the morphological transition and cellular dynamics during somite differentiation. Here, we address this by examining cellular rearrangements and morphogenesis in differentiating somites using live multi photon imaging of GFP-transgenic chick embryos. We specifically focussed on the dynamic changes in two principle regions within the somite (the medial and lateral domains) to investigate extensive morphological changes. Furthermore, by using quantitative analysis and cell tracking, we were able to capture for the first time a progenitor cell bulk movement towards the rostral-medial domain of the myotome, where skeletal muscle formation first initiates.

developmental biology↗