Ryan W. Null

Washington University in St. Louis

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B. Duygu Özpolat

Washington University in St. Louis

David S. Clausen

University of Washington

E. Wolfgang Kuehn

University of Freiburg

Amy D. Willis

University of Washington

Bria M. Metzger

Marine Biological Laboratory

Jerome H. L. Hui

Chinese University of Hong Kong

Mireia Osuna-López

European Molecular Biology Laboratory

Ernie Hwaun

Stanford University

Bruno C. Vellutini

University of Bergen

Sylke Winkler

Max Planck Institute of Molecular Cell Biology and Genetics

Cooperative Institutions

Marine Biological Laboratory

European Molecular Biology Laboratory

University of California, Berkeley

European Molecular Biology Organization

Centre National de la Recherche Scientifique

European Molecular Biology Laboratory

Stanford University

Max Planck Institute of Molecular Cell Biology and Genetics

University of Oxford

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Segment number threshold determines juvenile onset of germline cluster proliferation inPlatynereis dumerilii

bioRxiv (Cold Spring Harbor Laboratory) (2021)

E. Wolfgang Kuehn David S. Clausen Ryan W. Null Bria M. Metzger Amy D. Willis

Abstract Many animals rely on sexual reproduction to propagate by using gametes (oocytes and sperm). Development of sexual characters and generation of gametes are tightly coupled with the growth of an organism. Platynereis dumerilii is a marine segmented worm which has been used to study germline development and gametogenesis. Platynereis has 4 Primordial Germ Cells (PGCs) that arise early in development and these cells are thought to give rise to germ cell clusters found across the body in the juvenile worms. The germ cell clusters eventually form the gametes. The stages of germline development and how the 4 PGCs become the numerous germ cell clusters are not well-documented in the juvenile stages. Platynereis , like other segmented worms, grows by adding new segments at its posterior end. The number of segments generally reflect the growth state of the worms and therefore is a useful and easily measurable growth state metric. To understand how growth correlates with development and gametogenesis, we investigated germline development across several developmental stages using germline/multipotency markers. We found that segment number predicted the state of germline development and the abundance of germline clusters. Additionally, we found that keeping worms short in segment number via changing external conditions or via amputations supported segment number threshold requirement for germline development. Finally, we asked if these clusters in Platynereis play a role in regeneration (as similar free-roaming cells are observed in Hydra and planarian regeneration) and found that the clusters were not required for regeneration in Platynereis , suggesting a strictly germline nature. Overall, these molecular analyses suggest a previously unidentified developmental transition dependent on the growth state in juvenile Platynereis when germline proliferation is substantially increased.

Planarian

Sexual reproduction

10.1101/2021.04.22.439825

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Citations (7)

A genome resource for the marine annelidPlatynereis dumerilii

bioRxiv (Cold Spring Harbor Laboratory) (2024)

Kevin Nzumbi Mutemi Oleg Simakov Leslie Pan Luca Santangeli Ryan W. Null

The marine annelid

Annelid

10.1101/2024.06.21.600153

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Citations (3)

Creation of an albino squid line by CRISPR-Cas9 and its application for in vivo functional imaging of neural activity

Current Biology (2023)

Namrata Ahuja Ernie Hwaun Judit R. Pungor Ruhina Rafiq Sal Nemes

Cephalopod

Camouflage

Gene knockout

octopus (software)

10.1016/j.cub.2023.05.066

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Citations (15)

The Cellular and Developmental Biology of Wing Scales: Two Genera of Structurally-Colored Butterflies Provide Mechanisms for Evolution of Color Diversity

Ryan W. Null

Author(s): Null, Ryan W | Advisor(s): Patel, Nipam H | Abstract: The coloration of butterflies and moths, Lepidoptera, has been an important force in biological inquiry, providing among the first supporting evidence for biogeography, Darwinian evolution, and models of morphogen diffusion. In nature, color patterns have evolved that aid species’ navigation of many ecological interactions via crypsis, warning coloration, mate signaling, and the multiple forms of mimicry, which often lean heavily upon color to achieve their effect. Butterflies and moths as a whole have evolved the ability to produce all of the colors visible by humans, as well as into the UV range. As is true for most animals, the repertoire of pigments available for use in Lepidoptera is actually rather restricted – by and large limited to long-wavelength colors red, orange, and yellow, as well as, black and brown pigments. To expand into the short wavelength (violet, blue and green), Leps have repeatedly resorted to manufacturing photonically-active nanostructures. These harness physical properties of light to create the impression of color in an observer without having to manufacture a pigment. Despite knowledge of butterfly structural coloration for centuries, intense study has only taken off following the advent of the electron microscope, and despite interest, studies have been largely limited to descriptive studies and physical estimations of their function. I have undertaken efforts to understand the developmental and cellular underpinnings of structural coloration in butterflies. In the work presented here I have furthered the understanding of the field with a particular focus on how pigments modulate the diverse structural colors of 2 genera – the Morpho genus of the neotropics and the Achillides sub-genus of Papilio found throughout Oceania, East, and South Asia. In addition, I have addressed how scale ultrastructure is constructed in the developing pupa from a cell biological perspective. These studies have come hand-in-hand with the improvement of live-imaging techniques, which I argue, will be indispensable for future studies on scale development. What has emerged, is the suggestion that the Actin cytoskeleton, is essential for ultrastructural formation of scales including the modulation of nanostructure profiles. What’s more, I have shown that melanin is deployed to tune the saturation of structural color reflections and, in at least one case, to tune the hue of a multilayer-based structural color.

Structural Coloration

Iridescence

Heliconius

Aposematism

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Dynamics of F-actin prefigure the structure of butterfly wing scales

Developmental Biology (2014)

April Dinwiddie Ryan W. Null Maria Pizzano Lisa Chuong Alexis Leigh Krup

Bristle

Iridescence

Appendage

Dynamics

10.1016/j.ydbio.2014.06.005

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Citations (102)

Author response for "Segment number threshold determines juvenile onset of germline cluster expansion in Platynereis dumerilii"

E. Wolfgang Kuehn David S. Clausen Ryan W. Null Bria M. Metzger Amy D. Willis

10.1002/jez.b.23100/v3/response1

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Developmental transition to bilaterally symmetric cell divisions is regulated by Pax-mediated transcription in embryos of the leech Helobdella austinensis

Developmental Biology (2013)

Matthew Schmerer Ryan W. Null Marty Shankland

Cleavage (geology)

Transcription

10.1016/j.ydbio.2013.07.015

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Citations (15)

Segment number threshold determines juvenile onset of germline cluster expansion in Platynereis dumerilii

Journal of Experimental Zoology Part B Molecular and Developmental Evolution (2021)

E. Wolfgang Kuehn David S. Clausen Ryan W. Null Bria M. Metzger Amy D. Willis

Abstract Development of sexual characters and generation of gametes are tightly coupled with growth. Platynereis dumerilii is a marine annelid that has been used to study germline development and gametogenesis. P. dumerilii has germ cell clusters found across the body in the juvenile worms, and the clusters eventually form the gametes. Like other segmented worms, P. dumerilii grows by adding new segments at its posterior end. The number of segments reflect the growth state of the worms and therefore is a useful and measurable growth state metric to study the growth‐reproduction crosstalk. To understand how growth correlates with progression of gametogenesis, we investigated germline development across several developmental stages. We discovered a distinct transition period when worms increase the number of germline clusters at a particular segment number threshold. Additionally, we found that keeping worms short in segment number, by manipulating environmental conditions or via amputations, supported a segment number threshold requirement for germline development. Finally, we asked if these clusters in P. dumerilii play a role in regeneration (as similar free‐roaming cells are observed in Hydra and planarian regeneration) and found that the clusters were not required for regeneration in P. dumerilii , suggesting a strictly germline nature. Overall, these molecular analyses suggest a previously unidentified developmental transition dependent on the growth state of juvenile P. dumerilii leading to substantially increased germline expansion.

Annelid

Lernaean Hydra

Planarian

10.1002/jez.b.23100

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Citations (107)

Sex-biased gene expression precedes sexual dimorphism in the agonadal annelidPlatynereis dumerilii

bioRxiv (Cold Spring Harbor Laboratory) (2024)

Rannyele Passos Ribeiro Ryan W. Null B. Duygu Özpolat

Abstract Gametogenesis is the process by which germ cells differentiate into mature sperm and oocytes, cells essential for sexual reproduction. The sex-specific molecular programs that drive spermatogenesis and oogenesis can also serve as sex identification markers. Platynereis dumerilii is a research organism that has been studied in many areas of developmental biology. However investigations often disregard sex, as P. dumerilii juveniles lack sexual dimorphism. The molecular mechanisms of gametogenesis in the segmented worm P. dumerilii are also largely unknown. In this study, we used RNA sequencing to investigate the transcriptomic profiles of gametogenesis in P. dumerilii juveniles. Our analysis revealed that sex-biased gene expression becomes increasingly pronounced during the advanced developmental stages, particularly during the meiotic phases of gametogenesis. We identified conserved genes associated with spermatogenesis, such as dmrt1 , and a novel gene psmt , that is associated with oogenesis. Additionally, putative long non-coding RNAs were upregulated in both male and female gametogenic programs. This study provides a foundational resource for germ cell research in P. dumerilii, markers for sex identification, and offers comparative data to enhance our understanding of the evolution of gametogenesis mechanisms across species. Summary statement This study provides insights into the mechanisms of gametogenesis in Platynereis dumerilii through comparative transcriptomics, unveiling sex-biased genes, including conserved and novel genes, governing this largely unexplored process.

Annelid

Sexual dimorphism

10.1101/2024.06.12.598746

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Citations (1)

Author response for "Segment number threshold determines juvenile onset of germline cluster expansion in Platynereis dumerilii"

E. Wolfgang Kuehn David S. Clausen Ryan W. Null Bria M. Metzger Amy D. Willis

10.1002/jez.b.23100/v2/response1

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