Establishment of Spatial Pattern: Pigment Pattern Development in the Zebrafish - PowerPoint PPT Presentation

1 / 24
About This Presentation
Title:

Establishment of Spatial Pattern: Pigment Pattern Development in the Zebrafish

Description:

Presented by Tasha Hanes. March 20, 2002. Pattern formation 'process by which cells in a developing embryo acquire identities that lead to a ... – PowerPoint PPT presentation

Number of Views:45
Avg rating:3.0/5.0
Slides: 25
Provided by: susanh150
Category:

less

Transcript and Presenter's Notes

Title: Establishment of Spatial Pattern: Pigment Pattern Development in the Zebrafish


1
Establishment of Spatial PatternPigment Pattern
Development in the Zebrafish
Presented by Tasha Hanes March 20, 2002.
2
Pattern formation
  • process by which cells in a developing embryo
    acquire identities that lead to a well ordered
    spatial pattern of cell activities
    (Wolpert 1998)
  • five stages
  • defining the body axes
  • formation of germ layers
  • morphogenesis
  • cell differentiation
  • growth

3
Pigment cells are derived from neural crest cells
  • Neural crest cells originate at the edge of the
    neural tube

4
Neural crest cells are pluripotent
5
Neural crest cells migrate
  • Requires disruption of the basal lamina
    surrounding the neural tube
  • Requires loss of adhesion molecules on neural
    crest cells
  • Two migration pathways

6
Pigment cell precursors take the dorsolateral
pathway
  • Migration between the ectoderm and the somites

7
  • Mutational Analysis of Endothelin Receptor b1
    (rose) during Neural Crest and Pigment Pattern
    Development in the Zebrafish Danio rerio

David M. Parichy, Eve M. Mellgren, John F. Rawls,
Susana S. Lopes, Robert N. Kelsh, and Stephen L.
Johnson Developmental Biology, 227, 294-306 (2000)
8
Study organismZebrafish (Danio rerio)
  • Short life cycle
  • Transparent embryo

9
Pigment Patterns in the Zebrafish
  • Zebrafish exhibit alternating stripes of
    melanocytes, iridophores and xanthophores

Black melanocytes Silver iridophores Yellow
xanthophores
10
Zebrafish undergo metamorphosis
  • Pigment pattern changes during metamorphosis
  • early larva
  • stripes of melanocytes and iridophores in a
    background of xanthophores
  • adult
  • dark stripes of melanocytes and iridophores with
    light iridophore and xanthophore stripes in
    between

11
How is gene activity controlling pigment pattern
partitioned across life cycle stages?
  • Pigment patterns specified by genes
  • Some genes affect pigment pattern at only one
    life cycle stage

12
Rose mutants
  • Wild type pattern during early larval stage
  • Fewer melanocytes during late metamorphosis
  • Adults
  • melanocyte deficits
  • iridophore deficits
  • ventral spots

13
D. rerio ednrb1 may be responsible for the rose
phenotype
  • G-protein coupled receptors for ET-1, ET-2 and
    ET-3
  • Endothelin receptors (ednr) initially found to
    mediate vasoconstriction in amniotes
  • Mice ednrb1 knockouts exhibit melanocyte
    deficiencies
  • rose mutation and endothlelin receptor b1
    (ednrb1) have been mapped in the vicinity of each
    other

14
Goals of this paper
  • 1) Test the correspondence of rose and endothelin
    receptor b1 (ednrb1)
  • 2) Identify cell populations expressing edrnb1
  • 3) Test the role of endothelin-1 in signaling to
    ednrb1 in pigment cell precursors

15
Materials and Methods
  • Fish rearing
  • spontaneously-occurring or ethylnitrosourea-induce
    d mutant rose alleles
  • Cloning and sequencing
  • reverse transcriptase PCR to clone a D. rerio
    ednrb1 cDNA
  • compared exons from wild-type and rose mutant
    backgrounds to test the correspondence of ednrb1
    and rose
  • In situ hybridization
  • digoxygenin- and fluorescein-labelled riboprobes

16
Does ednrb1 correspond with the rose mutant
phenotype?
  • Mapped rose to within 0.1 cM of ednrb1
  • Discovered ednrb1 lesions in three rose alleles

17
Does the neural crest-melanocyte lineage express
ednrb1?
  • ednrb1 cells present at the pre-migration
    location of neural crest cells
  • ednrb1 cells present along the migration pathway
  • two-colour in situ hybridization
  • to stain simultaneously for ednrb1 and for three
    melanocyte-lineage markers
  • result co-expression of ednrb1 and the markers

18
Does endothelin-1 signal to ednrb1 neural crest
cells?
  • Expression diminishes anteriorly and increases
    posteriorly through development
  • Detectable before expression of ednrb1
  • However, endothelin-1 mutants did not exhibit
    pigment pattern abnormalities
  • Endothelin-1 may promote but is not sufficient
    for development of melanocytes

19
Is ednrb1 expressed in non-melanocyte lineages?
  • Xanthophores
  • two colour in situ hybridization to stain
    simultaneously for ednrb1 and for a xanthophore
    marker
  • result co-expression of ednrb1 and the marker,
    but only in xanthophore precursors
  • Iridophores
  • coincident pattern of iridophores and ednrb1
    cells

20
Is ednrb1 expressed during pigment pattern
metamorphosis?
  • Rose phenotype may result because
  • 1) early larval pigment cells fail to develop
    into adult cells due to a lack of ednrb1
  • 2) ednrb1 is required only during adult pigment
    pattern formation (ie. after metamorphosis)
  • Iridophores and melanocytes expresses ednrb1
    during early metamorphosis
  • Expression continues through late metamorphosis

21
Summary
  • ednrb1 and rose correspond
  • ednrb1 is expressed in the neural crest-pigment
    cell lineage
  • ednrb1 mutations affect adult but not early
    larval pigment pattern development

22
Future Directions
  • How does ednrb1 promote pigment cell development?
  • Why does ednrb1 affect adult but not early larval
    pigment pattern phenotypes
  • D. rerio may provide an important system for
    studying amniote development
  • metamorphism decoupling of traits
  • relevant model for post-embryonic and fetal
    development?

23
References
  • Beauvais-Jouneau, A., Pla, P., Bernex, F.,
    Dufour, S., Salamero, J., Fassler, R., Pathier,
    J., Thiery, J.P., and Larue, L. (1999). A novel
    model to study the dorsolateral migration of
    melanoblasts. Mechanisms of Development. 89,
    3-14.
  • Hayashi, H., Nakamura, S., and Fujii, R.. (1996).
    The endothelin receptors that mediate aggregation
    of pigment in fish melanophores. Comparative
    Biochemistry and Physiology. 115, 143-152.
  • Kelsh, R.N., Brand, M., Jiang, Y., Heisenberg,
    C., Lin, S., Haffter, P., Odenthal, J., Mullins,
    M.C., van Edden, F.J.M., Furutani-Seiki, M.,
    Granato, M., Hammerschmidt, M., Kane, D.A.,
    Warga, R.M., Beuchle, D., Vogelsang, L. and
    Nusslein-Volhard, C. Zebrafish pigmentation
    mutations and the processes of neural crest
    development. Development. 123, 369-389.
  • Parichy, D. M., Mellgren, E. M., Rawls, J. F.,
    Lopes, S. S., Kelsh, R. N., and Johnson, S. L.
    (2000). Mutational analysis of endothelin
    receptor b1 (rose) during neural crest and
    pigment pattern development in the Zebrafish
    Danio rerio. Developmental Biology.227, 294-306.
  • Wolpert, L. (1998). Principles of Development.
    Current Biology Ltd., New York.

24
Questions?
Write a Comment
User Comments (0)
About PowerShow.com