Thomas D. Kocher Department of Biology BSCI 338K Pigmentation Projects
Diversity of Color Patterns
Vertebrate pigment cells Endotherms (mammals, birds) –‘Melanocytes’ Ectotherms (fish, reptiles, amphibians) –‘Melanophores’ –Xanthophores –Iridophores
Epinephrine treatment
Iridophores
Guanine platelets Structural interference
Origin of the neural crest
Derivatives of the neural crest
NC migration pathways
Zebrafish mutants
Specification of pigment cells
Embryonic and adult melanophores
Model for chromatophore development from zebrafish NC (Curran et al. 2010)
Mother superior mutation Defect in foxd3 expression
Obelix mutation alters pattern
Zebrafish and cichlids compared
Metriaclima mbenjii vs. M. zebra
Standardized photos
Image analysis
Cell counts
Xanthophores in pelvic fin
Pigment traits in hybrids
Melanochromis auratus
Regeneration assays Figure 16. Regeneration of Metriaclima zebra fin at 2, 4 and 6 days post-amputation. Figure 17. Xanthophores in the regenerating caudal fin of a male M. saulosi.
Cell interactions Figure 18. Pigment patterning in the caudal fins of a) Aulonocara baenschi, b) Metriaclima mbenjii, c) Labeotropheus trewavasae, d) Metriaclima 'kompakt'.
Cell density Figure 19. Iridophore distribution changes with xanthophore density. Figure 20. Ontogenetic changes in the patterning of M. lombardoi.
L-DOPA assay for undifferentiated melanophores
Breeding biology Salzburger et al. 2007
Sexual dimorphism M. zebra masinjeM. zebra Nakantenga Male Female
Normal ‘BB’ female Orange-blotch ‘OB’ female QTL Is intersexual selection the whole answer? Reade B. Roberts
How many fish do you see?
OB is cryptic against some backgrounds
Loss of melanophores in OB
Family mapping
Association mapping Microsat genotypes aaAa
C D 100 km A Tetraodon Chr11 (Mb) M.zebra Makonde M.zebra ‘blaze’ Manda M.xanstomachus Nankoma Tropheops sp. Thumbi West L.trewavasae Thumbi West Lake-wide mapping panel LOD A B B C D E E Tetraodon Chr11 (Mb) F
Single OB haplotype in Malawi
OB allelic series
OB males are ugly! Females Males BB OB
A new sex chromosome Dominant OB mutation provides female crypsis OB reduces male mating success Divergent selection in males and females (genetic conflict) Selection favors mutations that create a dominant female sex determiner (W) near OB New sex determining system evolves: W OB Z femalesZZ males
Choosing a Project Choice of project starts with your interest Next step is to read the relevant research proposals (on the class wiki) Then schedule a meeting to talk with me about it Anytime - dig into the literature to see what others have done
Project Opportunities: Pigmentation Perform association studies of candidate genes Characterize pigment cell development from the neural crest Characterize differences in development among species Fine map genes controlling pigment variation Experimentally manipulate pigment cell populations during development or regeneration Annotate candidate pigmentation/neural crest genes in the cichlid genome sequence.