FIGURE SUMMARY
Title

A Conditional Zebrafish MITF Mutation Reveals MITF Levels Are Critical for Melanoma Promotion vs. Regression In Vivo

Authors
Lister, J.A., Capper, A., Zeng, Z., Mathers, M.E., Richardson, J., Paranthaman, K., Jackson, I.J., and Patton, E.E.
Source
Full text @ J. Invest. Dermatol.
Fig. 1

The microphthalmia-associated transcription factor (MITF) is oncogenic with BRAFV600E in melanomagenesis. (a) Adult wild-type zebrafish or (b) adult mitfavc7 mutant zebrafish living in water at 28 °C or (c, d) <26 °C. At <26 °C some melanocytes are visible in the body (d: enlarged region, white arrows). (e) Adult transgenic line expressing human BRAFV600E in the melanocytes. (f–i) Genetic crosses of BRAFV600Emitf at the semirestrictive temperatures develop nevi (*) and melanoma (on the tail of the middle fish, and on the head of the bottom fish). (j) Melanoma incidence curves of BRAFV600Ep53 and BRAFV600Emitf (<26 °C) genetic crosses. (k) Real-time PCR (RT-PCR) analysis of the mitfa transcript in BRAFV600Ep53 and BRAFV600Emitf melanomas.
Fig. 2

Comparative histopathology of BRAFV600E melanomas. (a) Cross-section of adult BRAFV600Emitf zebrafish with superficial spreading melanoma (dotted line). Infiltrating melanophages in the kidney are indicated (yellow arrows). i, intestine; k, kidney; l, liver; m, muscle; o, ovary; s, spinal column; sb, swimbladder. (Top and bottom panels) Hematoxylin and eosin (H&E) stain of BRAFV600Emitf melanoma, indicating large melanophages (red arrows), spindle or epithelioid cell shapes (yellow arrows), and pigmented melanoma cells (white arrow). Scale bars=20  μm. (b) Cross-section of adult BRAFV600Ep53 zebrafish with invasive melanoma (dotted line). (Top and bottom panels) H&E stain of BRAFV600Ep53 melanoma, indicating pigmented melanoma cells (white arrows) and nuclear pleomorphisms (yellow arrow). Scale bars=20 μm. (c–f) Immunohistochemistry staining for (c) phospho-extracellular signal–regulated kinase (ERK), (d) p53, (e) Melan-A, and (f) phospho-histone H3. Scale bars=50 μm. (g). Box plot of mean percentage phospho-histone H3–stained cells in BRAFV600Emitf and BRAFV600Ep53 tumors (n=11 melanomas of each genotype). Bars represent interquartile range; Student’s t-test P=0.0078.
Fig. 3

MITF target gene expression. (a–i) Box plots of quantitative real-time PCR (qRT-PCR) of MITF target genes and p53. The y-axis indicates the difference between the cycle threshold (Ct) value of the gene of interest and the Ct value of β-actin in each sample. Note that the y-axis is inverted for ease of interpretation. Bars represent interquartile range; P-values determined by Student’s t-test. Also see Supplementary Table S1 online. MITF, microphtholmia associated transcription factor.
Acknowledgments
This image is the copyrighted work of the attributed author or publisher, and ZFIN has permission only to display this image to its users. Additional permissions should be obtained from the applicable author or publisher of the image. Full text @ J. Invest. Dermatol.
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