Light-induced depigmentation in planarians models the pathophysiology of acute porphyrias
- Keene State College, United States
- The Hospital for Sick Children, Canada
- University of Toronto, Canada
- Ontario Institute for Cancer Research, Canada
Figures
Figure 1 with 5 supplements
Light-induced depigmentation in S. mediterranea.
(A) Animals exposed to visible light (incident intensity = 5000 lux; see figure supplement 3 for spectrum) exhibit progressive loss of bodily pigmentation. Images show a single live animal …
Figure 1—figure supplement 1
Sunlight-induced depigmentation.
To learn about the scientific method, non-science majors enrolled in a general education course analyzed the effects of environmental variables, including sunlight exposure, on regeneration in S. …
Figure 1—figure supplement 2
IR and UVB radiation are neither necessary nor sufficient to induce depigmentation.
(A) Animal photographed before (left) and 7 days after (right) a single day of sunlight exposure under IR- and UVB-blocking glass. (B) Animal photographed before (left) and after (right) 7 days in …
Figure 1—figure supplement 3
Incident spectrum for visible light exposure.
Relative light intensities (total = 5000 lux) measured under conditions experienced by animals subjected to visible light exposure. Applies to all experiments except those using a red LED (see below).
Figure 1—figure supplement 4
Feeding, regeneration, and repigmentation in depigmented animals.
(A) Depigmented animal fed with dyed calf liver; 21/26 depigmented animals and 25/26 controls consumed a visible amount of food. (B) Representative control (left) and depigmented (right) animals …
Figure 1—figure supplement 5
Depigmentation is not due to direct photobleaching.
Images show a single live animal photographed (left to right) at time 0, after a 24-hr pulse of light exposure, and every 24 hr thereafter while maintained in a dark incubator. Note that …
Figure 2
S. mediterranea produces an ommochrome body pigment.
(A) Absorbance spectra of body pigment purified from control animals (brown line) or mock purified from depigmented animals (grey line). Arrowheads denote local maxima at 367 and 463 nm, …
-
Figure 2—source data 1
S. mediterranea ommochrome biosynthesis enzymes.
Predicted protein sequences for S. mediterranea genes identified and cloned by reciprocal BLAST and RT-PCR (Materials and methods) were used as queries in BLASTP searches against the non-redundant H. sapiens protein database (NCBI). 1Smed Unigene transcripts are available at the Schmidtea mediterranea Genome Database (Robb et al., 2015).
- https://doi.org/10.7554/eLife.14175.012
Figure 3
Biochemical evidence of porphyrin biosynthesis in S. mediterranea.
(A) Like G. dorotocephala, D. japonica exhibits bright red fluorescence under black light (400–440 nm excitation). S. mediterranea exhibits negligible fluorescence by comparison. (B) KMO-1(RNAi) …
Figure 4 with 1 supplement
Genetic evidence of porphyrin biosynthesis in S. mediterranea pigment cells.
(A) Heme biosynthesis pathway. Numbers in parentheses to the right of each enzyme denote the number of S. mediterranea homologs identified via reciprocal BLAST (Materials and methods; source data …
-
Figure 4—source data 1
S. mediterranea porphyrin/heme biosynthesis enzymes.
Predicted protein sequences for S. mediterranea genes identified and cloned by reciprocal BLAST and RT-PCR (Materials and methods) were used as queries in BLASTP searches against the non-redundant H. sapiens protein database (NCBI). 1Smed Unigene transcripts are available at the Schmidtea mediterranea Genome Database (Robb et al., 2015). 2Not cloned (no RT-PCR product).
- https://doi.org/10.7554/eLife.14175.015
Figure 4—figure supplement 1
Additional RNAi phenotypes for porphyrin/heme biosynthesis genes.
(A) Animals were administered RNAi feedings every 2–3 days until less than 50% consumed a visible amount of food. This corresponded to a total of 8 (ALAS) or 9 (PBGD-4 and UROD-1, as well as …
Figure 5 with 1 supplement
Visible light exposure causes pigment cell loss.
(A) Red light (625 nm LED) is sufficient to induce full bodily depigmentation. Inset shows a magnified view of the dorsal surface, brightness, contrast, and gamma-enhanced to highlight remaining …
Figure 5—figure supplement 1
Antioxidants and hypoxia inhibit light-induced depigmentation.
(A) Representative control and ascorbic acid-treated animals photographed before and after white light exposure (left and right in each panel, respectively). Ascorbic acid treatment (10 mM final …
Figure 6 with 1 supplement
Porphyrins mediate light-induced pigment cell loss.
(A) PBGD-1 knockdown suppresses the porphyrin fluorescence observed in KMO-1(RNAi) animals. The difference in appearance of anterior tissues (top) between negative controls and KMO-1/PBGD-1(RNAi) …
Figure 6—figure supplement 1
Porphyrin fluorescence controls.
Unlike PBGD-1 knockdown, FECH-1 knockdown did not suppress the porphyrin fluorescence observed in KMO-1(RNAi) animals. The slightly elevated, uniform fluorescence in FECH-1(RNAi) animals relative to …
Figure 7 with 1 supplement
Starvation induces porphyrin biosynthesis and acute photosensitivity.
(A) Animals were fed 4 times in 1 week with dyed calf liver and then starved as indicated prior to 72 hr of red light exposure. Representative animals were photographed pre-exposure and 72 hr after …
Figure 7—figure supplement 1
Starvation does not sensitize animals to induction of cell death by gamma radiation.
(A) Cell death was visualized by whole-mount TUNEL in animals starved for 7 or 14 days, and exposed to a 1250 rad dose of gamma radiation as indicated. All animals were fixed 24 hr post-irradiation. …
Figure 8
Model of S. mediterranea pigment biosynthesis and photosensitivity.
Body pigment cells produce both porphyrins and ommochrome, using the indicated biosynthetic pathways (black arrows). Together, these molecules confer the normal brown body color, possibly as a …
Videos
Video 1
Depigmented animals exhibit normal movement.
Control animals maintained under standard laboratory conditions were filmed next to depigmented animals shortly after the conclusion of light exposure.
Video 2
Depigmented animals exhibit normal touch responsiveness.
Like controls, depigmented animals change direction in response to the touch of a pipet tip.
Additional files
-
Supplementary file 1
Cloning of S. mediterranea ommochrome and porphyrin/heme biosynthesis genes.
See Materials and methods for details. 1Smed Unigene transcripts are available at the Schmidtea mediterranea Genome Database (Robb et al., 2015). 2Smed_ASXL transcripts are available under NCBI BioProject PRJNA215411. 3Not cloned (no RT-PCR product).
- https://doi.org/10.7554/eLife.14175.024
