TIR-1/SARM1 inhibits axon regeneration and promotes axon degeneration
- Department of Neurobiology, UMass Chan Massachusetts Medical School, United States
Figures
Figure 1 with 1 supplement
TIR-1 inhibits axon regeneration.
(A) Human SARM1, fly dSarm, and worm TIR-1 contain an N-terminal auto-inhibitory domain, two sterile alpha motif (SAM) domains and a toll-interleukin-1 receptor (TIR) domain. Null alleles qd4 and tm3…
Figure 1—figure supplement 1
TOL-1 does not regulate axon regeneration.
Axon regeneration is not significantly different in tol-1(nr2033) mutants compared to wild-type controls 24 hr after laser surgery. N = 6 5, 47. Fisher’s exact test. Error bars represent 95% …
Figure 2
TIR-1 functions cell-autonomously to inhibit regeneration.
(A) Endogenous TIR-1 is expressed faintly in the nervous system, particularly in neurons along the dorsal and ventral (enlarged box) nerve cords. Note the intestinal expression significantly …
Figure 3 with 1 supplement
TIR-1 promotes axon degeneration in injured GABA motor neurons.
(A) Single and double injury models. After being severed once, GABA axons do not degenerate. Severing an axon twice creates a middle fragment that degenerates. (B) Micrographs of intact and …
Figure 3—figure supplement 1
CED-1 does not regulate middle fragment degeneration.
tir-1 functions independently from ced-1 to regulate degeneration of the middle fragment after injury. N = 125, 37, 40, 58. Significance relative to wild type is indicated by **p≤0.01, Fisher’s …
Figure 4 with 1 supplement
TIR-1 expression causes spontaneous axon degeneration in GABA motor neurons.
(A–C) Expression of mScarlet::tir-1b in GFP-labeled GABA motor neurons is sufficient to induce degeneration of the distal stump after a single axotomy. Micrographs and representative drawings …
Figure 4—figure supplement 1
TIR-1 expression induces degeneration.
Representative micrographs indicating axons that express the unc-47p::tir-1::mCherry transgene degenerate, whereas neighboring axons that do not express the transgene remain intact. Transgenic axons …
Figure 5 with 2 supplements
TIR-1 functions independently of its NADase activity and with the NSY-1 signaling pathway to inhibit axon regeneration.
(A) Conserved residues E788A/E642A, which is required for the NADase function of TIR-1 and SARM1, and D773A/D627 are not required to inhibit axon regeneration. (B) DLK-1 and TIR-1 function in the …
Figure 5—figure supplement 1
TIR-1 inhibits regeneration with the NSY-1/ASK1 and PMK-1/p38 MAPK after a single injury.
Axon regeneration is significantly increased in predicted null alleles of (A) nsy-1/ASK1 and (B) pmk-1/p38 following a single injury, in both the presence and absence of tir-1 function. Double …
Figure 5—figure supplement 2
The ATF-7 transcription factor does not regulate axon regeneration.
(A) Axon regeneration is not significantly different between atf-7(gk715) mutants and wild type controls 24 hr after laser surgery. N = 90, 68, 35. Significance relative to wild type or tir-1(qd4) …
Figure 6
TIR-1 is capable of NADase-independent and -dependent axon degeneration.
(A) Mutation of conserved residue E788A/E642A, which is required for the NADase function of TIR-1 and SARM1, does not affect axon degeneration after double axotomy. D773A/D627A modestly suppresses …
Figure 7 with 2 supplements
TIR-1 functions with the DLK-1 signaling pathway to regulate axon degeneration.
(A) Loss of pmk-1/p38 does not affect degeneration with or without tir-1 function. N = 198, 68, 54, 71. (B) Loss of dlk-1 function suppresses the decreased degeneration of tir-1(qd4) animals and …
Figure 7—figure supplement 1
Expression of endogenous dlk-1 mRNA did not significantly differ between tir-1(-) and wild-type animals.
Similarly, mRNA expression from the integrated pGABA::dlk-1 transgene was not changed by the loss of tir-1 function. Significance determined by one-way ANOVA with Tukey’s multiple corrections test. …
Figure 7—figure supplement 2
DLK-1 does not inhibit distal axon fragment degeneration after a single injury.
(A) Representative micrographs of severed distal stumps in wild type, dlk-1(-) loss-of-function mutants, and dlk-1(oe) overexpression mutants. (B) Distal axon stumps do not readily degenerate 24 hr …
Tables
Author response table 1
Motor axon degeneration is dependent on expression of tir-1, but not mCherry.
tir1(qd4) animals were injected with the indicated expression constructs and the number of degenerating GABA motor axons was quantified. Expression of GFP or mCherry in motor axons is not sufficient …
| Description | Expression Plasmid | % Damaged Axons |
|---|---|---|
| control | unc-47p::GFP | 0 |
| control | unc-47p::mCherry | 0 |
| untagged line 1 | unc-47p::tir-1 | 9 |
| untagged line 2 | unc-47p::tir-1 | 6 |
| untagged line 3 | unc-47p::tir-1 | 11 |
| untagged line 4 | unc-47p::tir-1 | 17 |
| GFP tagged line 1 | unc-47p::tir-1::GFP | 13 |
| GFP tagged line 2 | unc-47p::tir-1::GFP | 31 |
| GFP tagged line 3 | unc-47p::tir-1::GFP | 6 |
