Table 2.
Rescue of cardiac fusion by expression of tmem2 and variants
| Genotype | Injected mRNA | Not fused | Ring | Tube |
|---|---|---|---|---|
| Mtmem2 | uninjected | - | - | 38/38 (100%) |
| MZtmem2 | uninjected | 35/35 (100%) | - | - |
| Mtmem2 | tmem2 | - | - | 28/28 (100%) |
| MZtmem2 | tmem2 | 3/32 (9%) | 8/32 (25%) | 21/32 (66%) |
| Mtmem2 | htrc-tmem2 | - | - | 47/47 (100%) |
| MZtmem2 | htrc-tmem2 | 5/41 (12%) | 11/41 (27%) | 25/41 (61%) |
| Mtmem2 | sc-tmem2 | - | - | 34/34 (100%) |
| MZtmem2 | sc-tmem2 | 9/28 (32%) | 17/28 (61%) | 2/28 (7%) |
| Mtmem2 | ΔC-term | - | - | 15/15 (100%) |
| MZtmem2 | ΔC-term | 16/17 (94%) | 1/17 (6%) | - |
| Mtmem2 | ΔG8 | - | - | 37/37 (100%) |
| MZtmem2 | ΔG8 | 31/31 (100%) | - | - |
| Mtmem2 | ΔPLT | - | - | 27/27 (100%) |
| MZtmem2 | ΔPLT | 31/31 (100%) | - | - |
| Mtmem2 | ΔPbH1 | - | - | 36/36 (100%) |
| MZtmem2 | ΔPbH1 | 36/36 (100%) | - | - |
| Mtmem2 | ΔPL | - | - | 42/42 (100%) |
| MZtmem2 | ΔPL | 29/29 (100%) | - | - |
| Mtmem2 | R267H | - | - | 54/54 (100%) |
| MZtmem2 | R267H | - | 19/53 (36%) | 34/53 (64%) |
Summary of experiments evaluating whether expression of tmem2 or tmem2 variants can rescue the cardiac fusion defects in MZtmem2 mutants. Embryos displaying distinct bilateral populations of cardiomyocytes (as in Fig. 4B,J) or two groups of cardiomyocytes joined only at the posterior (as in Fig. 4C) were categorized as “not fused”. Embryos displaying a fused ring of cardiomyocytes, but not a heart tube, were categorized as “ring” (as in Fig. 4E). Embryos displaying a heart tube were categorized as “tube” (as in Fig. 4A,D,F,G,H,I). Data indicate the fraction of embryos in each category for injected Mtmem2 and MZtmem2 embryos. Full-length tmem2, sc-tmem2, htrc-tmem2, and R267H can rescue cardiac fusion in MZtmem2 mutants, while expression of tmem2 or tmem2 variants does not disrupt cardiac fusion in Mtmem2 siblings. Significant differences in the phenotypes seen in MZtmem2 mutants were determined using Fisher’s exact test: uninjected vs. tmem2, p<0.001; uninjected vs. htrc-tmem2, p<0.001; uninjected vs. sc-tmem2, p<0.001; uninjected vs. R267H, p<0.001; tmem2 vs. sc-tmem2, p<0.001; htrc-tmem2 vs. sc-tmem2, p<0.001. Other analyses with Fisher’s exact test did not yield significant differences: tmem2 vs. htrc-tmem2, p>0.1; tmem2 vs. R267H, p>0.01.