Deficiency of muscular dystrophy–related gene JAG2 causes NOTCH signaling dysfunction in muscle stem cells
Minoru Tanaka, Nam Chul Kim, Isabelle Draper, Hannah R. Littel, Mekala Gunasekaran, Johnnie Turner, Natalya M. Wells, Qasim Mujteba, Yoko Asakura, Peter B. Kang, Atsushi Asakura
Minoru Tanaka, Nam Chul Kim, Isabelle Draper, Hannah R. Littel, Mekala Gunasekaran, Johnnie Turner, Natalya M. Wells, Qasim Mujteba, Yoko Asakura, Peter B. Kang, Atsushi Asakura
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Research Article Development Muscle biology

Deficiency of muscular dystrophy–related gene JAG2 causes NOTCH signaling dysfunction in muscle stem cells

Abstract

We previously identified a muscular dystrophy caused by biallelic variants in JAGGED2 (JAG2), whose protein product, JAG2, is a canonical NOTCH ligand. However, the disease mechanism remains unclear, particularly with respect to muscle stem cell (muscle satellite cell/MuSC) function and muscle regeneration. We examined the consequences of JAG2 deficiency and modeled pathogenic JAG2 variants in vitro and in vivo, the latter in mouse and fly models and with particular attention to the MuSC–muscle endothelial cell (MuEC) niche. We found that both Jag2 deficiency and overexpression of pathogenic JAG2 variants impaired NOTCH signaling and myogenic self-renewal and differentiation. Hypomorphic Jag2 mutant (Jag2sm) mice displayed depleted MuSCs, corresponding with impaired muscle regeneration in those mice. Coculture experiments and the examination of cell type–specific Jag2 conditional knockout mice demonstrated that MuEC-specific Jag2 knockout resulted in reduced MuSC self-renewal, while MuSC-specific Jag2 knockout resulted in reduced myogenic differentiation. Human reference JAG2, but not human pathogenic variants of JAG2, rescued the deficiency of Serrate, the Drosophila ortholog of JAG2. Therefore, pathogenic variants in JAG2 impair muscle development and regeneration through disrupted cell-autonomous cis-inhibition and nonautonomous trans-activation involving NOTCH signaling dysfunction. Our findings indicate that optimizing JAG2-mediated NOTCH signaling is a potential therapeutic approach for JAG2-related muscular dystrophy.

Authors

Minoru Tanaka, Nam Chul Kim, Isabelle Draper, Hannah R. Littel, Mekala Gunasekaran, Johnnie Turner, Natalya M. Wells, Qasim Mujteba, Yoko Asakura, Peter B. Kang, Atsushi Asakura

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Figure 4

Jag2sm hypomorphic mice have muscle regenerative defects.

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Jag2sm hypomorphic mice have muscle regenerative defects. (A) Single or...
(A) Single or repeated CTX injections into the TA muscle were performed on Jag2smWT Pax7CreERT2 R26tdTomato and Jag2smhomo Pax7CreERT2 R26tdTomato mice following TMX injection. (B) TA histology (H&E and Oil Red O) and immunostaining (eMyHC/Laminin/DAPI and CD31/Laminin) 7 days following CTX injection into the TA. Scale bars from left to right: 100, 25, 50, and 250 μm. (C) Feret’s diameters of TA fibers in WT and Jag2sm homozygous mice at 7 days following CTX injection. (D) CD31+ capillaries in TA muscle in WT and Jag2sm homozygous mice 7 days following CTX injections. (E) Oil Red O+ area was evaluated at 7 days following CTX injection. (F) H&E staining at 21 days and 21+7 days following CTX injections into the TA. (G) Pax7tdTomato (Pax7tdT+) MuSCs (arrows) at 21 days following CTX injections into the TA. Scale bars: 100 μm. (H and I) Feret’s diameters of TA fibers in WT and Jag2sm homozygous mice at 21 days and 21+7 days following CTX injection. (J) Pax7tdT+ MuSCs in WT and Jag2sm homozygous at 21 days following CTX injections into TA muscle. DAPI stained all nuclei (blue). n = 4 independent experiments. Unpaired 2-tailed Student’s t tests; **P < 0.01 and ***P < 0.001. Data are shown as the mean ± SEM; n = 4 biological replicates.