Fig. 4: Spatial transcriptomics (ST) illustrate the myofiber composition of SMTs.

a Hematoxylin-and-eosin staining of psoas major (PM) muscle sections. Scale bars, 500 μm. A representative image of two independent experiments is shown. b Dimensionality reduction and clustering of 2607 spots (replicate 2) identified as type I, IIA, and IIB myofiber clusters. The identified putative myofiber/spot clusters are annotated based on MYH transcriptional profiles, as well as marker gene transcription, shown in detail in Supplementary Figs. 21 and 22. c Mapping of data points from three putative myofiber clusters to their spatial positions. d Comparison of the location of type I myofibers identified in ST (upper panel) and ATPase-stained histological sections (lower panel) for replicate 2 (tissue sections adjacent to that in a). In the ST plot (upper panel), type IIA and IIB myofibers were combined (shown in light blue). Scale bars, 500 μm. Insets show three typical regions/images (denoted with numbers) magnified for comparison matching results (1 vs. 4, 2 vs. 5, and 3 vs. 6). e Estimates of the myofiber proportions in bulk RNA-seq data using the expression signature matrix (442 and 450 genes for replicate 1 and replicate 2, respectively) of the three myofibers, shown as the average of replicate 1 and replicate 2. SMTs are ranked by their proportions of type I myofiber from high (left) to low (right). Source data are provided as a Source Data file.