Extraocular muscle is defined by a fundamentally distinct gene expression profile

TLDR

Skeletal muscle fibers are defined by patterned covariation of key traits, yet craniofacial muscles, such as extraocular muscles, exhibit fiber types that lie outside the common phenotypic range. We analyzed gene expression profiles of limb, masticatory, and extraocular muscle in adult mice using high‑density oligonucleotide arrays and significance analysis of microarrays to identify up to 400 genes with an EOM‑specific expression pattern. Pairwise comparisons identified 287 genes differentially expressed between EOM and limb/masticatory muscles, and these genes reflect key aspects of muscle biology, defining EOM as a distinct muscle class that may explain its unique response in neuromuscular diseases.

Abstract

Skeletal muscle fibers are defined by patterned covariation of key traits that determine contractile and metabolic characteristics. Although the functional properties of most skeletal muscles result from their proportional content of a few conserved muscle fiber types, some, typically craniofacial, muscles exhibit fiber types that appear to lie outside the common phenotypic range. We analyzed gene expression profiles of three putative muscle classes, limb, masticatory, and extraocular muscle (EOM), in adult mice by high-density oligonucleotide arrays. Pairwise comparisons using conservative acceptance criteria identified expression differences in 287 genes between EOM and limb and/or masticatory muscles. Use of significance analysis of microarrays methodology identified up to 400 genes as having an EOM-specific expression pattern. Genes differentially expressed in EOM reflect key aspects of muscle biology, including transcriptional regulation, sarcomeric organization, excitation-contraction coupling, intermediary metabolism, and immune response. These patterned differences in gene expression define EOM as a distinct muscle class and may explain the unique response of these muscles in neuromuscular diseases.