Contributes to muscle defects [20,21]; however, better models are needed to recapitulate disease characteristics and gain more meaningful insight into disease pathogenesis. Zebrafish are becoming an increasingly popular model for the study of muscle disorders; in addition to the many advantages of zebrafish as a model system, zebrafish muscle shares many histological features with mammalian muscle, their neuromuscular system is well-characterized, and various approaches facilitate the development of disease models. As a first step towards developing zebrafish models of DNM2-related neuromuscular disease, this manuscript describes the characterization of two zebrafish dynamin-2 orthologs, as well as the effects of altered gene expression on muscle histology and function. In this study, we characterize two dynamin-2 genes in the zebrafish genome. The two genes are likely a product of the whole genome duplication that occurred in the ray fin fish lineage prior to the evolution of the teleost [22,23]. The syntenic organization of both genes supports this conclusion. dnm2 (zebrafish chromosome 3) shares close syntenic conservation with DNM2 (human chromosome 19), as it is directly flanked by homologs of the upstream and downstream neighbors of human DNM2 (TMED1 and QTRT1). While dnm2-like (zebrafish chromosome 1) does not share this immediate syntenic block, the human homologs of at least four nearby genes are found within a 0.5 Mb distance of human DNM2 (TMED1, CDC37, OLFM2, COL5A3 and RDH8). Additionally, both zebrafish genes are found near chromosomal regions that have previously been reported to share homology with human chromosome 19 [24]. At both the gene and protein level, dnm2 and dnm2-like share structural similarity with human DNM2. All three genes have aHistopatholgical and Ultrastructural Abnormalities in dnm2 MedChemExpress 548-04-9 morphant MuscleIn light of the observed motor defects in dnm2 
morphants, we order SR3029 examined histological and ultrastructural features in muscle from 3 dpf larvae. Semi-thin sections were obtained from the trunks of 3 dpf larvae injected with control, dnm2, or dnm2-like morpholino (Figure 4D). While sections from dnm2 morphant 23727046 muscle revealed striking fiber disorganization, as well as small somites and indistinct striations as compared with control muscle, sections from dnm2-like morphant muscle only revealed moderate effects on myofibers. Quantification of myofiber size indicated that fibers from dnm2 morphants were significantly and substantially smaller than those of control embryos (p,0.009). Myofibers from dnm2-like morphants were also significantly smaller than fibers from larvae injected with control morpholino (p,0.05; Figure 4E). The dnm2 morphant myofibers were, in addition, smaller than those from dnm2-like morphants; however, this difference did not reach statistical significance (p = 0.056 for direct comparison of dnm2 to dnm2-like). Similarly, electron microscopy of dnm2 morphant muscle revealed substantial disorganization with irregular membrane accumulations (Figure 4F; arrow) but only subtle changes in the dnm2-like morphants (data not shown). Of note, sarcomeric structures appeared normal in both groups, suggesting that dnm2 is not required for establishing basic myofibril organization.Expression of Human DNM2 Rescues dnm2 and dnm2-like KnockdownTo rescue the dnm2 and dnm2-like morphant phenotypes, embryos were co-injected with human DNM2 capped mRNA and morpholino at the 1- to 2-cell stage (Figure 5). Expression.Contributes to muscle defects [20,21]; however, better models are needed to recapitulate disease characteristics and gain more meaningful insight into disease pathogenesis. Zebrafish are becoming an increasingly popular model for the study of muscle disorders; in addition to the many advantages of zebrafish as a model system, zebrafish muscle shares many histological features with mammalian muscle, their neuromuscular system is well-characterized, and various approaches facilitate the development of disease models. As a first step towards developing zebrafish models of DNM2-related neuromuscular disease, this manuscript describes the characterization of two zebrafish dynamin-2 orthologs, as well as the effects of altered gene expression on muscle histology and function. In this study, we characterize two dynamin-2 genes in the zebrafish genome. The two genes are likely a product of the whole genome duplication that occurred in the ray fin fish lineage prior to the evolution of the teleost [22,23]. The syntenic organization of both genes supports this conclusion. dnm2 (zebrafish chromosome 3) shares close syntenic conservation with DNM2 (human chromosome 19), as it is directly flanked by homologs of the upstream and downstream neighbors of human DNM2 (TMED1 and QTRT1). While dnm2-like (zebrafish chromosome 1) does not share this immediate syntenic block, the human homologs of at least 
four nearby genes are found within a 0.5 Mb distance of human DNM2 (TMED1, CDC37, OLFM2, COL5A3 and RDH8). Additionally, both zebrafish genes are found near chromosomal regions that have previously been reported to share homology with human chromosome 19 [24]. At both the gene and protein level, dnm2 and dnm2-like share structural similarity with human DNM2. All three genes have aHistopatholgical and Ultrastructural Abnormalities in dnm2 Morphant MuscleIn light of the observed motor defects in dnm2 morphants, we examined histological and ultrastructural features in muscle from 3 dpf larvae. Semi-thin sections were obtained from the trunks of 3 dpf larvae injected with control, dnm2, or dnm2-like morpholino (Figure 4D). While sections from dnm2 morphant 23727046 muscle revealed striking fiber disorganization, as well as small somites and indistinct striations as compared with control muscle, sections from dnm2-like morphant muscle only revealed moderate effects on myofibers. Quantification of myofiber size indicated that fibers from dnm2 morphants were significantly and substantially smaller than those of control embryos (p,0.009). Myofibers from dnm2-like morphants were also significantly smaller than fibers from larvae injected with control morpholino (p,0.05; Figure 4E). The dnm2 morphant myofibers were, in addition, smaller than those from dnm2-like morphants; however, this difference did not reach statistical significance (p = 0.056 for direct comparison of dnm2 to dnm2-like). Similarly, electron microscopy of dnm2 morphant muscle revealed substantial disorganization with irregular membrane accumulations (Figure 4F; arrow) but only subtle changes in the dnm2-like morphants (data not shown). Of note, sarcomeric structures appeared normal in both groups, suggesting that dnm2 is not required for establishing basic myofibril organization.Expression of Human DNM2 Rescues dnm2 and dnm2-like KnockdownTo rescue the dnm2 and dnm2-like morphant phenotypes, embryos were co-injected with human DNM2 capped mRNA and morpholino at the 1- to 2-cell stage (Figure 5). Expression.