Ibarra Joe, Hershenhouse Tyler, Almassalha Luay, MacQuarrie Kyle L
Division of Hematology, Oncology, and Stem Cell Transplantation, Department of Pediatrics, Feinberg School of Medicine, Northwestern University and Ann & Robert H. Lurie Children's Hospital of Chicago, IL.
Department of Gastroenterology and Hepatology, Northwestern Memorial Hospital, Northwestern University, Chicago, IL.
bioRxiv. 2023 May 11:2023.05.11.540394. doi: 10.1101/2023.05.11.540394.
Myogenesis, the progression of proliferating skeletal myoblasts to terminally differentiated myotubes, regulates thousands of target genes. Uninterrupted linear arrays of such genes are differentially associated with specific chromosomes, suggesting chromosome specific regulatory roles in myogenesis. Rhabdomyosarcoma (RMS), a tumor of skeletal muscle, shares common features with normal muscle cells. We hypothesized that RMS and myogenic cells possess differences in chromosomal organization related to myogenic gene arrangement. We compared the organizational characteristics of chromosomes 2 and 18, chosen for their difference in myogenic gene arrangement, in cultured RMS cell lines and normal myoblasts and myotubes. We found chromosome-specific differences in organization during normal myogenesis, with increased area occupied and a shift in peripheral localization specifically for chromosome 2. Most strikingly, we found a differentiation-dependent difference in positioning of chromosome 2 relative to the nuclear axis, with preferential positioning along the major nuclear axis present only in myotubes. RMS cells demonstrated no preference for such axial positioning, but induced differentiation through transfection of the pro-myogenic miRNA miR-206 resulted in an increase of major axial positioning of chromosome 2. Our findings identify both a differentiation-dependent, chromosome-specific change in organization in normal myogenesis, and highlight the role of chromosomal spatial organization in myogenic differentiation.
肌生成，即增殖的骨骼肌成肌细胞向终末分化肌管的转变过程，调控着数千个靶基因。这些基因的不间断线性阵列与特定染色体存在差异关联，提示在肌生成过程中染色体具有特定的调控作用。横纹肌肉瘤（RMS）是一种骨骼肌肿瘤，与正常肌肉细胞具有共同特征。我们推测RMS与成肌细胞在与成肌基因排列相关的染色体组织方面存在差异。我们比较了在培养的RMS细胞系、正常成肌细胞和肌管中，因成肌基因排列不同而选择的2号和18号染色体的组织特征。我们发现在正常肌生成过程中存在染色体特异性的组织差异，2号染色体占据的面积增加且外周定位发生改变。最显著的是，我们发现2号染色体相对于核轴的定位存在分化依赖性差异，仅在肌管中沿主要核轴优先定位。RMS细胞对此类轴向定位无偏好，但通过转染促肌生成的miRNA miR-206诱导分化会导致2号染色体主要轴向定位增加。我们的研究结果确定了正常肌生成过程中存在依赖于分化的、染色体特异性的组织变化，并突出了染色体空间组织在肌生成分化中的作用。
