At 5 mpf, in <i>col6a1</i>^{<i>ama605003</i>} mutants muscles, the number of nuclei was increased additionally HM muscle showed fibrosis.

<p>Light photomicrograph of 5 μm-thick paraffin section of trunk muscle of 5 mpf wild type (WT, A, D), heterozygous (HT, B, E) and homozygous (HM, C, F) <i>col6a1</i>^{<i>ama605003</i>} mutants. The section were cut according to transversal plane and stained with hematoxylin-eosin-safran (A-C) or with Masson’s trichrome (D-F) colorations. We observed a slight increase in nuclei in the fibrous septa of <i>col6a1</i>^{<i>ama605003</i>} HT (B) and numerous nuclei in HM (C, arrows). Additionally, we observed unidentified amorphous material only in HM (C, arrowheads), and a figure of putative fibrosis (C, star). The Masson’s trichrome confirmed the increasing number of nuclei (violet) from HT (E) to HM (F) as compared to WT (D). This staining also confirmed the presence of large collagen-rich areas most probably marking fibrosis (star, F) that was absent in WT (D) and HT (E). Scale bars 25μm.