Department of Animal and Veterinary Sciences, Clemson, USA.
Clemson Light Imaging Facility, Clemson, USA.
BMC Genomics. 2022 Aug 16;23(1):595. doi: 10.1186/s12864-022-08794-0.
Longissimus muscle samples were collected from lambs exposed in utero to mycotoxins [E-, endophyte-free tall fescue seed without ergot alkaloids (negative control) or E + , endophyte-infected tall fescue seed containing ergot alkaloids] during mid-gestation (MID; E + /E-) or late-gestation (LATE; E-/E +) harvested at two developmental stages (FETAL, gestational d133) or (MAT, near maturity, 250 d of age; n = 3/treatment/developmental stage). Muscle samples were examined to determine the impact of in utero mycotoxin exposure on skeletal muscle fiber hypertrophy and the miRNA profile at FETAL and MAT.
Longissimus weight was greater (P < 0.05) in E + /E- lambs compared to E-/E + lambs at MAT; however, FETAL longissimus weight did not differ (P > 0.10) between fescue treatments. Type I fiber cross sectional area was larger (P < 0.10) for E + /E- than E-/E + at MAT but did not differ (P > 0.10) between fescue treatments at FETAL. Type II fiber area was larger (P < 0.05) at MAT in E + /E- compared to E-/E + but did not differ (P < 0.05) between fescue treatments at FETAL. Cross-sectional Type I and Type II longissimus muscle fiber area increased (P < 0.05) from FETAL to MAT by 6.86-fold and 10.83-fold, respectively. The ratio of Type II:Type I muscle fibers was lower (P = 0.04) at MAT compared to FETAL. There were 120 miRNA differentially expressed (q < 0.05) between FETAL and MAT. Maternal fescue treatment did not alter (q > 0.05) expression of miRNAs in the longissimus muscle. miR-133, -29a, -22-3p, and -410-3p were identified as highly significant with a log fold change > 4. In vitro satellite cell cultures showed that selected miRNAs (miR-22-3p, 29a, 27a, and 133a) are differentially regulated during proliferation and differentiation indicating a role of miRNA in muscle hypertrophy.
Exposure to mycotoxins did not alter fiber type but had long-term impacts on postnatal muscle hypertrophy and cross-sectional area. The miRNA profile of the longissimus was not altered by Maternal mycotoxin exposure at FETAL or MAT. Developmental age altered the miRNA transcriptome and mRNA expression of known genes related to muscle growth. These results indicate that Maternal exposure to E + fescue seed during LATE gestation can alter postnatal muscle hypertrophy in sheep; however, these changes are not regulated by the miRNA transcriptome of the longissimus muscle.
在妊娠中期（MID；E-，不含麦角生物碱的无内生真菌高羊茅种子（阴性对照）或 E+，含有麦角生物碱的内生真菌高羊茅种子）或妊娠晚期（LATE；E-/E+），向子宫内暴露于霉菌毒素的羔羊中采集背最长肌样本，在两个发育阶段（FETAL，妊娠第 133 天）或（MAT，接近成熟，250 天龄；n=3/处理/发育阶段）收获。检查肌肉样本，以确定子宫内霉菌毒素暴露对 FETAL 和 MAT 时骨骼肌纤维肥大和 miRNA 谱的影响。
在 MAT 时，E+ / E-羔羊的背最长肌重量大于 E- / E+羔羊（P <0.05）；然而，在 FESCUE 处理之间，FETAL 背最长肌重量没有差异（P>0.10）。E+ / E-的 I 型纤维横截面积大于 E- / E+（P <0.10），但在 FETAL 时 FESCUE 处理之间没有差异（P>0.10）。E+ / E-的 II 型纤维面积在 MAT 时大于 E- / E+（P <0.05），但在 FETAL 时 FESCUE 处理之间没有差异（P <0.05）。I 型和 II 型背最长肌纤维的横截面积从 FETAL 到 MAT 分别增加了 6.86 倍和 10.83 倍（P <0.05）。与 FETAL 相比，MAT 时 II 型：I 型肌肉纤维的比例较低（P=0.04）。FETAL 和 MAT 之间有 120 个 miRNA 差异表达（q <0.05）。母体高羊茅处理不会改变背最长肌中 miRNA 的表达（q>0.05）。miR-133、-29a、-22-3p 和-410-3p 被确定为具有高度显著性，对数倍数变化>4。体外卫星细胞培养表明，选定的 miRNA（miR-22-3p、29a、27a 和 133a）在增殖和分化过程中差异调节，表明 miRNA 在肌肉肥大中的作用。
霉菌毒素暴露不会改变纤维类型，但对产后肌肉肥大和横截面积有长期影响。母体霉菌毒素暴露在 FETAL 或 MAT 时不会改变背最长肌的 miRNA 谱。发育年龄改变了与肌肉生长相关的已知基因的 miRNA 转录本和 mRNA 表达。这些结果表明，母体在妊娠晚期暴露于 E+高羊茅种子可改变羔羊的产后肌肉肥大；然而，这些变化不受背最长肌 miRNA 转录本的调节。
