Assessment Of Growth And Reproductive Performance As Well As Health Of Transgenic Mice That MSTN And SS Genes Were Interfered By RNA

Myostatin(MSTN) is a negative regulator factor in skeletal muscle growth, while somatostatin(SS) inhibits the secretion of growth hormones to suppress the body’s growth response. The transgenic mice were generated by prokaryotic microinjection with the RNA interference fragment of MSTN and SS(MSTN transgenic mice and SS transgenic mice), respectively. We screened transgenic mice for the positive insertions and observed its growth and reproductive performance. These were aimed at understanding the genetic regulation and growth-promoting effect of the transgenic mice with MSTN or SS fragment, to further elaborate the regulatory mechanism controlling growth and reproduction, and to assess the health parameters by physiological and biochemical aspects. The results were as follows:(1) The genetic stability of transgenic miceThe positive rate of transgenic mice were detected by PCR, which reveals that the positive rate of MSTN transgenic mice is 66.7%(56/84), 47.2%(17/36) and 43.8%(7/16) in F1, F2 and F3 generations, respectively; whereas the positive rate of SS transgenic mice is 61.7%(29/47), 63.6%(14/22) and 47.1%(8/17) in F1, F2 and F3 generations, respectively; these results indicated that the transgenic mice can exist and stably inherit it to the next generation.(2) The health of transgenic miceThe organ tissues of two kinds of F1 generation transgenic mice in 10 weeks, using HE staining to observe the histopathological changes, the results show that the tissues of transgenic mice had no pathological, physiological and biochemical changes and viscera index fluctuated within the normal range, these results indicated that MSTN or SS did not cause adverse effects on the health of offsprings.(3) The growth performance of transgenic miceMSTN transgenic mice F1, F2 and F3 generations’ body weight were increased by 25.3% and 15.6%(P < 0.05) in 1, and 3 weeks, respectively, as compared to the wild type mice; the male mice F1, F2 generations’ body weight were increased by 11.8%, 10.6%, 7.5% and 9.7%(P < 0.05) in 5, 6, 7, and 10 weeks, respectively, as compared to the wild type male mice; the female mice’ body weight were increased by 10.8%(P < 0.05) in 5 weeks, compared with the wild type female mice. These results showed that by inhibiting the expression of MSTN can promote growth, and the ability of growth-promoting factors associated with growth period, growth promoting effects can be more obvious in the growing period.SS transgenic mice F1, F2 and F3 generations’ body weight had no significant difference(P > 0.05), as compared to wild type mice. These results indicate that there might be other growth regulation mechanism for SS gene.(4) The reproductive performance of transgenic miceMSTN and SS transgenic mice F1 generation had no effects on weaning rate(97.4% vs. 97.8%, 97.4% vs. 97.8%), but litter size lower than wild type mice(8.8 vs.11.0; 9.4 vs.11.0)(P < 0.05). We speculated that by inhibiting the expression of MSTN and SS, may inhibit follicular development, but has no effect on lactation performance in mice.(5) The growth promoting mechanism of transgenic miceWe found that the MSTN m RNA expression and protein level of MSTN transgenic mice F1 generation in muscle tissue, were decreased obviously, eg.the MSTN m RNA of the tibialis anterior muscle were decreased by 45%, 65%(P < 0.01),respectively, in the 3, and 10 weeks; the gastrocnemius muscle were decreased by 20%(P < 0.05) in 10 weeks; In addition, the MSTN protein level were decreased in the 3, and 10 weeks; the MSTN levels were also down in serum, and significantly decreased(P < 0.01) in 10 weeks. Similarly, the Leptin m RNA expression were decreased by 44.2%(P < 0.05) in 3 weeks, the Leptin levels were also down in serum, and especially had big reduction(P < 0.01) in the 10 weeks. Compared with wild type mice, the muscle fiber density were increased by 31.9%(P < 0.05) in 3 weeks, the cross-sectional area and the diameter of muscle fiber were increased by 21.0%(P < 0.05) and 8.5%(P < 0.05) in 10 weeks, respectively. The results showed that by inhibiting the expression of MSTN can effectively reduce the MSTN and Leptin level, promote the growth of skeletal muscle in mice, inhibit the fat metabolism, promote weight gain in mice, and eventually promote the growth in mice.The SS m RNA expression and protein level of SS transgenic mice F1 generation in stomach, intestines, brain tissue, we found that the SS expression were not obvious. But the SS levels were down, and extremely significant difference in the 10 weeks period(P < 0.01); the GH levels were increased, and significant differences were observed in the 3,and 6 weeks time(P < 0.05). The results showed that by inhibiting the expression of SS can effectively reduce the SS levels in serum, and promote GH levels, further study is required to establish logical answers for observed no obvious growth of mice in present study.In summary, MSTN transgenic mice had genetic stability and health, by interfering the expression of MSTN, it can inhibit the expression levels of MSTN, and improve the growth performance in mice. Although SS transgenic mice had genetic stability and security, but the growth promoting effects were not obvious. This study can provide a theoretical reference for the production of excellent traits in genetically modified animals and lay the foundation.