Principle and development of single base editing technology and its application in livestock breeding / 生物工程学报

CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein) is widely used in the field of livestock breeding. However, its low efficiency, untargeted cutting and low safety have greatly hampered its use for introducing single base mutations in livestock breeding. Single base editing, as a new gene editing tool, can directly replace bases without introducing double strand breaks. Single base editing shows high efficiency and strong specificity, and provides a simpler and more effective method for precise gene modification in livestock breeding. This paper introduces the principle and development of single base editing technology and its application in livestock breeding.

Single base editing system mediates site-directed mutagenesis of genes GDF9 and FecB in Ouler Tibetan sheep / 生物工程学报

In this study, a single base editing system was used to edit the FecB and GDF9 gene to achieve a targeted site mutation from A to G and from C to T in Ouler Tibetan sheep fibroblasts, and to test its editing efficiency. Firstly, we designed and synthesized sgRNA sequences targeting FecB and GDF9 genes of Ouler Tibetan sheep, followed by connection to epi-ABEmax and epi-BE4max plasmids to construct vectors and electrotransfer into Ouler Tibetan sheep fibroblasts. Finally, Sanger sequencing was performed to identify the target point mutation of FecB and GDF9 genes positive cells. T-A cloning was used to estimate the editing efficiency of the single base editing system. We obtained gRNA targeting FecB and GDF9 genes and constructed the vector aiming at mutating single base of FecB and GDF9 genes in Ouler Tibetan sheep. The editing efficiency for the target site of FecB gene was 39.13%, whereas the editing efficiency for the target sites (G260, G721 and G1184) of GDF9 gene were 10.52%, 26.67% and 8.00%, respectively. Achieving single base mutation in FecB and GDF9 genes may facilitate improving the reproduction traits of Ouler Tibetan sheep with multifetal lambs.

Scope and method of image registration and clinical target volume margin for central-type non-small cell lung cancer in image-guided radiotherapy / 中南大学学报(医学版)

OBJECTIVE@#To determine the influence of different registration scopes and methods on kilo-voltage cone beam CT (kVCBCT) image and CT image and to estimate the appropriate clinical target volume (CTV)-to-planned target volume (PTV) margin for central-type non-small cell lung cancer in image-guided radiation therapy (IGRT).@*METHODS@#Twenty-six patients with central-type non-small cell lung cancer (NSCLC) who received IGRT were enrolled in this study and totally 104 flames of kVCBCT scanning acquired before radiotherapy were analyzed. First, registrations were performed by gray plus manual match and were compared among different registration scopes of tumor and tumor plus vertebra. Then, the results of registration as well as time cost using tumor plus vertebra as registration scope were compared among different registration methods of gray plus manual match and bone plus manual match. At last, 200 registrations using tumor plus vertebra as the registration scope performed by bone plus manual match were recorded and the CTV-to-PTV margin was calculated.@*RESULTS@#There was no significant difference in X, Y and Z translational and rotational movements between the registration scopes of tumor and tumor plus vertebra when gray plus manual match was used as the registration method (P>0.05). The registration results of gray plus manual match and bone plus manual match were equal when tumor plus vertebra was used as the registration scope (P>0.05), but the time cost of bone plus manual match [(1.9±0.3) min] was shorter than that of gray plus manual match [(3.1±0.2) min]. The CTV-to-PTV margins were 5.3, 4.9 and 5.7 mm in X, Y, and Z directions respectively.@*CONCLUSION@#For central-type NSCLC, tumor and vertebra can be used as registration scope and the bone plus manual match is suggested in IGRT. To avoid errors, we suggest a CTV-to-PTV margin of 6 mm.