Application of Repetitive Sequences in Fish Cell Depletion as a Target for the CRISPR/Cas9 System.

Specific cell depletion is a common means to study the physiological function of cell lineages and tissue regeneration. However, 100% depletion is difficult to achieve with existing cell depletion strategies. With the increasing maturity of CRISPR/Cas9 technology, it is increasingly used for the depletion of various cells. However, even with this technology, it is difficult to complete the depletion of specific gene knockout cells. For this reason, cell depletion with the use of repetitive sequences as the target of CRISPR/Cas9 was explored using zebrafish. All cells were used as the target cells for the first set of experiments. The results showed that injection of a mixture of DANA-gRNA and Cas9 mRNA into zygotes resulted in substantial cell apoptosis. Cells are almost invisible in the embryonic animal pole during the dome stage. The activities of the caspase-3 and caspase-9 proteins and the mRNA level of the P53 gene were significantly increased. Then, primordial germ cells (PGCs) in embryos were used as the target cells in subsequent experiments. To specifically knock out PGCs, we injected the mix of DANA-gRNA, pkop: Cas9 plasmid (the kop promotor allows Cas9 expression only in PGCs), and eGFP-nos3'UTR mRNA into zebrafish fertilized eggs. The results revealed that the activity of the caspase-3 protein was significantly increased, and the mRNA levels of P53, ku70, and ku80 were significantly upregulated, while the number of PGCs decreased gradually. Few PGCs labeled with GFP could be seen 20 h post-fertilization (hpf), and no PGCs could be seen at the germinal ridge 24 hpf. Therefore, the combination of CRISPR/Cas9 technology and repetitive sequences can achieve efficient cell depletion regardless of whether there is generalized expression or expression in specific cells. These results indicate that it is feasible to eliminate cells by using repeat sequences as CRISPR/Cas9 system target sites.

Novel and efficient synthesis of 22-alkynyl-13,24(23)-cyclo-18,21-dinorchol-22-en-20(23)-one analogues.

The efficient synthesis of some 22-alkynyl-13,24(23)-cyclo-18,21-dinorchol-22-en-20(23)-ones was investigated. 22-Iodocyclo-18,21-dinorcholenones were prepared from cyclo-18,21-dinorcholenones using I(2)/DMAP/pyridine system firstly. The cross coupling reaction of 22-iodocyclo-18,21-dinorcholenones and 1-alkynes was carried out efficiently catalyzed by tetrakis(triphenylphosphine) palladium/cuprous iodide in the presence of base diisopropylethylamine. This strategy offered a very straightforward and efficient method for access to conjugated alkynyl cyclo-18,21-dinorcholenones from the cyclo-18,21-dinorcholenones and 1-alkynes in excellent overall yields. Evaluation of the synthesized compounds for cytotoxicity against KB, HeLa, MKN-28 and MCF-7 cell lines showed that the 22-alkynylcyclodinorchoenones possessing hydroxylethyl and hydroxylmethyl mono-substituted side chain at the end of alkynyl group have significantly inhibition activity.

Pd(PPh(3))(4)/AgOAc-catalyzed coupling of 17-steroidal triflates and alkynes: Highly efficient synthesis of D-ring unsaturated 17-alkynylsteroids.

A novel and practical procedure was developed for the preparation of D-ring unsaturated 17-alkynyl steroids by Pd(PPh(3))(4)/AgOAc-catalyzed coupling of steroidal 17-triflates and alkynes. Firstly treatment of the steroid-17-ones with PhN(Tf)(2) and KHMDS in dried THF at -78 degrees C for 2h gives the corresponding steroidal 17-triflates products in high yields (97-98%), following the coupling of steroidal 17-triflates and various 1-alkynes by Pd(PPh(3))(4)/AgOAc-catalyzed in the presence of DIPEA for 24h to yield the desired D-ring unsaturated 17-alkynyl steroids (86-97%). Moreover, it was found that the coupling reaction catalyzed by Pd[(C(6)H(5))(3)P](4)/AgOAc system is selective for aryl triflates or vinyl triflates. By optimizing the reaction conditions, the sole C17-coupling products from steroidal bistriflates were obtained in satisfactory yields. Since D-ring unsaturated 17-alkynyl steroids with conjugated double and triplet bond can be subsequently converted into pentacyclic steroids and 17-oxosteroid derivatives at the side chain of D-ring, this general method provides a highly efficient route to these biologically important compounds.