Gene-knockout by iSTOP enables rapid reproductive disease modeling and phenotyping in germ cells of the founder generation

Cytosine base editing achieves C·G-to-T·A substitutions and can convert four codons(CAA/CAG/CGA/TGG)into STOP-codons(induction of STOP-codons,iSTOP)to knock out genes with reduced mosaicism.iSTOP enables direct phenotyping in founders’somatic cells,but it remains unknown whether this works in founders’germ cells so as to rapidly reveal novel genes for fertility.Here,we initially establish that iSTOP in mouse zygotes enables functional characterization of known genes in founders’germ cells:Cfap43-iSTOP male founders manifest expected sperm features resembling human“multiple morphological abnormalities of the flagella”syndrome(i.e.,MMAF-like features),while oocytes of Zp3-iSTOP female founders have no zona pellucida.We further illustrate iSTOP’s utility for dissecting the functions of unknown genes with Ccdc183,observing MMAF-like features and male infertility in Ccdc183-iSTOP founders,phenotypes concordant with those of Ccdc183-KO offspring.We ultimately establish that CCDC183 is essential for sperm morphogenesis through regulating the assembly of outer dynein arms and participating in the intra-flagellar transport.Our study demonstrates iSTOP as an efficient tool for direct reproductive disease modeling and phenotyping in germ cells of the founder generation,and rapidly reveals the essentiality of Ccdc183 in fertility,thus providing a time-saving approach for validating genetic defects(like nonsense mutations)for human infertility.

Auriferous karst breccias in East Hebei Province, China

RECENTLY, a new type of gold deposits was discovered along the Great Wall in East Hebei Province, thatis the so-called ’Great Wall Type gold deposit’, a-kind of carbonate breccias with micro-disseminated(invisible) gold hosted in Middle-Proterozoic carbonate rocks. In the 30th IGC in August 1996 in Beijing, it was reported as the largest belt of Carlin-type gold deposits in China, and over 1 000 tons of goldreserves were estimated (oral report). Up to now, very little is known about its genesis. Our researchshows large differences between Great Wall type and Carlin-type gold. Most remarkable is that gold ishosted in carbonate breccias, to be precise, in cements (matrix) of breccias. Because of this, we consider the breccias as a key to understanding the genesis. In some unpublished reports, breccias were regarded as hydrothermal eruptive breccias, fractured breccias, sedimentary breccias, etc. The present