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Recent advances with the type II clustered regularly interspaced short palindromic repeats （CRISPR） system promise an improved approach to genome editing. However, the applicability and efficiency of this system in model organisms, such as zebrafish, are little studied. Here, we report that RNA-guided Cas9 nuclease efficiently facilitates genome editing in both mammalian cells and zebrafish embryos in a simple and robust manner. Over 35% of site- specific somatic mutations were found when specific Cas/gRNA was used to target either etsrp, gata4 or gata5 in zebrafish embryos in vivo. The Cas9/gRNA efficiently induced biallelic conversion of etsrp or gata5 in the resulting somatic cells, recapitulating their respective vessel phenotypes in etsrpv11 mutant embryos or cardia bifida phenotypes in fautm236a mutant embryos. Finally, we successfully achieved site-specific insertion of mloxP sequence induced by Cas9/gRNA system in zebrafish embryos. These results demonstrate that the Cas9/gRNA system has the potential of becoming a simple, robust and efficient reverse genetic tool for zebrafish and other model organisms. Together with other genome-engineering technologies, the Cas9 system is promising for applications in biology, agriculture, envi- ronmental studies and medicine.

The pathogenesis of Cushing＇s dis- ease is poorly understood; two recent reports identifying somatic mutations in USP8 in pituitary corticotroph tu- mors provide exciting advances in this field. These mutations alter EGFR trafficking and signaling, raising the prospect that EGFR inhibitors may move the treatment of this disease into the era of precision medicine.

Cushing＇s disease, also known as adrenocorticotropic hormone （ACTH）-secreting pituitary adenomas （PAs） that cause excess cortisol production, accounts for up to 85% of corticotrophin-dependent Cushing＇s syndrome cases. However, the genetic alterations in this disease are unclear. Here, we performed whole-exome sequencing of DNA derived from 12 ACTH-secreting PAs and matched blood samples, which revealed three types of somatic mutations in a candidate gene, USP8 （encoding ubiquitin-specific protease 8）, exclusively in exon 14 in 8 of 12 ACTH-secreting PAs. We further evaluated somatic USP8 mutations in additional 258 PAs by Sanger sequencing. Targeted sequenc- ing further identified a total of 17 types of USP8 variants in 67 of 108 ACTH-secreting PAs （62.04%）. However, none of these mutations was detected in other types of PAs （n = 150）. These mutations aggregate within the 14-3-3 binding motif of USP8 and disrupt the interaction between USP8 and 14-3-3 protein, resulting in an elevated capacity to pro- tect EGFR from lysosomal degradation. Accordingly, PAs with mutated USP8 display a higher incidence of EGFR expression, elevated EGFR protein abundance and mRNA expression levels of POMC, which encodes the precursor of ACTH. PAs with mutated USP8 are significantly smaller in size and have higher ACTH production than wild- type PAs. In surgically resected primary USP8-mutated tumor cells, USP8 knockdown or blocking EGFR effectively attenuates ACTH secretion. Taken together, somatic gain-of-function USP8 mutations are common and contribute to ACTH overproduction in Cushing＇s disease. Inhibition of USP8 or EGFR is promising for treating USP8-mutated corticotrophin adenoma. Our study highlights the potentially functional mutated gene in Cushing＇s disease and pro- vides insights into the therapeutics of this disease.

The laboratory rat is a valuable mammalian model organism for basic research and drug discovery. Here we demonstrate an efficient methodology by applying transcription activator-like effector nucleases （TALENs） technology to generate Leptin receptor （Lepr） knockout rats on the Sprague Dawley （SD） genetic background. Through direct injection of in vitro transcribed mRNA of TALEN pairs into SD rat zygotes, somatic mutations were induced in two of three resulting pups. One of the found- ers carrying bi-allelic mutation exhibited early onset of obesity and infertility. The other founder carried a chimeric mutation which was efficiently transmitted to the progenies. Through phenotyping of the resulting three lines of rats bearing distinct mutations in the Lepr locus, we found that the strains with a frame-shifted or premature stop codon mutation led to obesity and metabolic disorders. However, no obvious defect was observed in a strain with an in-frame 57 bp deletion in the extracellular domain of Lepr. This suggests the deleted amino acids do not significantly affect Lepr structure and function. This is the first report of generating the Lepr mutant obese rat model in SD strain through a reverse genetic approach. This suggests that TALEN is an efficient and powerful gene editing technology for the generation of disease models.

A striking characteristic of cancer ceLls is their remarkable phenotypic plasticity, which is the ability to switch states or phenotypes in response to environmental fluctuations. Phenotypic changes such as a partial or complete epithelial to mesenchymal transition （EMT） that play important roles in their survival and proliferation, and development of resistance to therapeutic treatments, are widely believed to arise due to somatic mutations in the genome. However, there is a growing concern that such a deterministic view is not entirely consistent with multiple lines of evidence, which indicate that stochasticity may also play an important role in driving phenotypic plasticity. Here, we discuss how stochasticity in protein interaction networks （PINs） may play a key role in determining phenotypic plasticity in prostate cancer （PCa）. Specifically, we point out that the key players driving transitions among different phenotypes （epithelial, mesenchymal, and hybrid epithelial/mesenchymal）, including ZEB1, SNAIl, OVOL1, and OVOL2, are intrinsically disordered proteins （IDPs） and discuss how plasticity at the molecular level may contribute to stochasticity in phenotypic switching by rewiring PINs. We conclude by suggesting that targeting iDPs implicated in EMT in PCa may be a new strategy to gain additional insights and develop novel treatments for this disease, which is the most common form of cancer in adult men.

Acute myeloid leukemia（AML） is a clonal disorder characterized by the accumulation of complex genomic alterations that define the disease pathophysiology and overall outcome. Recent advances in sequencing technologies have described the molecular landscape of AML and identified several somatic alterations that impact overall survival. Despite all these advancement, several challenges remain in translating this information into effective therapy. Herein we will review the molecular landscape of AML and discuss the impact of the most common somatic mutations on disease biology and outcome.

Background： Schizophrenia （SCZ） is a severe, debilitating, and complex psychiatric disorder with multiple causative factors. An increasing number of studies have determined that rare variations play an important role in its etiology. A somatic mutation is a rare form of genetic variation that occurs at an early stage of embryonic development and is thought to contribute substantially to the development of SCZ. The aim of the study was to explore the novel pathogenic somatic single nucleotide variations （SNVs） and somatic insertions and deletions （indels） of SCZ. Methods： One Chinese family with a monozygotic （MZ） twin pair discordant for SCZ was included. Whole exome sequencing was performed in the co-twin and their parents. Rigorous filtering processes were conducted to prioritize pathogenic somatic variations, and all identified SNVs and indels were further confirmed by Sanger sequencing. Results： One somatic SNV and two somatic indels were identified after rigorous selection processes. However, none was validated by Sanger sequencing. Conclusions： This study is not alone in the failure to identify pathogenic somatic variations in MZ twins, suggesting that exonic somatic variations are extremely rare. Further efforts are warranted to explore the potential genetic mechanism of SCZ.

The speckle-type POZ protein （SPOP） is a tumor suppressor in prostate cancer （PCa）. SPOP somatic mutations have been reported in up to 15% of PCa of those of European descent. However, the genetic roles of SPOP in African American （AA）-PCa are currently unknown. We sequenced the SPOP gene to identify somatic mutations in 49 AA prostate tumors and identified three missense mutations （p.Y87C, p.F102S, and p.G111E） in five AA prostate tumors （10%） and one synonymous variant （p.11061） in one tumor. Intriguingly, all of mutations and variants clustered in exon six, and all of the mutations altered conserved amino acids. Moreover, two mutations （p.F102S and p.G111E） have only been identified in AA-PCa to date. Quantitative real-time polymerase chain reaction analysis showed a lower level of SPOP expression in tumors carrying SPOP mutations than their matched normal prostate tissues. In addition, SPOP mutations and novel variants were detected in 5 of 27 aggressive PCa and one of 22 less aggressive PCa （P 〈 0.05）. Further studies with increased sample size are needed to validate the clinicopathological significance of these SPOP mutations in AA-PCa.

Again-of-function stabilizing somatic mutation in 3β-hydroxysteroiddehydrogenase type 1 （3βHSDI, HSD3B1） was reported in castration-resistant prostate cancer. The A-C nucleotide polymorphism replaced asparagine-367 with threonine （3βHSD1-N367T） as a homozygous somatic mutation in a subset of castration-resistant prostate cancers by loss of heterozygosity of the wild-type allele. Increased stability of 3[HSD I-N367T was associated with decreased ubiquitin-mediated degradation and higher levels of dihydrotestosterone （DHT）. The studies suggest that genetic instability in castration-resistant prostate cancer favors the more stable 313HSD I-N367T mutant that contributes to drug resistance. A somatic mutation in a steroid metabolic enzyme required for DHT synthesis provides further support for intratumoral androgen synthesis contributing to prostate cancer progression.

Lung cancer is one of the leading causes of death with one of the lowest survival rates. However, a subset of lung cancer patients who are of Asian origin and carry somatic mutations in epidermal growth factor receptor or EGFR have responded remarkable well to two tyrosine kinase inhibitors, gefitinib and erlotinib. While EGFR mutation profiles havebeen reported from Japan, South Korea, and Taiwan, there is no such report from mainland of China where the largest pool of patients reside. In this report, we identified ten somatic mutations from a total of 41 lung cancer patients in China. Among them, seven mutations were found in 17 adenocarcinomas. In contrast to previous reports, eight of these mutations are deletions in exon 19 and two of these deletions are homozygous. These results suggest that a large portion of Chinese adenocarcinoma patients could benefit from gefitinib or erlotinib. This unique mutation profile provides a rationale to develop the next generation of EGFR inhibitors more suitable for the Chinese population.