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Proteins expressed by the paired box gene 9 (PAX9) and Msh Homeobox 1 (MSX1) are intimately involved in tooth development (odontogenesis). The regulation of PAX9 and MSX1 protein turnover by deubiquitinating enzymes (DUBs) plausibly maintain the required levels of PAX9 and MSX1 during odontogenesis. Herein, we used a loss-of-function CRISPR-Cas9-mediated DUB KO library kit to screen for DUBs that regulate PAX9 and MSX1 protein levels. We identify and demonstrate that USP49 interacts with and deubiquitinates PAX9 and MSX1, thereby extending their protein half-lives. On the other hand, the loss of USP49 reduces the levels of PAX9 and MSX1 proteins, which causes transient retardation of odontogenic differentiation in human dental pulp stem cells and delays the differentiation of human pluripotent stem cells into the neural crest cell lineage. USP49 depletion produced several morphological defects during tooth development, such as reduced dentin growth with shrunken enamel space, and abnormal enamel formation including irregular mineralization. In sum, our results suggest that deubiquitination of PAX9 and MSX1 by USP49 stabilizes their protein levels to facilitate successful odontogenesis.

Byline: Nasir. Jalal, Saba. Haq, Namrah. Anwar, Saadiya. Nazeer, Umar. Saeed Bystander effects (BSEs) have been investigated for a long time but without much deliberation as to the cause in [...]

Conventional screening methods for deubiquitinating enzymes (DUBs) have important limitations. A loss-of-function study based on the knockout of DUB genes in mammalian cells can provide an excellent model for exploring DUB function. Here, we used CRISPR-Cas9 to perform genome-scale knockout of the entire set of genes encoding ubiquitin-specific proteases (USPs), a DUB subfamily, and then systematically screened for DUBs that stabilize the Cdc25A oncoprotein. USP3 was identified as a deubiquitinase of Cdc25A. USP3 depletion reduces the Cdc25A protein level, resulting in a significant delay in cell-cycle progression, and reduces the growth of cervical tumor xenografts in nude mice. Clinically, USP3 expression is positively correlated with Cdc25A protein expression and the poorest survival in breast cancer. We envision that our DUB knockout library kit will facilitate genome-scale screening of functional DUBs for target proteins of interest in a wide range of biomedical fields.

We conducted a double-blind, placebo-controlled, randomized trial to evaluate the efficacy and safety of tetrachlorodecaoxide (TCDO) in patients with chemotherapy-induced mucositis. Sixty-two patients with World Health Organization grade II–IV oral mucositis were eligible for the study. They were randomized to receive TCDO or placebo, 10 mL twice daily, swish and swallow, for 7 days. Patients were evaluated for oral pain, dysphagia, and oral intake. Downgrading and total duration of mucositis were documented. Thirty-two were randomized to receive TCDO. Thirty received the placebo. All were evaluable. Both arms were well matched for age, gender, type of underlying neoplasm, and prior history of oral mucositis. Intensity of initial symptoms, degree of mucositis, and time period between delivery of chemotherapy and development of mucositis were also similar. Post-therapy evaluation revealed no significant difference in the mean grade of oral and esophageal pain, or dysphagia between TCDO and placebo. Downgrading or total duration of mucositis did not differ between the two groups. Oral intake improved significantly in patients taking TCDO. Time to subjective improvement in oral pain was significantly shorter with TCDO (3.1 versus 3.6 days). Evaluation on day 3 revealed that 77% of those receiving TCDO were free of oral pain in comparison to 46% receiving placebo (P= 0.05). These results indicate that TCDO may be helpful in palliating some of the symptoms related to oral mucositis. The therapeutic benefit, however, is small and needs to be confirmed in a larger trial.