Tyrosinase is the rate-limiting enzyme for the production of melanin pigmentation. In the mouse and other animals, homozygous null mutations in the Tyrosinase gene (Tyr) result in the absence of pigmentation, i.e. albinism. Here we used the CRISPR/Cas9 system to generate mono- and bi-allelic null mutations in the Tyr locus by zygote injection of two single-guide and Cas9 RNAs. Injection into C57BL/6N wild-type embryos resulted in one completely albino founder carrying two different Tyr mutations. In addition, three pigmentation mosaics and fully pigmented littermates were obtained that transmitted new mutant Tyr alleles to progeny in test crosses with albinos. Injection into Tyr heterozygous (B6CBAF1/J × FVB/NJ) zygotes resulted in the generation of numerous albinos and also mice with a graded range of albino mosaicism. Deep sequencing revealed that the majority of the albinos and the mosaics had more than two new mutant alleles. These visual phenotypes and molecular genotypes highlight the somatic mosaicism and allele complexity in founders that occurs for targeted genes during CRISPR/Cas9-mediated mutagenesis by zygote injection in mice.

Background Juvenile nasopharyngeal angiofibroma (JNA) is a benign tumor that presents in adolescent males. Although surgical excision is the mainstay of treatment, recurrences complicate treatment. There is a need to develop less invasive approaches for management. JNA tumors are composed of fibroblasts and vascular endothelial cells. We identified fibroblast growth factor receptor (FGFR) and vascular endothelial growth factor (VEGF) expression in JNA-derived fibroblasts. FGFR influences fibroblast proliferation and VEGF is necessary for angiogenesis. We hypothesized that targeting FGFR would mitigate JNA fibroblast proliferation, invasion, and migration, and that targeting the VEGF receptor would attenuate endothelial tubule formation. Methods After informed consent, fibroblasts from JNA explants of 3 patients were isolated. Fibroblasts were treated with FGFR inhibitor AZD4547, 0 to 25 µg/mL for 72 hours and proliferation was quantified using CyQuant assay. Migration and invasion of JNA were assessed using 24-hour transwell assays with subsequent fixation and quantification. Mitigation of FGFR and downstream signaling was evaluated by immunoblotting. Tubule formation was assessed in human umbilical vein endothelial cells (HUVECs) treated with vehicle control (dimethylsulfoxide [DMSO]) or semaxanib (SU5416) as well as in serum-free media (SFM) or JNA conditioned media (CM). Tubule length was compared between treatment groups. Results Compared to control, AZD4547 inhibited JNA fibroblast proliferation, migration, and invasion through inhibition of FGFR and downstream signaling, specifically phosphorylation of - p44/42 mitogen activated protein kinase (p44/42 MAPK). JNA fibroblast CM significantly increased HUVEC tubule formation (p = 0.0039). Conclusion AZD4547 effectively mitigates FGFR signaling and decreases JNA fibroblast proliferation, migration, and invasion. SU5416 attenuated JNA fibroblast-induced tubule formation. AZD4547 may have therapeutic potential in the treatment of JNA.

Juvenile nasopharyngeal angiofibroma (JNA) is a highly vascularized and locally aggressive tumor that typically presents in adolescent males. The molecular biology of this tumor remains understudied. We sought to identify differentially expressed genes in the JNA transcriptome through messenger RNA sequencing of primary fibroblasts from 2 tumor explants and tonsil tissue from tumor-free subjects. In total, 1088 significant, differentially expressed genes were identified with 749 upregulated and 339 downregulated. Pathway analysis identified a number of activated signaling pathways, most notably, the vascular endothelial growth factor (VEGF) pathway (adjusted overlap P = .03). VEGF-A showed a 4.4-fold upregulation in JNA samples. In addition, the angiogenic receptor, fibroblast growth factor receptor 2 (FGFR2), was not present in tumor-free samples but increased in JNA. We validate these findings with immunohistochemistry, demonstrating upregulation of VEGF and FGFR2 in patient sections. Inhibition of the VEGF or FGFR signaling axes may have therapeutic potential in the treatment of JNA.

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