Biology subjects

Zhong, Z. A.

Publications and source records attributed to Zhong, Z. A..

4 recordsLinked to original sources

bioRxiv2026

Deletion of the Wnt regulator Znrf3 alters bone geometry without inducing high bone mass

RNF43 and ZNRF3 are transmembrane E3 ubiquitin ligases that negatively regulate Wnt signaling by promoting ubiquitination and degradation of Frizzled receptors. Loss of either gene enhances Wnt/{beta}-catenin signaling and has been linked to tumorigenesis. Wnt signaling is a key regulator of skeletal development and bone homeostasis, and pharmacologic activation of this pathway is an established therapy for osteoporosis. In Xenopus laevis, simultaneous disruption of rnf43 and znrf3 results in supernumerary limb formation; however, their roles in mammalian limb development and skeletal maintenance remain unclear. We demonstrate that mice homozygous for null alleles of both Rnf43 and Znrf3 do not develop supernumerary limbs. Because activation of Wnt/{beta}-catenin signaling in osteoblasts increases bone mass, we hypothesized that osteoblast-specific deletion of Rnf43 and/or Znrf3 would produce a high-bone-mass phenotype. Instead, osteoblast-specific loss of Znrf3 resulted in age-and sex-dependent reductions in trabecular bone mass, characterized by decreased bone mineral density and bone volume fraction, reduced trabecular number, and increased trabecular separation. Cortical bone exhibited increased cross-sectional size with reduced cortical area fraction and altered structural properties, while tissue mineral density was unchanged. In contrast, deletion of Rnf43 had minimal skeletal effects, and combined deletion of both genes did not exacerbate the phenotype observed with loss of Znrf3 alone. These findings identify Znrf3 as the dominant functional paralog regulating bone architecture in mature osteoblasts and underscore the importance of evaluating skeletal geometry when modulating upstream Wnt regulators.

developmental biology↗

bioRxiv2026

Frizzled 6 Drives EMT and Stromal Remodeling Downstream of SP1 in Basal-like Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy, in part due to its rapid progression and early metastasis. To uncover novel drivers of this aggressive behavior, we first analyzed Frizzled receptor expression in human PDAC datasets and identified Frizzled 6 (FZD6) as uniquely predictive of poor clinical outcomes among all ten Frizzled family members. High FZD6 expression correlated with significantly worse overall survival for PDAC patients of any age. Functional studies in human PDAC cell lines showed that FZD6 promotes mesenchymal phenotypes, including enhanced migration and growth in 3D culture, while FZD6 loss induces E-cadherin expression and impairs motility without affecting 2D proliferation. In vivo, conditional epithelial deletion of Fzd6 in KPC mice significantly extended survival, reduced tumor burden and metastasis, and remodeled the tumor microenvironment to suppress stromal activation. Single-cell RNA sequencing analysis of human and mouse PDAC tumors confirms that FZD6 is primarily found within the tumor cells and FZD6-activating, noncanonical Wnt ligands are found to be produced by the cancer-associated fibroblasts surrounding the tumors. Mechanistically, we found that FZD6 is a transcriptional target of specificity protein 1 (SP1), a factor upregulated in mutant p53 contexts and within basal-like PDAC subtypes. SP1 knockdown reduced FZD6 expression and signaling through the PCP pathway. Furthermore, reduced SP1 impaired cell motility. Together this implicates the SP1-Fzd6-Wnt/PCP axis as a key driver of epithelial plasticity and disease progression. These findings suggest that FZD6 is a central effector of mutant p53-driven EMT, and a promising therapeutic target in metastatic PDAC.

cancer biology↗

bioRxiv2022

Dkk1 inhibition normalizes limb phenotypes in a mouse model of Fzd2 associated omodysplasia Robinow syndromes

FRIZZLED-2 (FZD2) is a transmembrane Wnt ligand receptor. We previously identified a pathogenic human FZD2 variant, encoding for a protein with a premature stop and loss of 17 amino acids. This includes a portion of the consensus DISHEVELLED binding sequence required for Wnt signal transduction. Patients with this variant exhibited FZD2-associated autosomal dominant Robinow Syndrome. To model this variant, we utilized zygote microinjection and i-GONAD-based CRISPR/Cas9-mediated genome editing to generate an allelic series in the mouse. Embryos mosaic for humanized Fzd2W553* knock-in exhibited cleft palate and shortened limbs, consistent with FZD2W548* patient phenotypes. We also generated two germline mouse alleles with small deletions, Fzd2D3 and Fzd2D4. Homozygotes for each allele survive embryonic development at normal ratios but exhibit a highly penetrant cleft palate phenotype, shortened limbs compared to wild-type and perinatal lethality. Fzd2D4 craniofacial tissues indicated decreased canonical WNT signaling. In utero treatment with IIIC3a (DKK inhibitor) normalized the limb lengths in Fzd2D4 homozygotes. The in vivo replication represents an approach to further investigate the mechanism of FZD2 phenotypes and validates the utility of CRISPR knock-in mice as a tool for demonstrating pathogenicity of human genetic variants. We also present evidence for a potential therapeutic intervention.

developmental biology↗

bioRxiv2021

Generation of a New Frizzled 2 Flox Mouse Model to Clarify Its Role in Development

It is currently accepted that Wnt receptors, Frizzleds (Fzd), have high functional redundancy, making individual receptors challenging to target therapeutically. Specifically, Fzd2 is believed to be functionally redundant with Fzd1 and Fzd7, findings which were based largely on previously published global knockout mouse studies. Conversely, a Fzd2 global knockout mouse model developed by the International Mouse Phenotype Consortium (IMPC) is early embryonic lethal, suggesting Fzd2 is critical for early embryonic development. If global deletion of Fzd2 leads to early lethality, floxed models are necessary to identify tissue-specific phenotypes. We found that a previously published Fzd2 flox model does not fully delete Fzd2 function. To reconcile the contradictory findings in Fzd2 mouse models and allow for tissue-specific studies of Fzd2, we have generated a new flox model using a modified two-cell homologous recombination CRISPR approach. We demonstrated successful simultaneous insertion of two loxP sites fully surrounding the Fzd2 gene and confirmed cre-mediated recombination deletes the sequence between the loxP sites leading to a Fzd2 null allele. Preliminary studies suggest global knockouts are early embryonic lethal and full characterization of the tissue-specific effects of Fzd2 deletion is currently underway. This work suggests Fzd2 uniquely regulates development and emphasizes the importance of thorough validation of newly generated mouse models.

cell biology↗