Generation and Identification of Genetically Modified Mice for BMP Receptors

Taste papilla cell differentiation requires the regulation of secretory protein production by ALK3-BMP signaling in the tongue mesenchyme

Taste papillae are specialized organs, each of which comprises an epithelial wall hosting taste buds and a core of mesenchymal tissue. In the present study, we report that during early taste papilla development in mouse embryos, bone morphogenetic protein (BMP) signaling mediated by type 1 receptor ALK3 in the tongue mesenchyme is required for epithelial Wnt/β-catenin activity and taste papilla differentiation. Mesenchyme-specific knockout (cKO) of Alk3 using Wnt1-Cre and Sox10-Cre resulted in an absence of taste papillae at E12.0. Biochemical and cell differentiation analyses demonstrated that mesenchymal ALK3-BMP signaling governed the production of previously unappreciated secretory proteins, i.e. it suppressed those that inhibit and facilitated those that promote taste papilla differentiation. Bulk RNA-sequencing analysis revealed many more differentially expressed genes (DEGs) in the tongue epithelium than in the mesenchyme in Alk3 cKO versus control. Moreover, we detected downregulated epithelial Wnt/β-catenin signaling and found that taste papilla development in the Alk3 cKO was rescued by the GSK3β inhibitor LiCl, but not by Wnt3a. Our findings demonstrate for the first time the requirement of tongue mesenchyme in taste papilla cell differentiation.

Generation of a new mouse line with conditionally activated signaling through the BMP receptor, ACVR1: A tool to characterize pleiotropic roles of BMP functions

BMP signaling plays pleiotropic roles in various tissues during embryogenesis and after birth. We have previously generated a constitutively activated Acvr1(ca-Acvr1) transgenic mouse line (line L35) through pronuclei injection to investigate impacts of enhanced BMP signaling in a tissue specific manner. However, line L35 shows a restricted expression pattern of the transgene. Here, we generated another ca-Acvr1 transgenic line, line A11, using embryonic stem (ES) transgenesis. The generated line A11 shows distinctive phenotypes from line L35, along with very limited expression levels of the transgene. When the transgene is activated in the neural crest cells in a Cre-dependent manner, line A11 exhibits cleft palate and shorter jaws, while line L35 develops ectopic cartilages and highly hypomorphic facial structures. When activated in limb buds, line A11 develops organized but smaller limb skeletal structures, while line L35 forms disorganized limbs with little mineralization. Additionally, no heterotopic ossification (HO) is identified in line A11 when bred with NFATc1-Cre mice even after induction of tissue injury, which is an established protocol for HO for line L35. Therefore, the newly generated conditional ca-Acvr1 mouse line A11 provides an additional resource to dissect highly context dependent functions of BMP signaling in development and disease.

A new glioma grading model based on histopathology and Bone Morphogenetic Protein 2 mRNA expression

Glioma, the most common form of primary malignant brain tumors, is graded based solely on histopathological appearance, which has led to prognostic discrepancies. This study aimed to establish a new glioma grading model by analyzing the expression of Bone Morphogenetic Protein 2 (BMP2) mRNA in patients with gliomas as well, named the Histopathological-BMP2 (HB) system. Clinical information was collected from 692 patients from the Chinese Glioma Genome Atlas database. According to pathological glioma subtypes and the expression of BMP2 mRNA in tumor tissues, the new subtypes HBs, HBh, HBm and HB1 were established, with BMP2 expression highest in HBs and lowest in HB1. Survival periods were analyzed. Based on this, the expression of three BMP2 receptors (BMPR1A, BMPR1B, and BMPR2) was also analyzed, which was related to the prognosis of patients. This new classification model was validated in further groups of patients from the CGGA database (n = 291) and the Cancer Genome Atlas (n = 625). A new glioma grade (HB grade) based on histopathology and BMP2 expression can predict the prognosis of glioma patients, with BMPR1B and BMPR2 expression indicating a different prognosis in different types of gliomas. The higher the concentration of BMP2, the better the prognosis of patients.