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Loss of function of the Pejvakin (Pjvk) gene has been associated with deafness induced by cellular stress. This has been postulated to occur due to defective peroxisome biogenesis. Here, we have characterized a novel mouse mutation lacking exon 3 of the Pjvk coding region. A mouse mutant carrying this mutation showed loss of hair cells associated with profound deafness and reduced outer hair cell function. A cell line carrying a deletion of Pjvk exon 3 revealed upregulation of the peroxisomal enzyme catalase upon oxidative stress. In order to further clarify the localization of Pjvk, we introduced amino- and carboxy-terminal tags in its cDNA which failed to confirm its presence in peroxisomes but is likely to be due to mis-targeting of the protein. Our study thus confirms the requirement of Pjvk for maintenance of hair cells and intact hearing and a specific role in peroxisomes upon exposure to cellular stress.

The development of the mouse submandibular gland (SMG) is a classic model for branching morphogenesis, orchestrated by key signaling pathways such as Hedgehog (Hh) and Wnt. While Sonic Hedgehog (Shh) is known to be essential for early SMG development, its downstream mechanisms and potential crosstalk with other pathways remain unclear. This study investigates the functional interaction between Hh and Wnt signaling during SMG morphogenesis. Using both in vivo (pharmacological inhibition in pregnant mice) and ex vivo (organ culture) models, we inhibited Hh signaling with vismodegib from embryonic day 13.5 (E13.5). Hh inhibition led to severe morphological defects, including reduced epithelial branching and disorganized ductal structures. As expected, the expression of Hh target genes Ptch1 and Gli1 was downregulated. Notably, Hh suppression resulted in a concomitant upregulation of Wnt pathway activity, evidenced by increased nuclear β-catenin and elevated expression of the target genes Axin2 and Lef1. This suggested that Hh signaling normally acts to repress Wnt activity during SMG development. Critically, the co-administration of the Wnt inhibitor XAV939 with vismodegib in ex vivo cultures partially rescued the branching defects caused by Hh inhibition. We conclude that Hh signaling promotes murine SMG morphogenesis, at least in part, by tonically inhibiting the Wnt pathway. This study unveils a novel inhibitory crosstalk between Hh and Wnt signaling that is essential for normal salivary gland development.

Craniofacial morphogenesis requires precisely coordinated proliferation, migration, and differentiation of cranial neural crest (CNC) cells during development. Although DDB1- and CUL4-associated factor 13 (DCAF13) is known to play critical roles in early embryogenesis and tumorigenesis, its function in neural crest development remains unknown. Here, we identify a novel role for DCAF13 in craniofacial development. Conditional knockout of Dcaf13 in neural crest lineages resulted in severe craniofacial malformations characterized by impaired skeletal growth and differentiation. Mechanistically, DCAF13 deficiency in mesenchymal cells led to PTEN accumulation, a key negative regulator of PI3K/AKT signaling, thereby suppressing proliferation and differentiation of CNC-derived cells. Our findings establish DCAF13 as a crucial regulator of craniofacial morphogenesis through its control of the PTEN-PI3K/AKT signaling axis, which orchestrates neural crest cell proliferation and differentiation.

Non-syndromic tooth agenesis (TA) is a rare developmental disorder that impairs oral function, systemic health, psychological well-being, and quality of life. The Wnt signaling pathway plays a central role in TA pathogenesis, and emerging evidence implicates that the low-density lipoprotein receptor-related protein 6 (LRP6) is involved in autosomal-dominant inheritance of TA. In this study, whole-exome sequencing (WES) of a Chinese family uncovered a novel missense mutation (c.692C>T, p.T231M) in LRP6. Sanger sequencing validated this variant, which was identified as a de novo mutation in the proband. Functional assays using qRT-PCR and immunofluorescent staining demonstrated that this mutation impairs LRP6 protein function and disrupts Wnt signaling. Our findings broaden the mutational spectrum of non-syndromic TA and underscore the critical role of LRP6 in TA.

The placenta plays an essential role during pregnancy in mammals, with the placental endocrine trophoblast subtypes secreting many growth factors and cytokines to promote fetal growth and maternal adaptation. These endocrine cells, including trophoblast giant cells (TGCs), glycogen trophoblast cells (GlyTs) and spongiotrophoblast cells (SpTs), are mainly derived from Tpbpα-positive (Tpbpα⁺) trophoblast cells primarily located in the ectoplacental cone (EPC) and later junctional zone (JZ) of the mouse placenta. However, the mechanism driving Tpbpα⁺ trophoblast cell differentiation and the functions of the factors secreted by these endocrine cells remain largely unknown. In the present study, we generated the Tpbpα-iCre-EGFP knock-in mice with codon-improved Cre recombinase (iCre) inserted into the endogenous locus of the Tpbpα gene. To examine the specificity and efficiency of iCre recombinase, we crossed the Tpbpα-iCre-EGFP mice with ROSA26Sor^{tm9(CAG-tdTomato)Hze} reporter mice. The co-expression of EGFP and Td-tomato was detected obviously in the EPC at E8.5 and E9.5, and in the JZ at E13.5. Meanwhile, employing lineage tracing and in situ hybridization, we demonstrated that Tpbpα⁺ trophoblast cells could differentiate into SpTs, GlyTs, maternal blood canal (C)-TGCs, parietal (P)-TGCs, and spiral artery-associated (Spa)-TGCs. In addition, no Tpbpα expression or iCre recombinase activity was detected in other organs examined, indicating the specificity of the iCre activity in placental trophoblast cells. In summary, we successfully generated the Tpbpα-iCre-EGFP knock-in mice with enhanced Cre recombinase for modulating specific genes and investigating their functions during pregnancy.

Skeletal muscle is the most widespread tissue in mammals and mediates several functions, and whose development is controlled by a coordinated transcriptional hierarchy that regulates the activities of a range of muscle genes. Skeletal muscle comprises various cells that create communication strategies for exchanging biological information. Nevertheless, the features and developmental programs of several of these cell lines remain unknown. We constructed a complete single-cell landscape of prenatal to postnatal developing bovine skeletal muscle and compared its single-cell transcriptomic characteristics with those of humans and mice. This landscape involved cellular heterogeneity, dynamic gene expression profiles, critical regulons during cell fate decisions, extensive networks of intercellular communication, and a gene regulation network. Overall, our results identify a developmental coordinate of the pluripotency spectrum among bovines, humans, and mice. This finding suggests evolutionary conservation and species-specific differences in the skeletal muscle systems, extending to cell types, gene expression, and regulatory elements. These results offer insights into evolutionary conserved and divergent processes during mammalian skeletal muscle development.

Genetic variants of CHD7, encoding a chromatin remodeler, lead to CHARGE syndrome with congenital deficits in multiple organs. One crucial unsolved question is the causal mechanisms of most protein-altering variants of CHD7. One hypothesis is that these variants impair the enzymatic activity of CHD7, that is ATPase and nucleosome remodeling activities. Herein, we compared the phenotype of two new mouse models for CHARGE syndrome in parallel, with the Dppa3-cre/Chd7^f/+ line carrying a Chd7 truncation variant and the Chd7^S824F/+ line carrying an enzymatic-deficient missense variant. While the Dppa3-cre/Chd7^f/+ line displayed typical disease-relevant phenotypes of CHARGE syndrome as other reported lines, some of these phenotypes, such as body growth and circling behavior, were surprisingly mild in the ATPase-deficient Chd7^S824F/+ mouse line. Thus, our results demonstrated the different contribution of the enzymatic activity of CHD7 in growth and organogenesis.