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.
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.
To determine whether TXNDC15 variation causes Meckel-Gruber syndrome (MKS), we assessed the pathogenicity of the frameshift variant c.560delA. A CRISPR-Cas9 generated mouse model carrying the equivalent Txndc15 c.512delA mutation was analyzed at embryonic day 15.5. Homozygous Txndc15(mt/mt) embryos displayed the complete MKS phenotype-fetal lethality, exencephaly, omphalocele, post-axial polydactyly, and polycystic kidneys-together with markedly reduced TXNDC15 protein in brain, liver, and kidney. These findings confirm TXNDC15 as a bona fide MKS disease gene.
Bicaudal C1 (Bicc1) encodes an RNA-binding protein critical for many organ development and epithelial tissue homeostasis. Bicc1 null mutations have been shown to lead to the development of polycystic kidney disease (PKD) and death at an early prenatal stage. To elucidate the tissue-specific functions of Bicc1, we engineered two independent conditional knockout (cKO) mouse lines targeting distinct exonic regions of the gene. The first line was generated using a traditional embryonic stem (ES) cell-based approach, wherein loxP sites were inserted flanking exon 4 (E4), enabling Cre-mediated excision of a functionally essential coding region. The second line was created using CRISPR/Cas9 genome editing, introducing loxP sites around both exon 4 and exon 5 (E4-5) in a double-step zygote injection strategy. Both alleles were validated by PCR genotyping, sequencing, and functional recombination was confirmed via a tissue-specific Cre driver. These independent cKO models provide a robust platform for dissecting the role of Bicc1 in specific tissues and developmental stages, and offer new avenues for studying the mechanistic basis of PKD and other Bicc1-related pathologies.
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 ROSA26Sortm9(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/Chd7f/+ line carrying a Chd7 truncation variant and the Chd7S824F/+ line carrying an enzymatic-deficient missense variant. While the Dppa3-cre/Chd7f/+ 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 Chd7S824F/+ mouse line. Thus, our results demonstrated the different contribution of the enzymatic activity of CHD7 in growth and organogenesis.
Chromatin remodeling proteins are evolutionarily conserved factors involved in a wide range of biological processes. In this review, we describe ATRX, a chromatin remodeling protein belonging to the SWI/SNF2 family. Its association with different protein complexes, and its roles in embryonic development, sexual differentiation, as well as retinal and brain function. We further discuss and integrate current findings on pathologies associated with ATRX dysfunction such as ATR-X syndrome, focusing on its etiology, clinical features, and potential diagnostic tools. Finally, we propose that ATRX may contribute to the progression of certain neurodegenerative diseases and review recent literature supporting this hypothesis.
The Arabidopsis Information Resource (TAIR) is a continuously updated, online database of genetic and molecular biology data for the model plant Arabidopsis thaliana that provides a global research community with centralized access to data for over 30,000 Arabidopsis genes. TAIR's biocurators systematically extract, organize, and interconnect experimental data from the literature along with computational predictions, community submissions, and high throughput datasets to present a high quality and comprehensive picture of Arabidopsis gene function. TAIR provides tools for data visualization and analysis, and enables ordering of seed and DNA stocks, protein chips, and other experimental resources. TAIR actively engages with its users who contribute expertise and data that augments the work of the curatorial staff. TAIR's focus in an extensive and evolving ecosystem of online resources for plant biology is on the critically important role of extracting experimentally based research findings from the literature and making that information computationally accessible. In response to the loss of government grant funding, the TAIR team founded a nonprofit entity, Phoenix Bioinformatics, with the aim of developing sustainable funding models for biological databases, using TAIR as a test case. Phoenix has successfully transitioned TAIR to subscription-based funding while still keeping its data relatively open and accessible.
The Cre/loxP system has been used extensively for conditional mutagenesis in mice. Reporters of Cre activity are important for defining the spatial and temporal extent of Cre-mediated recombination. Here we describe mT/mG, a double-fluorescent Cre reporter mouse that expresses membrane-targeted tandem dimer Tomato (mT) prior to Cre-mediated excision and membrane-targeted green fluorescent protein (mG) after excision. We show that reporter expression is nearly ubiquitous, allowing visualization of fluorescent markers in live and fixed samples of all tissues examined. We further demonstrate that mG labeling is Cre-dependent, complementary to mT at single cell resolution, and distinguishable by fluorescence-activated cell sorting. Both membrane-targeted markers outline cell morphology, highlight membrane structures, and permit visualization of fine cellular processes. In addition to serving as a global Cre reporter, the mT/mG mouse may also be used as a tool for lineage tracing, transplantation studies, and analysis of cell morphology in vivo.
Conditional mutagenesis permits the cell type-specific analysis of gene functions in vivo. Here, we describe a mouse line that expresses Cre recombinase under control of regulatory sequences of NEX, a gene that encodes a neuronal basic helix-loop-helix (bHLH) protein. To mimic endogenous NEX expression in the dorsal telencephalon, the Cre recombinase gene was targeted into the NEX locus by homologous recombination in ES cells. The Cre expression pattern was analyzed following breeding into different lines of lacZ-indicator mice. Most prominent Cre activity was observed in neocortex and hippocampus, starting from around embryonic day 11.5. Within the dorsal telencephalon, Cre-mediated recombination marked pyramidal neurons and dentate gyrus mossy and granule cells, but was absent from proliferating neural precursors of the ventricular zone, interneurons, oligodendrocytes, and astrocytes. Additionally, we identified formerly unknown domains of NEX promoter activity in mid- and hindbrain. The NEX-Cre mouse will be a valuable tool for behavioral research and the conditional inactivation of target genes in pyramidal neurons of the dorsal telencephalon.
We generated two complementary systems for Cre‐mediated recombination of target genes in the mouse digestive epithelium and tested them with a Cre‐reporter mouse strain. Cre was expressed under the control of a 9 kb regulatory region of the murine villin gene (vil‐Cre). Genetic recombination was initiated at embryonic day (E) 9 in the visceral endoderm, and by E12.5 in the entire intestinal epithelium, but not in other tissues. Cre expression was maintained throughout adulthood. Furthermore, transgenic mice bearing a tamoxifen‐dependent Cre recombinase (vil‐Cre‐ER T2 ) expressed under the control of the villin promoter were created to perform targeted spatiotemporally controlled somatic recombination. After tamoxifen treatment, recombination was detectable throughout the digestive epithelium. The recombined locus persisted for 60 days after tamoxifen administration, despite rapid intestinal cell renewal, indicating that epithelial progenitor cells had been targeted. The villin‐Cre and villin‐Cre‐ER T2 mice provide valuable tools for studies of cell lineage allocation and gene function in the developing and adult intestine. genesis 39:186–193, 2004. © 2004 Wiley‐Liss, Inc.
genesisVolume 34, Issue 1-2 p. 1-15 ReviewFree Access GAL4 system in drosophila: A fly geneticist's swiss army knife Joseph B. Duffy, Corresponding Author Joseph B. Duffy [email protected] Department of Biology, Indiana University, Bloomington, IndianaDepartment of Biology, Indiana University, 1001 E. 3rd Street, Bloomington, IN 47405Search for more papers by this author Joseph B. Duffy, Corresponding Author Joseph B. Duffy [email protected] Department of Biology, Indiana University, Bloomington, IndianaDepartment of Biology, Indiana University, 1001 E. 3rd Street, Bloomington, IN 47405Search for more papers by this author First published: 12 September 2002 https://doi.org/10.1002/gene.10150Citations: 713AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL LITERATURE CITED Aplin AC, Kaufman TC. 1997. Homeotic transformation of legs to mouthparts by proboscipedia expression in Drosophila imaginal discs. Mech Dev 62: 51– 60. Brand AH, Perrimon N. 1993. 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We have used a Prx1 limb enhancer to drive expression of Cre Recombinase in transgenic mice. This regulatory element leads to Cre expression throughout the early limb bud mesenchyme and in a subset of craniofacial mesenchyme. Crossing a murine line carrying this transgene to a reporter mouse harboring a floxed Cre-reporter cassette revealed that recombinase activity is first observed in the earliest limb bud at 9.5 dpc. By early to mid bud stages at 10.5 dpc recombination is essentially complete in all mesenchymal cells in the limb. Expression of the Cre recombinase was never detected in the limb bud ectoderm. The use of Prx1-Cre mice should facilitate analysis of gene function in the developing limb.
FGF10 and FGF8, which are reciprocally expressed by the mesoderm and AER of the developing limb bud, have been implicated in limb initiation, outgrowth, and patterning. FGF10 and FGF8 signal through the FGFR2b and FGFR2c alternative splice isoforms, respectively [Ornitz DM, et al. 1996. J Biol Chem 271:15292-15297; Igarashi M, et al. 1998. J Biol Chem 273:13230-13235]. A paracrine signaling loop model has been proposed whereby FGF10 expressed by limb mesoderm signals via ectodermally restricted FGFR2b to regulate FGF8 expression by the apical ectoderm; in turn, FGF8 signals via mesodermally restricted FGFR2c to maintain FGF10 expression [Ohuchi H, et al. 1997. Development 124:2235-2244; Xu X, et al. 1998. Development 125:753-765]. To explore this model, we have examined FGFR2b and FGFR2c mRNA expression, using isoform-specific probes during the early stages of development of the chick limb when limb initiation, AER induction, and outgrowth are occurring. We have found that FGFR2b is expressed by limb ectoderm, including the AER, consistent with paracrine signaling of FGF10. By contrast, FGFR2c is expressed by both mesoderm and ectoderm, indicating that FGF8 has the potential to function in an autocrine as well as paracrine fashion. Indeed, as the limb grows out in response to the AER, FGFR2c expression attenuates in the mesoderm of the progress zone, but is maintained in the AER itself, arguing against exclusive paracrine signaling of FGF8 during limb outgrowth. We also report that transcripts for FGF10, FGFR2b, and FGFR2c are expressed normally in the limb buds of limbless mutant embryos, which fail to form an AER and do not express FGF8. Furthermore, we detect no mutations in exons specific for the FGFR2c or FGFR2b isoforms in limbless embryos. Since gene targeting has shown that expression of FGF8 in limb ectoderm depends on FGF10 [Min H, et al. 1998. Genes Dev 12:3156-3161; Sekine K, et al. 1999. Nature Genet 21:138-141], these results indicate that the product of the limbless gene is required for FGF10 to induce expression of FGF8.
The reproductive organs of conifers, the pollen cones and seed cones, differ in morphology from the angiosperm flower in several fundamental respects. In this report we present evidence to suggest that the two plant groups, in spite of these morphological differences and the long evolutionary distance between them, share important features in regulating the development of the reproductive organs. We present the cloning of three genes, DAL11, DAL12, and DAL13, from Norway spruce, all of which are related to the angiosperm B-class of homeotic genes. The B-class genes determine the identities of petals and stamens. They are members of a family of MADS-box genes, which also includes C-class genes that act to determine the identity of carpels and, in concert with B genes specify stamens in the angiosperm flower. Phylogenetic analyses and the presence of B-class specific C-terminal motifs in the DAL protein sequences imply homology to the B-class genes. Specific expression of all three genes in developing pollen cones suggests that the genes are involved in one aspect of B function, the regulation of development of the pollen-bearing organs. The different temporal and spatial expression patterns of the three DAL genes in the developing pollen cones indicate that the genes have attained at least in part distinct functions. The DAL11, DAL12, and 13 expression patterns in the pollen cone partly overlap with that of the previously identified DAL2 gene, which is structurally and functionally related to the angiosperm C-class genes. This result supports the hypothesis that an interaction between B- and C-type genes is required for male organ development in conifers like in the angiosperms. Taken together, our data suggests that central components in the regulatory mechanisms for reproductive organ development are conserved between conifers and angiosperms and, thus, among all seed plants.
