Transgenic rescue of enamel phenotype in Ambn null mice.
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ABSTRACT:
SUBMITTER: Chun YH
PROVIDER: S-EPMC3085845 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The amelogenins are the most abundant secreted proteins in developing dental enamel. Enamel from amelogenin (Amelx) null mice is hypoplastic and disorganized, similar to that observed in X-linked forms of the human enamel defect amelogenesis imperfecta resulting from amelogenin gene mutations. Both transgenic strains that express the most abundant amelogenin (TgM180) have relatively normal enamel, but strains of mice that express a mutated amelogenin (TgP70T), which leads to amelogenesis imperfecta in humans, have heterogeneous enamel structures. When Amelx null (KO) mice were mated with transgenic mice that produce M180 (TgM180), the resultant TgM180KO offspring showed evidence of rescue in enamel thickness, mineral density, and volume in molar teeth. Rescue was not observed in the molars from the TgP70TKO mice. It was concluded that a single amelogenin protein was able to significantly rescue the KO phenotype and that one amino acid change abrogated this function during development.
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Project description:Rett syndrome (RTT) is a disorder that affects patients' ability to communicate, move and behave. RTT patients are characterized by impaired language, stereotypic behaviors, frequent seizures, ataxia and sleep disturbances, with the onset of symptoms occurring after a period of seemingly normal development. RTT is caused by mutations in methyl-CpG binding protein 2 (MECP2), an X-chromosome gene encoding for MeCP2, a protein that regulates gene expression. MECP2 generates two alternative splice variants encoding two protein isoforms that differ only in the N-terminus. Although no functional differences have been identified for these splice variants, it has been suggested that the RTT phenotype may occur in the presence of a functional MeCP2-e2 protein. This suggests that the two isoforms might be functionally distinct. Supporting this notion, the two variants show regional and age-related differences in transcript abundance. Here, we show that transgenic expression of either the MeCP2-e1 or MeCP2-e2 splice variant results in prevention of development of RTT-like phenotypic manifestations in a mouse model lacking Mecp2. Our results indicate that the two MeCP2 splice variants can substitute for each other and fulfill the basic functions of MeCP2 in the mouse brain.
| S-EPMC3234513 | biostudies-literature
Project description:BackgroundThe enamel layerof kallikrein 4 (Klk4)-null mice has a normal thickness and a decussating pattern of enamel rods, but it contains residual enamel proteins, is less highly mineralized, and fractures in its deepest part just above the dentino-enamel junction (DEJ). The plane of fracture is puzzling because the deepest enamel is deposited earliest and, through the action of the secretory stage enamel protease (Mmp20), is the most mature part of the enamel layer at the time of the onset of Klk4 expression.ObjectivesTo characterize the planes of fracture in Mmp20- and Klk4-null mice and to localize Klk4 expression in developing teeth.MethodsKlk4- and Mmp20-null mice were sacrificed at 7 weeks and their mandibular incisors were characterized by scanning electron microscopy. Klk4(+/)(lac)(Z) mice were mated with Klk4(+/)(lac)(Z) mice. Offspring were genotyped by polymerase chain reaction. Klk4(+/)(+), Klk4(+/)(lac)(Z), and Klk4(lac)(Z/)(lac)(Z) (null) littermates on postnatal days 5, 8, 11, and 14 were processed for β-galactosidase histochemistry.ResultsThe enamel layer fractures at the DEJ in Mmp20-null mice, and fractures occur in enamel above the DEJ in Klk4-null mice. Klk4 is not expressed by secretory-stage ameloblasts, murine odontoblasts beneath the secretory stage, or maturation-stage ameloblasts. Klk4 is specifically expressed by transition and maturation-stage ameloblasts.ConclusionsThe breakage of enamel near the DEJ in Klk4-null mice is not due to a failure of odontoblasts to express Klk4, but it relates to a progressive hypomineralization of enamel with depth.
| S-EPMC3178080 | biostudies-literature
Project description:Previously, it was shown that the volume of forming enamel of molar teeth in biglycan-null mice was greater than that in genetically matched wild-type mice. This phenotypic change appeared to result from an increase in amelogenin expression, implying that biglycan directly influences amelogenin synthesis. To determine whether biglycan overexpression resulted in decreased amelogenin expression, we engineered transgenic mice to overexpress biglycan in the enamel organ epithelium. Biglycan overexpression did not significantly affect the amelogenin expression in incisor and molar teeth in 3-day postnatal transgenic mice. In the transgenic animals, we observed that the immature and mature enamel appeared normal. These results suggested that increasing the biglycan expression, in the cells that synthesize the precursor protein matrix for enamel, has a negligible influence on amelogenesis.
| S-EPMC2562349 | biostudies-literature
Project description:Claudins comprise a large family of tight junction (TJ) proteins that are often expressed broadly during development and in adult tissues and constitute the physical barriers that occlude the paracellular space in polarized epithelia. In mouse testis, the integrity of TJs is critical to normal spermatogenesis and is dependent on CLDN11 expression. In the current study, we have generated multiple transgenic mouse lines in which steady-state levels of transgene-derived Cldn11 mRNA are up to fourfold greater than endogenous gene expression. Spermatogenesis in all founder mice harboring two copies of the endogenous Cldn11 gene is normal. These animals breed well, indicating that transgene overexpression, at least at the level of mRNA, is well tolerated by Sertoli cells. In addition, we demonstrate that the promoter/enhancer of the transgene, comprising 5 kb of genomic sequence upstream of exon 1 of the mouse Cldn11 gene, is sufficient to rescue azoospermia in Cldn11-null mice. Finally, using transient transgenic mice, we narrow the location of Sertoli cell-specific cis regulatory elements to a 2-kb region upstream of the Cldn11 transcription start site. Together, these data provide essential information for further investigation of the biological regulation of CLDN11 TJs in the testis.
| S-EPMC3364922 | biostudies-literature
Project description:Fibrillin-2 (Fbn2) is the dominant fibrillin isoform expressed during development of the mouse eye. To test its role in morphogenesis, we examined the ocular phenotype of Fbn2(-/-) mice.Ocular morphology was assessed by confocal microscopy using antibodies against microfibril components.Fbn2(-/-) mice had a high incidence of anterior segment dysgenesis. The iris was the most commonly affected tissue. Complete iridal coloboma was present in 37% of eyes. Dyscoria, corectopia and pseudopolycoria were also common (43% combined incidence). In wild-type (WT) mice, fibrillin-2-rich microfibrils are prominent in the pupillary membrane (PM) during development. In Fbn2-null mice, the absence of Fbn2 was partially compensated for by increased expression of fibrillin-1, although the resulting PM microfibrils were disorganized, compared with WTs. In colobomatous adult Fbn2(-/-) eyes, the PM failed to regress normally, especially beneath the notched region of the iris. Segments of the ciliary body were hypoplastic, and zonular fibers, although relatively plentiful, were unevenly distributed around the lens equator. In regions where the zonular fibers were particularly disturbed, the synchronous differentiation of the underlying lens fiber cells was affected.Fbn2 has an indispensable role in ocular morphogenesis in mice. The high incidence of iris coloboma in Fbn2-null animals implies a previously unsuspected role in optic fissure closure. The observation that fiber cell differentiation was disturbed in Fbn2(-/-) mice raises the possibility that the attachment of zonular fibers to the lens surface may help specify the equatorial margin of the lens epithelium.
| S-EPMC3816615 | biostudies-literature
Project description:BackgroundTruncation FAM83H mutations cause human autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI), an inherited disorder characterized by severe hardness defects in dental enamel. No enamel defects were observed in Fam83h null mice suggesting that Fam83h truncation mice would better replicate human mutations.MethodsWe generated and characterized a mouse model (Fam83hTr/Tr ) expressing a truncated FAM83H protein (amino acids 1-296), which recapitulated the ADHCAI-causing human FAM83H p.Tyr297* mutation.ResultsDay 14 and 7-week Fam83hTr/Tr molars exhibited rough enamel surfaces and slender cusps resulting from hypoplastic enamel defects. The lateral third of the Fam83hTr/Tr incisor enamel layer was thinner, with surface roughness and altered enamel rod orientation, suggesting disturbed enamel matrix secretion. Regular electron density in mandibular incisor enamel indicated normal enamel maturation. Only mildly increased posteruption attrition of Fam83hTr/Tr molar enamel was observed at 7-weeks. Histologically, the Fam83hTr/Tr enamel organ, including ameloblasts, and enamel matrices at sequential stages of amelogenesis exhibited comparable morphology without overt abnormalities, except irregular and less evident ameloblast Tomes' processes in specific areas.ConclusionsConsidering Fam83h-/- mice showed no enamel phenotype, while Fam83hTr/Tr (p.Tyr297*) mice displayed obvious enamel malformations, we conclude that FAM83H truncation mutations causing ADHCAI in humans disturb amelogenesis through a neomorphic mechanism, rather than haploinsufficiency.
| S-EPMC6565571 | biostudies-literature
Project description:BackgroundAmeloblastin (AMBN) is a secreted matrix protein that is critical for the formation of dental enamel and is enamel-specific with respect to its essential functions. Biallelic AMBN defects cause non-syndromic autosomal recessive amelogenesis imperfecta. Homozygous Ambn mutant mice expressing an internally truncated AMBN protein deposit only a soft mineral crust on the surface of dentin.MethodsWe characterized a family with hypoplastic amelogenesis imperfecta caused by AMBN compound heterozygous mutations (c.1061T>C; p.Leu354Pro/ c.1340C>T; p.Pro447Leu). We generated and characterized Ambn knockout/NLS-lacZ (AmbnlacZ/lacZ ) knockin mice.ResultsNo AMBN protein was detected using immunohistochemistry in null mice. ß-galactosidase activity was specific for ameloblasts in incisors and molars, and islands of cells along developing molar roots. AmbnlacZ/lacZ 7-week incisors and unerupted (D14) first molars showed extreme enamel surface roughness. No abnormalities were observed in dentin mineralization or in nondental tissues. Ameloblasts in the AmbnlacZ/lacZ mice were unable to initiate appositional growth and started to degenerate and deposit ectopic mineral. No layer of initial enamel ribbons formed in the AmbnlacZ/lacZ mice, but pockets of amelogenin accumulated on the dentin surface along the ameloblast distal membrane and within the enamel organ epithelia (EOE). NLS-lacZ signal was positive in the epididymis and nasal epithelium, but negative in ovary, oviduct, uterus, prostate, seminal vesicles, testis, submandibular salivary gland, kidney, liver, bladder, and bone, even after 15 hr of incubation with X-gal.ConclusionsAmeloblastin is critical for the initiation of enamel ribbon formation, and its absence results in pathological mineralization within the enamel organ epithelia.
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Project description:Proper activation of nuclear factor (NF)-kappaB transcription factors is critical in regulating fundamental biological processes such as cell survival and proliferation, as well as in inflammatory and immune responses. Recently, the NF-kappaB signaling pathways have been categorized into the canonical pathway, which results in the nuclear translocation of NF-kappaB complexes containing p50, and the noncanonical pathway, which involves the induced processing of p100 to p52 and the formation of NF-kappaB complexes containing p52 (Bonizzi, G., and M. Karin. 2004. Trends Immunol. 25:280-288). We demonstrate that loss of tumor necrosis factor (TNF) receptor-associated factor 3 (TRAF3) results in constitutive noncanonical NF-kappaB activity. Importantly, TRAF3-/- B cells show ligand-independent up-regulation of intracellular adhesion molecule 1 and protection from spontaneous apoptosis during in vitro culture. In addition, we demonstrate that loss of TRAF3 results in profound accumulation of NF-kappaB-inducing kinase in TRAF3-/- cells. Finally, we show that the early postnatal lethality observed in TRAF3-deficient mice is rescued by compound loss of the noncanonical NF-kappaB p100 gene. Thus, these genetic data clearly demonstrate that TRAF3 is a critical negative modulator of the noncanonical NF-kappaB pathway and that constitutive activation of the noncanonical NF-kappaB pathway causes the lethal phenotype of TRAF3-deficient mice.
| S-EPMC2118128 | biostudies-literature
Project description:CPD1 (also known as ANP32-E) belongs to a family of evolutionarily conserved acidic proteins with leucine rich repeats implicated in a variety of cellular processes regulating gene expression, vesicular trafficking, intracellular signaling and apoptosis. Because of its spatiotemporal expression pattern, CPD1 has been proposed to play an important role in brain morphogenesis and synaptic development.We have generated CPD1 knock-out mice that we have subsequently characterized. These mice are viable and fertile. However, they display a subtle neurological clasping phenotype and mild motor deficits.CPD1 is not essential for normal development; however, it appears to play a role in the regulation of fine motor functions. The minimal phenotype suggests compensatory biological mechanisms.
| S-EPMC2936576 | biostudies-literature