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Brain natriuretic peptide (BNP) contributes to heart formation during embryogenesis. After birth, despite a high number of studies aimed at understanding by which mechanism(s) BNP reduces myocardial ischemic injury in animal models, the actual role of this peptide in the heart remains elusive. In this study, we asked whether BNP treatment could modulate the proliferation of endogenous cardiac progenitor cells (CPCs) and/or their differentiation into cardiomyocytes. CPCs expressed the NPR-A and NPR-B receptors in neonatal and adult hearts, suggesting their ability to respond to BNP stimulation. BNP injection into neonatal and adult unmanipulated mice increased the number of newly formed cardiomyocytes (neonatal: +23 %, p = 0.009 and adult: +68 %, p = 0.0005) and the number of proliferating CPCs (neonatal: +142 %, p = 0.002 and adult: +134 %, p = 0.04). In vitro, BNP stimulated CPC proliferation via NPR-A and CPC differentiation into cardiomyocytes via NPR-B. Finally, as BNP might be used as a therapeutic agent, we injected BNP into mice undergoing myocardial infarction. In pathological conditions, BNP treatment was cardioprotective by increasing heart contractility and reducing cardiac remodelling. At the cellular level, BNP stimulates CPC proliferation in the non-infarcted area of the infarcted hearts. In the infarcted area, BNP modulates the fate of the endogenous CPCs but also of the infiltrating CD45 cells. These results support for the first time a key role for BNP in controlling the progenitor cell proliferation and differentiation after birth. The administration of BNP might, therefore, be a useful component of therapeutic approaches aimed at inducing heart regeneration. [ABSTRACT FROM AUTHOR]

Natriuretic peptide type C (NPPC) and its high affinity receptor, natriuretic peptide receptor 2 (NPR2), have been assumed to be involved in female reproduction and have recently been shown to play an essential role in maintaining meiotic arrest of oocytes. However, the overall role of NPPC/NPR2 signaling in female reproduction and ovarian function is still less clear. Here we report the defects observed in oocytes and follicles of mice homozygous for Nppcfbab or Npr2cn mutant alleles of Nppc or Npr2 respectively to clarify the exact consequences of lack of NPPC/NPR2 signaling in female reproductive systems. We found that: i) Npr2cn/Npr2cn female mice ovulated a comparable number of oocytes as normal mite but never produced a litter; ii) ail ovulated oocytes of Npr2cn/Npr2cn and Nppclbab/ Nppc,lbab mice exhibited abnormalities, such as fragmented or degenerated ooplasm and never developed to the two-cell stage after fertilization; iii) histological examination of the ovaries of Npr2cn/Npr2cn and Nppclbab/Nppclbab mice showed that oocytes in antral follicles prematurely resumed meiosis and that immediately before ovulation, oocytes showed disorganized chromosomes or fragmented ooplasm; and iv) ovulated oocytes and oocytes in the periovulatory follicles of the mutant mice were devoid of cumulus cells. These findings demonstrate that NPPC/NPR2 signaling is essential for oocyte meiolic arrest and cumulus oophorus formation, which affects female fertility through the production of oocytes with developmental capacity. [ABSTRACT FROM AUTHOR]

Long bone abnormality ( lbab/lbab) is a strain of dwarf mice. Recent studies revealed that the phenotype is caused by a spontaneous mutation in the Nppc gene, which encodes mouse C-type natriuretic peptide (CNP). In this study, we analyzed the chondrodysplastic skeletal phenotype of lbab/lbab mice. At birth, lbab/lbab mice are only slightly shorter than their wild-type littermates. Nevertheless, lbab/lbab mice do not undergo a growth spurt, and their final body and bone lengths are only ~60% of those of wild-type mice. Histological analysis revealed that the growth plate in lbab/lbab mice, especially the hypertrophic chondrocyte layer, was significantly thinner than in wild-type mice. Overexpression of CNP in the cartilage of lbab/lbab mice restored their thinned growth plate, followed by the complete rescue of their impaired endochondral bone growth. Furthermore, the bone volume in lbab/lbab mouse was severely decreased and was recovered by CNP overexpression. On the other hand, the thickness of the growth plate of lbab/+ mice was not different from that of wild-type mice; accordingly, impaired endochondral bone growth was not observed in lbab/+ mice. In organ culture experiments, tibial explants from fetal lbab/lbab mice were significantly shorter than those from lbab/+ mice and elongated by addition of 10 M CNP to the same extent as lbab/+ tibiae treated with the same dose of CNP. These results demonstrate that lbab/lbab is a novel mouse model of chondrodysplasia caused by insufficient CNP action on endochondral ossification. [ABSTRACT FROM AUTHOR]

Short-limbed dwarfism (SLW) is a new mutant mouse characterized by a dwarf phenotype with markedly short body, limbs, and tail. In the present study, we investigated the skeletal phenotypes of the SLW mouse and determined the chromosomal localization to identify the gene responsible for the phenotypes (slw). Skeletal preparations stained with alcian blue and alizarin red revealed that longitudinal growth of the extremities of the affected (slw/slw) mice was significantly reduced in comparison with that of normal mice, whereas the positions and numbers of skeletal elements were normal. Histological examination of tibial growth plates of the affected mice showed that the numbers of proliferating and hypertrophic chondrocytes were obviously diminished. These phenotypes resembled to those of human chondrodysplasias caused by defective chondrocyte proliferation and differentiation. We mapped the slw locus on an 11.7-cM interval of the proximal region of mouse chromosome 4 by linkage analysis. Furthermore, allelism test using Npr2cn locus, a mutant allele of Npr2 gene encoding a natriuretic peptide receptor B, revealed that slw locus is an allele of the Npr2 gene. These results suggest that the dwarf phenotype of the SLW mouse is caused by the disturbed endochondral ossification, and a mutation in the Npr2 gene is expected to be responsible for the phenotypes of the SLW mouse. [ABSTRACT FROM AUTHOR]

The hairy ears ( Eh) mutation in the mouse originated from neutron irradiation experiments and is associated with chromosomal inversion on chromosome 15. Eh/+ mice have small pinna and extra hairs on the pinna but the phenotypic features of Eh/Eh mice are unclear. In this study we found that Eh/Eh mice died shortly after birth and had a cleft palate caused by impaired growth of palate shelves. Because genes located on the breakpoints of inversion are likely to be responsible for the defects associated with chromosomal inversions, we determined the breakpoints of the Eh inversion. We used a new genetic method that uses recombinant chromosomes resulting from crossing over between two overlapping inversions to determine the breakpoints. Koa is a mouse mutation associated with inversion of chromosome 15, which partially overlaps with the Eh inversion. We made Eh +/+ Koa double heterozygotes and obtained the recombinant chromosomes possessing deletion and duplication of the regions flanked by the breakpoints of both inversions, which were generated by crossing over within the overlapped region of these inversions. By defining the deleted regions we identified the breakpoints of the Eh inversion. We then examined the expression of genes in the vicinities of the breakpoints and found ectopic expression of the Hoxc5 gene and a transcript with unknown function in the developing palate of Eh/Eh mice, which is likely to be responsible for the cleft palate. [ABSTRACT FROM AUTHOR]

Objective Our objectives were to determine the expression of EVC2 in craniofacial tissues and investigate the effect of Evc2 deficiency on craniofacial bones using Evc2 knockout (KO) mouse model. Design Evc2 KO mice were generated by introducing a premature stop codon followed by the Internal Ribosomal Entry Site fused to β-galactosidase (LacZ). Samples from wild-type (WT), heterozygous (Het) and homozygous Evc2 KO mice were prepared. LacZ staining and immunohistochemistry (IHC) with anti-β-galactosidase, anti-EVC2 and anti-SOX9 antibodies were performed. The craniofacial bones were stained with alcian blue and alizarin red. Results The LacZ activity in KO was mainly observed in the anterior parts of viscerocranium. The Evc2 -expressing cells were identified in many cartilageous regions by IHC with anti-β-galactosidase antibody in KO and Het embryos. The endogenous EVC2 protein was observed in these areas in WT embryos. Double labeling with anti-SOX9 antibody showed that these cells were mainly chondrocytes. At adult stages, the expression of EVC2 was found in chondrocytes of nasal bones and spheno-occipital synchondrosis, and osteocytes and endothelial-like cells of the premaxilla and mandible. The skeletal double staining demonstrated that craniofacial bones, where the expression of EVC2 was observed, in KO had the morphological defects as compared to WT. Conclusion To our knowledge, our study was the first to identify the types of Evc2 -expressing cells in craniofacial tissues. Consistent with the expression pattern, abnormal craniofacial bone morphology was found in the Evc2 KO mice, suggesting that EVC2 may be important during craniofacial growth and development. [ABSTRACT FROM AUTHOR]

Rev7 is a subunit of Polζ, one of the translesion DNA synthesis (TLS) polymerases involved in DNA damage repair. We recently found that Rev7 is also essential for germ cell development in mouse. In the present study, we found the development of ovarian tumors in Rev7 mutant mouse, suggesting the involvement of TLS deficiency in the etiology of ovarian tumor. The Rev7 mutant mice showed complete lack of oocytes and follicles in the ovary. The lack of follicles causes a significant increase of gonadotropin level and an increase in the proliferation of ovarian cells. As a result, the weight of the ovaries of Rev7 mutant mice increased with age and they developed tubulostromal adenomas. However, the remarkable overgrowth of ovaries occurred after gonadotropin level decreases at older ages, suggesting gonadotropin-independent progression of the ovarian tumors. In addition, the Rev7 mutant fibroblasts and ovarian cells showed significant accumulation of DNA damage. These findings suggest that not only increased gonadotropin levels but also lack of DNA damage repair function could be responsible for the development of ovarian tumors in the Rev7 mutant mouse. [ABSTRACT FROM AUTHOR]